JP2012110054A - Image encoding apparatus, image encoding method, program and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make image degradation around slice division boundaries inconspicuous.SOLUTION: An image encoding apparatus includes: a slice division unit configured to divide an encoding target picture included in an input video signal into a plurality of slices each composed of one or more data blocks; an encoding unit configured to encode the video signal in a unit of the divided slice; and a slice setting unit configured to set division positions and the number of divisions of the slices, to the slice division unit. The slice setting unit, for each picture, equalizes the number of divisions of the slices, and regularly changes the division positions of the slices according to a predetermined pattern.

Description

  The present invention relates to an image encoding apparatus and method for compressing and encoding a video signal, and more specifically to an image encoding apparatus and method for encoding a video signal by performing slice division.

  MPEG (Moving Picture Experts Group) -2 and MPEG-4 are known as high-efficiency compression encoding methods for transmitting or storing image information. Furthermore, MPEG-4 Part-10: AVC (Non-Patent Document 1) is standardized. MPEG4 Part-10: AVC (ISO / IEC 14496-10) is an H.264 standard. It is also called H.264. These compression methods are basically techniques for realizing a high compression ratio by utilizing orthogonal transformation such as DCT (Discrete Cosine Transform), motion compensation, and redundancy between screens and within screens.

  H. In H.264, pictures to be encoded are classified into I pictures, P pictures, and B pictures depending on the prediction method. Each picture is composed of a plurality of macro blocks (MB). Further, H.C. In H.264, one picture can be divided into slices composed of a plurality of macroblocks, and encoding processing can be performed in units of slices. When the slice is divided, each slice is called an I slice, a P slice, a B slice, and the like. H. In the H.264 baseline profile, B pictures are not used.

  H. An image encoding apparatus using H.264 may perform encoding in units of pictures (frames or fields). However, a method in which a frame or field is divided into a plurality of slices and encoding is performed using the slices as basic units. However, processing may be easier. For example, for a high-resolution image such as 1920 pixels × 1088 pixels, the image encoding device divides the image into a plurality of slices, and encodes and decodes each slice in parallel or in time division. Sometimes. By dividing into slices and distributing encoding / decoding, the image encoding apparatus can perform processing efficiently.

  As a technique related to slice division, Patent Document 1 describes a technique for changing a slice shape according to a transmission path error or an image motion. In addition, Patent Document 2 describes H.264. In a coding method (referred to as H.26L or JVT) in the H.264 / AVC standardization process, a technique for performing slice division by adjusting the code amount is described.

  H. H.264 slices are divided in units of data blocks, that is, macroblocks, which are units of encoding processing. That is, the slice is composed of one or a plurality of macroblocks in the horizontal direction or the vertical direction. FIG. 17 is a diagram illustrating the relationship between slices and macroblocks. FIG. 17 shows that one screen is divided into three in the horizontal direction, and one screen includes three slices (first slice, second slice, and third slice). Each slice is composed of a plurality of macroblocks (MB). Macroblocks 152 and 154 belong to the first slice and are adjacent to the boundary with the second slice. The macroblock 150 belongs to the second slice and is adjacent to the boundary with the first slice.

  Note that the slice can take an arbitrary shape by a technique called FMO (Flexible Macro-block Order) or slice group as well as a rectangular shape or a strip shape as shown in FIG. Note that slice division can be executed in any profile as long as the raster order of the macroblocks, but slice groups are used only in the baseline profile and extended profile.

JP 2005-124041 A Japanese Patent Laid-Open No. 2004-235683

ISO / IEC 14496-10 “Part-10 Advanced Video Coding”

  H. When an image encoding apparatus using H.264 uses slice division, since a slice is a basic encoding unit, information on macroblocks included in other slices cannot be used for encoding. For example, in the example illustrated in FIG. 17, the information of the macroblocks 152 and 154 cannot be used for encoding the macroblock 150. As a result, the prediction efficiency of intra-picture (intra) prediction and inter-picture (inter) prediction is reduced in the vicinity of the boundary between slices, so that the encoding efficiency is lowered.

