KR101449688B1 - Video Encoding/Decoding Method and Apparatus by Efficiently Processing Intra Prediction Mode - Google Patents

Abstract

An embodiment of the present invention relates to a video encoding / decoding method and apparatus for efficiently processing an intra prediction mode.
The embodiment of the present invention encodes the current intra mode according to whether an intra mode of the current block is included in at least one MPM (Most Probable Mode), and the current intra mode is encoded by the MPM Decoding method and apparatus for encoding the current intra mode by considering the number of intra modes not belonging to the MPM among the entire intra modes, and decoding the encoded bit stream when the current intra mode is not coincident with any one of the intra mode .

Description

[0001] The present invention relates to a video encoding / decoding method and apparatus for efficiently processing an intra prediction mode,

An embodiment of the present invention relates to a video encoding / decoding method and apparatus for efficiently processing an intra prediction mode. More specifically, if the current intra mode is inconsistent with one of the MPMs, the current intra mode is encoded and decoded according to whether the intra mode is included in at least one derived MPM (Most Probable Mode) Decoding method and apparatus for encoding and decoding a current intra mode in consideration of the number of intra modes not belonging to the intra mode.

The contents described in this section merely provide background information on the embodiment of the present invention, but do not necessarily constitute the prior art.

H.264 / AVC is the newest video compression / decoding standard among the standardized video codec to date. H.264 / AVC uses Intra Prediction, 4x4 Integer Transform, various block modes from 16x16 to 4x4, deblocking filter, etc., considering directionality to improve compression efficiency .

In order to improve the efficiency of intraprediction, HEVC (High Efficiency Video Coding), which is under discussion on standardization recently, uses a prediction method supporting from 4x4 block to 64x64 block and uses a prediction method considering directionality and a method not considering . The prediction method considering the directionality uses at least two to at most 33 directions according to the size of the current block. Considering the DC mode and the Planar mode which do not consider the direction, there are at least 35 modes in at least four modes. FIG. 1 illustrates 33 directions of an intra-prediction mode, and FIG. 2 illustrates a number of applicable prediction modes according to a prediction block size.

The 4 to 35 intra prediction modes used according to the block size are encoded using 2 to 6 bits.

An embodiment of the present invention is to increase coding efficiency in intraprediction and selects a plurality of candidates of a mode (MPM: Most Probable Mode) having the highest probability of being an intra prediction mode of the current block among all intra modes And encoding and decoding the intra prediction mode in different ways depending on whether the intra prediction mode of the current block belongs to the plurality of candidates. For example, if the current intra mode is inconsistent with one of the MPMs, the current intra mode is encoded according to whether the derived intra mode is included in the derived one or more MPMs, and if the current intra mode is inconsistent with one of the MPMs, The present invention aims to encode and decode the current intra mode.

According to an aspect of the present invention, there is provided an image decoding method comprising: selecting a plurality of intra prediction mode candidates from among all intra prediction modes using neighboring blocks of a current block; Obtaining a MPM (Most Probable Mode) flag of the current block from the bitstream; If the MPM flag indicates a first value, acquires MPM identification information from the bitstream and determines a candidate indicated by the MPM identification information among the plurality of intra prediction mode candidates as an intra prediction mode of the current block process; And determining, if the MPM flag indicates a second value, intra prediction mode identification information from the bitstream and determining an intra prediction mode of the current block based on the intra prediction mode identification information And a video decoding method.

The intra prediction mode candidate may be selected based on a block adjacent to the left side of the current block and a block adjacent to the upper side of the current block. The intra prediction mode of the block adjacent to the left side of the current block, And an intra prediction mode of the intra prediction mode.

According to an embodiment of the present invention, when the MPM flag indicates the second value, intra prediction of the current block among the intra prediction modes excluding the plurality of intra prediction mode candidates using the intra prediction mode identification information, Mode can be determined.

Wherein the intra prediction mode identification information is binarized into a number of bits determined by the number of intra prediction modes other than the plurality of intra prediction mode candidates and if the MPM flag indicates the second value, Prediction mode of the current block from the remaining intra-prediction mode using the information and the plurality of intra-prediction mode candidates.

