JP2013021612A - Image encoder, image encoding method and image encoding program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve encoding efficiency of motion information including a motion vector.SOLUTION: In an image encoder which performs motion compensation prediction, a connection type determination part 155 determines whether to use a first inter-image prediction mode of using the motion information that one reference block candidate has or to use a second inter-image prediction mode of using the motion information that two reference block candidates have. The first inter-image prediction mode is a mode of performing motion compensation of an encoding object block using a unidirectional or bidirectional motion vector included in the motion information of one reference block candidate. The second inter-image prediction mode is a mode of generating a new bidirectional motion vector combination by combining the two motion vectors that can be acquired from the motion information of the two reference block candidates, and performing motion compensation of an encoding object block using the new bidirectional motion vector.

Description

  The present invention relates to a moving image encoding technique using motion compensated prediction, and more particularly to an image encoding device, an image encoding method, and an image encoding program for encoding motion information used in motion compensated prediction.

  In general video compression coding, motion compensation prediction is used. Motion compensation prediction divides the target image into fine blocks, uses the decoded image as a reference image, and based on the amount of motion indicated by the motion vector, the position of the position moved from the target block of the target image to the reference block of the reference image This is a technique for generating a signal as a prediction signal. Some motion compensation predictions are performed unidirectionally using one motion vector, and others are performed bidirectionally using two motion vectors.

  As for the motion vector, the motion vector of the encoded block adjacent to the processing target block is used as a prediction motion vector (also simply referred to as “prediction vector”), and the difference between the motion vector of the processing target block and the prediction vector is obtained. The compression efficiency is improved by transmitting the difference vector as an encoded vector.

  MPEG-4AVC improves the efficiency of motion compensation prediction by making the block size of motion compensation prediction finer and more diversified than MPEG-2. On the other hand, since the number of motion vectors increases by making the block size finer, the code amount of the encoded vector becomes a problem.

  Therefore, in MPEG-2, the motion vector of the block adjacent to the left of the block to be processed is simply used as the prediction vector, but in MPEG-4 AVC, the prediction vector is obtained by using the median of the motion vectors of the plurality of adjacent blocks as the prediction vector. And the increase in the code amount of the encoded vector is suppressed. Further, direct motion compensation prediction is known in MPEG-4 AVC. Direct motion compensated prediction generates a new motion vector by scaling the motion vector of a block at the same position as the processing target block of another encoded image by the distance between the target image and two reference images. The motion compensation prediction is realized without transmitting the quantization vector.

  In addition, motion compensation prediction that realizes motion compensation prediction without transmitting an encoded vector using motion information of a block adjacent to a processing target block is known (see, for example, Patent Document 1).

JP-A-10-276439

  As described above, direct motion compensated prediction that does not transmit an encoded vector focuses on the continuity of motion of a block that is in the same position as a processing target block and a processing target block of another encoded image. Further, Patent Document 1 focuses on the continuity of movement of a processing target block and a block adjacent to the processing target block. As a result, by using the motion information of other blocks, the encoding efficiency is improved without encoding the motion information including the difference vector as the encoded vector.

  However, in the conventional motion compensated prediction, the motion of the processing target block is shifted to the motion of the processing target block and the adjacent block, or the motion of a block around the same position as the processing target block of another encoded image. In such a case, the motion information including the difference vector must be encoded, and there is a difficult aspect that the improvement of the encoding efficiency is not sufficiently exhibited.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for further improving the efficiency of encoding motion information including a motion vector.

  In order to solve the above-described problem, an image coding apparatus according to an aspect of the present invention is an image coding apparatus that performs motion compensation prediction, and uses the motion information of one reference block candidate between first images. A determination unit (155) is provided for determining whether to use the prediction mode or to use the second inter-picture prediction mode that uses motion information of two reference block candidates. The first inter-picture prediction mode is a mode in which motion compensation of a coding target block is performed using a unidirectional or bidirectional motion vector included in motion information of one reference block candidate, and the second image The inter prediction mode combines two motion vectors that can be acquired from motion information of two reference block candidates, generates a new bidirectional motion vector combination, and encodes using the new bidirectional motion vector. In this mode, motion compensation is performed on the target block.

  A candidate list generation unit (150) that generates a candidate list by selecting a plurality of blocks having motion information from a plurality of encoded blocks adjacent to the encoding target block, and a motion that overlaps the candidate list When there are a plurality of blocks having information, a deletion unit (151) that leaves one and deletes the remaining may be further provided. The determination unit (155) may determine not to use the second inter-picture prediction mode when the number of blocks deleted by the deletion unit (151) is equal to or greater than a set number. The “multiple encoded blocks adjacent to the encoding target block” may include blocks of images that are temporally different from the image including the encoding target block.

  A candidate list generation unit (150) that generates a candidate list by selecting a plurality of blocks having motion information from a plurality of encoded blocks adjacent to the encoding target block, and the determination unit (155), The candidate list has a bi-directional motion vector, and two reference images of the bi-directional motion vector are blocks that are the immediately preceding image and the immediately following image of the target image. If included, it may be determined that the second inter-picture prediction mode is not used. The “multiple encoded blocks adjacent to the encoding target block” may include blocks of images that are temporally different from the image including the encoding target block.

  Two blocks are selected from a plurality of encoded blocks adjacent to the encoding target block, and the motion information of the two encoded blocks is different from the motion information held by the plurality of encoded blocks. A selection candidate generation unit (152) that generates motion information including a bidirectional motion vector as a new selection candidate, and a plurality of selection candidates including the new selection candidate generated by the selection candidate generation unit (152). A selection unit (141) for selecting one from among, a code string generation unit (104) for encoding identification information (for example, an identification number) for specifying a candidate selected by the selection unit (141), , May be further provided. The new selection candidate identification information generated by the selection candidate generation unit (152) includes the identification information of the motion information candidate in the first prediction direction and the motion information candidate in the second prediction direction that compose the selection candidate. It may be defined by a combination of identification information.

  Among the motion information candidates in the first prediction direction and the motion information candidates in the second prediction direction, identification information is assigned to each of the motion information candidates in the reference direction, and a combination target is set for each motion information candidate in the reference direction. The number of motion information candidates in the non-reference direction may be counted, and identification information may be assigned to each motion information candidate in the non-reference direction based on each count value. When the count value is 1, the identification information of the motion information candidate in the non-reference direction may be omitted.

  Another aspect of the present invention is an image encoding method. This method is an image coding method that performs motion compensation prediction, and uses the first inter-picture prediction mode that uses the motion information of one reference block candidate or the motion information of two reference block candidates. Determining whether to use the second inter-picture prediction mode using. The first inter-picture prediction mode is a mode in which motion compensation of a coding target block is performed using a unidirectional or bidirectional motion vector included in motion information of one reference block candidate, and the second image The inter prediction mode combines two motion vectors that can be acquired from motion information of two reference block candidates, generates a new bidirectional motion vector combination, and encodes using the new bidirectional motion vector. In this mode, motion compensation is performed on the target block.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, and the like are also effective as an aspect of the present invention.

  According to the present invention, it is possible to further improve the encoding efficiency of motion information including motion vectors.

It is a figure for demonstrating the example which divides | segments an image into the largest encoding block. 2A and 2B are diagrams for explaining an encoded block. 3A to 3D are diagrams for explaining a prediction block. It is a figure for demonstrating a prediction block size. It is a figure for demonstrating prediction encoding mode. FIGS. 6A to 6D are diagrams for explaining the prediction direction of motion compensation prediction. FIGS. 7A to 7C are diagrams for explaining a truncated unary code string of a merge index. It is a figure for demonstrating an example of the syntax of a prediction block. It is a figure for demonstrating the structure of the moving image encoder which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the management method of the motion information in the motion information memory of FIG. It is a figure for demonstrating the structure of the motion information generation part of FIG. It is a figure for demonstrating the structure of the difference vector calculation part of FIG. It is a figure for demonstrating a space candidate block group. It is a figure for demonstrating a time candidate block group. It is a figure for demonstrating the structure of the joint motion information determination part of FIG. It is a figure for demonstrating the structure of the joint motion information candidate production | generation part of FIG. It is a figure for demonstrating the structure of the double combined motion information candidate combination list production | generation part of FIG. It is a figure for demonstrating a candidate number management table. FIGS. 19A and 19B are diagrams for explaining conversion from a merge candidate number to a merge index. It is a flowchart for demonstrating the operation | movement of the encoding of the moving image encoder which concerns on Embodiment 1 of this invention. 10 is a flowchart for explaining an operation of a motion information generation unit in FIG. 9. 12 is a flowchart for explaining an operation of a difference vector calculation unit in FIG. 11. It is a flowchart for demonstrating operation | movement of the joint motion information determination part of FIG. FIG. 17 is a flowchart for explaining the operation from the double coupled motion information candidate list generation unit to the dual coupled motion information candidate combination list generation unit of FIG. It is a flowchart for demonstrating operation | movement of the production | generation of a space joint motion information candidate list. It is a flowchart for demonstrating the operation | movement of the production | generation of a time combination motion information candidate list. It is a figure explaining the calculation method of the motion vector of a time joint motion information candidate. FIGS. 28A to 28D are diagrams for explaining the generation of a double-coupled motion information candidate list (Example 1). FIGS. 29A to 29D are diagrams for explaining the generation of a double-coupled motion information candidate list (example 2). FIGS. 30A to 30D are diagrams for explaining the determination of a combination of bi-coupled motion information candidates (example 1). FIGS. 31A to 31D are diagrams for explaining the determination of a combination of dual-coupled motion information candidates (Example 1). FIGS. 32A and 32B are diagrams for explaining the change of the double-coupled motion information candidate list of FIGS. 31A and 31B. It is a figure for demonstrating the structure of the moving image decoding apparatus which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the structure of the motion information reproduction | regeneration part of FIG. FIG. 35 is a diagram for describing a configuration of a motion vector reproduction unit in FIG. 34. FIG. 35 is a diagram for describing a configuration of a combined motion information reproduction unit in FIG. 34. It is a flowchart for demonstrating the decoding operation | movement of the moving image decoding apparatus which concerns on Embodiment 1 of this invention. It is a flowchart for demonstrating operation | movement of the motion information reproduction | regeneration part of FIG. FIG. 35 is a flowchart for explaining an operation of a motion vector reproducing unit in FIG. 34. FIG. FIG. 35 is a flowchart for explaining an operation of a combined motion information reproducing unit in FIG. 34. FIG. FIGS. 41A and 41B are diagrams for explaining generation of a combination of bi-join motion information candidates from a single join motion information candidate list according to the first modification of the first embodiment. FIGS. 42A to 42C are diagrams for explaining generation of a combination of bi-join motion information candidates from a single join motion information candidate list according to the second modification of the first embodiment. 43 (a) and 43 (b) are diagrams for explaining the syntax for encoding the number of combined motion information candidates to be selected with priority in the second modification of the first embodiment in the encoded stream. . It is a figure for demonstrating the production | generation of the combination of a double bond motion information candidate from the single bond motion information candidate list which concerns on the modification 3 of Embodiment 1. FIG. 45 (a) and 45 (b) are diagrams for explaining the syntax for encoding a flag indicating whether or not a predetermined combination of bi-join motion information candidates according to the third modification of the first embodiment can be used. is there. 46 (a) and 46 (b) are diagrams (part 1) for explaining the effect of the first embodiment. 47 (a) and 47 (b) are diagrams (part 2) for explaining the effect of the first embodiment. 48A and 48B are views (No. 3) for explaining the effect of the first embodiment. FIG. 10 is a diagram for explaining a syntax to which a function MergeType () of the second embodiment is added. FIG. 16 is a diagram for explaining a configuration in which a combination type determination unit according to Embodiment 2 is added to the configuration of the combined motion information candidate generation unit in FIG. 15. 10 is a flowchart for explaining an operation of a combination type determination unit according to the second embodiment. FIG. 16 is a diagram illustrating an example of an image and a motion vector referred to by an adjacent block in Modification 1 of Embodiment 2.

  First, a technique that is a premise of the embodiment of the present invention will be described.

  Currently, apparatuses and systems that comply with an encoding method such as MPEG (Moving Picture Experts Group) are widely used. In such an encoding method, a plurality of images that are continuous on the time axis are handled as digital signal information. At that time, for the purpose of broadcasting, transmission or storage of highly efficient information, compression codes using orthogonal compensation such as motion compensated prediction using temporal redundancy and discrete cosine transform using spatial redundancy are used. Turn into.

  In 1995, the MPEG-2 video (ISO / IEC 13818-2) encoding method was established as a general-purpose video compression encoding method, such as DVD and D-VHS (registered trademark) standard digital VTR magnetic tapes, etc. It is widely used as an application for storage media and digital broadcasting.

  Furthermore, in 2003, joint work of the International Technical Organization (ISO) and the International Electrotechnical Commission (IEC) Joint Technical Committee (ISO / IEC) and the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) -4 AVC / H. An encoding method called H.264 (the ISO / IEC has a standard number of 14496-10 and ITU-T has an H.264 standard number, hereinafter referred to as MPEG-4AVC) has been established as an international standard.

  Coding currently called HEVC by the joint work of the International Technical Organization (ISO) and the International Electrotechnical Commission (IEC) Joint Technical Committee (ISO / IEC) and the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Standardization of the method is being studied.

(Encoding block)
In the embodiment of the present invention, an input image signal is divided into maximum coding block units as shown in FIG. 1, and the divided coding blocks are processed in a raster scan order. The encoded block has a hierarchical structure, and can be made smaller encoded blocks by sequentially equally dividing into 4 in consideration of the encoding efficiency. The encoded block divided into four is encoded in the zigzag scan order. An encoded block that cannot be further reduced is called a minimum encoded block. An encoded block is a unit of encoding, and the maximum encoded block is also an encoded block when the number of divisions is zero. In this embodiment, the maximum coding block is 64 pixels × 64 pixels, and the minimum coding block is 8 pixels × 8 pixels.

  FIGS. 2A and 2B show an example of division of the maximum coding block. In the example of FIG. 2A, the encoded block is divided into ten. CU0, CU1 and CU9 are 32 pixel x 32 pixel coding blocks, CU2, CU3 and CU8 are 16 pixel x 16 pixel coding blocks, and CU4, CU5, CU6 and CU7 are 8 pixel x 8 pixel coding blocks It has become. In the example of FIG. 2B, the encoded block is divided into one.

(Prediction block)
In the embodiment of the present invention, the encoded block is further divided into prediction blocks. The prediction block division patterns are shown in FIGS. 3A shows 2N × 2N that does not divide the encoded block, FIG. 3B shows 2N × N that divides horizontally, FIG. 3C shows N × 2N that divides vertically, and FIG. 3D. Indicates N × N divided horizontally and vertically. In other words, as shown in FIG. 4, the prediction block size includes a CU division number of 0 and a maximum prediction block size of 64 pixels × 64 pixels to a CU division number of 3 and a minimum prediction block size. There are 13 predicted block sizes up to 4 pixels x 4 pixels.

  In the embodiment of the present invention, the maximum coding block is 64 pixels × 64 pixels and the minimum coding block is 8 pixels × 8 pixels, but the present invention is not limited to this combination. Further, although the prediction block division patterns are shown in FIGS. 3A to 3D, the division is not limited to this as long as it is divided into one or more.

(Predictive coding mode)
In the embodiment of the present invention, the prediction direction of motion compensation prediction and the number of encoded vectors can be switched by the block size of the prediction block. Here, an example of a predictive coding mode in which the prediction direction of motion compensation prediction and the number of coding vectors are associated will be briefly described with reference to FIG.

  The prediction coding mode shown in FIG. 5 includes a unidirectional mode (UniPred) in which the prediction direction of motion compensation prediction is unidirectional and the number of coding vectors is 1, and the prediction direction of motion compensation prediction is bidirectional. There are a bidirectional mode (BiPred) in which the number of encoded vectors is 2 and a merge mode (MERGE) in which the prediction direction of motion compensation prediction is unidirectional or bidirectional and the number of encoded vectors is 0. There is also an intra mode (Intra) which is a predictive coding mode in which motion compensation prediction is not performed.

(Reference image index)
In the embodiment of the present invention, it is possible to select an optimal reference image from a plurality of reference images in motion compensation prediction in order to improve the accuracy of motion compensation prediction. Therefore, the reference image used in the motion compensation prediction is encoded in the encoded stream together with the encoded vector as a reference image index. The reference image index used in motion compensation prediction is a numerical value of 0 or more.

  A plurality of reference images that can be selected by the reference image index are managed in a reference index list. If the prediction direction of motion compensation prediction is unidirectional, one reference image index is encoded. If the prediction direction of motion compensation prediction is bidirectional, a reference image index indicating a reference image in each prediction direction is encoded. (FIG. 5).

(Predicted vector index)
In HEVC, in order to improve the accuracy of a prediction vector, it is considered to select an optimal prediction vector from among a plurality of prediction vector candidates and to encode a prediction vector index for indicating the selected prediction vector. Yes. In the embodiment of the present invention, the prediction vector index is introduced. If the prediction direction of motion compensation prediction is unidirectional, one prediction vector index is encoded. If the prediction direction of motion compensation prediction is bidirectional, a prediction vector index indicating a prediction vector in each prediction direction is encoded. (FIG. 5).