  H. CABAC (Context-based Adaptive Binary Arithmetic Coding), which is an entropy coding method that can be said to be a feature of H.264, improves coding efficiency by adaptively changing the probability table as the coding proceeds. Since this probability table is initialized at the start of slice encoding, the probability table tends to be different from the probability distribution of the encoding target. This state continues until the encoding progresses to some extent and the probability table is adapted to the encoding target. Therefore, the coding efficiency is substantially reduced near the slice boundary immediately after the initialization of the probability table.

  As described above, as a result of the decrease in coding efficiency near the slice boundary, the generated code amount increases, particularly in the macroblock located near the slice boundary, but the generated code amount is suppressed from the viewpoint of overall code amount control. Is done. Therefore, image quality degradation occurs in the macroblock located near the slice boundary, and the slice boundary becomes visually noticeable. In particular, when macroblocks arranged in the horizontal direction are continuously deteriorated, they are easily recognized as noise.

  Further, as shown in FIGS. 18 and 19, it is assumed that slices are divided at the same position in each successive picture. FIG. 18 shows an example in which consecutive pictures (00, 01, 02, 03, 04, 05,...) Are divided into slices at the same position. FIG. 19 is a diagram showing slice division positions when the pictures in FIG. 18 are represented in cross section. “I” added before the number of each picture indicates an I picture, “B” indicates a B picture, and “P” indicates a P picture. For example, B02 indicates a picture number 02 that is a B picture. In FIG. 19, horizontal broken lines 170 and 172 connecting the slice division positions of each picture indicate that the boundary of the slice is at a certain position on the screen over time. Thus, if the slice boundary is located at a certain position on the screen for a plurality of consecutive pictures, noise near the slice boundary is easily recognized.

  Such image degradation in the vicinity of the slice boundary may be made inconspicuous by irregularly changing the slice shape as in the technique described in Patent Document 2, but the slice shape may be irregular. If changed, the encoding process and the decoding process become complicated. For example, the positional relationship between the macroblocks must be confirmed, such as determining whether the macroblock to be encoded is adjacent to the boundary of the slice.

  In view of the above-described problems, an object of the present invention is to provide an image encoding apparatus and method for making image deterioration in the vicinity of a slice boundary inconspicuous with a small processing load.

In order to achieve the above object, an image encoding apparatus according to the present invention is an image encoding apparatus for encoding a video signal, wherein each picture of the video signal is composed of one or more data blocks. A dividing unit that divides the video signal into a plurality of slices; a coding unit that encodes the video signal in units of slices divided by the dividing unit; and a setting that sets a division position and the number of divisions of the slice in the dividing unit The setting means equalizes the number of divisions of the slices for each picture and changes the division positions of the slices with regularity according to a predetermined pattern .

An image encoding method according to the present invention is an image encoding method for encoding a video signal, wherein each picture of the video signal is divided into a plurality of slices each composed of one or more data blocks. And the encoding step of encoding the video signal in units of the divided slices, and the number of divisions of the slices is made equal for each picture, and the division position of the slices is determined in advance. And a step of setting so as to change with regularity according to the pattern .

  According to the present invention, image degradation near a slice boundary becomes inconspicuous with a small processing load. Further, by giving the slice division periodicity or regularity, it becomes easier to determine the slice division position at the time of decoding, and the decoding process is simplified.