According to another aspect of the present invention, there is provided an apparatus and method for decoding an image, the MPM identification information and the intra prediction method according to a MPM (Most Probable Mode) flag and a value of the MPM flag, A prediction information decoding unit which obtains any one of mode identification information; And selecting a plurality of intra prediction mode candidates from all intra prediction modes using the neighboring blocks of the current block, and if the MPM flag indicates a first value, indicating among the plurality of intra prediction mode candidates by the MPM identification information And a prediction mode decoding unit for determining the intra prediction mode of the current block based on the intra prediction mode identification information when the MPM flag indicates the second value, And a video decoding device.

As described above, according to the embodiment of the present invention, the current intra mode is encoded according to whether or not the current intra mode is included in one or more MPMs. If the current intra mode does not match one of the MPMs, The present intra mode is encoded and decoded considering the number of intra modes that do not belong.

1 is a diagram illustrating 33 directions of an intra prediction mode.
2 is a diagram illustrating the number of applicable prediction modes according to a prediction block size.
3 is a block diagram schematically illustrating an image encoding apparatus according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating an intra-prediction coding unit 310. FIG.
5 is a diagram illustrating an example of the intra-mode of the neighboring blocks and the positions of the current block and neighboring blocks.
FIG. 6 is a diagram illustrating a case where a total of four intra prediction modes (I_1, I_2, I_3, and I_4) of a current block are considered as a further embodiment of the present invention.
7 is a diagram illustrating a flowchart for coding a current intra mode in a prediction mode encoding unit 320 according to an embodiment of the present invention.
FIG. 8 is a block diagram schematically illustrating the configuration of an image decoding apparatus 800 according to an embodiment of the present invention.
9 is a diagram illustrating the configuration of the intra prediction decoding unit 830. In FIG.
10 is a diagram illustrating a flowchart for extracting a current intra mode from a prediction mode decoding unit 820 according to an embodiment of the present invention.
11 is a diagram illustrating a procedure of an image encoding method according to an embodiment of the present invention.
12 is a diagram illustrating a procedure of a video decoding method according to an embodiment of the present invention.

The Video Encoding Apparatus and the Video Decoding Apparatus to be described below may be implemented as a personal computer (PC), a notebook computer, a personal digital assistant (PDA), a portable multimedia player (PMP) A portable terminal, a portable multimedia player, a PlayStation Portable (PSP), a wireless terminal, a smart phone, a TV, or a server terminal such as an application server and a service server. A communication device such as a communication modem for performing communication with a wired or wireless communication network, a memory for storing various programs and data for inter- or intra prediction for encoding or decoding an image, encoding or decoding for encoding or decoding, A microprocessor or the like for < RTI ID = 0.0 > I can understand.

In addition, the image encoded by the video encoding apparatus can be transmitted in real time or in non-real time through a wired or wireless communication network such as the Internet, a local area wireless communication network, a wireless LAN network, a WiBro network, a mobile communication network, A serial bus, and the like, and can be decoded and reconstructed into an image and reproduced by an image decoding apparatus.

The moving picture may be generally composed of a series of pictures, and each picture may be divided into a predetermined area such as a frame or a block. When an image area is divided into blocks, the divided blocks can be classified into an intra block and an inter block according to a coding method. The intra-block refers to a block that is coded using Intra Prediction Coding (P-Coding) scheme. The intra-prediction coding is performed by using the pixels of previously decoded and decoded blocks in the current picture, A prediction block is generated by predicting the pixels of the block and a difference value between the pixel of the current block and the pixel of the current block is encoded. Inter-block refers to a block that is coded using Inter Prediction Coding. Inter-prediction coding refers to one or more past pictures or a future picture to generate a prediction block by predicting a current block in the current picture, And the difference value is encoded. Here, a frame to be referred to in encoding or decoding a current picture is referred to as a reference frame.

3 is a block diagram schematically illustrating an image encoding apparatus according to an embodiment of the present invention.

The image encoding apparatus 300 according to an embodiment of the present invention is an apparatus for encoding an image and includes an intra prediction encoding unit 310 and a prediction mode encoding unit 320.

The intra prediction coding unit 310 intra-predicts and encodes the current block.