(Merge index)
In HEVC, in order to further improve the coding efficiency, an optimum block is selected from among a plurality of adjacent block candidates and a block located at the same position as a processing target block of another coded image, and the selected block is selected. Encoding and decoding a merge index indicating This is a motion compensation prediction technique (merge technique) in which motion information including a prediction direction, motion vector information, and reference image information of a motion compensation prediction of a block indicated by a selected merge index is used in a processing target block. In the embodiment of the present invention, the above merge index is introduced. As shown in FIG. 5, one merge index is encoded when the prediction encoding mode is the merge mode. If the motion information is bidirectional, the motion information includes motion vector information and reference image information in each prediction direction.

  Hereinafter, the motion information of a block that may be indicated by the merge index is referred to as a combined motion information candidate, and the aggregate of combined motion information candidates is referred to as a combined motion information candidate list.

(Forecast direction)
In the embodiment of the present invention, two directions of the L0 direction and the L1 direction are set as the prediction directions of the motion compensation prediction. Here, the prediction direction of motion compensation prediction will be briefly described with reference to FIGS. When the prediction direction of motion compensation prediction is unidirectional, either the L0 direction or the L1 direction is used. FIG. 6A shows a case where the reference image (RefL0Pic) in the unidirectional direction and the L0 direction is at a time before the encoding target image (CurPic). FIG. 6B shows a case where the reference image in the unidirectional direction and the L0 direction is at a time after the encoding target image. The reference image in the L0 direction in FIGS. 6A and 6B may be replaced with a reference image in the L1 direction (RefL1Pic).

  In the case of bidirectional, the BI direction is expressed using two of the L0 direction and the L1 direction. FIG. 6C shows a case where the reference image in the L0 direction is at a time before the encoding target image and the reference image in the L1 direction is at a time after the encoding target image. . FIG. 6D shows a case in which the reference image in the L0 direction and the reference image in the L1 direction are at a time before the encoding target image. The reference image in the L0 direction in FIGS. 6C and 6D can be replaced with a reference image in the L1 direction (RefL1Pic), and the reference image in the L1 direction can be replaced with a reference image in the L0 direction (RefL0Pic). As described above, the L0 direction and the L1 direction, which are prediction directions of motion compensation prediction, can be indicated in either the forward direction or the backward direction in terms of time.

  In addition, there may be a plurality of reference images in each of the L0 direction and the L1 direction. The reference image in the L0 direction is registered in the reference image list L0, and the reference image in the L1 direction is registered in the reference image list L1. The position of the reference image in the reference image list is designated by the reference image index in each prediction direction, and the reference image is determined. Hereinafter, the prediction direction is the L0 direction is a prediction direction that uses motion information associated with the reference image registered in the reference image list L0, and the prediction direction is the L1 direction is registered in the reference image list L1. The prediction direction uses motion information associated with the reference image.

(Code amount of motion information)
In the merge mode, motion information can be transmitted using a merge index. Therefore, if the prediction errors in the merge mode (merge flag is 1) and the non-merge mode (merge flag is 0) are approximately the same, the merge mode can encode the motion information more efficiently. In other words, the efficiency of motion information encoding can be improved by increasing the selection rate of the merge mode.

(Characteristics of merge index)
In the merge mode, the number of merge candidates is calculated before the merge index decoding (encoding). In the non-merge mode, the number of prediction vector candidates is calculated before the prediction vector index decoding (encoding). Each process to calculate is installed. These are processes necessary for obtaining the number of candidates because the number of merge candidates and the number of prediction vector candidates change for each prediction block depending on the validity of motion information of adjacent blocks. Note that the motion information of the adjacent block is valid means that the adjacent block is not a block outside the area or the intra mode, and the motion information of the adjacent block is invalid means that the adjacent block is out of the area. It is a block or intra mode.

  When the number of merge candidates is 1, the merge index is not decoded (encoded). This is because when the number of merge candidates is 1, it can be uniquely determined without specifying. The same applies to the prediction vector index.

  The merge index code string will be described with reference to FIGS. In the embodiment of the present invention, a Trunked Unary code string is used as the code string of the merge index. FIG. 7A shows a merge index code string based on a truncated unary code string when the number of merge candidates is two, and FIG. 7B shows a merge based on a truncated unary code string when the number of merge candidates is three. FIG. 7C shows a code sequence of the index, and FIG. 7C shows a code sequence of the merge index by the Truncated Unary code sequence when the number of merge candidates is four.

  7A to 7C that even when the same merge index value is encoded, the smaller the number of merge candidates, the smaller the number of code bits assigned to the merge index. For example, if the merge index is 1, if the number of merge candidates is two, it is 1 bit of “1”, but if the number of merge candidates is 3 or 4, it is 2 bits of “10”. Become.

  As described above, the encoding efficiency of the merge index improves as the number of merge candidates decreases. That is, the coding efficiency of the merge index can be improved by leaving candidates with a relatively high selectivity and reducing candidates with a relatively low selectivity. In addition, when the number of candidates is the same, the code amount of the smaller merge index is smaller, so that the encoding efficiency can be improved by assigning a small merge index to a candidate having a relatively high selectivity. .

(POC)
In the embodiment of the present invention, POC (Picture Order Count) is used as time information (distance information) of an image. POC is a counter indicating the display order of images defined by MPEG-4 AVC. When the image display order is increased by 1, the POC is also increased by 1. Therefore, the time difference (distance) between images can be acquired from the POC difference between images.

(Characteristics of motion information of adjacent blocks)
In general, the degree of correlation between the motion information of the processing target block and the motion information of the block adjacent to the processing target block (hereinafter referred to as an adjacent block) is high when the processing target block and the adjacent block have the same motion. For example, this is a case where the region including the processing target block and the adjacent block is translated. In general, the degree of correlation between the motion information of the processing target block and the motion information of the adjacent block also depends on the length of contact between the processing target block and the adjacent block.

(Characteristics of motion information of another image)
On the other hand, a block in the same position as the processing target block (hereinafter referred to as the same position block) on another decoded image generally used in the temporal direct mode or the spatial direct mode, and the processing target block The degree of correlation is high when the block at the same position and the block to be processed are in the same motion information, that is, at a constant velocity motion.

  Hereinafter, with reference to the drawings, the details of a moving image encoding apparatus, a moving image encoding method, a moving image encoding program, a moving image decoding apparatus, a moving image decoding method, and a moving image decoding program according to a preferred embodiment of the present invention will be described. explain. In the description of the drawings, the same elements are denoted by the same reference numerals and redundant description is omitted.

[Embodiment 1]
(Syntax)
An example of the syntax of a prediction block defined by encoding and decoding in Embodiment 1 of the present invention will be described using FIG. Whether the prediction block is intra or inter is specified by a higher-order encoding block, and FIG. 8 shows the syntax when the prediction block is inter. The prediction block includes a merge flag (merge_flag), a merge type (merge_type), a merge index (merge_idx, merge_idx_l0, merge_idx_l1), an inter prediction mode (inter_pred_type), a reference index (ref_idx_l_0, v1_d_l0, v1_l_0, 0) mvd_l0 [1], mvd_l1 [0], mvd_l1 [1]) and prediction vector indexes (mvp_idx_l0 and mvp_idx_l1) are installed. [0] of the difference vector indicates a horizontal component and [1] indicates a vertical component.

  When the merge mode using the motion information of the adjacent block indicated by the selected merge index is applied to the prediction block, merge_flag is set to “1”. On the other hand, merge_flag is set to “0” when the merge mode is not applied to the prediction block and the non-merge mode using the motion vector detected by the normal motion vector detection is applied.

  When merge_flag is “1”, merge_type is set first. merge_type is a flag for switching whether to use one or two merge indexes. When merge_type is “0”, one merge index is used, and an adjacent block using motion information is designated by the merge index (merge_idx).

  When merge_type is “1”, two merge indexes are used. Merge_idx_l0 and merge_idx_l1 are set in the L0 direction and the L1 direction, respectively, and the merge index specifies adjacent blocks that use motion information in the L0 direction and the L1 direction, respectively. When merge_type is “1”, since two merge indexes in the L0 and L1 directions are used, this is applied only when the slice type including the prediction block is a B slice.

  Therefore, it is determined whether or not the slice type is a B slice, and if the slice type is a B slice, whether or not one or two merge indexes are to be used is specified by merge_type. When the slice type is P slice, since there is only one prediction direction of L0 prediction, merge_type is equivalent to being implicitly set to “0”, and adjacent using motion information with one merge index Specify a block.

  A function NumMergeCand () for calculating the number of merge candidates is provided in the previous stage of the merge index. This is a function necessary for obtaining the number of candidates because the number of merge candidates changes for each prediction block depending on the validity of motion information of adjacent blocks. When the number of merge candidates is larger than 1, the merge index is used to designate the merge candidate. When the number of merge candidates is 1, the merge candidate is uniquely determined, so the merge index is not used. Here, when there is a description in parentheses of the function NumMergeCand (), the validity of motion information only in the prediction direction indicated by the description is determined, and the number of candidates is calculated. The prediction direction is the L0 direction or the L1 direction. When there is no description in parentheses of the function NumMergeCand (), the effectiveness in the L0 direction or the L1 direction is determined, and the number of candidates is calculated.

  When merge_flag is “0”, the non-merge mode is set, and in order to efficiently transmit the motion vector detected by the normal motion vector detection, the motion vector of the adjacent block indicated by the prediction vector index for each of the L0 and L1 directions. As a prediction vector, motion vector prediction is performed. An adjacent block used as a prediction vector is designated by a prediction vector index (mvp_idx_l0 and mvp_idx_l1) for each of the L0 and L1 directions. In the syntax shown in FIG. 8, a form in which merge_idx_l0 and merge_idx_l1 are combined into one may be used. For example, merge_idx_l0 is MSB, merge_idx_l1 is LSB, and (merge_idx_l0 << (number of bits of merge_idx_l1)) | merge_idx_l1 is merge_idx. In this case, the conditional statement is if ((NumMergeCand (L0)> 1) || (NumMergeCand (L1)> 1)).

  A function NumMvpCand () for calculating the number of prediction vector candidates is provided in the preceding stage of the prediction vector index. Like NumMergeCand (), the number of prediction vector candidates depends on the validity of motion information of adjacent blocks. This is a function necessary to obtain the number of candidates for changing to. Here, ref_idx_l0, mvd_l0 [0], mvd_l0 [1], and mvp_idx_l0 are information regarding the L0 direction, and ref_idx_l1, mvd_l1 [0], mvd_l1 [1], and mvp_idx_l1 are information regarding the L1 direction. There are three types of inter_pred_type: Pred_L0 (unidirectional in the L0 direction), Pred_L1 (unidirectional in the L1 direction), and Pred_BI (bidirectional in the BI).

(Configuration of moving picture coding apparatus 100)
FIG. 9 shows a configuration of moving picture coding apparatus 100 according to Embodiment 1 of the present invention. The moving image encoding apparatus 100 is an apparatus that encodes a moving image signal in units of prediction blocks for performing motion compensation prediction. It is assumed that the coding block division, the prediction block size determination, and the prediction encoding mode determination are determined by the higher-order encoding control unit.

  The moving image encoding apparatus 100 is realized by hardware such as an information processing apparatus including a CPU (Central Processing Unit), a frame memory, and a hard disk. The moving image encoding apparatus 100 realizes functional components described below by operating the above components. Note that the position information of the prediction block to be processed, the prediction block size, and the prediction direction of the motion compensated prediction are assumed to be shared in the video encoding device 100 and are not shown.

  The moving image encoding apparatus 100 according to Embodiment 1 includes a prediction block image acquisition unit 101, a subtraction unit 102, a prediction error encoding unit 103, a code string generation unit 104, a prediction error decoding unit 105, a motion compensation unit 106, and an addition unit. 107, a motion vector detecting unit 108, a motion information generating unit 109, a frame memory 110, and a motion information memory 111.

(Function of moving picture coding apparatus 100)
Hereinafter, functions of each unit will be described. The prediction block image acquisition unit 101 acquires the image signal of the prediction block to be processed from the image signal supplied from the terminal 10 based on the position information and the prediction block size of the prediction block, and subtracts the image signal of the prediction block 102, and supplied to the motion vector detection unit 108 and the motion information generation unit 109.

  The subtraction unit 102 subtracts the image signal supplied from the prediction block image acquisition unit 101 and the prediction signal supplied from the motion compensation unit 106 to calculate a prediction error signal, and calculates the prediction error signal to the prediction error encoding unit 103. To supply.

  The prediction error encoding unit 103 performs processing such as quantization and orthogonal transformation on the prediction error signal supplied from the subtraction unit 102 to generate prediction error encoded data, and encodes the prediction error encoded data. The data is supplied to the column generation unit 104 and the prediction error decoding unit 105.

  The code string generation unit 104 includes the prediction error encoded data supplied from the prediction error encoding unit 103, the merge flag supplied from the motion information generation unit 109, the merge candidate number, the prediction direction of motion compensation prediction, and the reference image index. The difference vector and the prediction vector index are entropy-encoded according to the syntax together with the prediction direction of the motion compensation prediction to generate a code string, and the code string is supplied to the terminal 11.

  Here, the merge candidate number is converted into a merge index to generate a code string. Here, the merge candidate number is a number indicating the selected combined motion information candidate. The conversion from the merge candidate number to the merge index will be described later. In the first embodiment, as described above, the truncated unified code string is used for encoding the merge index and the prediction vector index. However, the code string is not limited to this as long as the number of candidates is small and the code string can be encoded with fewer bits. .

  The prediction error decoding unit 105 performs a process such as inverse quantization or inverse orthogonal transform on the prediction error encoded data supplied from the prediction error encoding unit 103 to generate a prediction error signal, and the prediction error signal Is supplied to the adder 107.

  The motion compensation unit 106 performs motion compensation on the reference image in the frame memory 110 indicated by the reference image index supplied from the motion information generation unit 109 based on the motion vector supplied from the motion information generation unit 109, and generates a prediction signal. Generate. If the prediction direction is bidirectional, the prediction signal is obtained by averaging the prediction signals in the L0 direction and the L1 direction.

  The addition unit 107 adds the prediction error signal supplied from the prediction error decoding unit 105 and the prediction signal supplied from the motion compensation unit 106 to generate a decoded image signal, and supplies the decoded image signal to the frame memory 110. To do.

  The motion vector detection unit 108 detects a motion vector and a reference image index indicating the reference image from the image signal supplied from the prediction block image acquisition unit 101 and an image signal corresponding to a plurality of reference images, and the motion vector and the motion vector The reference image index is supplied to the motion information generation unit 109. If the prediction direction is bidirectional, motion vectors and reference image indexes in the L0 direction and the L1 direction are detected.

  A general motion vector detection method calculates an error evaluation value for an image signal corresponding to a reference image moved by a predetermined movement amount from the same position as the image signal of the target image, and moves to minimize the error evaluation value. Let the amount be a motion vector. As the error evaluation value, SAD (Sum of Absolute Difference) indicating the sum of absolute differences, MSE (Mean Square Error) indicating the mean square error, or the like can be used.

  The motion information generation unit 109 includes a motion vector and a reference image index supplied from the motion vector detection unit 108, a candidate block group supplied from the motion information memory 111, and a reference image indicated by a reference image index in the frame memory 110. A merge candidate number, or a difference vector and a prediction vector index are generated, and a merge flag, a merge type, a merge candidate number, a reference image index, a difference vector, and a prediction vector index are generated according to need, a code string generation unit 104, a motion compensation unit 106 and the motion information memory 111. A detailed configuration of the motion information generation unit 109 will be described later.

  The frame memory 110 stores the decoded image signal supplied from the adding unit 107. In addition, for a decoded image in which decoding of the entire image is completed, a predetermined number of images of 1 or more is stored as a reference image. The frame memory 110 supplies the stored reference image signal to the motion compensation unit 106 and the motion information generation unit 109. A storage area for storing the reference image is controlled by a FIFO (First In First Out) method.

  The motion information memory 111 stores the motion information supplied from the motion information generation unit 109 for a predetermined number of images in units of the minimum predicted block size. The motion information of the adjacent block of the prediction block to be processed is set as a space candidate block group.

  In addition, the motion information memory 111 sets the motion information of the block on the ColPic located in the same position as the prediction block to be processed and its neighboring blocks as a time candidate block group. The motion information memory 111 supplies the spatial candidate block group and the temporal candidate block group to the motion information generation unit 109 as candidate block groups. The motion information memory 111 is synchronized with the frame memory 110 and is controlled by a FIFO (First In First Out) method.

  Here, ColPic refers to a decoded image different from the prediction block to be processed and stored in the frame memory 110 as a reference image. In Embodiment 1, ColPic is a reference image decoded immediately before. In the first embodiment, ColPic is a reference image decoded immediately before, but may be an encoded image. For example, the reference image immediately before in display order or the reference image immediately after in display order may be used. It can also be specified in the encoded stream.