It is a block diagram which shows the structure of the image coding apparatus which concerns on Example 1 of this invention. 3 is an example of slice division in the first embodiment. FIG. 6 is a diagram illustrating slice division positions in the first embodiment. It is a block diagram which shows the structure of the image coding apparatus which concerns on Example 2 of this invention. It is an example of the slice division | segmentation in Example 2. FIG. It is a figure which shows the slice division | segmentation position in Example 2. FIG. 10 is an example of slice division in the third embodiment. It is a figure which shows the slice division | segmentation position in Example 3. FIG. 12 is an example of slice division in a modification of the third embodiment. It is a figure which shows the slice division | segmentation position in the modification of Example 3. FIG. FIG. 10 is a diagram illustrating slice division positions in the extension example 1 of the embodiment 3. FIG. 10 is a diagram illustrating slice division positions in an extension example 2 of the third embodiment. It is an example of the slice division | segmentation in Example 4. FIG. It is a figure which shows the slice division | segmentation position in Example 4. FIG. 10 is an example of slice division in the fifth embodiment. It is a figure which shows the slice division | segmentation position in Example 5, and the position of I slice. It is a figure which shows the relationship between a slice and a macroblock. It is an example of slice division. It is a figure which shows a slice division position.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram illustrating a configuration of an image encoding device according to Embodiment 1 of the present invention. The image encoding device 10 encodes a video signal in accordance with the MPEG4 part-10: AVC (ISO / IEC 14496-10, so-called H.264) system. The video signal input to the image encoding device 10 is digital data digitized at a predetermined sampling rate. The image encoding device 10 can be applied to a digital video camera, a digital video recorder, or the like.

  The picture attribute determination unit 42 determines the attribute of each picture included in the input video signal. That is, it is determined whether to select an I picture, a P picture, or a B picture. The picture attribute determination unit 42 determines the attribute of each slice when dividing the slice. The slice setting unit 44 determines the boundary position of slice division and the coding type (I slice, B slice, P slice, etc.) of each slice based on the content determined by the picture attribute determination unit 42, and the slice division unit Set to 12. A method for determining slice division will be described later. A slice is composed of one or more macroblocks in units of data blocks, that is, macroblocks that are units of encoding processing.

  The slice dividing unit 12 divides each picture (frame or field) of the input video signal into slices based on the setting information from the slice setting unit 44. That is, the slice dividing unit 12 identifies and outputs image data constituting each picture (frame or field) of the input video signal for each slice. Further, the slice dividing unit 12 supplies slice division information indicating the position of the macroblock obtained by the slice division, the coding type of the slice, and the like to the intra prediction unit 28, the motion estimation unit 36, and the entropy coding unit 40 described later. . Hereinafter, a picture to be encoded will be described using a frame as an example.

  When using predictive coding, the subtractor 14 calculates a difference between the image data from the slice dividing unit 12 and the predicted value from the switch 38, and the difference data is converted to an integer precision discrete cosine transform (DCT). Is output to the integer conversion unit 16. The subtractor 14 outputs the image data from the slice division unit 12 to the integer conversion unit 16 as it is when the predictive coding is not used.

  The integer transform unit 16 performs discrete cosine transform on the image data from the subtractor 14 in units of 4 × 4 pixel blocks with integer precision, and outputs the resulting DCT transform coefficient to the quantization unit 18.

  The quantization unit 18 performs a quantization process on the DCT transform coefficient from the integer transform unit 16 and outputs the obtained quantized transform coefficient to the entropy coding unit 40 and the inverse quantization unit 20.

  The entropy encoding unit 40 entropy encodes the quantized transform coefficient from the quantization unit 18. H. In H.264, CAVLC (Context-Based Adaptive Variable Length) and CABAC (Context-Based Adaptive Binary Coding) can be selectively used as entropy coding. The entropy encoding unit 40 performs an encoding process using a slice as a basic unit based on the input slice division information by CABAC, for example. The entropy encoder 40 also multiplexes the motion vector information from the motion estimator 36 with the encoded data and outputs it as an output bit stream. In the output bitstream, information such as the position of the macroblock divided into slices and the coding type of the slice are also multiplexed.

  The inverse quantization unit 20 returns the quantization variable coefficient from the quantization unit 18 to the DCT transform coefficient and sends it to the inverse integer transform unit 22. The inverse integer transform unit 22 performs an inverse integer transform process on the DCT transform coefficient from the inverse quantization unit 20 to restore data corresponding to the output data of the subtractor 14.