The prediction mode encoding unit 320 encodes the current intra mode according to whether the derived intra mode (i.e., current intra mode) of the current block is included in the derived one or more MPMs. If the current intra mode does not match one of the MPMs , The current intra mode is encoded considering the number of intra modes not belonging to the MPM among the entire intra modes.

FIG. 4 is a diagram illustrating an intra-prediction coding unit 310. FIG.

4, the intra prediction coding unit 310 includes a prediction unit 410, a subtractor 420, a transform unit 430, a quantization unit 440, an inverse quantization unit 450, an inverse transform unit 460, an adder 470, a bitstream generator 480, a deblocking filter 490, and a memory 492. Some of the above configurations may not necessarily be included, and some or all of them may be selectively included depending on the implementation.

The input image to be encoded may be inputted in units of blocks. In the embodiment of the present invention, the block may be of M × N type, M and N may have various sizes, and M and N may be the same Or may be different.

The prediction unit 410 generates a prediction block by predicting a current block to be coded in an image using an intra prediction or an inter prediction method. That is, when intra prediction is performed, the prediction unit 410 predicts a pixel value of each pixel of an object block to be encoded in an image according to a determined optimal prediction mode (Prediction Mode) And generates a predicted block having a predicted pixel value. Here, the optimal prediction mode is a mode in which various intra prediction modes for intra prediction (for example, nine prediction modes in intra 8x8 prediction and intra 4x4 prediction in H.264 / AVC and intra 16x16 The prediction mode in which the coding cost is the smallest among the four prediction modes in the prediction) can be determined.

For example, the intra 4x4 prediction of H.264 / AVC includes a vertical mode, a horizontal mode, a DC (direct current) mode, a diagonal down-left mode, a diagonal right there are nine prediction modes including down-right, vertical-right, horizontal-down, vertical-left, and horizontal-up modes.

 Accordingly, when any one of the intra modes is selected and prediction is performed, the selected current intra mode is transmitted to the prediction mode encoding unit 320 to perform current intra mode encoding.

Subtraction unit 420 subtracts the prediction block from the current block to be encoded (i.e., the current block) to generate a residual block. That is, the subtractor 420 calculates the difference between the pixel value of each pixel of the target block to be encoded and the predicted pixel value of each pixel of the predicted block predicted by the predictor 410, and outputs a residual signal ). ≪ / RTI >

The transforming unit 430 transforms the residual block into a frequency domain and transforms each pixel value of the residual block into a frequency coefficient. Here, the transforming unit 430 transforms a spatial axis image signal, such as a Hadamard transform, a discrete cosine transform based transform (DCT) transform, The residual signal can be transformed into the frequency domain, and the residual signal transformed into the frequency domain becomes the frequency coefficient.

The quantization unit 440 quantizes the residual block having the frequency coefficient converted into the frequency domain by the transform unit 430. [ The quantization unit 440 quantizes the transformed frequency coefficient block using a dead zone uniformity threshold (DZUTQ) method, a quantization weighted matrix, Or the like.

The bitstream generation unit 480 outputs a bitstream by encoding the quantized frequency coefficient sequence using an entropy coding technique or the like. As such an encoding technique, entropy encoding technology may be used, but various other encoding techniques may be used without being limited thereto.

In addition, the bitstream generator 480 may include various types of information necessary for decoding the encoded bit stream as well as the bit stream in which the quantized frequency coefficients are encoded. That is, the encoded data may include a coded block pattern (CBP), a delta quantization parameter and a bit stream in which a quantization frequency coefficient is encoded and a bit stream for information required for prediction. In addition, the image encoding apparatus 300 according to an embodiment of the present invention may be configured to integrate the function of encoding the current intra mode performed by the prediction mode encoding unit 320 with the function of the bit stream generating unit 480, And may be performed by the generating unit 480.

The inverse quantization unit 450 inverse quantizes the frequency transform block quantized by the quantization unit 440. That is, the dequantizer 450 dequantizes the quantized frequency coefficients of the quantized frequency transform block to generate a residual block having a frequency coefficient.