  Here, a method of managing motion information in the motion information memory 111 will be described with reference to FIG. The motion information is stored in each memory area in units of the smallest prediction block. FIG. 10 shows a state where the predicted block size to be processed is 16 pixels × 16 pixels. In this case, the motion information of the prediction block is stored in 16 memory areas indicated by hatching in FIG.

  When the predictive coding mode is the intra mode, (0, 0) is stored as the motion vector in the L0 direction and the L1 direction, and “−1” is stored as the reference image index in the L0 direction and the L1 direction. The reference image index “−1” may be any value as long as it can be determined that the mode does not perform motion compensation prediction. From this point onward, unless expressed otherwise, the term “block” refers to the smallest predicted block unit when expressed simply as a block. Also, in the case of a block outside the area, as in the intra mode, (0, 0) is stored as the motion vector in the L0 direction and the L1 direction, and “−1” is stored as the reference image index in the L0 direction and the L1 direction. . The LX direction (X is 0 or 1) is valid when the reference image index in the LX direction is 0 or more, and the LX direction is invalid (not valid). The reference image index in the LX direction is “− 1 ”.

  Next, a detailed configuration of the motion information generation unit 109 will be described with reference to FIG. FIG. 11 shows the configuration of the motion information generation unit 109. The motion information generation unit 109 includes a difference vector calculation unit 120, a combined motion information determination unit 121, and a predictive coding mode determination unit 122. The terminal 12 is in the motion information memory 111, the terminal 13 is in the motion vector detection unit 108, the terminal 14 is in the frame memory 110, the terminal 15 is in the prediction block image acquisition unit 101, the terminal 16 is in the code string generation unit 104, and the terminal 50 Are connected to the motion compensation unit 106, and the terminal 51 is connected to the motion information memory 111, respectively.

  Hereinafter, functions of each unit will be described. The difference vector calculation unit 120 predicts a prediction vector from the candidate block group supplied from the terminal 12, the motion vector and reference image index supplied from the terminal 13, the reference image supplied from the terminal 14, and the image signal supplied from the terminal 15. An index is determined, and a difference vector and a rate distortion evaluation value are calculated. Then, the reference image index, the motion vector, the difference vector, the prediction vector index, and the rate distortion evaluation value are supplied to the prediction encoding mode determination unit 122. The detailed configuration of the difference vector calculation unit 120 will be described later.

  The combined motion information determination unit 121 generates a combined motion information candidate list from the candidate block group supplied from the terminal 12, the reference image supplied from the terminal 14, and the image signal supplied from the terminal 15. Then, the combined motion information determination unit 121 selects a combined motion information candidate from the generated combined motion information candidate list, determines a merge candidate number, calculates a rate distortion evaluation value, and combines the combined motion information candidate. Motion information, the merge candidate number, and the rate distortion evaluation value are supplied to the predictive coding mode determination unit 122. A detailed configuration of the combined motion information determination unit 121 will be described later.

  The predictive coding mode determination unit 122 compares the rate distortion evaluation value supplied from the difference vector calculation unit 120 with the rate distortion evaluation value supplied from the combined motion information determination unit 121. If the former is less than the latter, the merge flag is set to “0”. The prediction encoding mode determination unit 122 supplies the reference image index, the difference vector, and the prediction vector index supplied from the merge flag and difference vector calculation unit 120 to the terminal 16, and the motion vector supplied from the difference vector calculation unit 120. The reference image index is supplied to the terminal 50 and the terminal 51.

  If the latter is less than or equal to the former, the merge flag is set to 1. The predictive coding mode determination unit 122 supplies the merge flag and the merge candidate number supplied from the combined motion information determination unit 121 to the terminal 16, and the motion vector of the motion information supplied from the combined motion information determination unit 121 and the reference image The index is supplied to the terminal 50 and the terminal 51. Although a specific calculation method of the rate distortion evaluation value is not the main point of the present invention, the details thereof will be omitted, but the evaluation value has a characteristic that the encoding efficiency becomes higher as the rate distortion evaluation value is smaller.

  Next, a detailed configuration of the difference vector calculation unit 120 will be described with reference to FIG. FIG. 12 shows the configuration of the difference vector calculation unit 120. The difference vector calculation unit 120 includes a prediction vector candidate list generation unit 130, a prediction vector determination unit 131, and a subtraction unit 132. The terminal 17 is connected to the predictive coding mode determination unit 122.

  The prediction vector candidate list generation unit 130 is also installed in the video decoding device 200 (FIG. 33) that decodes the code string generated by the video encoding device 100 according to Embodiment 1 in the same manner, and performs video encoding. The apparatus 100 and the moving picture decoding apparatus 200 generate a prediction vector candidate list having no contradiction.

  Hereinafter, functions of each unit will be described. The prediction vector candidate list generation unit 130 deletes candidate blocks outside the region and candidate blocks in the intra mode from the candidate block group supplied from the terminal 12. Further, when there are a plurality of candidate blocks having overlapping motion vectors, one candidate block is left and at least one remaining candidate block is deleted. The prediction vector candidate list generation unit 130 generates a prediction vector candidate list from these candidate blocks after deletion, and supplies the prediction vector candidate list to the prediction vector determination unit 131. It is assumed that the prediction vector candidate list generated in this way includes one or more prediction vector candidates without duplication. For example, when there is no candidate block having a motion vector, the vector (0, 0) is added to the prediction vector candidate list. If the prediction direction is bidirectional, a prediction vector candidate list is generated and supplied for the L0 direction and the L1 direction.

  The prediction vector determination unit 131 selects an optimal prediction vector for the motion vector supplied from the terminal 13 from the prediction vector candidate list supplied from the prediction vector candidate list generation unit 130. The prediction vector determination unit 131 supplies the selected prediction vector to the subtraction unit 132 and also supplies the terminal 17 with a reference image index and a prediction vector index that is information indicating the selected prediction vector. If the prediction direction is bidirectional, an optimal prediction vector is selected and supplied for the L0 direction and the L1 direction.

  Here, based on the motion vector of the prediction vector candidate, the prediction error amount is calculated from the reference image supplied from the terminal 14 and the image signal supplied from the terminal 15. Then, the rate distortion evaluation value is calculated from the code amount of the reference image index, the difference vector, and the prediction vector index, and the above-described prediction error amount, and the prediction vector candidate that minimizes the rate distortion evaluation value is determined as the optimal prediction vector. Selected.

  The subtraction unit 132 subtracts the prediction vector supplied from the prediction vector determination unit 131 from the motion vector supplied from the terminal 13 to calculate a difference vector, and supplies the difference vector to the terminal 17. If the prediction direction is bidirectional, a difference vector is calculated and supplied for the L0 direction and the L1 direction.

(Candidate block group supplied to prediction vector candidate list generation unit 130)
Here, the candidate block group supplied to the prediction vector candidate list production | generation part 130 is demonstrated using FIG. 13 and FIG. The candidate block group includes a spatial candidate block group and a temporal candidate block group.

  FIG. 13 shows adjacent blocks of a prediction block to be processed when the prediction block size to be processed is 16 pixels × 16 pixels. In the first embodiment, the space candidate block group is assumed to be five blocks of block A1, block C, block D, block B1, and block E shown in FIG. Here, the spatial candidate block group is five blocks of block A1, block C, block D, block B1, and block E. However, the spatial candidate block group is at least one or more processed adjacent to the prediction block to be processed. However, the present invention is not limited to these blocks. For example, all of block A1, block A2, block A3, block A4, block B1, block B2, block B3, block B4, block C, block D, and block E may be spatial candidate blocks.

  Next, the time candidate block group will be described with reference to FIG. FIG. 14 shows a block in a prediction block on ColPic and its peripheral blocks at the same position as the prediction block to be processed when the prediction block size to be processed is 16 pixels × 16 pixels. In the first embodiment, the time candidate block group includes two blocks, block H and block I6 shown in FIG.

  Here, the time candidate block group is two blocks of block H and block I6 on ColPic, but the time candidate block group is at least one block on a decoded image different from the prediction block to be processed. However, the present invention is not limited to these. For example, all of block I1 to block I16, block A1 to block A4, block B1 to block B4, block C, block D, block E, block F1 to block F4, block G1 to block G4 and block H on ColPic It may be a candidate block. Hereinafter, unless otherwise specified, block A4 is referred to as block A, and block B4 is referred to as block B. Hereinafter, unless otherwise specified, blocks H and I6 are referred to as time blocks.

(Configuration of the combined motion information determination unit 121)
Next, a detailed configuration of the combined motion information determination unit 121 will be described with reference to FIG. FIG. 15 shows the configuration of the combined motion information determination unit 121. The combined motion information determination unit 121 includes a combined motion information candidate generation unit 140 and a combined motion information selection unit 141. The combined motion information candidate generation unit 140 is also installed in the moving image decoding device 200 that decodes the code sequence generated by the moving image encoding device 100 according to the first embodiment. The image decoding apparatus 200 generates a combined motion information list that is consistent.

  Hereinafter, functions of each unit will be described. The combined motion information candidate generation unit 140 generates a combined motion information candidate list from the candidate block group supplied from the terminal 12, and supplies the combined motion information candidate list to the combined motion information selection unit 141. A detailed configuration of the combined motion information candidate generation unit 140 will be described later.

  The combined motion information selection unit 141 is information that selects an optimal combined motion information candidate from the combined motion information candidate list supplied from the combined motion information candidate generation unit 140 and indicates the selected combined motion information candidate. The merge candidate number is supplied to the terminal 17.

  Here, the prediction error amount is calculated from the reference image supplied from the terminal 14 obtained based on the prediction direction, the motion vector, and the reference image index of the combined motion information candidate, and the image signal supplied from the terminal 15. A rate distortion evaluation value is calculated from the code amount of the merge candidate number and the prediction error amount, and the combined motion information candidate that minimizes the rate distortion evaluation value is selected as the optimal combined motion information candidate.

(Candidate block group supplied to the combined motion information candidate generation unit 140)
Here, the candidate block group supplied to the combined motion information candidate generation unit 140 will be described with reference to FIGS. 13 and 14. The candidate block group includes a spatial candidate block group and a temporal candidate block group. In the first embodiment, the space candidate block group is assumed to be four blocks of block A4, block B4, block C, and block E shown in FIG. Here, the spatial candidate block group is four blocks, block A4, block B4, block C, and block E, but the spatial candidate block group is at least one processed block adjacent to the prediction block to be processed. The number and position of blocks are not limited to these. For example, the space candidate block group may be five blocks of block A1, block B1, block C, block E, and block D.

  Next, the time candidate block group will be described with reference to FIG. In the first embodiment, the time candidate block group includes two blocks, block H and block I6 shown in FIG. Here, the time candidate block group is the same as the time candidate block group supplied to the prediction vector candidate list generation unit 130, but the time candidate block group is on a decoded image different from the prediction block to be processed. It is sufficient that the number of blocks is at least 0, and the number and position of the blocks are not limited to these.

(Configuration of combined motion information candidate generation unit 140)
Next, a detailed configuration of the combined motion information candidate generation unit 140 will be described with reference to FIG. FIG. 16 shows a configuration of the combined motion information candidate generation unit 140. The terminal 18 is connected to the combined motion information selection unit 141. The combined motion information candidate generating unit 140 includes a single combined motion information candidate list generating unit 150, a single combined motion information candidate list reducing unit 151, a dual combined motion information candidate list generating unit 152, a dual combined motion information candidate list reducing unit 153, and a dual combined motion information candidate list reducing unit 153. A combined motion information candidate combination list generation unit 154 is included.

  Hereinafter, functions of each unit will be described. The single bond motion information candidate list generation unit 150 generates a single bond motion information candidate list from the candidate block group supplied from the terminal 12, and supplies the single bond motion information candidate list to the single bond motion information candidate list reduction unit 151. To do.

  When there are a plurality of combined motion information candidates that have overlapping motion information from the single combined motion information candidate list supplied from the single combined motion information candidate list generation unit 150, the single combined motion information candidate list reduction unit 151 One combined motion information candidate is left, the remaining combined motion information candidates are deleted, and the single combined motion information candidate list is updated. The single bond motion information candidate list reduction unit 151 supplies the single bond motion information candidate list to the double bond motion information candidate list generation unit 152 and also to the terminal 18.

  The bi-coupled motion information candidate list generating unit 152 generates a bi-coupled motion information candidate list from the single-coupled motion information candidate list supplied from the single-coupled motion information candidate list reducing unit 151, and generates the bi-coupled motion information candidate list. This is supplied to the combined motion information candidate list reduction unit 153.

  In the first embodiment, it is assumed that bi-coupled motion information candidate list generation unit 152 generates a candidate list of L0-direction bi-coupled motion information candidates and L1 direction bi-coupled motion information candidates.

  When there are a plurality of combined motion information candidates having motion information overlapping from the bi-coupled motion information candidate list supplied from the dual-coupled motion information candidate list generating unit 152, the dual-coupled motion information candidate list reducing unit 153 One combined motion information candidate is left, the remaining combined motion information candidates are deleted, and the bidirectional combined motion information candidate list is updated. The double coupled motion information candidate list reduction unit 153 supplies the dual coupled motion information candidate list to the dual coupled motion information candidate combination list generation unit 154.

  The bi-coupled motion information candidate combination list generation unit 154 generates a combination of motion information of the combined motion information candidates in the L0 direction and the L1 direction from the bi-coupled motion information candidate list supplied from the bi-coupled motion information candidate list reduction unit 153. Then, it is determined whether or not the motion information of the combined motion information candidate in the single combined motion information candidate list supplied from the single combined motion information candidate list reduction unit 151 overlaps. If there is a non-overlapping combination of bi-coupled motion information candidate lists, a bi-coupled motion information candidate combination list is generated and supplied to the terminal 18.

  Here, the single combined motion information candidate is a motion information candidate of a candidate block used in a so-called merge technique, and is motion information obtained from one candidate block. On the other hand, bi-coupled motion information is motion information obtained by using both of two motion information of two candidate blocks. In the present embodiment, one L0 direction and one L1 direction are used as two pieces of motion information of two candidate blocks.

(Bi-join motion information candidate combination list generation unit 154)
Next, a detailed configuration of the dual coupled motion information candidate combination list generation unit 154 will be described with reference to FIG. FIG. 17 shows a configuration of the dual-coupled motion information candidate combination list generation unit 154. The terminal 19 is connected to the double-coupled motion information candidate list reducing unit 153, the terminal 20 is connected to the single-coupled motion information candidate list reducing unit 151, and the terminal 21 is connected to the terminal 18. The double coupled motion information candidate combination list generation unit 154 includes an L0, L1 direction motion information candidate combination unit 160 and a dual coupled motion information candidate determination unit 161.

  Hereinafter, functions of each unit will be described. The L0 and L1 direction motion information candidate combination unit 160 combines the motion information of the combined motion information candidates of the L0 prediction and the L1 prediction acquired from the dual combined motion information candidate list supplied from the terminal 19 to combine the combined motion information. A candidate combination list is generated. The L0 and L1 direction motion information candidate combination unit 160 sends the double coupled motion information candidate combination list to the dual coupled motion information candidate determination unit 161.

  The bi-coupled motion information candidate determination unit 161 includes a combined motion information candidate in the bi-coupled motion information candidate combination list supplied from the L0 and L1 direction motion information candidate combination unit 160 and a single combined motion information candidate list supplied from the terminal 20. Are compared with the combined motion information candidates. If there is an overlap between both candidates as a result of the comparison, the bi-coupled motion information candidate determination unit 161 removes the duplicate coupled motion information candidate from the bi-coupled motion information candidate combination list, and the bidirectional coupled motion information The candidate combination list is updated, and the bidirectional combined motion information candidate combination list is sent to the terminal 21.

(Candidate number management table)
Here, a candidate number management table indicating the relationship between merge candidate numbers and combined motion information candidates used in Embodiment 1 will be described with reference to FIG. The association with the merge candidate number is applied to both of the combined motion information candidates registered in the single combined motion information candidate list and the dual combined motion information candidate list. Merge candidate numbers 0 to 4 are combined motion information candidates (A) of block A, combined motion information candidates (B) of block B, and combined motion information candidates (COL) of time blocks, respectively, included in the combined motion information candidate list. The combined motion information candidate (C) of block C and the combined motion information candidate (E) of block E are shown. Further, it is assumed that the maximum number of combined motion information candidates included in the combined motion information candidate list is 5 (the maximum value of the merge index is 4). Although the candidate number management table used in Embodiment 1 is shown in FIG. 18, the merged motion information candidate having a relatively high selection rate may be assigned with a smaller merge candidate number, and is not limited to this.

  Here, the maximum number of combined motion information candidates included in the candidate number management table and the combined motion information candidate list is assumed to be shared in the moving image encoding apparatus 100, and is not illustrated. Hereinafter, conversion from the merge candidate number to the merge index will be described with reference to FIGS.

