JP5206772B2 - Moving picture coding apparatus, moving picture coding method, and moving picture coding program - Google Patents

Description

  The present invention relates to a moving picture coding technique, and more particularly to a moving picture coding technique using motion compensated prediction.

  In compression coding of moving images represented by MPEG (Moving Picture Experts Group), motion compensation prediction that compresses a code amount by using correlation between screens is often used. In motion compensated prediction used in MPEG or the like, a predicted image is generated for each block of a predetermined size from a reference image that has already been decoded using a motion vector that indicates the relative positional relationship between the encoding target image and the reference image. Thereafter, the encoding side calculates a prediction error that is a difference between the original image to be encoded and a prediction image generated by motion compensated prediction, and transmits only the prediction error to the decoding side. Thereby, compared with the case where motion compensation prediction is not used, the code amount transmitted can be reduced significantly.

  In general, encoding / decoding processing is performed in units of macroblocks (pixel group having a predetermined block size, for example, 16 × 16). Motion compensation prediction is often performed in units of macroblocks, but in this case, it is difficult to capture the motion of an object or the like that is smaller than the macroblock, resulting in a decrease in coding efficiency. Therefore, multi-block pattern motion compensated prediction is used as a method for making motion compensated prediction function more efficiently.

  In multi-block pattern motion compensation prediction, a macro block can be further divided into sub blocks, and motion compensation prediction can be performed using different motion vectors for each sub block. The division pattern of the motion compensation prediction block to be used is defined in advance as the same rule on the encoding side and the decoding side. On the encoding side, a block pattern for motion compensation prediction is selected from the defined block patterns, and block pattern selection information is transmitted to the decoding side. On the decoding side, motion compensation prediction is performed based on the received block pattern selection information. In multi-block pattern motion compensated prediction, when the optimum block pattern for motion compensated prediction is selected on the encoding side, the prediction error after motion compensated prediction is reduced, and the encoding efficiency is improved.

  As an example of a specific block pattern, in MPEG-4 AVC (Advanced Video Coding) internationally standardized by a joint video team (JVT) of ISO / IEC and ITU-T, there are further 16 macroblocks (16 × 16 blocks). It is possible to perform motion compensation prediction by dividing into block patterns of × 8/8 × 16/8 × 8/8 × 4/4 × 8/4 × 4. On the encoding side, a block pattern is selected, and block pattern selection information is encoded in the bitstream. On the decoding side, the macroblock is divided into regions according to the block pattern encoded in the bitstream, and motion compensation prediction is performed for each divided region.

  Furthermore, Patent Literature 1 and Patent Literature 2 disclose techniques for defining motion compensation prediction shape patterns and performing motion compensation prediction with a more flexible shape.

Japanese Patent No. 4025570 Republished Patent No. WO2003-026315

  However, in the methods disclosed in Patent Document 1 and Patent Document 2, when the number of motion compensated prediction shape patterns to be defined is increased, the amount of code consumed for selection information of the shape pattern to be transmitted increases as the number of shape patterns increases. End up. In other words, a decrease in prediction error due to an increase in shape patterns and an increase in code amount related to shape pattern selection are in a trade-off relationship, so it is difficult to improve overall coding efficiency simply by increasing the number of shape patterns. .

  As described above, in the conventional moving image encoding / decoding, only motion compensation prediction of a predefined shape pattern can be performed. Therefore, motion compensation prediction cannot be performed with an optimal shape, and encoding efficiency cannot be improved. . In addition, when the number of motion compensation predicted shape patterns to be defined is increased, the amount of additional information related to the selection of motion compensated predicted shape patterns increases, and thus the overall coding efficiency is not always improved.

  The present invention has been made in view of such circumstances, and an object of the present invention is to enable motion compensation prediction in various block patterns without increasing the amount of additional information regarding the block pattern of motion compensation prediction. Therefore, an object of the present invention is to provide a technique for improving the coding efficiency by reducing the prediction error.