The inverse transform unit 460 inverse transforms the frequency transform block inversely quantized by the inverse quantization unit 450. That is, the inverse transform unit 460 inversely transforms the frequency coefficients of the frequency transform block reconstructed by the inverse quantization unit 450 to generate a residual block having a pixel value, that is, a reconstructed residual block. Here, the inverse transform unit 460 can inversely transform the transformed method used in the transform unit 430. [

The adder 470 adds the residual block restored by the inverse transform unit 460 to the predicted block predicted by the predictor 410 and restores the current block that is the target block. The restored object block passes through a deblocking filter 490. The deblocking filter 490 deblocks and filters the restored current block to remove block distortion and the like, and the memory 492 decodes the current block And can be used as a reference picture when coding a next block or a future block of a target block.

5 is a diagram illustrating an example of the intra-mode of the neighboring blocks and the positions of the current block and neighboring blocks.

When one or more MPMs are used to encode the current intra prediction mode, the prediction mode encoding unit 320 of the present invention uses one or more MPMs to encode the current intra prediction mode, A method of not encoding the prediction direction information of the current block is proposed.

An example for solving the problems of the existing method will be described with reference to Fig. When the intra-prediction direction of the current block is considered for all three directions (I_1, I_2, I_3) and the intra mode of the left side block of the current block and the intra mode of the upper side block of the current block are set to MPM, Similarly, if the intra prediction direction of the upper block of the current block is I_1 and the prediction direction of the left block of the current block is I_2, MPM_1 becomes I_1 and MPM_2 becomes I_2. 5, if the current block's intra prediction direction is I_3, the prediction direction of the current block is not the same as any of the two MPMs, so the prediction mode encoding unit 320 determines that the current intra mode is not the same as any one of the MPMs (First identifier) to be represented is generated as a bit stream and transmitted to the decoding apparatus. In this case, since there is only one mode other than the MPM, the prediction mode encoding unit 320 adds the information representing the prediction direction I_3 of the current block in addition to the indicator indicating that the current intra mode is not the same as any one of the MPMs, Do not encode.

5, if the current intra mode is I_1 (or I_2), the prediction mode encoding unit 320 encodes an indicator (first identifier) representing that the current intra mode is the same as an MPM, And transmits it to the decoding apparatus, and further encodes an identifier (second identifier) indicating which MPM matches the current intra mode. If the MPM_1, the MPM_2, and the current intra mode are all the same (i.e., the number of intra modes included in the MPM is 1) instead of the intra mode configuration shown in FIG. 5, (First identifier) to be generated as a bit stream and transmitted to the decoding apparatus, and there is no need to encode the additional second identifier. That is, when the intra mode of the current block coincides with one of the MPMs and the number of intra modes belonging to the MPM is 1 (practically, the intra mode of the current block matches all the MPMs) The intra mode of the current block can be encoded with 1-bit information indicating belonging to the MPM.

Considering the intra prediction modes of the current block as a total of four (I_1, I_2, I_3, I_4) and combining the modes of I_3 and I_4, when coding the prediction mode of the prediction mode shown in FIG. 5, I_1 A bit string indicating I_2, or a bit string indicating I_3 or I_4, respectively. Accordingly, when the intra mode of the current block is I_3 or I_4, an indicator (first identifier) expressing that the current intra mode is not the same as any MPM is encoded and generated as a bit stream (MPM_1 = I_1, MPM_2 = I_2 Therefore, In this case, there is no information for discriminating whether the mode of the current block is I_3 or I_4 in the information included in the indicator, and it is possible to distinguish whether it is I_3 or I_4 using an additional 1 bit identifier (second identifier). That is, when the intra mode of the current block is a mode expressed by grouping a plurality of intra modes, the intra mode of the current block is encoded using additional information identifying one of the plurality of intra modes expressed in a bundle.

The total intra mode information to be considered in this case is four in total, but I_3 and I_4 are coded in a bundled manner, so that three modes are considered, and intra modes (for example, I_3 and I_4) expressed by bundling a plurality of modes When one of them is identified, the second identifier is used as the delimiter.

5, if the prediction mode of the upper block of the current block is I_1 and the prediction mode of the left block of the current block is I_2, MPM_1 becomes I_1 and MPM_2 becomes I_2. In this case, when the intra prediction mode of the current block is I_3 or I_4, an indicator (first identifier) indicating that the intra prediction mode of the current block is not the same as any of the plurality of MPMs is transmitted, And further transmits a bit (second identifier) for discriminating whether I_3 or I_4.