  In FIG. 19A, the combined motion information candidate for block A, the combined motion information candidate for block B, the combined motion information candidate for time block, the combined motion information candidate for block C, and the combined motion information candidate for block E are all valid. In some cases, the merge candidate number is directly used as a merge index.

  FIG. 19B shows a case where merge indexes are assigned in ascending order of merge candidate numbers after filling invalid merge candidate numbers when the combined motion information candidates include invalid blocks. As shown in FIG. 19B, when the combined motion information candidate of the block B with the merge candidate number 1 and the block C with the merge candidate number 3 is invalid, the merge index 0 is set to the merge candidate number 0 and the merge index 1 is converted into merge candidate number 2, and merge index 2 is converted into merge candidate number 4.

  In the moving picture decoding apparatus 200 that decodes the code sequence generated by the moving picture encoding apparatus 100 according to the first embodiment, the reverse conversion from the merge index to the merge candidate number is performed, and the moving picture encoding apparatus 100 And the moving picture decoding apparatus 200 generates a candidate number management table with no contradiction.

(Operation of moving picture coding apparatus 100)
Next, an encoding operation in the moving image encoding apparatus 100 according to Embodiment 1 will be described with reference to the flowchart of FIG. The prediction block image acquisition unit 101 acquires the image signal of the prediction block to be processed from the image signal supplied from the terminal 10 based on the position information of the prediction block and the prediction block size (S100).

  The motion vector detection unit 108 detects a motion vector and a reference image index indicating the reference image from the image signal supplied from the predicted block image acquisition unit 101 and image signals corresponding to a plurality of reference images (S101).

  The motion information generation unit 109 is supplied with a motion vector and a reference image index from the motion vector detection unit 108, and a merge candidate number or a difference vector of a candidate block group and a prediction vector index from the motion information memory 111. The motion information for generating is generated (S102).

  The motion compensation unit 106 performs motion compensation on the reference image indicated by the reference image index in the frame memory 110 based on the motion vector supplied from the motion vector detection unit 108 to generate a prediction signal. If the prediction direction is bidirectional, an average of the prediction signals in the L0 direction and the L1 direction is generated as a prediction signal (S103).

  The subtraction unit 102 calculates a difference between the image signal supplied from the prediction block image acquisition unit 101 and the prediction signal supplied from the motion compensation unit 106 to calculate a prediction error signal (S104). The prediction error encoding unit 103 performs processing such as quantization and orthogonal transformation on the prediction error signal supplied from the subtraction unit 102 to generate prediction error encoded data (S105).

  The code string generation unit 104 includes prediction error encoded data supplied from the prediction error encoding unit 103, a merge flag, a merge type, a merge candidate number, a reference image index, a difference vector, and a difference vector supplied from the motion information generation unit 109. The prediction vector index is entropy-coded according to the syntax along with the prediction direction to generate a code string (S106).

  The adding unit 107 adds the prediction error signal supplied from the prediction error decoding unit 105 and the prediction signal supplied from the motion compensation unit 106 to generate a decoded image signal (S107). The frame memory 110 stores the decoded image signal supplied from the adding unit 107 (S108). The motion information memory 111 stores one image of the motion vector supplied from the motion vector detection unit 108 in units of the minimum predicted block size (S109).

  Subsequently, the operation of the motion information generation unit 109 will be described using the flowchart of FIG. The difference vector calculation unit 120 performs prediction based on the candidate block group supplied from the terminal 12, the motion vector and reference image index supplied from the terminal 13, the reference image supplied from the terminal 14, and the image signal supplied from the terminal 15. A vector index is determined, and a difference vector and a rate distortion evaluation value are calculated (S110).

  The combined motion information determination unit 121 calculates the rate distortion evaluation value by determining the merge candidate number from the candidate block group supplied from the terminal 12, the reference image supplied from the terminal 14, and the image signal supplied from the terminal 15. (S111).

  The predictive coding mode determination unit 122 compares the rate distortion evaluation value supplied from the difference vector calculation unit 120 with the rate distortion evaluation value supplied from the combined motion information determination unit 121, and merges if the former is smaller than the latter The flag is set to “0”, otherwise, the merge flag is set to “1” (S112).

  Subsequently, the operation of the difference vector calculation unit 120 will be described using the flowchart of FIG. The prediction vector candidate list generation unit 130 excludes candidate blocks that are out of the area from the candidate block group supplied from the terminal 12, candidate blocks that are in the intra mode, and candidate blocks that have overlapping motion vectors. A prediction vector candidate list is generated. If the prediction direction is bidirectional, a prediction vector candidate list is generated for the L0 direction and the L1 direction (S120).

  The prediction vector determination unit 131 selects an optimal prediction vector for the motion vector supplied from the terminal 13 from the prediction vector candidate list supplied from the prediction vector candidate list generation unit 130. If the prediction direction is bidirectional, an optimal prediction vector is selected for the L0 direction and the L1 direction (S121). The subtraction unit 132 subtracts the prediction vector supplied from the prediction vector determination unit 131 from the motion vector supplied from the terminal 13 to calculate a difference vector. If the prediction direction is bidirectional, a difference vector is calculated for the L0 direction and the L1 direction (S122).

(Operation of the combined motion information determination unit 121)
Subsequently, the operation of the combined motion information determination unit 121 will be described in detail using the flowchart of FIG. The combined motion information candidate generation unit 140 generates a combined motion information candidate list from the candidate block group supplied from the terminal 12 (S130). The combined motion information selection unit 141 selects from the combined motion information candidate list supplied from the combined motion information candidate generation unit 140, the motion vector and reference image index supplied from the terminal 13, and the optimal combined motion information for the prediction direction. Is determined (S131).

(Operation of combined motion information candidate generation unit 140)
Subsequently, the operation of the combined motion information candidate generation unit 140 will be described in detail using the flowchart of FIG. The single combined motion information candidate list generation unit 150 generates a spatial combined motion information candidate list from candidate blocks obtained by excluding candidate blocks outside the region and candidate blocks in the intra mode from the spatial candidate block group supplied from the terminal 12. (S140). Detailed operations for generating the spatially coupled motion information candidate list will be described later.

  The single combined motion information candidate list generation unit 150 generates a time combined motion information candidate list from candidate blocks obtained by excluding candidate blocks outside the region and candidate blocks in the intra mode from the time candidate block group supplied from the terminal 12. (S141). The detailed operation of generating the time combination motion information candidate list will be described later.

  The single combined motion information candidate list generation unit 150 combines the spatially combined motion information candidate list and the temporally combined motion information candidate list in the order of merge candidate numbers to generate a single combined motion information candidate list (S142).

  When there are a plurality of combined motion information candidates that have overlapping motion information from the single combined motion information candidate list supplied from the single combined motion information candidate list generation unit 150, the single combined motion information candidate list reduction unit 151 One combined motion information candidate is left, the other combined motion information candidates having overlapping motion information are deleted, and the single combined motion information candidate list is updated (S143).

  The double-coupled motion information candidate list generating unit 152 generates a double-coupled motion information candidate list from the single-coupled motion information candidate list supplied from the single-coupled motion information candidate list reducing unit 151 (S144). Two candidate lists of double coupled motion information are created in the L0 direction and the L1 direction. The motion information in the L0 direction and the L1 direction of each combined motion information candidate in the single combined motion information candidate list is divided, and a combined motion information candidate list created for each direction is divided into a double combined motion information candidate list. To do. When the slice type is P slice, or when the merge type is “0”, it is not necessary to generate a bi-join motion information candidate list, and the processes after step S144 by the bi-join motion information candidate list generation unit 152 are performed. You don't have to.

  When there are a plurality of combined motion information candidates having motion information overlapping from the bi-coupled motion information candidate list supplied from the dual-coupled motion information candidate list generating unit 152, the dual-coupled motion information candidate list reducing unit 153 One combined motion information candidate is left, and other combined motion information candidates having overlapping motion information are deleted to update the double combined motion information candidate list (S145). Detailed operation of the reduction of the double coupled motion information candidate list will be described later.

  The bi-join motion information candidate combination list generation unit 154 combines the motion information of the combined motion information candidates in the L0 direction and the L1 direction of the bi-join motion information candidate list supplied from the bi-join motion information candidate list reduction unit 153, A double-coupled motion information candidate combination list is generated (S146). The detailed operation of generating the double combined motion information candidate combination list will be described later.

  The combined motion information candidate combination list generation unit 154 combines the combined motion information candidate list of the combined motion information candidate list that is supplied from the combined motion information candidate list reduction unit 151 by the combined motion information candidate motion information. If it overlaps with the motion information of the motion information candidate, the overlapping combination candidate is deleted from the double combined motion information candidate combination list, and the double combined motion information candidate combination list is updated (S147). The detailed operation of updating the double combined motion information candidate combination list will be described later.

  Subsequently, the detailed operation of generating the spatially coupled motion information candidate list will be described using the flowchart of FIG. In Embodiment 1, it is assumed that the spatial combination motion information candidate list includes motion information of four or less candidate blocks.

  The following processing is repeated for block A, block B, block C, and block E, which are four candidate blocks included in the space candidate block group (S150 to S153). The validity of the candidate block is checked (S151). A candidate block is valid when the candidate block is not out of the region and is not in intra mode. If the candidate block is valid (Y in S151), the motion information of the candidate block is added to the spatially combined motion information candidate list (S152). If the candidate block is not valid (N in S151), step S152 is skipped.

  In the first embodiment, it is assumed that the spatial combination motion information candidate list includes motion information of four or less candidate blocks. However, the number of spatial combination motion information candidates may be changed depending on the validity of the candidate block, and the present invention is not limited thereto. Not.

  Subsequently, a detailed operation of generating a time combination motion information candidate list will be described using the flowchart of FIG. In Embodiment 1, it is assumed that the temporal combination motion information candidate list includes motion information of one or less candidate blocks.

  The following processing is repeated for time blocks that are two candidate blocks included in the time candidate block group (S160 to S166). The validity of the candidate block is checked (S161). A candidate block is valid when the candidate block is not out of the region and is not in intra mode. If the candidate block is valid (Y in S161), a temporally combined motion information candidate is generated, the temporally combined motion information candidate is added to the temporally combined motion information candidate list (from step S162 to step S165), and the process ends. If the candidate block is not valid (N in S161), the next candidate block is inspected (S166).

  If the candidate block is valid, the prediction direction of the temporally combined motion information candidate is determined (S162). In the first embodiment, the prediction direction of the combined motion information candidate is bidirectional. Next, the reference images in the L0 direction and the L1 direction of the time combination motion information candidate are determined (S163). In the first embodiment, the reference image in the L0 direction is the reference image that is the closest to the processing target image among the reference images in the L0 direction, and the reference image in the L1 direction is the processing target image among the reference images in the L1 direction. The reference image is the closest distance. Here, the reference image in the L0 direction is the reference image that is the closest to the processing target image among the reference images in the L0 direction, and the reference image in the L1 direction is the closest to the processing target image among the reference images in the L1 direction. Although the reference image is at a distance, it is only necessary to determine the reference image in the L0 direction and the reference image in the L1 direction, and the present invention is not limited to this. For example, the reference images in the L0 direction and the L1 direction may be encoded in the encoded stream, the reference image indexes in the L0 direction and the L1 direction may be set to 0, and the L0 used by the adjacent block of the processing target block. Of the reference image in the direction and the reference image in the L1 direction, the most frequently used reference image may be used as a reference image for reference in each of the L0 direction and the L1 direction.

  Next, the motion vector of the time combination motion information candidate is calculated (S164). In this embodiment, the temporally combined motion information candidate calculates bidirectional motion information based on the reference image ColRefPic and the motion vector mvCol, which are effective prediction directions in the motion information of the candidate block.

  When the prediction direction of the candidate block is the unidirectional direction of the L0 direction or the L1 direction, it is selected based on the reference image and the motion vector in the prediction direction.

  When the prediction direction of the candidate block is bidirectional, the selection is made based on either the reference image in the L0 direction or the L1 direction and the motion vector. For example, a reference image that is present in the same time direction as ColPic and a motion vector is selected as a reference, and either a reference image in the L0 direction or L1 direction of a candidate block is selected based on the one that has a shorter distance between ColPic images. For example, the candidate vector may be selected on the basis that the motion vector in the L0 direction or the L1 direction of the candidate block intersects the processing target image.

  When a reference image and a motion vector as a reference for generating bidirectional motion information are selected, a motion vector of a temporally combined motion information candidate is calculated.

  Here, a method of calculating the motion vectors mvL0t and mvL1t of the temporally combined motion information candidates from the motion vector ColMv and the reference image ColRefPic used as the basis for bidirectional motion information generation will be described with reference to FIG.

The distance between the images of ColPic and ColRefPic is ColDist, the distance between the reference images ColL0Pic in the L0 direction of the temporally coupled motion information candidate and the image to be processed CurPic is CurL0Dist, the reference image ColL1Pic of the temporally coupled motion information candidate in the L1 direction and the target of processing Assuming that the distance between images of the image CurPic is CurL1Dist, a motion vector of the following equation 1 obtained by scaling ColMv with a distance ratio of ColDist, CurL0Dist, and CurL1Dist is set as a motion vector of a temporally combined motion information candidate. Here, the calculation of the inter-image distance is performed using the POC, and has a positive and negative sign. Division is rounded off.
mvL0t = mvCol × CurrL0Dist / ColDist
mvL1t = mvCol × CurrL1Dist / ColDist (Formula 1)
Note that ColPic, ColRefPic, ColL0Pic, and ColL1Pic in FIG. 27 are examples, and other relationships may be used.

  As described above, a temporally coupled motion information candidate list is added to the motion vector of the temporally coupled motion information candidate thus calculated (S165). Here, the time combination motion information candidates are generated as described above. However, bidirectional motion information may be determined using motion information of another encoded image, and the present invention is not limited to this. For example, a motion vector scaled according to the distance between the reference image in each direction and the processing target image as in direct motion compensation may be used as a bidirectional motion vector. If the candidate block is invalid (N in S161), the next candidate block is inspected (S166).

  Here, the temporally combined motion information candidate list includes motion information of one or less candidate blocks, but the number of temporally combined motion information candidates may be changed depending on the validity of the candidate block, and is not limited to this. Similarly, the prediction direction, the reference image, and the motion vector determination method are not limited to these.

(Reduction of candidate list of double coupled motion information)
Subsequently, a detailed operation of reducing the combined motion information candidates in the dual combined motion information candidate list will be described with reference to FIGS. 28 (a) to 28 (e) and FIGS. 29 (a) to 29 (e). FIG. 28A shows an example of a single combined motion information candidate list updated by deleting a combined motion information candidate having overlapping motion information in the single combined motion information candidate list reduction unit 151. FIG. 28A shows a case where all the combined motion information candidates in FIG. 18 used for explaining the candidate number management table showing the relationship between the merge candidate number and the combined motion information candidate are in the bidirectional mode (BiPred). It is assumed that the motion information of the information candidate in the L0 direction and the L1 direction is set as shown in FIG.

  The motion information set for each combined motion information candidate is different in the L0 direction motion information as L0_0, L0_1, L0_2, and the L1 direction motion information as L1_0, L1_1, L1_2. Therefore, although overlapping motion information exists in the L0 and L1 direction units, when L0 and L1 are regarded as one motion information, there is no overlapping motion information and the single combined motion information candidate list is reduced. In the unit 151, these combined motion information candidates are not deleted, but five combined motion information candidates are left as shown in FIG.

  The double-coupled motion information candidate list generated by the dual-coupled motion information candidate list generation unit 152 is configured such that the motion information of each combined motion information candidate in the single-coupled motion information candidate list shown in FIG. Dividing in the direction, it is generated as shown in FIGS. 28 (b) and 28 (c). FIG. 28 (b) shows an L0 direction, and FIG. 28 (c) shows a double coupled motion information candidate list in the L1 direction. The generated double coupled motion information candidate list is supplied to the dual coupled motion information candidate list reduction unit 153.

  The dual coupled motion information candidate list reduction unit 153 deletes the combined motion information candidate including motion information overlapping in the dual coupled motion information candidate list for each of the L0 and L1 directions. First, deletion of combined motion information candidates in the L0 prediction bi-join motion information candidate list in FIG. 28B will be described.

  In FIG. 28B, the combined motion information candidate A includes motion information L0_0, B and COL include L0_1, and C and E include L0_2. The motion information is compared in the order of the combined motion information candidates with the smallest merge candidate number. First, a comparison between A having a merge candidate number of 0 and other combined motion information candidates is started. Since there is only one A having L0_0 in the L0 direction bi-join motion information candidate list, the merge candidate number of A is left as 0 in the L0 direction bi-join motion information candidate list.

  Since B and COL have the same motion information L0_1, motion information is duplicated in the L0 direction bi-join motion information candidate list, and one of them is deleted from the L0 direction bi-join motion information candidate list. . Here, since a merge candidate number that is smaller is assigned to a combined motion information candidate having a relatively high selection rate, the larger merge candidate number is set as a deletion target. In this case, since the merge candidate number of B is 1 and COL is 2, COL is deleted, and B is left in the bi-join motion information candidate list in the L0 direction.