  In order to solve the above problems, a moving picture encoding apparatus according to an aspect of the present invention includes a temporary area dividing unit (101) that divides an encoding target block into a plurality of temporary areas at a predetermined temporary boundary, and the encoding. A first motion vector detection unit (102) for detecting a motion vector of a first temporary region that has the least portion in contact with an encoded block adjacent to a target block by motion estimation between images; A second motion vector detecting unit (110) for detecting a motion vector using motion information of an encoded block adjacent to the encoding target block for each of the temporary regions other than the temporary region; Generating a plurality of prediction blocks corresponding to the encoding target block from a reference image using a motion vector of the region, determining a main boundary based on activities of the plurality of prediction blocks, A motion compensation unit (103) that generates a combined prediction block by combining regions obtained by dividing a prediction block at the main boundary between the prediction blocks, and the combined prediction block from the encoding target block The encoding part (105) which encodes the subtracted prediction difference block and the motion vector of a 1st temporary area | region is provided.

  Another aspect of the present invention is a video encoding method. In this method, a block to be encoded is divided into a plurality of temporary regions at a predetermined temporary boundary, and the first temporary region having the least portion in contact with the encoded block adjacent to the target block is encoded. A motion vector is detected by motion estimation between images, and motion is performed using motion information of an encoded block adjacent to the encoding target block for each of the temporary regions other than the first temporary region. A plurality of prediction blocks corresponding to the coding target block are generated from a reference image using a vector detecting step and a motion vector of each temporary region, and the boundary is determined based on the activities of the plurality of prediction blocks. A combined prediction block is generated by combining regions obtained by dividing the prediction blocks at the main boundary between the prediction blocks. Tsu comprising a flop, and the combined predicted prediction difference block to block by subtracting from the encoding target block, and encoding the motion vector of the first temporary area.

  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, etc. are also effective as an aspect of the present invention.

  According to the present invention, it is possible to reduce the prediction error and increase the coding efficiency by enabling the motion compensation prediction in various block patterns without increasing the code amount of the additional information regarding the block pattern of the motion compensation prediction. Can be improved.

1 is a block diagram illustrating a configuration of a moving image encoding apparatus according to Embodiment 1. FIG. 1 is a block diagram illustrating a configuration of a moving image decoding apparatus according to Embodiment 1. FIG. It is a figure explaining the pattern which divides a macroblock into 2 in a horizontal direction. It is a figure explaining the pattern which divides a macroblock into 2 in the perpendicular direction. It is a figure which shows the motion vector detected for every temporary area | region of a macroblock. It is a figure explaining the relationship between the division | segmentation direction of the temporary area | region of an encoding object block, and the adjacent block used for the motion detection which the 2nd motion vector detection part 110 performs. Conventional MPEG-4 AVC / H. 2 is a diagram illustrating a method of motion detection in units of macroblocks in H.264. It is a figure explaining the method of the motion detection by the 2nd motion vector detection part 110 of this Embodiment. It is a figure explaining the method of selecting the surrounding macroblock which refers a motion vector based on the direction which divides | segments a macroblock. It is a figure explaining another method of selecting the surrounding macroblock which refers to a motion vector. It is a figure which shows the motion compensation estimated image produced | generated from the motion vector detected for every temporary area | region. It is a figure which shows the synthetic | combination motion compensation prediction image obtained by synthesize | combining the motion compensation prediction image produced | generated from the motion vector of each temporary area | region. It is a figure explaining the method of synthesize | combining the motion compensation estimated image produced | generated from the motion vector of each temporary area | region, and producing | generating a synthetic | combination motion compensation prediction image. It is a flowchart which shows the process which calculates | requires an optimal value from three modes of motion detection, and the motion vector calculated by each mode. 6 is a flowchart for explaining a main boundary determination procedure by the main region dividing / motion compensating unit in FIG. 1. It is a figure explaining the activity regarding this boundary determination about a motion compensation prediction image. It is a figure explaining the detection method of the 2nd motion vector by the 2nd motion vector detection part 110 of the moving image encoder of Embodiment 2. FIG. It is a figure which shows the 1st syntax pattern of the bit stream of the moving image encoded by the moving image encoding apparatus of Embodiment 1-2. The second syntax pattern which transmits the 2nd flag which shows whether the shape of motion compensation prediction is automatically determined by the decoding side in a macroblock unit is shown. It is a figure which shows the 3rd syntax pattern which switches the algorithm which determines automatically the shape of a motion compensation prediction at the slice level by the decoding side. It is a figure which shows the 4th syntax pattern which transmits the 4th flag which shows whether the presence or absence of area division and a direction are automatically determined by a decoding side per macroblock. It is the table which showed an example of the meaning of the value of the 4th flag of FIG.