FIG. 6 is a diagram illustrating a case where a total of four intra prediction modes (I_1, I_2, I_3, and I_4) of a current block are considered as a further embodiment of the present invention.

In another embodiment of the present invention, if intra prediction modes of the current block are considered as four (I_1, I_2, I_3, I_4) in total, and the modes of I_3 and I_4 are expressed in groups, Let's consider the case of predicted mode. As shown in FIG. 6, when the upper block of the current block is intra-predicted in the I_4 mode and the left block of the current block is intra-predicted in the I_2 mode, I_3 and I_4 are bundled and displayed modes. Therefore, MPM_1 indicates I_3 or I_4 Can be expressed. At this time, MPM_1 having the modes I_3 and I_4 represented by I_3 and I_4 may be defined as I_3 and I_4, respectively. In the present embodiment, it is assumed that the display of MPM_1 having I_3 or I_4 represented by I is set to I_3.

On the other hand, in FIG. 6, MPM_2 is defined as I_2. In this case, since the intra prediction mode (i.e., I_1) of the current block does not match any of the MPMs, the prediction mode encoding unit 320 outputs an indicator (first identifier) . In this case, since there is only one intra mode specified by the first identifier, I_1 does not transmit information on the additional intra prediction mode. 6, if the intra prediction mode of the current block is not I_1 but I_3 or I_4, an indicator (first identifier) representing the same as one of the MPMs is encoded to encode the current intra mode Bit stream, and further encodes an identifier (information indicating that the second identifier, that is, coincides with the intra mode of the upper block) indicating which MPM matches the current intra mode. In addition, since the intra mode of the upper block is expressed as a bundle, an additional identifier (third identifier) indicating which mode among the modes represented by the bundled expressions (i.e., one of I_3 and I_4) is the current intra mode is transmitted.

The MPM allocation numbers described in the embodiments of the present invention are by way of example and these examples do not limit the invention. In the embodiment of the present invention, the case of expressing I_3 and I_4 in a bundled manner is described in the embodiment, and the number and type of directional modes represented by bundling are not limited. Also, the object of the MPM to be applied is not limited to the intra mode of the upper block of the current block and the intra mode of the left block, as described in the present embodiment, and the intra mode of various blocks may be set as a set of MPMs. For example, various blocks such as the intra mode of the adjacent left block and / or the upper block of the neighboring block of the current block can be extracted as objects of the entire MPM. Therefore, the MPM may be two or three or more depending on whether the intra mode of any one of the neighboring blocks of the current block is used or the application target is defined.

7 is a diagram illustrating a flowchart for coding a current intra mode in a prediction mode encoding unit 320 according to an embodiment of the present invention.

After the intra prediction mode of the current block is determined by the prediction unit 410, the intra prediction coding unit 310 derives the MPM (S701). The MPM uses the intra mode of the promised block set with the image decoding apparatus and can derive the intra mode of the upper block and the left block of the current block to the MPM and derive the intra mode of each block of the other block set to the MPM The MPM can be used to set the intra mode of the block of various objects such as the block mode, and the MPM can be derived from various blocks.

After deriving the MPM, it is checked whether the current intra mode matches one of the MPMs (S702). If the current intra mode matches one of the MPMs, the MPM flag (MPM_flag, for example, assigned binary 1) indicating that the current intra mode corresponds to one of the MPMs is set and encoded (S703) It is checked whether the number of included intra modes is greater than 1 (S704). If the number of intra modes included in the MPM is 1 and the number of intra modes included in the MPM is 2 or more, the MPM_index (corresponding to the intra mode of the MPM coincides with the current intra mode) The information identifying the MPM to be used). For example, if the intra mode of the left block of the current block in the MPM coincides with the intra mode of the current block, the MPM_index generates information indicating the left block of the current block.