  By deleting COL, merge candidate number 2 assigned to COL is assigned to C of merge candidate number 3 immediately after COL. Assign the number obtained by subtracting 1 from the merge candidate number of the combined motion information candidates to the combined motion information candidates (E in the example of FIG. 28B) remaining in the subsequent L0 direction bi-coupled motion information candidate list, The candidate list for double coupled motion information in the L0 direction is updated.

  Next, the motion information of the combined motion information candidates after the merge candidate number 2 is compared. Since C and E have the same motion information L0_2, motion information is duplicated in the L0 direction double coupled motion information candidate list, and E is deleted from the L0 direction dual coupled motion information candidate list. As described above, the combined motion information candidates having overlapping motion information in the L0 direction dual combined motion information candidate list are deleted, and FIG. 28B is updated as illustrated in FIG.

  The hatched lines in FIG. 28 (d) indicate deleted combined motion information candidates. The merge candidate numbers assigned to these are assigned to the combined motion information candidates remaining in the L0 direction bi-join motion information candidate list in ascending order. The combined motion information candidate remaining in the L0 direction double-coupled motion information candidate list is represented by the function NumMergeCand (L0), and is 3 here.

  Similarly, when deletion of the combined motion information candidates in the L1 direction double combined motion information candidate list in FIG. 28C is performed, an update is made as shown in FIG. The combined motion information candidate remaining in the L1 direction dual-coupled motion information candidate list is represented by the function NumMergeCand (L1), and is 3 here.

  Next, the motion information of the combined motion information candidates shown in FIGS. 28A to 28E includes not only the bidirectional mode (BiPred) but the unidirectional mode (UniPred), and the L0 and L1 directions are combined to 1 FIG. 29A shows an example of a single combined motion information candidate list in which there is no overlapping motion information when it is regarded as one piece of motion information. FIG. 29A shows an example of a single combined motion information candidate list updated by deleting the combined motion information candidate having the overlapping motion information in the single combined motion information candidate list reducing unit 151. In FIG. 29A, it is assumed that the combined motion information candidate B includes motion information only in the L1 direction, C includes motion information only in the L0 direction, and other combined motion information candidates include motion information in the L0 and L1 directions. Here, when there is no motion information in the L0 direction or the L1 direction, it is represented by the symbol “-” in FIGS.

  The double-coupled motion information candidate list generated by the dual-coupled motion information candidate list generation unit 152 is configured such that the motion information of each combined motion information candidate in the single-coupled motion information candidate list shown in FIG. Dividing in the direction, it is generated as shown in FIGS. 29 (b) and 29 (c). FIG. 29 (b) shows an L0 direction, and FIG. 29 (c) shows a double coupled motion information candidate list in the L1 direction. The generated double coupled motion information candidate list is supplied to the dual coupled motion information candidate list reduction unit 153.

  The dual coupled motion information candidate list reduction unit 153 deletes the combined motion information candidate including motion information overlapping in the dual coupled motion information candidate list for each of the L0 and L1 directions. First, deletion of combined motion information candidates in the L0 prediction bi-coupled motion information candidate list in FIG. 29B will be described.

  In FIG. 29 (b), combined motion information candidates A and E have motion information L0_0, COL and C have L0_1, and B has a unidirectional mode in the L1 direction, so there is no motion information in the L0 direction. Similarly to the description in FIGS. 28A to 28E, when motion information is compared in the order of combined motion information candidates with the smallest merge candidate number, and there are a plurality of combined motion information candidates having overlapping motion information. Since the merge candidate number is assigned to the combined motion information candidate having a relatively high selection rate, the merged motion information candidate having the smallest merge candidate number is left and the others are deleted from the list.

  First, a comparison between A having a merge candidate number of 0 and other combined motion information candidates is started. A and E have the same motion information L0_1. Since the merge candidate number of A is 0 and E is 4, E is deleted, and A is left in the L0 direction bi-join motion information candidate list. E to be deleted is assigned the largest number in the bi-join motion information candidate list in the L0 direction, and no join motion information candidate exists after E. Therefore, it is not necessary to update the allocation of merge candidate numbers in the L0 direction double-coupled motion information candidate list.

  Since the next B has no motion information in the L0 direction and there is no other combined motion information candidate that does not have the motion information in the L0 direction, the B merge candidate number is set to 1 without changing the B merge candidate number. Leave on the candidate list. Subsequently, since COL with merge candidate number 2 and C with merge candidate number 3 have the same motion information L0_1, C is deleted, and COL is left in the L0 direction bi-join motion information candidate list. In the L0 direction bi-join motion information candidate list, E has already been deleted, and there is no join motion information candidate after C. Therefore, it is necessary to update the merge candidate number assignment in the L0 direction bi-join motion information candidate list. Absent. As described above, the combined motion information candidates having overlapping motion information in the L0 direction double combined motion information candidate list are deleted, and FIG. 29B is updated as shown in FIG.

  The hatched lines in FIG. 29 (d) indicate deleted combined motion information candidates. The combined motion information candidate remaining in the L0 direction double-coupled motion information candidate list is represented by the function NumMergeCand (L0), and is 3 here.

  Similarly, when deletion of the combined motion information candidates in the L1 direction double combined motion information candidate list in FIG. 29C is performed, the information is updated as illustrated in FIG. The combined motion information candidate remaining in the L1 direction dual-coupled motion information candidate list is represented by the function NumMergeCand (L1), and is 3 here.

  In the example of the single combined motion information candidate list shown in FIGS. 29A to 29E, the combined motion information candidate including only one of the pieces of motion information in the L0 or L1 direction in the single combined motion information candidate list is L0 and The combined motion information candidate registered in the L1 direction double-coupled motion information candidate list is used, but may be excluded from the combined motion information candidate in the dual-coupled motion information candidate list. For example, the combined motion information candidate B in the single combined motion information candidate list in FIG. 29A is in the unidirectional mode and includes only the motion information in the L1 direction. Therefore, even if it is registered as a combined motion information candidate in the L0 direction bi-coupled motion information candidate list, there is no motion information in the L0 direction, so motion compensation is performed using only the motion information in the L1 direction of other combined motion information candidates. Make predictions.

  Therefore, the prediction accuracy of motion compensation prediction may be reduced. Therefore, a combination of combined motion information candidates that always includes two pieces of motion information in the L0 and L1 directions may be selected from only the combined motion information candidates in the bidirectional mode in the single combined motion information candidate list. . As described above, the combined motion information candidate list in the L0 and L1 direction double combined motion information candidate lists is reduced, and the L0 and L1 direction double combined motion information candidate lists are updated.

(Generation of double combined motion information candidate combination list)
Subsequently, a detailed operation of generating a double-coupled motion information candidate combination list will be described with reference to FIGS. 30 (a) to 30 (d) and FIGS. 31 (a) to 31 (d). 30 (a), 30 (b), 31 (a), and 31 (b), the dual-join motion information candidate list reduction unit 153 performs the processes shown in FIGS. 28 (a) to 28 (e) and FIGS. This is a double coupled motion information candidate list updated by deleting a combined motion information candidate having overlapping motion information from the example of the dual coupled motion information candidate list shown in e). 30 (a) and 31 (a) show the L0 direction and FIGS. 30 (b) and 31 (b) show the bi-join motion information candidate list in the L1 direction.

  First, a description will be given of the double-coupled motion information candidate list shown in FIGS. 30A and 30B as an example. The double coupled motion information candidate list shown in FIGS. 30A and 30B updated by the dual coupled motion information candidate list reduction unit 153 is supplied to the dual coupled motion information candidate combination list generation unit 154. The double-coupled motion information candidate combination list generation unit 154 generates a double-coupled motion information candidate combination list shown in FIG. 30C by combining the combined motion information candidates in the L0 direction and the L1 direction of the dual-coupled motion information candidate list. To do. In the example of FIGS. 30A and 30B, since there are three combined motion information candidates in both the L0 direction and the L1 direction, nine bi-coupled motion information candidates are generated.

  Next, the combined motion information candidate of the single combined motion information candidate list supplied from the single combined motion information candidate list reduction unit 151 is obtained as the motion information of the dual combined motion information candidate in the generated combined dual motion information candidate combination list. It is determined whether or not it overlaps with the motion information. Here, the motion information of the double combined motion information candidates combined in the L0 direction and the L1 direction in FIG. 30C is the combined motion information candidate in the single combined motion information candidate list shown in FIG. It is determined whether or not the motion information is the same.

  When the motion information of the bi-coupled motion information candidate in the bi-coupled motion information candidate combination list overlaps with the motion information of the combined motion information candidate in the single-coupled motion information candidate list, the motion information of the single-coupled motion information candidate is referred to. This combination is determined to be invalid and is not used. This is because, in order to refer to the same motion information, two merge indexes in the L0 and L1 directions are necessary for the dual coupled motion information candidate, and one merge index is sufficient for the single coupled motion information candidate. On the other hand, if they do not overlap, they are considered as effective double coupled motion information candidates as motion information candidates of a new combination that does not exist in the single coupled motion information candidate list.

  Here, for convenience of explanation, the combination of motion information in the L0 direction and the L1 direction of the bi-join motion information candidate in FIG. 30C is represented by (L0, L1), and the merge candidate number is described in parentheses. In the following, the motion information included in the combination in FIG.

  (0, 0) is the motion information (L0_0) of A in the L0 direction and the motion information (L0_0) of A is in the L1 direction, and is the same as A in the single combined motion information candidate list. A is given priority and this combination is not used.

  (0, 1) is the motion information (L0_0) of the A in the L0 direction, and the motion information (L0_1) of the COL in the L1 direction, and there is no combined motion information candidate corresponding to the single combined motion information candidate list. Let it be a combined motion information candidate.

  (0, 2) is the motion information of A in the L0 direction (L0_0), the L1 direction is the motion information of E (L0_2), and there is no combined motion information candidate corresponding to the single combined motion information candidate list. Let it be a combined motion information candidate.

  (1, 0) is the motion information (L0_1) of the B in the L0 direction and the motion information (L0_0) of the A1 is the same as B in the single combined motion information candidate list. B is given priority and this combination is not used.

  (1, 1) is the motion information (L0_1) of the B in the L0 direction and the motion information (L0_1) of the COL in the L1 direction, which is the same as the COL of the single combined motion information candidate list. COL is preferred and this combination is not used.

  (1, 2) is B motion information (L0_1) in the L0 direction and E motion information (L0_2) in the L1 direction, and there is no combined motion information candidate corresponding to the single combined motion information candidate list. Let it be a combined motion information candidate.

  (2, 0) is C motion information (L0_2) in the L0 direction and A motion information (L0_0) in the L1 direction, and there is no combined motion information candidate corresponding to the single combined motion information candidate list. Let it be a combined motion information candidate.

  (2, 1) is C motion information (L0_2) in the L0 direction and COL motion information (L0_1) in the L1 direction, which is the same as C in the single combined motion information candidate list. C is preferred and this combination is not used.

  (2, 2) is C motion information (L0_2) in the L0 direction and E motion information (L0_2) in the L1 direction, which is the same as E in the single combined motion information candidate list. E is given priority and this combination is not used.

  FIG. 30D shows the combination of the double-coupled motion information candidates determined in this way. In the example of FIGS. 30A to 30D, the double-coupled motion information candidates that are valid combinations not existing in the single-coupled motion information candidate list are (0, 1), (0, 2), (1, 2). And (2, 0) (represented by “◯” in FIG. 30 (c)), the merge candidate numbers in the L0 and L1 directions representing these combinations, together with the merge candidate numbers in the single combined motion information candidate list This is supplied to the combined motion information selection unit 141.

  As described above, it is possible to refer to motion information of adjacent blocks that are different in the L0 direction and the L1 direction. However, there are NumMergaCand (L0) × NumMergeCand (L1) = 3 × 3 = 9 combinations of the double-coupled motion information candidates shown in FIG. 30C, but there are only four actually effective combinations. When the code allocation shown in FIG. 7B is applied to the merge candidate numbers for representing the four ways, one direction is represented by 2 bits, and a maximum of 4 bits are required. If the four combinations are simply represented, applying the code allocation of FIG. 7C requires a maximum of 3 bits, which reduces the encoding efficiency. This is because the double coupled motion information candidates in the L0 direction and the L1 direction are two-dimensionally arranged independently.

  Therefore, first, an effective bi-coupled motion information candidate in the L0 direction is determined, and then combined with the determined effective bi-coupled motion information candidate in the L1 direction, an L1 direction bi-coupled motion information candidate that is an effective combination. A merge candidate number is assigned to. This will be described with reference to FIG.

  When A is selected as the L0 direction bi-coupled motion information candidate, COL and E are effective bi-coupled motion information candidates in the L1 direction including motion information of combinations that do not exist in the single-coupled motion information candidate list. At this time, the number of effective candidates for bi-join motion information in the L1 direction is NumMergeCand (L1) = 2, and a merge candidate number is assigned to COL and 1 is assigned to E. At this time, since the number of candidates for the merge candidate number in the L1 direction is 2, the code assignment in FIG. 7A is applied, and the L1 direction needs only 1 bit, which is necessary for the L0 direction. Even if 2 bits are added, only 3 bits are required, and the coding efficiency is improved.

  Similarly, when B is selected as the L0 direction double-coupled motion information candidate, only E is the only effective double-coupled motion information candidate in the L1 direction including motion information of a combination that does not exist in the single-coupled motion information candidate list. At this time, the number of valid bi-join motion information candidates in the L1 direction is NumMergeCand (L1) = 1, and is uniquely selected as a valid bi-join motion information candidate in the L1 direction, so a merge candidate number is not required. .

  In this case, only 2 bits representing the L0-direction bi-join motion information candidate are required, and the coding efficiency is improved. When C is selected as a candidate for double coupled motion information in the L0 direction, the description is omitted because it is similar to the case where B is selected. As described above, after selecting an effective bi-coupled motion information candidate in the L0 direction, by selecting an effective bi-coupled motion information candidate in the L1 direction as an effective combination, the bi-coupled motion information candidate to be referred to is selected. It is possible to reduce the amount of code shown. Since the processing proceeds in the order of the L0 direction and the L1 direction, it is not necessary to change the syntax defined in the first embodiment.

  Next, a description will be given of the double-coupled motion information candidate list of FIGS. 31A and 31B as an example. The double coupled motion information candidate list shown in FIGS. 31A and 31B updated by the dual coupled motion information candidate list reducing unit 153 is supplied to the dual coupled motion information candidate combination list generating unit 154. The bi-coupled motion information candidate combination list generation unit 154 combines the combined motion information candidates in the L0 direction and the L1 direction of the bi-coupled motion information candidate list to generate the bi-coupled motion information candidate combination list shown in FIG. To do. In the example of FIGS. 31A and 31B, since there are three combined motion information candidates in both the L0 direction and the L1 direction, nine bidirectional combined motion information candidates are generated.

  Next, the combined motion information candidate of the single combined motion information candidate list supplied from the single combined motion information candidate list reduction unit 151 is obtained as the motion information of the dual combined motion information candidate in the generated combined dual motion information candidate combination list. It is determined whether or not it overlaps with the motion information. Here, the motion information of the double coupled motion information candidates combined in the L0 direction and the L1 direction in FIG. 31 (c) is the combined motion information candidate in the single coupled motion information candidate list shown in FIG. 28 (a). It is determined whether or not the motion information is the same.

  When the motion information of the bi-coupled motion information candidate in the bi-coupled motion information candidate combination list overlaps with the motion information of the combined motion information candidate in the single-coupled motion information candidate list, the motion information of the single-coupled motion information candidate is referred to. This combination is determined to be invalid and is not used. This is because, in order to refer to the same motion information, two merge indexes in the L0 and L1 directions are necessary for the dual coupled motion information candidate, and one merge index is sufficient for the single coupled motion information candidate. On the other hand, if they do not overlap, they are considered as effective double coupled motion information candidates as motion information candidates of a new combination that does not exist in the single coupled motion information candidate list.

  Here, for convenience of explanation, the combination of motion information in the L0 direction and the L1 direction of the bi-join motion information candidate in FIG. 31C is represented by (L0, L1), and the merge candidate number is described in parentheses. In the following, the motion information included in the combination in FIG.

  (0, 0) is the motion information (L0_0) of A in the L0 direction and the motion information (L0_0) of A is in the L1 direction, and is the same as A in the single combined motion information candidate list. A is given priority and this combination is not used.

  (0, 1) is the motion information (L0_0) of A in the L0 direction, and the motion information (L0_1) of COL is in the L1 direction, and is the same as E in the single combined motion information candidate list. A is given priority and this combination is not used.

  (0, 2) is the motion information (L0_0) of A in the L0 direction, and the motion information (-) of C in the L1 direction, and there is no combined motion information candidate corresponding to the single combined motion information candidate list. Let it be a combined motion information candidate.

  (1,0) is the motion information (−) of B in the L0 direction and the motion information (L0_0) of A in the L1 direction, which is the same as B in the single combined motion information candidate list. B is given priority and this combination is not used.