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

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of the moving picture encoding apparatus according to the first embodiment. The moving image encoding apparatus according to Embodiment 1 includes a temporary region dividing unit 101, a first motion vector detecting unit 102, a main region dividing / motion compensating unit 103, an orthogonal transform / quantizing unit 104, a variable length encoding unit 105, An inverse quantization / inverse orthogonal transform unit 106, a memory 107, a subtraction unit 108, an addition unit 109, and a second motion vector detection unit 110 are provided.

  The temporary area dividing unit 101 divides an area at an arbitrary boundary for a pixel group to be encoded, such as a 16 × 16 macroblock. This region division is a unique method on the coding side for motion vector detection, and the region may be divided at any boundary, but it is desirable to perform region division at a boundary that improves the efficiency of motion compensation prediction. Here, as the simplest provisional area division, a case where a macroblock is divided into two only in the horizontal direction or the vertical direction will be described as an example.

  FIGS. 3A to 3C are diagrams for explaining a pattern in which a macroblock is divided into two in the horizontal direction. FIG. 3A shows a pattern in which a macroblock is divided into a 16 × 4 upper region and a 16 × 12 lower region at the horizontal boundary of the fourth pixel from the top, and FIG. This is a pattern in which the macroblock is divided into a 16 × 8 upper area and a 16 × 8 lower area at the horizontal boundary of the eighth pixel, and FIG. 3C shows the macroblock at the horizontal boundary of the twelfth pixel from the top. Is divided into a 16 × 12 upper region and a 16 × 4 lower region.

  FIGS. 4A to 4C are diagrams for explaining a pattern in which a macroblock is divided into two in the vertical direction. FIG. 4A shows a pattern in which a macroblock is divided into a 4 × 16 left region and a 12 × 16 right region at the vertical boundary of the fourth pixel from the left, and FIG. The macroblock is divided into two 8 × 16 left and 8 × 16 right regions at the vertical boundary of the pixel, and FIG. 4C shows 12 macroblocks at the vertical boundary of the 12th pixel from the left. The pattern is divided into two parts, a left side area of x16 and a right side area of 4x16.

  The boundary of the macroblock determined by the provisional region dividing unit 101 is called a “provisional boundary”, and each region in the macroblock divided by the provisional boundary is called a “provisional region”.

  Here, three patterns that are divided into two in the horizontal direction or the vertical direction are shown, but four or more division patterns may be provided by increasing the candidate positions of the horizontal boundary or the vertical boundary. Further, it may be divided at an oblique boundary or may be divided at a bent boundary.

  The temporary area dividing unit 101 calculates a horizontal activity related to each horizontal boundary or a vertical activity related to each vertical boundary for the original image signal to be encoded. As described later, when a macroblock is divided at a bent boundary, the activity is calculated along the bent boundary.

The activity of the image signal is a value obtained by performing some operation on the pixel. For example, an absolute difference sum (SAD) between two pixels across the boundary can be used as an activity related to the boundary for dividing the macroblock. For example, assuming that the X coordinate in the macroblock is i, the Y coordinate is j, and the pixel value at the point (i, j) is _{Ai, j} , the horizontal activity at the horizontal boundary j of the jth pixel from the top is as follows: Defined in
Horizontal activity = Σ _{i = 0} ¹⁵ | A _{i, j} −A _{i, j−1} |
Here, Σ _{i = 0} ¹⁵ is the total sum when the subscript i is moved from 0 to 15.

However, the activity may not be an absolute difference sum (SAD). An absolute sum of squares (SSD) as shown below may be used.
Horizontal activity = Σ _{i = 0} ¹⁵ (A _{i, j} −A _{i, j−1} ) ²

Similarly, the vertical activity at the vertical boundary i of the i-th pixel from the left of the macroblock is defined as follows.
Vertical activity = Σ _{j = 0} ¹⁵ | A _{i, j} −A _{i−1, j} |

  The activity becomes a large value at the edge of the object. The temporary area dividing unit 101 tentatively divides a macroblock area at a boundary having the largest activity value.

  A motion vector is detected for each temporary area divided by the temporary area dividing unit 101. The detection of the motion vector of the temporary area is performed by the first motion vector detection unit 102 or the second motion vector detection unit 110.

  FIG. 5 is a diagram showing motion vectors detected for each temporary area of the macroblock. For example, when the temporary area dividing unit 101 tentatively divides the macroblock at the horizontal boundary of the fourth pixel from the top as shown in FIG. 3A, a 16 × 4 upper area is obtained as shown in FIG. And a motion vector for each of the lower regions of 16 × 12.