If the current intra mode is not included in the MPM, the MPM_flag () indicates that the current intra mode is inconsistent with any of the MPMs (S702) (Step S706). Then, it is determined whether the result obtained by subtracting the number of intra modes included in the MPM from the total number of intra modes is 1 (S707). If the result obtained by subtracting the number of intra modes included in the MPM from the total number of intra modes is 1, no further encoding process for the current intra mode is skipped and the number of intra modes included in the MPM If the subtraction result is greater than 1, information identifying the current intra mode is encoded for all the intra modes except for the MPM (S708).

In the flowchart of FIG. 7, in the case of expressing two or more modes described in the above embodiments, the process of encoding a delimiter that distinguishes the bound modes is omitted.

FIG. 8 is a block diagram schematically illustrating the configuration of an image decoding apparatus 800 according to an embodiment of the present invention.

The image decoding apparatus 800 according to an embodiment of the present invention includes a prediction information decoding unit 810, a prediction mode decoding unit 820, and an intra prediction decoding unit 830.

The prediction information decoding unit 810 decodes the intra mode information including the MPM flag from the bit stream.

The predictive mode decoding unit 820 determines whether the intra mode of the current block (i.e., the current intra mode) is included in at least one derived MPM (Most Probable Mode) by using the decoded MPM flag to decode the current intra mode, When the meaning of the MPM flag indicates that the current intra mode is inconsistent with any one of the MPMs, the current intra mode is extracted considering the number of intra modes not belonging to the MPM among the entire intra modes.

The prediction mode decoding unit 820 means that the intra mode of the current block does not coincide with any one of the MPMs, and if the number of intra modes that do not belong to the MPM among all intra modes is 1, The intra mode of the current block is restored to the intra mode of the current block. If the MPM flag means that the intra mode of the current block does not coincide with any one of the MPMs, and if the number of intra modes not belonging to the MPM among all intra modes is larger than 1, Extracts additional information on the location of the MPM, and identifies the intra mode of the current block from the MPM. In this way, the intra mode of the current block can be identified by extracting additional information from the MPMs that identify the intra mode of the current block.

The prediction mode decoding unit 820 determines that the MPM flag means that the intra mode of the current block matches one of the MPMs, and when the number of intra modes belonging to the MPM is 1, the MPM is set to the intra mode of the current block do. If the intra mode belonging to the MPM is a mode expressed by grouping a plurality of intra modes, additional information identifying one of a plurality of intra modes represented by being decoded from the decoded intra mode information is extracted to restore the intra mode of the current block .

If the number of intra modes belonging to the MPM is larger than 1, the prediction mode decoding unit 820 determines that the intra mode of the current block is identical to the intra mode of the current block, Extracts additional information identifying the intra mode of the current block from the MPM from the decoded intra mode information to identify the intra mode, and restores the intra mode of the current block. If the intra mode of the identified current block is a mode expressed by grouping a plurality of intra modes, additional information identifying one of the plurality of intra modes represented by the decoded intra mode information is extracted and the intra mode of the current block .

The intra prediction decoding unit 830 reconstructs the current block using the extracted current intra mode.

9 is a diagram illustrating the configuration of the intra prediction decoding unit 830. In FIG.

9, the intra prediction decoding unit 830 includes a bit stream decoding unit 910, an inverse quantization unit 920, an inverse transform unit 930, a prediction unit 950, an adding unit 960, A blocking filter 970, and a memory 980.

The bitstream decoding unit 910 decodes the bitstream, extracts a quantized frequency coefficient sequence, and inversely scans the quantized frequency coefficient sequence to generate a quantized frequency coefficient block.

The inverse quantization unit 920 dequantizes the quantized frequency coefficient block to generate a frequency coefficient block, and the inverse transform unit 930 inversely transforms the frequency coefficient block to recover the residual block.

The inverse quantization unit 920 and the inverse transformation unit 930 perform the same or similar functions as the inverse quantization unit 450 and the inverse transformation unit 460 described above with reference to FIG.

The prediction unit 950 generates a prediction block using information on the current intra mode extracted by the prediction mode decoding unit 820. [

The addition unit 960 adds the residual block reconstructed by the inverse transform unit 930 to the prediction block generated by the prediction unit 950 to reconstruct the current block. The restored current block is deblock filtered by the deblocking filter unit 970 and then stored in the memory 980 so that the restored current block can be used as a reference picture when restoring the next block or a future block of the current block.