  (1,1) is B motion information (-) in the L0 direction and COL motion information (L0_1) in the L1 direction, and there is no combined motion information candidate corresponding to the single combined motion information candidate list. Let it be a combined motion information candidate.

  In (1, 2), the L0 direction is B motion information (-), the L1 direction is C motion information (-), and there is no motion information of both combined motion information candidates, so this combination is not used.

  (2, 0) is COL motion information (L0_1) in the L0 direction and A motion information (L0_0) in the L1 direction, and there is no combined motion information candidate corresponding to the single combined motion information candidate list. Let it be a combined motion information candidate.

  (2, 1) is COL motion information (L0_1) in the L0 direction and COL motion information (L0_1) in the L1 direction, which is the same as COL in the single combined motion information candidate list. C is preferred and this combination is not used.

  (2, 2) is C motion information (L0_2) in the L0 direction and C motion information (-) in the L1 direction, which is the same as C in the single combined motion information candidate list. E is given priority and this combination is not used.

  FIG. 31C shows a combination of the dual-coupled motion information candidates determined in this way. In the examples of FIGS. 31A to 31C, the double-coupled motion information candidates that are valid combinations not existing in the single-coupled motion information candidate list are (0, 2), (1, 1), and (2, 0). (Represented by “◯” in FIG. 31 (c)), the merge candidate numbers in the L0 and L1 directions representing these combinations are combined with the merge candidate numbers in the single combined motion information candidate list, and the combined motion information selection unit 141. To supply.

  As described above, it is possible to refer to motion information of adjacent blocks that are different in the L0 direction and the L1 direction. In the example of FIGS. 31A to 31C as well, as described with reference to FIGS. 30A to 30D, an effective bi-join motion information candidate in the L0 direction is determined, and then the determined L1 When a merge candidate number is assigned to an L1 direction bi-join motion information candidate that is an effective combination in combination with a direction effective bi-join motion information candidate, the result is as shown in FIG. Regardless of whether A, B, or COL is selected as the L0 direction bi-coupled motion information candidate, there is one effective bi-coupled motion information candidate in the L1 direction that includes motion information of a combination that does not exist in the single coupled motion information candidate list Only exists. At this time, the number of valid bi-join motion information candidates in the L1 direction is NumMergeCand (L1) = 1, and is uniquely selected as a valid bi-join motion information candidate in the L1 direction, so a merge candidate number is not required. . In this case, only 2 bits representing the L0-direction bi-join motion information candidate are required, and the coding efficiency is improved.

  In the example of FIG. 31, even in the case of a combined motion information candidate having no motion information in one direction of the L0 direction or the L1 direction, the same determination of the candidate motion information is performed as one of the dual coupled motion information candidates, and duplication is performed. The combined motion information candidate to be deleted is deleted, and the combined motion information candidate having no motion information is left in the dual-coupled motion information candidate list. As bi-coupled motion information candidates, it is possible to relatively improve the prediction accuracy of motion compensated prediction when motion information is provided in each of the L0 direction and the L1 direction, so that motion information is stored in the L0 direction or the L1 direction. It is desirable to set the combined motion information candidate provided at the top of the dual combined motion information candidate list. From the above, if there is a combined motion information candidate with no motion information, the combined motion information candidate is not registered in the bi-coupled motion information candidate list, and “motion information is used at the end of the bi-coupled motion information candidate list. A merge candidate number for designating a state meaning “no” may be set. FIGS. 32A and 32B show examples applied to FIGS. 31A and 31B. By applying this processing, priority is given to using motion information in both directions of L0 and L1, so that the accuracy of motion compensation prediction can be improved and coding efficiency can be improved.

  As described above, the moving picture coding apparatus 100 according to Embodiment 1 provides motion information of a new combination of double-coupled motion information candidates that does not exist in the motion information of single-coupled motion information candidates. By deleting the double coupled motion information candidate determined to be the same as the motion information of the single coupled motion information candidate so that the motion information of the generated dual coupled motion information candidate does not overlap with the motion information of the single coupled motion information candidate , Reduce the number of double-coupled motion information candidates. Thereby, encoding efficiency is improved by suppressing the amount of codes of merge candidate numbers specifying bi-join motion information candidates.

  However, the load of encoding processing increases due to the same determination of motion information. In order to reduce the load of the encoding process, the motion information in the L0 direction and the L1 direction of the combined motion information candidate in the single combined candidate number management table shown in FIG. A combination of candidates for the double coupled motion information may be generated from the 20 types obtained in the above. Since the same determination of the combined motion information candidates of the single bond and the double bond performed by the combined motion information candidate generation unit 140 is not performed, the load of the encoding process is reduced. In this case, in the encoding, the motion information of the combined motion information candidate shown in FIG. 18 is invalid, or the combination of the bi-join motion information candidate is excluded when there is no motion information in both the L0 direction and the L1 direction. Only valid combinations are selected. However, since there are five candidates in both the L0 direction and the L1 direction, the merge index for specifying the combination of the double-join motion information candidates is 4 bits at the longest, and when the two merge indexes are combined, an 8-bit code amount is required. Thus, the encoding efficiency is lowered.

(Configuration of moving picture decoding apparatus 200)
Next, the moving picture decoding apparatus according to the first embodiment will be described. FIG. 33 shows a moving picture decoding apparatus 200 according to the first embodiment. The video decoding device 200 is a device that generates a playback image by decoding the code string encoded by the video encoding device 100.

  The moving picture decoding apparatus 200 is realized by hardware such as an information processing apparatus including a CPU (Central Processing Unit), a frame memory, and a hard disk. The moving picture decoding apparatus 200 realizes functional components described below by operating the above components. Note that the position information and the prediction block size of the prediction block to be decoded are shared in the video decoding device 200 and are not shown. In addition, the maximum number of combined motion information candidates included in the candidate number management table and the combined motion information candidate list is assumed to be shared in the video decoding device 200 and is not illustrated.

  The moving picture decoding apparatus 200 according to Embodiment 1 includes a code string analysis unit 201, a prediction error decoding unit 202, an addition unit 203, a motion information reproduction unit 204, a motion compensation unit 205, a frame memory 206, and a motion information memory 207.

(Function of moving picture decoding apparatus 200)
Hereinafter, functions of each unit will be described. The code string analysis unit 201 decodes the code string supplied from the terminal 30 to generate prediction error encoded data, a merge flag, a merge type, a merge candidate number, a prediction direction of motion compensation prediction, a reference image index, a difference vector, and Decode the prediction vector index according to the syntax. Then, the prediction error encoded data is sent to the prediction error decoding unit 202, the merge flag, the merge type, the merge candidate number, the prediction direction of the motion compensation prediction, the reference image index, the difference vector, and the prediction vector. The index is supplied to the motion information playback unit 204. The merge candidate number is obtained by conversion from the merge index.

  The prediction error decoding unit 202 performs a process such as inverse quantization or inverse orthogonal transform on the prediction error encoded data supplied from the code string analysis unit 201 to generate a prediction error signal, and the prediction error signal is It supplies to the addition part 203.

  The addition unit 203 adds the prediction error signal supplied from the prediction error decoding unit 202 and the prediction signal supplied from the motion compensation unit 205 to generate a decoded image signal. Supply to terminal 31.

  The motion information reproduction unit 204 includes a merge flag, a merge type, a merge candidate number, a prediction direction of motion compensation prediction, a reference image index, a difference vector, and a prediction vector index supplied from the code string analysis unit 201, and a motion information memory 207. The motion information is reproduced from the supplied candidate block group, and the motion information is supplied to the motion compensation unit 205. A detailed configuration of the motion information reproducing unit 204 will be described later.

  Based on the motion information supplied from the motion information reproducing unit 204, the motion compensation unit 205 performs motion compensation on the reference image indicated by the reference image index in the frame memory 206 based on the motion vector to generate a prediction signal. If the prediction direction is bidirectional, an average of the prediction signals in the L0 direction and the L1 direction is generated as a prediction signal, and the prediction signal is supplied to the adding unit 203.

  The frame memory 206 and the motion information memory 207 have the same functions as the frame memory 110 and the motion information memory 111 of the video encoding device 100.

(Detailed configuration of the motion information playback unit 204)
Next, a detailed configuration of the motion information reproducing unit 204 will be described with reference to FIG. FIG. 34 shows the configuration of the motion information playback unit 204. The motion information reproducing unit 204 includes an encoding mode determining unit 210, a motion vector reproducing unit 211, and a combined motion information reproducing unit 212. The terminal 32 is connected to the code string analysis unit 201, the terminal 33 is connected to the motion information memory 207, and the terminal 34 is connected to the motion compensation unit 205.

  Hereinafter, functions of each unit will be described. If the merge flag supplied from the code stream analysis unit 201 is “0”, the encoding mode determination unit 210 determines the prediction direction, the reference image index, the difference vector, and the motion compensation prediction supplied from the code stream analysis unit 201. The prediction vector index is supplied to the motion vector reproduction unit 211. If the merge flag is “1”, the merge candidate number supplied from the code string analysis unit 201 is supplied to the combined motion information reproduction unit 212.

  The motion vector reproduction unit 211 obtains motion information from the prediction direction of motion compensation prediction supplied from the encoding mode determination unit 210, the reference image index, the difference vector, and the prediction vector index, and the candidate block group supplied from the terminal 33. Reproduce and supply to terminal 34. A detailed configuration of the motion vector reproducing unit 211 will be described later.

  The combined motion information reproduction unit 212 reproduces motion information from the merge candidate number supplied from the encoding mode determination unit 210 and the candidate block group supplied from the terminal 33 and supplies the motion information to the terminal 34. A detailed configuration of the combined motion information reproducing unit 212 will be described later.

(Detailed Configuration of Motion Vector Reproducing Unit 211)
Next, a detailed configuration of the motion vector reproducing unit 211 will be described with reference to FIG. FIG. 35 shows the configuration of the motion vector reproducing unit 211. The motion vector reproduction unit 211 includes a prediction vector candidate list generation unit 220, a prediction vector determination unit 221, and an addition unit 222. The terminal 35 is connected to the encoding mode determination unit 210.

  Hereinafter, functions of each unit will be described. The prediction vector candidate list generation unit 220 has the same function as the prediction vector candidate list generation unit 130 of the video encoding device 100. The prediction vector determination unit 221 determines a prediction vector from the prediction vector candidate list supplied from the prediction vector candidate list generation unit 220 and the prediction vector index supplied from the terminal 35, and supplies the prediction vector to the addition unit 222.

  The adder 222 adds the difference vector supplied from the terminal 35 and the prediction vector supplied from the prediction vector determination unit 221 to calculate a motion vector, and supplies the motion vector to the terminal 34.

(Detailed Configuration of Combined Motion Information Reproducing Unit 212)
Next, a detailed configuration of the combined motion information reproduction unit 212 will be described with reference to FIG. FIG. 36 shows the configuration of the combined motion information playback unit 212. The combined motion information reproduction unit 212 includes a combined motion information candidate generation unit 230 and a combined motion information selection unit 231.

  Hereinafter, functions of each unit will be described. The combined motion information candidate generation unit 230 has the same function as the combined motion information candidate generation unit 140 shown in FIG. The combined motion information selection unit 231 selects motion information from the combined motion information candidate list based on the combined motion information candidate list supplied from the combined motion information candidate generation unit 230 and the merge candidate number supplied from the terminal 35. Then, the motion information is supplied to the terminal 34.

(Operation of the video decoding device 200)
Subsequently, a decoding operation in the moving picture decoding apparatus 200 according to Embodiment 1 will be described with reference to the flowchart of FIG. The code string analysis unit 201 decodes the code string supplied from the terminal 30 to predict prediction error encoded data, merge flag, merge type, merge candidate number, prediction direction of motion compensation prediction, reference image index, difference vector, and prediction The vector index is decoded according to the syntax (S210).

  The motion information reproduction unit 204 includes a merge flag, a merge type, a merge candidate number, a prediction direction of motion compensation prediction, a reference image index, a difference vector, and a prediction vector index supplied from the code string analysis unit 201, and a motion information memory 207. Motion information is reproduced from the supplied candidate block group (S211).

  Based on the motion information supplied from the motion information reproducing unit 204, the motion compensation unit 205 performs motion compensation on the reference image indicated by the reference image index in the frame memory 206 based on the motion vector to generate a prediction signal. If the prediction direction is bidirectional, an average of the prediction signals in the L0 direction and the L1 direction is generated as a prediction signal (S212).

  The prediction error decoding unit 202 performs a process such as inverse quantization and inverse orthogonal transform on the prediction error encoded data supplied from the code string analysis unit 201 to generate a prediction error signal (S213). The adding unit 203 adds the prediction error signal supplied from the prediction error decoding unit 202 and the prediction signal supplied from the motion compensation unit 205 to generate a decoded image signal (S214).

  The frame memory 206 stores the decoded image signal supplied from the adding unit 203 (S215). The motion information memory 207 stores the motion vector supplied from the motion information reproducing unit 204 for one image in the minimum predicted block size unit (S216).

  Subsequently, the operation of the motion information reproducing unit 204 will be described using the flowchart of FIG. The encoding mode determination unit 210 determines whether the merge flag supplied from the code string analysis unit 201 is “0” or “1” (S220). If the merge flag is “1”, the combined motion information reproducing unit 212 reproduces motion information from the merge type supplied from the encoding mode determining unit 210, the merge candidate number, and the candidate block group supplied from the terminal 33. (S221).

  If the merge flag is “0”, the motion vector reproduction unit 211 supplies the prediction direction of motion compensation prediction supplied from the encoding mode determination unit 210, the reference image index, the difference vector, the prediction vector index, and the terminal 33. Motion information is reproduced from the candidate block group (S222).

  Subsequently, the operation of the motion vector reproducing unit 211 will be described with reference to the flowchart of FIG. The prediction vector candidate list generation unit 220 generates a prediction vector candidate list by the same operation as the prediction vector candidate list generation unit 130 of the video encoding device 100 (S300).

  The prediction vector determination unit 221 selects a prediction vector candidate indicated by the prediction vector index supplied from the terminal 35 from the prediction vector candidate list supplied from the prediction vector candidate list generation unit 220, and determines a prediction vector. (S301). The adder 222 adds the difference vector supplied from the terminal 35 and the prediction vector supplied from the prediction vector determination unit 221 to calculate a motion vector (S302).

  Subsequently, the operation of the combined motion information reproducing unit 212 will be described using the flowchart of FIG. The combined motion information candidate generation unit 230 generates a combined motion information candidate list by the same operation as the combined motion information candidate generation unit 140 of the video encoding device 100 (S310). The combined motion information selection unit 231 selects a combined motion information candidate indicated by the merge candidate number supplied from the terminal 35 from the combined motion information candidate list supplied from the combined motion information candidate generation unit 230, and combines them. The motion information is determined (S311).

(Modification of Embodiment 1)
The first embodiment can be modified as follows.

(Modification 1: Use in the same direction)
In the first embodiment described above, an example in which a block candidate having motion information in the L0 direction or the L1 direction in the adjacent block candidate to be referred to becomes the motion information in the L0 direction or the L1 direction of the bi-join motion information candidate is given. . In the case of bi-directional prediction, as shown in the example of FIG. 6 (d), it is possible to improve the accuracy of motion compensated prediction by referring to two pieces of motion information from the same direction as the selection of motion information. The present invention can also be applied to the embodiment.

  As shown in FIG. 41 (a), when only the motion information in the same prediction direction exists in the combined motion information candidates included in the single combined motion information candidate list, the generation probability of the dual combined motion information candidates is increased. By increasing the selection rate of motion information candidates, the efficiency of motion information encoding can be improved. In this case, the bi-coupled motion information candidate determination unit 161 originally supplies the merge candidate numbers in the L0 direction and the L1 direction, but the bi-coupled motion information candidate is predicted only in one direction (L0 direction or L1 direction). In such a case, the encoding side and the decoding side may prevent the processing from failing in encoding and decoding even if a combined motion information candidate having motion information only in the L0 direction is selected as an effective bi-joint motion information candidate in the L1 direction. It is necessary to match.

  FIG. 41 (b) shows a combination of double coupled motion information candidates generated from the single coupled motion information candidate list of FIG. 41 (a). When B is selected in both the L0 direction and the L1 direction (0, 0), or when COL is selected in both the L0 direction and the L1 direction (1, 1), the same as B or COL in the single combined motion information candidate list Therefore, priority is given to B or COL of the single combined motion information candidate list, and this combination is not used. A double-coupled motion information candidate that is an effective combination that does not exist in the single-coupled motion information candidate list is (0, 1) or (1, 0). The merge candidate numbers in the L0 and L1 directions representing these combinations are supplied to the combined motion information selection unit 141 together with the merge candidate numbers in the single combined motion information candidate list. As described above, it is possible to refer to motion information of adjacent blocks different in the L0 direction and the L1 direction.