  The adder 24 outputs the output data of the inverse integer transform unit 22 as it is when the predictive encoding is not used, and the output data of the inverse integer transform unit 22 when the predictive encoding is used. The predicted value from the switch 38 is added to and output. The output data of the adder 24 is so-called local decoded data. The output of the adder 24 is stored in the frame memory 26 for intra-picture prediction (intra prediction). Further, it is stored in the frame memory 32 via the deblocking filter 30 for inter picture prediction (inter prediction). The deblocking filter 30 is used to reduce block noise in the locally decoded data.

  The motion estimation unit 36 compares the image data from the slice division unit 12 with the locally decoded data stored in the frame memory 32 and estimates the motion of the object in the image in relation to inter prediction described later. The locally decoded data stored in the frame memory 32 constitutes a frame located before or after the display timing of the current frame, and is used as a reference image for inter-frame prediction. The motion vector detected by the motion estimation unit 36 is supplied to the inter prediction unit 34 and the entropy encoding unit 40. In particular, the motion estimation unit 36 prohibits detection of a motion vector that exceeds the boundary between slices based on the input slice division information.

  The intra prediction unit 28 refers to the locally decoded data stored in the frame memory 26, performs a prediction process, calculates a prediction value from the frame, and outputs it. When the slice prediction is performed, the intra prediction unit 28 performs prediction processing using only information in the same slice and in the frame based on the input slice division information, and calculates a prediction value. H. In the H.264 intra prediction, information on adjacent pixels included in an encoded pixel block is used to generate a prediction value of a prediction target block.

  The inter prediction unit 34 determines image data to be used for prediction from the reference image stored in the frame memory 32 according to the motion vector estimated by the motion estimation unit 36, and predicts inter-frame prediction values (so-called motion compensation prediction). Value) is calculated and output.

  The switch 38 selects the prediction value of the intra prediction unit 28 or the prediction value of the inter prediction unit 34 depending on whether the image data to be encoded is encoded by intra prediction or encoding by inter prediction, The value is supplied to the subtractor 14 as a prediction value for predictive coding. In addition, when the slice coding type is I slice, intra-frame coding is performed, when P slice is used, intra-frame coding and inter-frame coding using one reference image are performed, and when B slice is used, intra-frame coding is performed. Inter-frame coding using one or two reference images is allowed.

  Next, with reference to FIG. 2 and FIG. 3, the operation of slice division in the present embodiment will be described. FIG. 2 shows an example in which consecutive pictures (00, 01, 02, 03, 04, 05,...) Are divided into slices at different boundary positions according to the picture attributes. FIG. 3 is a diagram showing slice division positions when the pictures in FIG. 2 are represented in cross section. The slice division is performed according to the raster order of the macroblocks. As a result of the slice division, a plurality of horizontally long rectangular slices (three I frames, four B frames, and P frames are obtained) as in the example shown in FIG. 5) Complete.

  The picture attribute determining unit 42 determines which of I, P, and B the encoding target frame of the input video signal is in accordance with a predetermined encoding method, and notifies the determined picture attribute to the slice setting unit 44 To do. For the I frame, the slice setting unit 44 sets the slice dividing unit 12 so that the frame is equally divided into, for example, three. For the P frame, the slice dividing unit 12 is set so that the frame is equally divided into, for example, five. Further, for the B frame, the slice dividing unit 12 is set so that the picframe is equally divided into four, for example.

  The slice dividing unit 12 divides each frame of the input video signal into a set number of slices based on the setting by the slice setting unit 44. The operation after the slice division is as described above.

  As described above, in this embodiment, the number of slices and the position of the slice are regularly changed according to the picture attribute, so that the slice division position does not become the same for a long time. Accordingly, image degradation (image quality degradation) near the slice boundary becomes inconspicuous. In the example shown in FIG. 2 and FIG. 3, the slice division position is the same in two consecutive B frames (such as frames 01 and 02), but it is a B frame compared to an I frame and a P frame, so The image degradation is not noticeable.