10 is a diagram illustrating a flowchart for extracting a current intra mode from a prediction mode decoding unit 820 according to an embodiment of the present invention.

The prediction mode decoding unit 820 derives the MPM (S1001). The MPM uses the intra mode of the block set agreed with the image encoding apparatus and can derive the intra mode of the upper block and the left block of the current block to the MPM and derive the intra mode of each block of the other block set to the MPM The MPM can set the intra mode of the blocks of various objects such as the MPM.

After the MPM is derived, the prediction mode decoding unit 820 extracts the MPM flag (MPM_flag, e.g., binary information of 1 or 0) included in the decoded intra mode information) (S1002).

The prediction mode decoding unit 820 confirms whether the MPM flag is 1 (e.g., whether the current intra mode corresponds to one of the MPMs) (S1003).

If the meaning of the MPM flag indicates that the current intra mode corresponds to one of the MPMs, the prediction mode decoding unit 820 determines whether the number of intra modes included in the MPM is greater than one (S1004). If the number of intra modes included in the MPM is greater than 1, since one of the plurality of MPMs becomes the current intra mode, the MPM_index included in the decoded intra mode information MPM) to extract the current intra mode (S1005). For example, if the meaning of MPM_index indicates the left block of the current block, the intra mode of the left block of the current block is set to the current intra mode. If the number of intra modes included in the MPM is 1, further decoding on the decoded intra mode information is skipped, and one intra mode included in the MPM becomes the intra mode.

If the meaning of the MPM flag indicates that the current intra mode is inconsistent with any of the MPMs, the prediction mode decoding unit 820 determines whether the number of intra modes not belonging to the MPM among all intra modes is 1 (S1006). If the number of intra modes not belonging to the MPM among all intra modes is 1, the intra mode not belonging to the MPM is set to the current intra mode (S1007). If the number of intra modes not belonging to the MPM among the entire intra modes is greater than 1, the intra mode information decoded by the prediction information decoding unit 810 is additionally decoded to extract information identifying the current intra mode in the MPM And restores the current intra mode (S1008).

In the flowchart of FIG. 10, when two or more modes described in the foregoing embodiments are grouped together, the process of decrypting a delimiter that distinguishes the bound modes is omitted.

The image encoding / decoding apparatus according to an embodiment of the present invention can be implemented by connecting the bit stream output end of the image encoding apparatus 300 of FIG. 3 to the bit stream input end of the image decoding apparatus 800 of FIG.

An apparatus for encoding / decoding an image according to an exemplary embodiment of the present invention is an apparatus for encoding / decoding an image, the apparatus comprising: a current intra-mode prediction unit for encoding a current block in an intra mode and encoding the current block in at least one MPM (Most Probable Mode) The present intra mode is encoded according to whether the current intra mode is included in the current intra mode or not, and if the current intra mode is inconsistent with any one of the MPMs, the current intra mode, considering the number of intra modes not belonging to the MPM, And decodes the intra mode information including the MPM flag from the bitstream and determines whether the current intra mode is included in one or more MPMs as an MPM flag included in the decoded intra mode information to decode the current intra mode, If the decoded MPM flag indicates that the intra mode is currently the MPM If it is determined that the current intra mode is not coincident with any one of the intra modes, the current intra mode is extracted taking into consideration the number of intra modes not belonging to the MPM, Decoders.

Here, the image encoder can be implemented by the image encoding apparatus 300 according to an embodiment of the present invention, and the image decoding apparatus can be implemented with the image decoding apparatus 800 according to an embodiment of the present invention.

11 is a diagram illustrating a procedure of an image encoding method according to an embodiment of the present invention.

The method of encoding an image according to an embodiment of the present invention includes an intra prediction encoding step S1110 of intra-prediction encoding a current block in an intra mode and a step S1110 of determining whether the current intra mode is included in one or more MPM (Most Probable Mode) Encoding the current intra mode in consideration of the number of intra modes not belonging to the MPM among all intra modes when the current intra mode is inconsistent with any one of the MPMs, Mode encoding step S1120.