(Modification 2: Higher priority of merge candidate numbers)
In the above-described first embodiment, the combined motion information candidate is combined with the combined motion information candidate block effective in the L0 direction and the L1 direction, and new motion information using the motion information in the L0 direction and the L1 direction is provided. A candidate for double coupled motion information is generated. By combining the motion information of the combined motion information candidate blocks effective in the L0 direction and the L1 direction, a double coupled motion information candidate is generated as a combination of new motion information that does not exist in the motion information of the single coupled motion information candidate. In addition, the accuracy of motion compensation prediction can be improved and the coding efficiency of motion information can be improved, but the processing amount increases.

  Therefore, in this modification, an increase in the amount of processing is suppressed by limiting the number of generated dual coupled motion information candidates. Specifically, in the double-coupled motion information candidate list reduction unit 153, the one with the smaller merge candidate number with respect to the double-coupled motion information candidate list that has been updated by deleting the combined motion information candidate having overlapping motion information Are selected with priority from the two combined motion information candidates.

  42 (a) and 42 (b) are updated by deleting the combined motion information candidates including the overlapping motion information from the example of the dual combined motion information candidate list shown in FIGS. 28 (b) to 28 (e). FIG. 42A shows the bi-join motion information candidate list, and FIG. 42B shows the bi-join motion information candidate list in the L1 direction. Here, two merge candidate numbers are selected from the smaller L0 and L1 directions.

  Therefore, the combined motion information candidates (C in the L0 direction and E in the L1 direction) indicated by the hatched rows in FIGS. 42A and 42B are deleted from the double combined motion information candidate list. 42 (a) and 42 (b), the double coupled motion information candidate combination list generation unit 154 combines the combined motion information candidates in the L0 direction and the L1 direction of the dual coupled motion information candidate list, 2) is generated.

  In the example of FIGS. 42A and 42B, since the number of combined motion information candidates is limited to two in both the L0 direction and the L1 direction, four dual combined motion information candidates are generated. From the combination of FIG. 42 (c), only (0, 1) is a double-coupled motion information candidate that does not exist in the single-coupled motion information candidate list, and merge candidate numbers in the L0 and L1 directions representing this combination are designated as single-coupled motion information. The data is supplied to the combined motion information selection unit 141 together with the merge candidate number of the candidate list.

  As described above, the combination determination process in the bi-coupled motion information candidate combination list generation unit 154 is performed by preferentially selecting the smaller of the merge candidate numbers of the bi-join motion information candidate list in the L0 direction and the L1 direction. It can be reduced. In this modification, two combined motion information candidates are preferentially selected in both the L0 direction and the L1 direction, but different values may be used in the L0 direction and the L1 direction. Furthermore, it may be implicitly defined so that the number of combined motion information candidates selected with priority in encoding and decoding is matched so that the processing does not contradict between encoding and decoding.

  In addition, a syntax having a function of defining the number of combined motion information candidates to be preferentially selected in encoding and decoding may be defined for each slice that is a unit of the encoded stream or a part of the encoded stream. The code string generation unit 104 encodes and transmits the number of combined motion information candidates in the encoded stream as shown in FIGS. 43 (a) and 43 (b). 43 (a) and 43 (b), the number of combined motion information candidates to be preferentially selected by SPS (Sequence Parameter Set) for control in units of encoded streams and Slice_header for control in units of slices. The example of the syntax which encodes is shown. “Limited_merge_index_lX_flag” (X is 0 or 1) specifies whether or not to limit the number of combined motion information candidates to be selected in the LX-direction bi-joint motion information candidate list, and “max_no_of_merge_index_lX_minus1” (X is 0 or 1). Specify the number to select.

  By restricting the number of combined motion information candidates in the double-coupled motion information candidate list in units of streams or units of slices in the video encoding device and video decoding device according to this modification, motion characteristics can be improved in units of streams or slices. In such a case, the coding efficiency of the merge index can be made constant.

(Modification 3: Predetermined combination)
In the above-described first embodiment, the combined motion information candidate is combined with the combined motion information candidate block effective in the L0 direction and the L1 direction, and new motion information using the motion information in the L0 direction and the L1 direction is provided. A candidate for double coupled motion information is generated. By searching in the L0 direction and the L1 direction, a double-coupled motion information candidate is generated as a combination of new motion information that does not exist in the motion information of the single-coupled motion information candidate, and the accuracy of motion compensation prediction is improved compared to the conventional method. The encoding efficiency of motion information can be improved, but the processing amount increases.

  Therefore, as shown in FIG. 44, by defining the double-coupled motion information candidate as a combination of predetermined combined motion information candidate blocks having higher reliability, the search process is omitted, and the double-coupled motion information candidate is selected. The selectivity can be improved and the encoding efficiency can be improved.

  FIG. 44 shows an example in which motion information in the L0 and L1 directions of the candidate block A with the highest reliability and the candidate block B with the second highest reliability is combined as a merge reference candidate and defined as a dual coupled motion information candidate. is there. Here, a combination of (0, 1) and (1, 0) is defined as a double coupled motion information candidate. Note that other combinations may be used as long as the combinations of candidate blocks have relatively high reliability. Furthermore, it may be implicitly defined so that combined motion information candidates that are preferentially selected in encoding and decoding are matched so that processing does not contradict between the encoding and decoding sides.

  Also, a syntax having a function of changing the candidate number management table may be defined for each slice that is a coded stream unit or a part of the coded stream. The code string generation unit 104 encodes and transmits the candidate number management table in the encoded stream as shown in FIGS. 44 (a) and 44 (b). 44 (a) and 44 (b), syntaxes for encoding the candidate number management table with SPS (Sequence Parameter Set) for control in units of encoded streams and Slice_header for control in units of slices. An example is shown. “Prior_merge_index_flag” specifies whether or not to give priority to the combined motion information candidates determined in advance in the dual combined motion information candidate list.

  By giving priority to the combined motion information candidates in the bi-join motion information candidate list in units of streams or units of slices in the video encoding device and video decoding device according to this modification, the motion characteristics change in units of streams or slices. In such a case, the encoding efficiency of the merge index can be made constant.

(Effect of Embodiment 1)
(Effects of bi-joint motion information in bidirectional prediction)
The effect by Embodiment 1 is demonstrated using FIG. 46 (a), (b). In the following description, the motion vector in the L0 direction of the block N is mvL0N, the motion vector in the L1 direction is mvL1N, the reference image index in the L0 direction is refIdxL0N, the reference image index in the L1 direction is refIdxL1N, the difference vector in the L0 direction is dmvL0N, The difference vector in the L1 direction is represented as dmvL1N, the difference in the reference image index in the L0 direction is represented as drefIdxL0N, and the reference image index in the L1 direction is represented as drefIdxL1N. Note that the motion information of each combined motion information candidate in FIG. 45 is represented by (mvLXNx, mvLXNy) / refIdxLXN in accordance with the symbols described above. A parenthesis before “/” represents a motion vector of the block N in the LX direction (X is 0 or 1), mvLXNx in the parenthesis represents a horizontal motion vector component, and mvLXNy represents a vertical motion vector component. RefIdxLXN after “/” represents the reference image index of the block N in the LX direction (X is 0 or 1).

  The motion information with the smallest prediction error for the processing target block (Z) is that the prediction direction is bidirectional (BI), mvL0Z = (2,8), mvL1Z = (4,2), refIdxL0Z = 0, refIdxL1N = 0 Suppose that

  At this time, it is assumed that the single combined motion information candidates are A, B, COL, C, and E described in the single combined motion information candidate list shown in FIG. Among these single combined motion information candidates, there is no motion information identical to the motion information that minimizes the prediction error for the processing target block (Z). Therefore, a single combined motion information candidate having a minimum rate distortion evaluation value is selected from these single combined motion information candidates. Then, the candidate rate distortion evaluation value and the rate distortion evaluation value calculated by the difference vector calculation unit 120 are compared, and the merge mode is used as the encoding mode only when the former is smaller than the latter. Become.

  When the merge mode is selected as the encoding mode, it is because the balance between the encoding efficiency of motion information and the prediction error is optimal, and the prediction error is not optimal. On the other hand, when the non-merge mode is selected as the encoding mode, the encoding efficiency of motion information is not optimal.

  Here, the double-coupled motion information candidates generated according to Embodiment 1 have the combinations shown in FIG. In the single combined motion information candidate list in FIG. 46A, there are three effective combined motion information candidates in both the L0 direction and the L1 direction, but the combined motion information candidates A and C are the same motion information in the L1 direction. It is. Therefore, as shown in FIG. 46 (b), three combined motion information candidates in the L0 direction and two combined motion information candidates in the L1 direction are selected and newly generated from the single combined motion information candidate list in FIG. 46 (a). There are a total of six combinations of bi-coupled motion information candidates. Here, among the combinations of motion information, (0, 0), (1, 1) and (2, 0) are the same as the single combined motion information candidates A, B and C, and are not used. Three of (0, 1), (1, 0) and (2, 1) are set as double coupled motion information candidates. At this time, it can be seen that the combination (0, 1) of the dual coupled motion information candidates has the same motion information as the motion information that minimizes the prediction error for the processing target block (Z). That is, by selecting the (0, 1) combination of bi-coupled motion information candidates, the prediction error can be minimized and the coding efficiency of motion information can be optimized.

(Effects of bi-joint motion information for unidirectional prediction)
The effect of unidirectional prediction according to Embodiment 1 will be described with reference to FIGS. 47 (a) and 47 (b). It is assumed that the motion information that minimizes the prediction error for the processing target block (Z) is unidirectional (UNI), mvL0Z = (0,8), and refIdxL0Z = 2.

  It is assumed that B, C, and COL of the single combined motion information candidates are invalid (x), and valid single combined motion information candidates A and E indicate the motion information indicated by the single combined motion information candidate list in FIG. I will have it. Also in this case, there is no motion information in the single combined motion information candidate that minimizes the prediction error for the processing target block (Z).

  Again, the bidirectional combined motion information candidates generated by the first embodiment are the combinations shown in FIG. 47 (b). The combination of bi-coupled motion information candidates newly generated from the unidirectional combined motion information candidate list in FIG. 47A is two effective combined motion information candidates in the L0 direction in the single-coupled motion information candidate list. In the L1 direction, there is actually one, but two. That is, E has only the motion information in the L0 direction and does not have the motion information in the L1 direction. However, the fact that there is no motion information is regarded as one motion information, and there is motion information in the L1 direction of E. Accordingly, two combined motion information candidates are selected also in the L1 direction, and a total of four combinations of the dual combined motion information candidates are newly generated from the single combined motion information candidate list in FIG. 47A.

  Here, among the combinations of motion information, (0, 0) and (1, 1) are the same as the single combined motion information candidates A and E, so they are not used, and the remaining (0, 1) and ( 1,0) are the double-coupled motion information candidates. At this time, it can be seen that the combination (0, 1) of the dual coupled motion information candidates has the same motion information as the motion information that minimizes the prediction error for the processing target block (Z). That is, by selecting the (0, 1) combination of bi-coupled motion information candidates, the prediction error can be minimized and the coding efficiency of motion information can be optimized.

(Example of effect of bi-joint motion information by combination of unidirectional prediction)
Moreover, the effect by the combination of motion information in which the prediction direction according to Embodiment 1 is unidirectional will be described with reference to FIGS. The motion information with the smallest prediction error for the processing target block (Z) is that the prediction direction is unidirectional (BI), mvL0Z = (2, 2), refIdxL0Z = 0, mvL1Z = (− 2, 2), refIdxL1Z = Assume that it is zero.

  Assume that single-bond motion information candidates A, COL, and C are invalid (x), and valid single-link motion information candidates B and E are motion information indicated by the single-link motion information candidate list in FIG. I will have it. Also in this case, there is no motion information that has the smallest prediction error for the processing target block (Z) in the single combined motion information candidates.

  Again, the double coupled motion information candidates generated by the first embodiment are the combinations shown in FIG. The effective combined motion information candidates in the single combined motion information candidate list in FIG. 48A are effective even when there is no motion information in one prediction direction, and two combined in the L0 direction and two combined in the L1 direction. Select motion information candidates. Therefore, there are a total of four combinations of double-coupled motion information candidates newly generated from the single-coupled motion information candidate list in FIG.

  Here, in the combination of motion information, (0, 0) and (1, 1) are not used because they are the same as the single combined motion information candidates A and E. Further, (1, 0) is a case where there is no motion information in both the L0 direction and the L1 direction, so this is also not used. One of the remaining (0, 1) is set as a double coupled motion information candidate. At this time, it can be seen that the combination (0, 1) of the dual coupled motion information candidates has the same motion information as the motion information that minimizes the prediction error for the processing target block (Z). That is, by selecting the (0, 1) combination of bi-coupled motion information candidates, the prediction error can be minimized and the coding efficiency of motion information can be optimized.

(Bi-bond motion information)
As described above, by using the motion information in the L0 direction and the L1 direction of the single combined motion information candidate to generate a new combination of dual combined motion information candidates, the motion of the processing target block is encoded. Even when there is a deviation from the motion of the same position block of another image or the adjacent block of the processing target block, the motion information can be encoded using only the index without encoding. Therefore, it is possible to realize a moving image encoding device and a moving image decoding device that can optimize encoding efficiency and prediction efficiency.

(Single bond motion information)
Also, when generating new single-direction combined motion information candidates using the single-link motion information candidate L0-direction and L1-direction motion information, the single-link motion information candidate L0-direction and L1-direction motion information is also generated. The same effect is produced as in the case of generating a double-coupled motion information candidate using.

(Bi-coupled motion information using the same direction)
Also, in the case of generating a double coupled motion information candidate using motion information in the same prediction direction of the single coupled motion information candidate, the dual coupled motion information candidate using the motion information in the L0 direction and the L1 direction is also used. The same effect is produced as when the combined motion information candidate is generated.

(Simplified video decoding process)
As described above, by generating motion information candidates for each direction using motion information in each direction of the motion information candidate for single connection, the motion of the block to be processed is the same position block in another encoded image, Even when there is a deviation from the motion of the adjacent block of the processing target block, the decoding of the prediction direction, the reference index and the difference vector, the addition processing of the prediction vector and the difference vector, etc. are unnecessary, and the processing of the video decoding device is reduced. I can do it.

(Merge candidate number assignment in order of selectivity)
As described above, by assigning a smaller merge candidate number to a combined motion information candidate that has a relatively high selection rate, the selection rate of motion information that is more reliable in each direction is increased, and highly accurate motion information in each direction. Can be used to generate a high-precision bi-joint motion information candidate. In addition, the search process can be simplified, and even if the number of candidates is reduced and the number of processes is reduced, a decrease in encoding efficiency can be suppressed.

(Memory lead time)
As described above, by using the motion information in each direction of the single combined motion information candidates, the combined motion is generated without increasing the number of single combined motion information candidates by generating a new combination of dual combined motion information candidates. The number of information candidates can be increased. Accordingly, in a moving picture encoding apparatus and moving picture decoding apparatus using a general LSI in which the memory read time is increased due to an increase in the number of single combined motion information candidates, a memory due to an increase in the number of single combined motion information candidates Increase in lead time can be suppressed.

[Embodiment 2]
(Syntax)
An example of the syntax of a prediction block defined by encoding and decoding in Embodiment 2 of the present invention will be described using FIG. Whether the prediction block is intra or inter is specified by a higher-order encoding block, and FIG. 49 shows syntax when the prediction block is inter. The difference from the first embodiment is that the function of merge_flag is different. The merge_type according to the first embodiment is encoded as a flag that specifies single merge or dual merge, and is recorded in the bitstream. On the other hand, merge_type in the second embodiment is merely a variable to which the return value of the function MergeType () is substituted, and is not recorded in the bitstream. When the function MergeType () for passing a return value to merge_type in the second embodiment is “1”, merge_type in the first embodiment is equivalent to “1”, and a single merge is applied. When the function MergeType () is “0”, the merge_type of the first embodiment is equivalent to “0”, and bimerging is applied. Other than the function MergeType () is the same as in the first embodiment, so only the function MergeType () will be described here.

(Configuration of moving picture coding apparatus 100)
The configuration of the moving picture encoding apparatus according to the second embodiment is the same as that of the moving picture encoding apparatus 100 according to the first embodiment except for the function of the motion information generation unit 109 of the moving picture encoding apparatus. Hereinafter, the difference of the function of the motion information generation unit 109 of the moving picture encoding apparatus in Embodiment 2 from that in Embodiment 1 will be described.

  FIG. 50 shows a configuration of information candidate generation section 140 in the second embodiment. This is a configuration in which a combination type determination unit 155 is newly added to the configuration of the information candidate generation unit 140 in Embodiment 1 of FIG. The combination type determination unit 155 functions as a function MergeType () defined by syntax, and will be described with reference to the flowchart of FIG.

  The combined type determination unit 155 is supplied with the updated single combined motion information candidate list together with the total number s from which the combined motion information candidates including the overlapping motion information are deleted in the single combined motion information candidate list reduction unit 151, Obtained (S400).