  6A and 6B are diagrams for explaining the relationship between the division direction of the temporary area of the encoding target block and the adjacent blocks used for motion detection performed by the second motion vector detection unit 110. FIG. FIGS. 6A and 6B respectively show a macroblock to be encoded divided in the horizontal direction and the vertical direction and three encoded macroblocks MBA, MBB, and MBC adjacent to the periphery.

  When the encoding target macroblock is divided in the horizontal direction as shown in FIG. 6A, the temporary area above the horizontal boundary is adjacent to the two surrounding macroblocks MBA and MBB, but below the horizontal boundary. The temporary area on the side is adjacent to only one surrounding macroblock MBA. When the encoding target macroblock is divided in the vertical direction as shown in FIG. 6B, the temporary area on the left side of the vertical boundary is adjacent to the two surrounding macroblocks MBA and MBB, but on the right side of the vertical boundary. The temporary area is adjacent to only one surrounding macroblock MBB.

  The first motion vector detection unit 102 is used for a temporary region (referred to as a “first temporary region”) that has the least number of portions adjacent to the encoded surrounding macroblock among the divided temporary regions of the encoding target block. Performs the conventional motion detection, and the second motion vector detection unit 110 uses the motion information of the surrounding macroblocks for other temporary regions (referred to as “second temporary region” in the case of two divisions). Detect vectors.

  In the case of the horizontal division in FIG. 6A, the second motion vector detection unit 110 performs the surrounding macro for the upper temporary region and in the vertical division of FIG. 6B for the left temporary region. A motion vector is obtained from the motion information of the block. The other temporary area, that is, the lower temporary area in the case of horizontal division in FIG. 6A, and the right temporary area in the case of vertical division in FIG. One motion vector detection unit 102 detects a motion vector by a normal method.

  The first motion vector detection unit 102 detects a motion vector using a block matching method. As a motion vector detection algorithm, there are various methods such as a full search that evaluates all candidate vectors in a designated search region and a high-speed search that narrows down and searches candidate vectors based on various motion characteristics. Any motion vector detection algorithm can be used as long as a motion vector can be detected for each block divided by the temporary region dividing unit 101.

  The operation of the second motion vector detection unit 110 will be described in more detail. The second motion vector detection unit 110 detects the second motion vector by using the motion information of the encoded surrounding macroblock. Before describing the operation of the second motion vector detection unit 110, a conventional motion detection method in units of macroblocks will be described with reference to FIGS. 7A to 7C, and then FIG. , (B), the operation of the second motion vector detection unit 110 of the present embodiment will be described.

  7 (a) to 7 (c) show conventional MPEG-4 AVC / H. 2 is a diagram illustrating a method of motion detection in units of macroblocks in H.264.

  FIG. 7B shows an encoding target picture. A macro block composed of 16 × 16 pixels to be encoded is indicated by a thick dotted line, and four encoded blocks around the encoding target block are thin. Shown with dotted lines. The picture shown in FIG. 7B is displayed at time t1, and the picture at time t0 (<t1) whose display time is earlier than time t1 is shown in FIG. 7A or FIG. 7C. Show. These two pictures are used as reference pictures for motion prediction of the current picture in FIG. 7B. As shown in FIGS. 7A to 7C, from time t0 to time t1, the stipple circle in the picture moves in parallel from left to right, and the background stripe pattern moves from bottom to top. .

  FIG. 7A shows a case where motion detection is performed with a macro block of 16 × 16 pixels. Since the ratio of the stipple circle in the encoding target block shown in FIG. 7B is large, the movement from the encoding target block indicated by the thick dotted line frame in FIG. 7A to the position indicated by the thick solid line frame A white arrow indicating is detected as a motion vector. When motion compensation is performed using this motion vector, a hatched portion in FIG. 7A becomes a prediction error between images.

  FIG. 7C shows an example in which the macroblock is divided into 16 × 8 pixel regions, and motion detection is performed for each. Since the proportion of the stipple circle is large in the lower area, the same motion detection as in FIG. 7A is performed, and a left-pointing white arrow is detected as a motion vector. On the other hand, the upper region captures the motion of the striped background, and an upward white arrow indicating movement to a position directly above the block to be encoded is detected as a motion vector. When motion compensation is performed using these two motion vectors, a hatched portion in FIG. 7C becomes a prediction error between images.