Here, the intraprediction encoding step S11101 corresponds to the operation of the intraprediction encoding unit 310, and the predictive mode encoding step S1120 corresponds to the operation of the predictive mode encoding unit 320, detailed description thereof will be omitted.

12 is a diagram illustrating a procedure of a video decoding method according to an embodiment of the present invention.

The method of decoding an image according to an embodiment of the present invention includes a prediction information decoding step (S1210) of decoding intra mode information including an MPM flag from a bitstream, a step of decoding an intra mode in at least one MPM (Most Probable Mode) If the MPM flag indicates that the current intra mode is inconsistent with any one of the MPMs, it is determined whether the current intra mode is an intra-mode A prediction mode decoding step (S1220) for extracting the current intra mode considering the number of modes, and an intra prediction decoding step (S1230) for recovering a current block using the extracted current intra mode.

Here, the prediction information decoding step S1210 corresponds to the operation of the prediction information decoding unit 810, the prediction mode decoding step S1220 corresponds to the operation of the prediction mode decoding unit 820, and the operation of the intra prediction decoding step S1230 corresponds to And the operation of the intra prediction decoding unit 830, respectively, and thus detailed description thereof will be omitted.

An image encoding / decoding method according to an embodiment of the present invention can be realized by combining an image encoding method according to an embodiment of the present invention and an image decoding method according to an embodiment of the present invention.

According to an embodiment of the present invention, an image encoding / decoding method includes the steps of intra-prediction encoding a current block in an intra mode and encoding the current intra-mode in an intra mode according to whether the current intra mode is included in one or more MPM (Most Probable Mode) Encoding the current intra mode in consideration of the number of intra modes not belonging to the MPM among all intra modes when the current intra mode is inconsistent with any one of the MPMs; Decodes the intra mode information including the MPM flag, determines whether the current intra mode is included in one or more MPMs, determines an MPM flag included in the decoded intra mode information to decode the current intra mode, Meaning that the mode does not match any of the MPMs The case, taking into account the number of intra modes that are not part of the MPM of the total intra mode the current extracting an intra mode includes an image decoding method comprising: restoring the current block by using the extracted current intra mode.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

As described above, according to the embodiment of the present invention, the current intra mode is encoded according to whether or not the current intra mode is included in one or more MPMs. If the current intra mode does not match one of the MPMs, The present intra mode is encoded and decoded considering the number of intra modes that do not belong, which is a very useful invention.

Claims (6)

In the image decoding apparatus,
A prediction information decoding unit for obtaining, from the bitstream, one of MPM identification information and intra-prediction mode identification information according to an MPM (Most Probable Mode) flag and a value of the MPM flag;
A plurality of intra prediction mode candidates are selected from all intra prediction modes using neighboring blocks of a current block, and if the MPM flag indicates a first value, a candidate indicated by the MPM identification information among the plurality of intra prediction mode candidates A prediction mode decoding unit for determining an intra prediction mode of the current block based on the intra prediction mode identification information if the MPM flag indicates a second value; And
An intra prediction decoding unit for predicting and restoring the current block using an intra prediction mode determined by the prediction mode decoding unit,
And an image decoding unit for decoding the image.
The method according to claim 1,
Wherein the prediction mode decoding unit selects the plurality of intra prediction mode candidates based on a block adjacent to the left and a block adjacent to the upper end of the current block.
3. The method of claim 2,
Wherein the plurality of intra prediction mode candidates include at least one of an intra prediction mode of a block adjacent to the left of the current block and an intra prediction mode of a block adjacent to an upper end of the current block.
The method according to claim 1,
Wherein the prediction mode decoding unit determines an intra prediction mode of the current block from intra prediction modes excluding the plurality of intra prediction mode candidates using the intra prediction mode identification information if the MPM flag indicates the second value And outputs the decoded image.
The method according to claim 1,
Wherein the intra prediction mode identification information is binarized into a number of bits determined by the number of intra prediction modes excluding the plurality of intra prediction mode candidates.
6. The method of claim 5,
Wherein the prediction mode decoding unit decodes the intra prediction mode of the current block from the remaining intra prediction mode using the intra prediction mode identification information and the plurality of intra prediction mode candidates if the MPM flag indicates the second value And decides whether or not the image is decoded.

Images