  The combination type determination unit 155 compares s with the threshold value TH (S401). When s is less than TH (Y in S401), a combination of bi-coupled motion information candidates from the double-coupled motion information candidate list generation unit 152 to the bi-coupled motion information candidate combination list generation unit 154 is selected, and the bi-coupled motion information The single combined motion information candidate list supplied from the single combined motion information candidate list reduction unit 151 together with the candidate combination list is supplied to the terminal 18 (S402). When s is greater than or equal to TH (N in S401), the combination selection of the bi-coupled motion information candidates is not performed, and only the single-coupled motion information candidate list supplied from the single-coupled motion information candidate list reduction unit 151 is connected to the terminal 18. Supply (S403).

  Here, the setting range of the threshold TH is 1 or more, and from the number of candidates in the single combined motion information candidate list before deleting the combined motion information candidates including the overlapping motion information in the single combined motion information candidate list reduction unit 151. A value obtained by subtracting 1 is used. Even if all candidates of the single combined motion information candidate list have the same motion information, one candidate of the single combined motion information candidate list remains, so here, it is set in the range of 1 to 4 (= 5-1) The s is equal to or greater than the threshold value TH when there are many combined motion information candidates deleted by the single combined motion information candidate list reduction unit 151.

  In this case, since most of the motion information of the plurality of reference candidate blocks adjacent to the processing target block is similar, even if a combination of them is generated to generate a new bi-joint motion information candidate, the single-joint motion information The occurrence frequency of candidates that are the same as or similar to the candidates increases, and there is a high possibility that appropriate reference candidates cannot be obtained. On the other hand, when s is greater than or equal to TH, there are many different pieces of motion information among a plurality of reference candidate blocks adjacent to the processing target block. The possibility of being different from the combined motion information candidate is increased. Therefore, there is a high probability that an appropriate reference candidate can be selected from motion information having different characteristics, and an effect of reducing the amount of code of motion information by merging can be expected. The setting range of the threshold TH is not limited to the above range, and may be adjusted based on knowledge obtained through experiments or simulations by the designer.

  As described above, it is determined whether or not the combination of the bi-coupled motion information candidates is selected, and it is determined whether or not the combination of the bi-coupled motion information candidates is effective as a reference candidate in the merge mode. This can be determined before the combined motion information candidate is generated. Accordingly, the processing from the dual coupled motion information candidate list generation unit 152 to the dual coupled motion information candidate combination list generation unit 154 can be omitted as appropriate, and the processing load can be reduced. Furthermore, since it is not necessary to encode the flag merge_type for designating single merge or dual merge, it is possible to improve the encoding efficiency.

  The configuration of the moving picture decoding apparatus according to the second embodiment is the same as that of the moving picture decoding apparatus 200 according to the first embodiment except for the function of the motion information reproducing unit 204. Hereinafter, the difference of the function of the motion information reproducing unit 204 of the moving picture decoding apparatus in the second embodiment from that in the first embodiment will be described.

  The configuration of the combined motion information candidate generation unit 230 in the second embodiment is different from that in the first embodiment, and a new combined type determination unit 155 is installed. The joint type determination unit 155 performs the function of the function MergeType () calculated at the time of decoding, and has the same function as the configuration in the joint motion information candidate generation unit 140 of the video encoding device in the second embodiment. doing. When the merge flag decoded by the code string analysis unit 201 is “1”, the merge value selected by the function MergeType () calculated at the time of decoding is selected, and further, the code string analysis unit 201 selects The motion information of the candidate of the adjacent block to be referred to by the decoded merge index is selected.

(Modification of Embodiment 2)
The second embodiment can be modified as follows.

(Modification 1)
In the above-described second embodiment, whether or not to execute the function MergeType () for determining whether or not to perform bimerging is determined based on the number of candidates registered in the single combined motion information candidate list. did. In this modification, a reference image having the smallest inter-image distance between an image including the processing target block and an image referred to by an adjacent block that is a reference candidate for the processing target block is referred to in both the L0 direction and the L1 direction. Judgment based on whether or not. In the embodiment of the present invention, in order to improve the accuracy of motion compensation prediction, an optimal reference image is selected from a plurality of reference images in motion compensation prediction. In order to identify a reference image selected from a plurality of reference images, a reference image index is assigned to the reference image for management. Since the reference image is in each of the L0 direction and the L1 direction, the reference image index is also set in each of both directions. The reference image index is an integer value of 0 or more, and is encoded in the encoded stream together with the motion vector so that the reference image used in motion compensated prediction can be specified at the time of decoding. In general, the correlation between an image including a processing target block and a plurality of reference images is higher for a reference image having a smaller inter-image distance and an image including a processing target block. The probability of selection is relatively high. For this reason, a reference image index having a small value is assigned to an image including the processing target block and a reference image having a small inter-image distance. By doing so, the code amount of the reference image index can be suppressed, and the encoding efficiency is improved. In the present modification, in view of the above points, the L0 direction and the L1 direction are used as reference images having the smallest inter-image distance between an image including a processing target block and an image referred to by an adjacent block serving as a reference candidate for the processing target block. Based on whether or not there is an adjacent block in which the reference image index in both the L0 direction and the L1 direction is “0”. Judgment is made.

  This will be described using an example shown in FIG. In FIG. 52, CurPic indicates an image including a processing target block, and the numbers in the lower part of the diagram indicate reference image indexes of reference lists L0 and L1 of images referred to by CurPic. An area indicated by a black oblique line in the center of CurPic is a processing target block, and adjacent blocks that are reference candidates for the processing target block are represented by BL0 and BL1.

  In the motion information of the block BL0, the prediction direction is the bidirectional mode, and the image RefL0Pic (BL0) indicated by the reference index 2 of the reference list L0 and the image RefL1Pic (BL0) indicated by the reference index 0 of the reference list L1 are reference images. The motion vector in the L0 direction is represented by mvL0 (BL0), and the motion vector in the L1 direction is represented by mvL1 (BL0).

  Similarly, in the motion information of the block BL1, the prediction direction is the bidirectional mode, the image RefL0Pic (BL1) indicated by the reference index 0 in the reference list L0 and the image RefL1Pic (BL1) indicated by the reference index 1 in the reference list L1. Is a reference image, the motion vector in the L0 direction is represented by mvL0 (BL1), and the motion vector in the L1 direction is represented by mvL1 (BL1).

  The single combined motion information candidate referred to by the processing target block is a dual combined motion information candidate generated by combining the motion information of the blocks BL0 and BL1 and the blocks BL0 and BL1, and the combination of the dual combined motion information candidates is (L0, When represented by L1), two of (BL0, BL1) and (BL1, BL0) are generated. The single combined motion information candidates BL0 and BL1 have no motion information in which the reference image index is “0” in both the L0 direction and the L1 direction, but the combination (BL1, BL0) of the dual combined motion information candidates is in the L0 direction, Motion information with a reference image index of “0” is provided in both L1 directions.

  The reference image with a smaller inter-image distance from the image including the processing target block has a higher temporal correlation with the image including the processing target block, and thus the motion detected with reference to the reference image with a smaller inter-image distance. The accuracy of the vector increases, the residual signal can be reduced, and the encoding efficiency can be improved. Therefore, (BL1, BL0) can be a candidate for motion information more useful than a single combined motion information candidate.

  When there is no adjacent block in which the reference image index in both the L0 direction and the L1 direction is “0” in the motion information of the single combined motion information candidate, bimerging is applied, and the reference image index in the L0 direction and the L1 direction is By generating a new combination of double-coupled motion information candidates that are “0”, higher encoding efficiency can be expected.

  On the other hand, when there is an adjacent block in which the reference image index in the L0 direction and the L1 direction is both “0” in the motion information of the single combined motion information candidate, bimerging is applied to create a new combined bijoint motion information. Even if the candidates are generated, it is hardly expected to improve the encoding efficiency. Therefore, when there is a candidate in which the reference image index in both the L0 direction and the L1 direction is “0” in at least one of the motion information of the single combined motion information candidate, the combined type determination unit 155 It determines with not performing an information candidate production | generation process.

  If there is a candidate in which the reference image index in the L0 direction and the L1 direction are both “0” in the predetermined number (for example, two) of motion information of the single coupled motion information candidate, the dual coupled motion information candidate If it is determined that the generation process is not to be executed and there is no candidate in which the reference image index in both the L0 direction and the L1 direction is “0” in the predetermined number of pieces of motion information of the single combined motion information candidate, It may be determined that the candidate generation process is executed.

  Further, in the determination process, the motion information of the time block candidate may be excluded from the single combined motion information candidates. Whether or not to remove motion information candidates for time blocks depends on how to determine reference images for time block candidates.

  In this modification, the determination is performed based on the reference image index. However, the determination is based on the inter-image distance between the image including the processing target block and the image referred to by the adjacent block that is a reference candidate of the processing target block. It is not limited to this if possible. For example, the inter-image distance may be calculated using a POC (Picture Order Count) which is a counter indicating the display order of images defined in the MPEG-4 AVC described above. When the image display order is increased by 1, the POC is also increased by 1. Therefore, the inter-image distance can be obtained from the POC difference between the images.

(Modification 2)
In the above-described second embodiment, as in the first embodiment, the description has been made on the assumption that the merge index is assigned to each of the L0 direction bi-join motion information and the L1 direction bi-join motion information. The process for determining whether or not to execute the bi-joint type motion information candidate generation process according to the second embodiment is a syntax that assigns one merge index to the combination of the bi-join motion information in the L0 direction and the L1 direction. Applicable.

(Effect of Embodiment 2)
In the second embodiment, it is determined whether or not a combination of bi-coupled motion information candidates is effective as a reference candidate in the merge mode by determining whether or not a combination of bi-coupled motion information candidates is selected. This can be determined before the combined motion information candidate is generated. Accordingly, the processing from the dual coupled motion information candidate list generation unit 152 to the dual coupled motion information candidate combination list generation unit 154 can be omitted as appropriate, and the processing load can be reduced. Furthermore, since it is not necessary to encode the flag merge_type for designating single merge or dual merge, there is an effect of improving the encoding efficiency.

  The moving image encoded stream output from the moving image encoding apparatus according to the first and second embodiments described above is specified so that it can be decoded according to the encoding method used in the first and second embodiments. Data format. A moving picture decoding apparatus corresponding to the moving picture encoding apparatus can decode an encoded stream of this specific data format.

  Specifically, a merge index indicating a candidate for bi-join motion information and a candidate number management table are encoded in the encoded stream. Also, only the merge index indicating the bi-join motion information candidate is encoded in the encoded stream, and the candidate number management table is shared by the video encoding device and the video decoding device, so that the candidate number management table is included in the encoded stream. It may not be encoded.

  When a wired or wireless network is used to exchange an encoded stream between a moving image encoding device and a moving image decoding device, the encoded stream is converted into a data format suitable for the transmission form of the communication path. It may be transmitted. In that case, a video transmission apparatus that converts the encoded stream output from the video encoding apparatus into encoded data in a data format suitable for the transmission form of the communication channel and transmits the encoded data to the network, and receives the encoded data from the network Then, a moving image receiving apparatus that restores the encoded stream and supplies the encoded stream to the moving image decoding apparatus is provided.

  The moving image transmitting apparatus is a memory that buffers the encoded stream output from the moving image encoding apparatus, a packet processing unit that packetizes the encoded stream, and transmission that transmits the packetized encoded data via the network. Part. The moving image receiving apparatus generates a coded stream by packetizing the received data, a receiving unit that receives the packetized coded data via a network, a memory that buffers the received coded data, and packet processing. And a packet processing unit provided to the video decoding device.

  The processing related to encoding and decoding described above can be realized as a transmission, storage, and reception device using hardware, as well as firmware stored in a ROM (Read Only Memory), flash memory, and the like. It can also be realized by software such as a computer. The firmware program and software program can be recorded and provided on a computer-readable recording medium, provided from a server through a wired or wireless network, or provided as a data broadcast of terrestrial or satellite digital broadcasting. Is also possible.

  The present invention has been described based on the embodiments. The embodiments are exemplifications, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. .

  DESCRIPTION OF SYMBOLS 100 moving image encoder, 101 prediction block image acquisition part, 102 subtraction part, 103 prediction error encoding part, 104 code stream production | generation part, 105 prediction error decoding part, 106 motion compensation part, 107 addition part, 108 motion vector detection , 109 motion information generation unit, 110 frame memory, 111 motion information memory, 120 difference vector calculation unit, 121 combined motion information determination unit, 122 prediction coding mode determination unit, 130 prediction vector candidate list generation unit, 131 prediction vector determination , 132 subtraction unit, 140 combined motion information candidate generation unit, 141 combined motion information selection unit, 150 single combined motion information candidate list generation unit, 151 single combined motion information candidate list reduction unit, 152 double combined motion information candidate list generation unit 153 Double-coupled motion information Information candidate list reduction unit, 154 double coupled motion information candidate combination list generation unit, 155 coupled type determination unit, 160 L0, L1 direction motion information combination unit, 161 dual coupled motion information candidate determination unit, 200 moving image decoding device, 201 code Sequence analysis unit, 202 prediction error decoding unit, 203 addition unit, 204 motion information reproduction unit, 205 motion compensation unit, 206 frame memory, 207 motion information memory, 210 encoding mode determination unit, 211 motion vector reproduction unit, 212 combined motion An information reproduction unit; 220 a prediction vector candidate list generation unit; 221 a prediction vector determination unit; 222 an addition unit.

Claims (7)

An image encoding device that performs motion compensation prediction,
It is determined whether to use the first inter-picture prediction mode that uses the motion information of one reference block candidate or to use the second inter-picture prediction mode that uses the motion information of two reference block candidates. It has a judgment part,
The first inter-picture prediction mode is a mode for performing motion compensation of a coding target block using a unidirectional or bidirectional motion vector included in motion information of one reference block candidate,
The second inter-picture prediction mode generates a new bidirectional motion vector combination by combining two motion vectors that can be acquired from the motion information of two reference block candidates. In this mode, motion compensation is performed on the current block using a vector.
An image encoding apparatus characterized by that. A candidate list generation unit that generates a candidate list by selecting a plurality of blocks having motion information from a plurality of encoded blocks adjacent to the encoding target block;
When there are a plurality of blocks having overlapping motion information in the candidate list, a deletion unit that leaves one and deletes the rest is further provided,
The determination unit determines not to use the second inter-picture prediction mode when the number of blocks deleted by the deletion unit is equal to or greater than a set number.
The image coding apparatus according to claim 1. A candidate list generation unit that generates a candidate list by selecting a plurality of blocks having motion information from a plurality of encoded blocks adjacent to the encoding target block;
The determination unit has a bidirectional motion vector in the candidate list, and the number of blocks in which two reference images of the bidirectional motion vector are the temporally immediately preceding image and the immediately following image of the target image is greater than or equal to the set number. If included, it is determined not to use the second inter-image prediction mode.
The image coding apparatus according to claim 1. Two blocks are selected from a plurality of encoded blocks adjacent to the encoding target block, and the motion information of the two encoded blocks is different from the motion information held by the plurality of encoded blocks. A selection candidate generating unit that generates motion information including a bidirectional motion vector as a new selection candidate;
A selection unit that selects one of a plurality of selection candidates including a new selection candidate generated by the selection candidate generation unit;
A code string generation unit that encodes identification information for specifying the candidate selected by the selection unit;
The new selection candidate identification information generated by the selection candidate generation unit includes identification information of motion information candidates in the first prediction direction and identification information of motion information candidates in the second prediction direction that composes the selection candidates. Stipulated by the combination,
The image encoding device according to claim 1, wherein the image encoding device is an image encoding device. Among the motion information candidates in the first prediction direction and the motion information candidates in the second prediction direction, identification information is assigned to each of the motion information candidates in the reference direction, and a combination target is set for each motion information candidate in the reference direction. The number of motion information candidates in the non-reference direction is counted, and identification information is assigned to each of the motion information candidates in the non-reference direction based on the respective count values.
The image coding apparatus according to claim 4, wherein: An image encoding method for performing motion compensation prediction,
It is determined whether to use the first inter-picture prediction mode that uses the motion information of one reference block candidate or to use the second inter-picture prediction mode that uses the motion information of two reference block candidates. With steps,
The first inter-picture prediction mode is a mode for performing motion compensation of a coding target block using a unidirectional or bidirectional motion vector included in motion information of one reference block candidate,
The second inter-picture prediction mode generates a new bidirectional motion vector combination by combining two motion vectors that can be acquired from the motion information of two reference block candidates. In this mode, motion compensation is performed on the current block using a vector.
An image encoding method characterized by the above. An image encoding program for performing motion compensation prediction,
It is determined whether to use the first inter-picture prediction mode that uses the motion information of one reference block candidate or to use the second inter-picture prediction mode that uses the motion information of two reference block candidates. Let the computer execute the process,
The first inter-picture prediction mode is a mode for performing motion compensation of a coding target block using a unidirectional or bidirectional motion vector included in motion information of one reference block candidate,
The second inter-picture prediction mode generates a new bidirectional motion vector combination by combining two motion vectors that can be acquired from the motion information of two reference block candidates. In this mode, motion compensation is performed on the current block using a vector.
An image encoding program characterized by the above.

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