  In the example shown in FIG. 2, the I frame, the P frame, and the B frame are all equally divided. However, if the B frame always exists between the I frame and the P frame, the I frame and the P frame are divided. Even if the frame slice division method is the same, a sufficient effect can be obtained.

  Thus, by providing regularity to the slice division position, it is easy to determine the slice division position at the time of decoding, and there is an advantage that the decoding process is simplified.

  In the first embodiment, the slice division number and the division position are regularly changed according to the picture attribute. However, the slice division number and the division position may be changed in the order of the picture number (that is, the frame number). FIG. 4 is a block diagram illustrating the configuration of the image encoding device according to the second embodiment. In FIG. 4, the same components as those in the block diagram shown in FIG.

  The image encoding device 10 a illustrated in FIG. 4 includes a slice setting unit 46. The slice setting unit 46 counts the number of frames of the input video signal, and sets slice division conditions in the slice division unit 12 as follows according to the count value. For example, when three types of slice division methods are used, the picture number of the encoding target frame is divided by 3, and 3 divisions, 4 divisions, or 5 divisions are assigned according to the remainder. FIG. 5 shows an example in which consecutive pictures (00, 01, 02, 03, 04, 05,...) Are divided into slices at different boundary positions according to picture numbers. FIG. 6 is a diagram showing slice division positions when the pictures of FIG. 5 are represented in cross section. The slice division is executed according to the raster order of the macroblocks. As a result of the slice division, a plurality of horizontally long rectangular slices are completed as in the example shown in FIG. 5 and FIG. 6, in the case of a picture (I00, P03, P06, P09...) Whose picture number is divisible by 3, for example, three divisions are set. In the case of a picture (B01, B04, B07, B10...) Whose picture number is divided by 3 and the remainder is 1, for example, four divisions are set. Further, when the picture number is divided by 3 and the remainder is 2 (B02, B05, B08, B11...), For example, 5 divisions are set. In this example, the slice division is repeated at a period of 3 pictures.

  The slice dividing unit 12 divides each frame of the input video signal into a set number of slices based on the setting by the slice setting unit 46. The operation after the slice division is as described above.

  As described above, in this embodiment, since the number of slices and the position of division are regularly changed according to the picture number, the slice division positions do not become the same between adjacent pictures. Accordingly, image degradation (image quality degradation) near the slice boundary becomes inconspicuous.

  In the third embodiment, the division number and the division position of the slice may be changed according to a certain rule in the order of picture numbers by a method different from that of the second embodiment. The block diagram of FIG. 4 is used as the block diagram illustrating the configuration of the image encoding device according to the third embodiment. FIG. 7 shows an example in which consecutive pictures (00, 01, 02, 03, 04, 05,...) Are divided into slices at different boundary positions according to picture numbers. FIG. 8 is a diagram showing slice division positions when the pictures in FIG. 7 are represented in cross section.

  In FIG. 8, white circles, black circles, black triangles, and black squares all indicate slice division positions. The auxiliary line A indicates a change in the slice division position indicated by a black circle of a group (first group) composed of pictures (I00, P03, P06, P09...) Whose picture number is divisible by 3. The auxiliary line B is a change in slice division position indicated by a black triangle of a group (second group) composed of pictures (B01, B04, B07, B10...) Whose remainder is 1 when the picture number is divided by 3 Indicates. The auxiliary line C is a change in slice division position indicated by a black rectangle of a group (third group) composed of pictures (B02, B05, B08, B11...) Whose remainder is 2 when the picture number is divided by 3 Indicates.

  As can be easily understood from FIG. 7, in the pictures belonging to the first group, the slice division position is shifted by a certain amount, for example, one macroblock (MB) in the upward direction of the screen for each picture. In addition, in the pictures belonging to the second group, the slice division position is shifted by a certain amount, for example, by one macroblock (MB) in the downward direction for each picture. Furthermore, in the pictures belonging to the third group, the slice division position is shifted by a certain amount, for example, 2 macroblocks (MB) in the upward direction of the screen for each picture.