  Conventional MPEG-4 AVC / H. When motion detection is performed according to the type of macroblock defined by H.264, the number of occurrences of prediction errors increases in the case of 16 × 16 pixels, and coding efficiency decreases. On the other hand, when divided vertically into 16 × 8 pixels, the number of predicted pixel occurrences is smaller than that in a 16 × 16 pixel unit, and the coding efficiency is improved. However, motion information such as a motion vector is added to each upper and lower region. It is necessary to encode and transmit.

  In this embodiment, when the macroblock to be encoded is divided in this way, the movement of the divided area is similar to the movement of the encoded surrounding macroblock adjacent to the upper side or the left side of the division boundary. Assuming that, the motion information of surrounding macroblocks is referred to.

  FIGS. 8A and 8B are diagrams for explaining a method of motion detection by the second motion vector detection unit 110 according to the present embodiment.

  FIG. 8B is a picture to be encoded at time t1, and a macroblock composed of 16 × 16 pixels to be encoded is indicated by a thick dotted line, and four encoded data around the encoding target block are shown. The block is indicated by a thin dotted line. FIG. 8A shows a picture at time t0, which is used as a reference picture for motion prediction of the current picture in FIG. 8B. As shown in FIGS. 7 (a) and 7 (b), from time t0 to time t1, the stipple circle in the picture is translated from left to right, and the background stripe pattern is from top to bottom. Has moved to.

  FIG. 8A shows a state in which the encoding target block is divided into regions, and motion detection is performed for each of the divided regions. When the macroblock to be encoded is divided horizontally, the area above the boundary of the horizontal division is adjacent to the block above or to the left of the area below the boundary. It often shows the same movement as a finished macroblock. Therefore, assuming that the upper region is the same as the motion of the surrounding macroblock immediately above, motion compensation is performed using the motion vector of the macroblock immediately above indicated by the black arrow in FIG. Since this motion vector is obtained by surrounding macroblocks and it is not necessary to perform encoding / transmission, the amount of codes can be suppressed.

  The second motion vector detection unit 110 obtains the motion vector of the divided region of the encoding target macroblock using the motion information of the encoded surrounding macroblock adjacent to the encoding target macroblock in this way. . Which motion vector of neighboring macroblocks to use is determined based on the division direction of the macroblock to be encoded.

  FIGS. 9A and 9B are diagrams illustrating a method for selecting surrounding macroblocks that refer to motion vectors based on the direction in which the macroblocks are divided.

  As shown in FIG. 9A, the encoding target macroblock is divided in the horizontal direction, the second motion vector detection unit 110 obtains the second motion vector MV2 for the upper region, and the first motion vector for the lower region. The detection unit 102 obtains the first motion vector MV1. At this time, it is presumed that the upper region shows a similar motion to the macroblock MBB immediately above it, so the second motion vector detection unit 110 refers to the motion vector of the macroblock MBB directly above as motion information. To do.

  Various types of encoded macroblock information are stored in the memory 107, and the second motion vector detection unit 110 should refer to the memory 107 based on the address corresponding to the position of the macroblock to be encoded. Information on the surrounding macroblock MBB can be read. The second motion vector detection unit 110 sets the read motion vector MVB of the surrounding macroblock MBB as the second motion vector MV2 for the upper region of the macroblock to be encoded.

  Here, when the macroblock type of the surrounding macroblock MBB is an intra-frame coding (intra) type, there is no motion vector, so the left macroblock MBA or the macroblock on the upper right as the surrounding macroblock to be referred to MBC may be used instead, and the motion vectors of macroblocks MBA and MBC may be used as second motion vector MV2 for the upper region of the macroblock to be encoded.

  As shown in FIG. 9B, when the macroblock to be encoded is divided in the vertical direction and the second motion vector detection unit 110 obtains a motion vector for the left region, the left region is a macroblock MBA adjacent to the left. Therefore, the second motion vector detection unit 110 reads out the motion vector of the left macroblock MBA as the motion information from the memory 107 and refers to it. The second motion vector detection unit 110 sets the read motion vector MVA of the surrounding macroblock MBA as the second motion vector MV2 for the left region of the macroblock to be encoded.