  For example, a new dividing line is added to the slice whose size is increased by the movement of the slice dividing position, as illustrated as additional dividing positions A, B, and C in FIG.

  As described above, in this embodiment, the number of slice divisions is changed according to the picture number, and the division position is shifted. Therefore, the probability that the slice division positions are the same among a plurality of neighboring pictures is reduced, and further. Image degradation (image quality degradation) near the slice boundary becomes inconspicuous. For example, in the search reproduction or the like, only the first group described above may be displayed, but even in this case, the image quality deterioration at the slice division boundary is not noticeable in this embodiment.

  In this embodiment, the description has been made on the assumption that the picture is equally divided into slices. However, the slice division position may be different between adjacent pictures. Similar effects can be obtained.

  In this embodiment, the slice division condition is determined according to the picture number. However, the slice division condition may be changed according to the prediction method.

  Further, as a modification of the present embodiment, in order to maintain the number of divisions for each group, as shown in FIGS. 9 and 10, an existing boundary line may be deleted according to the addition of the slice boundary line. . FIG. 9 is an example of slice division that is a modification of the third embodiment, which is changed as described above. FIG. 10 is a diagram showing slice division positions when the pictures in FIG. 9 are represented in cross section. By comparing FIG. 9 and FIG. 10 with FIG. 7 and FIG. 8 respectively, the borderline to be deleted is shown.

  In each of the above embodiments, the combination of 3, 4 and 5 is illustrated as the basic number of slice divisions, but the present invention is not limited to such a number of slice divisions. In the third embodiment, the pictures are classified into three groups, but may be classified into four or more. FIG. 11 is a diagram showing slice division positions when the division method shown in FIGS. 7 and 8 is extended to four groups (extension example 1).

  In FIG. 11, white circles, black circles, black triangles, black squares, and black stars all indicate slice division positions. The auxiliary line D indicates a change in slice division position indicated by a black circle of a group (first group) made up of pictures (I00, B04, B08...) Whose picture number is divisible by 4. The auxiliary line E indicates a change in slice division position indicated by a black triangle of a group (second group) composed of pictures (B01, B05, P09,...) Whose remainder is 1 when the picture number is divided by 4 . The auxiliary line F indicates a change in slice division position indicated by a black square of a group (third group) composed of pictures (B02, P06, B10...) Whose remainder is 2 when the picture number is divided by 4 . The auxiliary line G indicates a change in slice division position indicated by a black star of a group (fourth group) composed of pictures (P03, B07, B11...) Whose remainder is 3 when the picture number is divided by 4 .

  Further, in FIG. 11, in the pictures belonging to the first group, the slice division position is shifted by a certain amount, for example, by one macroblock (MB) in the screen upward direction for each picture. In addition, in the pictures belonging to the second group, the slice division position is shifted by a certain amount, for example, by 2 macroblocks (MB) in the upward direction for each picture. Also, in the pictures belonging to the third group, the slice division position is shifted by a certain amount, for example, by 2 macroblocks (MB), in the downward direction of the screen for each picture. Further, in the pictures belonging to the fourth group, the slice division position is shifted by a certain amount, for example, by one macroblock (MB) in the lower direction of the screen for each picture.

  FIG. 12 is a diagram showing slice division positions when the division method shown in FIGS. 9 and 10 is extended to four groups (extended example 2). By comparing FIG. 12 with FIG. 11, the borderline to be deleted is shown.

  In the first to third embodiments, slice division is performed with a different number of divisions between pictures. However, in the present invention, it suffices if slice division positions (slice boundaries) are different between adjacent pictures. Therefore, the fourth embodiment shows an example in which the number of slices of each picture is made equal and only the division position is changed. The block diagram of FIG. 4 is used as the block diagram illustrating the configuration of the image encoding device according to the fourth embodiment. FIG. 13 shows an example in which each picture of consecutive pictures (00, 01, 02, 03, 04, 05,...) Is divided into slices at the same number of divisions and at different division positions. FIG. 14 is a diagram showing slice division positions when the pictures in FIG. 13 are represented in cross section.

  In the example of FIGS. 13 and 14, all the pictures are divided into three slices. At this time, as shown in the figure, by setting the slice division position of each picture to be different between adjacent pictures, it is possible to prevent slice boundaries from appearing at the same position continuously.

  At this time, the change in the slice division position need not be completely random, and can be set as a pattern having regularity that is repeated at a constant period. By setting to repeat at a predetermined cycle for each number of pictures, it becomes easy to determine the slice division position at the time of decoding, and the decoding process is simplified. In the example of FIG. 13 and FIG. 14, the same division position is shown to be repeated with a period of 3 pictures, but is not limited to this example, and if it is periodic, it has a longer number of pictures. Of course, it is possible to set the period.

  H. In the H.264 method, a prediction method can be set for each slice. That is, it is possible to set an I slice, a P slice, or a B slice for each divided slice. For example, it is possible to encode a partial slice of a B picture as an I slice, and in that case, it is possible to improve error resilience and display reproducibility at high speed playback in an area made into an I slice.

  In the fifth embodiment, a case where the function of setting some of the slices as I slices in this way is applied to the present invention will be described. The block diagram of FIG. 4 is used as the block diagram illustrating the configuration of the image encoding device according to the fifth embodiment. FIG. 15 shows an example in which each picture of consecutive pictures (00, 01, 02, 03, 04, 05,...) Is divided into slices. Furthermore, a state is shown in which some slices are set as I slices. FIG. 16 is a diagram showing slice division positions and I-slice positions when the pictures of FIG. 15 are represented in cross section.

As shown in FIGS. 15 and 16, in this embodiment, each picture is set such that the division position is different between adjacent pictures, and a part of the slices of each picture is set as an I slice and encoded. ing. For example, the I slice is set such that the first slice of the I00 picture, the second slice of the B01 picture, the third slice of the B02 picture, and the third slice of the P03 picture. (In the case of I00, other slices are also I slices, but they are not shown because they are unnecessary for the description of the present embodiment. Hereinafter, in the case of simply I slices, other I slices of I00 are not included.) Suppose)
Slices to be I slices are set while shifting the position little by little for each picture, and the division position is set to a position different from the slice division position of the adjacent picture. Note that the division positions of other slices are also set to positions different from those of adjacent pictures. Since the normal I slice has only intra prediction that can be used, the coding efficiency is low, and although it depends on the allocated code amount, it is basically in a state where noise is likely to occur. In particular, when the adjacent slice is a P slice or B slice with good coding efficiency, the degree of degradation of the I slice is easily noticeable, and the slice boundary is easily recognized.

  Therefore, in the present embodiment, the slice division position of each picture is set so as to be different from the adjacent picture as in the above-described embodiments, and the I slice is set while being shifted for each picture. As a result, the slice boundary can be made inconspicuous, and the error tolerance in the area set for the I slice and the display reproducibility at high speed reproduction can be improved.

  As described above, the present invention sets at least one of the slice division position and the number of divisions, basically changes the slice division position between adjacent pictures, or the probability that the slice division position is different. It is what raises. By making the change of the slice division position regular, it becomes easy to determine the slice division position at the time of decoding, and the decoding process can be facilitated.

(Other embodiments)
Each means constituting the image coding apparatus and each step of the image coding method in the embodiment of the present invention described above can be realized by operating a program stored in a RAM or ROM of a computer. This program and a computer-readable recording medium on which the program is recorded are included in the present invention.

  Further, the present invention can be embodied as a system, apparatus, method, program, storage medium, or the like. Specifically, the present invention may be applied to a system composed of a plurality of devices, or may be applied to an apparatus composed of a single device.

  In the present invention, a software program that implements the functions of the above-described embodiments may be directly applied to a system or apparatus. Alternatively, it may be achieved by supplying from a remote location and the computer of the system or apparatus reads and executes the supplied program code.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, and the like.

  Examples of the recording medium for supplying the program include a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, and CD-RW. Moreover, a magnetic tape, a non-volatile memory card, ROM, DVD (DVD-ROM, DVD-R), etc. are also included.

  As another program supply method, the program can be supplied by connecting to an Internet homepage using a browser of a client computer and downloading the computer program of the present invention from the homepage. Alternatively, it can be supplied by downloading a compressed file including an automatic installation function to a recording medium such as a hard disk.

  It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the present invention.

  In addition, the program of the present invention is encrypted, stored in a storage medium such as a CD-ROM, distributed to users, and key information for decryption is downloaded from a homepage via the Internet to users who have cleared predetermined conditions. Let It is also possible to execute the encrypted program by using the key information and install the program on a computer.

  Further, the functions of the above-described embodiments are realized by the computer executing the read program. In addition, based on the instructions of the program, an OS or the like running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments can also be realized by the processing.

  Further, the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, the CPU of the function expansion board or function expansion unit performs part or all of the actual processing based on the instructions of the program, and the functions of the above-described embodiments are realized by the processing.

DESCRIPTION OF SYMBOLS 10 Image coding apparatus 12 Slice division part 14 Subtractor 16 Integer conversion part 18 Quantization part 20 Inverse quantization part 22 Inverse integer conversion part 24 Adder 26 Frame memory 28 Intra prediction part 30 Deblocking filter 32 Frame memory 34 Inter prediction Unit 36 motion estimation unit 38 switch 40 entropy encoding unit 42 picture attribute determination unit 44 slice setting unit 10a image encoding device 46 slice setting unit

Claims (12)

In an image encoding device for encoding a video signal,
Dividing means for dividing each picture of the video signal into a plurality of slices each composed of one or more data blocks;
Encoding means for encoding the video signal in units of slices divided by the dividing means;
Setting means for setting the division position and the number of divisions of the slice in the division means;
The image coding apparatus according to claim 1, wherein the setting means equalizes the number of divisions of the slices for each picture, and changes the division positions of the slices with regularity according to a predetermined pattern .   The image encoding apparatus according to claim 1, wherein the encoding unit performs predictive encoding limited by the slice.   The image coding apparatus according to claim 1, wherein the dividing unit supplies information related to slice division to the coding unit.   The image coding apparatus according to claim 3, wherein the coding unit includes an entropy coding unit that performs coding in units of the slice according to the information.   4. The image encoding apparatus according to claim 3, wherein the encoding unit includes a motion estimation unit that performs motion estimation related to inter-picture prediction in units of the slice according to the information.   The image coding apparatus according to claim 3, wherein the coding unit includes an intra-picture prediction unit that performs a prediction process in units of the slice according to the information.   The image encoding apparatus according to claim 1, wherein the setting unit sets an encoding type for each slice to be set.   The image coding apparatus according to claim 1, wherein the setting unit sets a part of the set slice to a slice in which only intra prediction is possible in the slice. The image coding apparatus according to claim 1, wherein the setting unit repeats the setting of the division position according to the pattern at a cycle of three pictures or more. An image encoding method for encoding a video signal, comprising:
Dividing each picture of the video signal into a plurality of slices each composed of one or more data blocks;
An encoding step of encoding the video signal in units of divided slices;
An image encoding method comprising the steps of: equalizing the number of divisions of the slices for each picture and setting the division positions of the slices so as to change with regularity according to a predetermined pattern . Dividing each picture of the input video signal into a plurality of slices each composed of one or more data blocks;
An encoding step of encoding the video signal in units of divided slices;
Causing the computer to execute a method including the steps of: equalizing the number of divisions of the slices for each picture and setting the division positions of the slices so as to change regularly according to a predetermined pattern. Program. A computer-readable storage medium storing the program according to claim 11 .

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