  FIG. 10 is a diagram illustrating another method of selecting surrounding macroblocks that refer to motion vectors. In FIG. 9 (a), a macro block MBB located immediately above the upper region of the macro block to be encoded is selected, and the motion vector MVB of the macro block MBB is selected as the second motion vector for the upper region. It was set as MV2. In FIG. 10, the selection range of the encoded surrounding macroblock is expanded, and the motion vectors MVA, MVB, MVC, and MVD of four adjacent surrounding macroblocks MBA, MBB, MBC, and MBD are used as the second motion vector for the upper region. Let it be a candidate for MV2. The second motion vector detection unit 110 sets any one of these four motion vectors as the second motion vector MV2 for the upper region.

  Returning to FIG. 1, the region segmentation / motion compensation unit 103 is stored in the memory 107 using the motion vectors of the temporary regions detected by the first motion vector detection unit 102 and the second motion vector detection unit 110. Motion compensation prediction is performed from the reference image. The region segmentation / motion compensation unit 103 synthesizes a plurality of motion compensated prediction images generated from the motion vectors of the temporary regions in a procedure described later to generate a combined motion compensated prediction image.

  FIGS. 11A and 11B show motion compensated prediction images generated from motion vectors detected for each temporary region. FIGS. 12A to 12C show synthesized motion compensated predicted images obtained by synthesizing motion compensated predicted images generated from the motion vectors of the temporary regions.

  An example will be described in which the temporary region dividing unit 101 tentatively divides a macroblock at the horizontal boundary of the fourth pixel from the top as shown in FIG. As illustrated in FIG. 5, the motion vector detection unit 102 detects motion vectors for each of the 16 × 4 upper region and the 16 × 12 lower region, and as a result, the motion target macroblock includes two motion vectors ( There are first and second motion vectors). As shown in FIGS. 11A and 11B, the region dividing / motion compensating unit 103 uses a reference image for each motion vector detected by the motion vector detecting unit 102, and temporarily determines the size of the macroblock. Then, an image in the case of motion compensation prediction is generated at (here, 16 × 16). FIG. 11A is a first motion-compensated prediction image generated using the first motion vector of the 16 × 4 upper region, and FIG. 11B is a second image of the lower region of 16 × 12. It is the 2nd motion compensation prediction picture generated using a motion vector.

  The region segmentation / motion compensation unit 103 synthesizes the first and second motion compensated prediction images shown in FIGS. 11A and 11B into any one of the patterns (a) to (c) shown in FIG. Thus, a combined motion compensated prediction image is generated. The first and second motion compensated prediction images are the same size as the encoding target macroblock, and are divided at a certain boundary in order to generate a combined motion compensation prediction image. The boundary of the macroblock determined by the region dividing / motion compensating unit 103 is referred to as “actual boundary”, the region of the macroblock divided by the boundary is referred to as “actual region”. It is distinguished from “temporary boundary” and “temporary region” determined by the region dividing unit 101.

  FIGS. 12A to 12C show main boundary candidates determined by the main region dividing / motion compensating unit 103. FIG. 12A, the horizontal boundary of the fourth pixel from the top is the main boundary, FIG. 12B is the horizontal boundary of the eighth pixel from the top, and FIG. 12C is the twelfth pixel from the top. With the horizontal boundary as the main boundary, the main region above the main boundary is represented by the region corresponding to the first motion compensated prediction image, and the main region below the main boundary is represented by the region corresponding to the second motion compensated prediction image. Is.

  The main region dividing / motion compensating unit 103 determines the main boundary based on the evaluation value indicating the edge strength and the like, and divides and synthesizes the first and second motion compensated prediction images at the determined main boundary.

  FIGS. 13A to 13C are diagrams illustrating a method of generating a combined motion compensated prediction image by combining motion compensated prediction images generated from the motion vectors of the temporary regions. After the boundary determination, the main segmentation / motion compensation unit 103 determines the first motion compensated prediction image corresponding to the first motion vector in FIG. 13A and the second motion vector corresponding to the second motion vector in FIG. Using the motion compensated prediction image, motion compensation prediction is performed using the region above the main boundary as the first motion compensation prediction image, and the region below the main boundary is used as the second motion compensation prediction image. In this example, the corresponding region of the first motion compensated prediction image is duplicated in the 16 × 4 region above the main boundary, and the second motion compensated prediction image is reproduced in the 16 × 12 region below the main boundary. The corresponding region of is duplicated.

  Up to this point, horizontal region division has been described as an example of two divisions. However, region division does not necessarily exist only in the horizontal direction inside the macroblock, and region division in the vertical direction is also conceivable. In addition, as in the case where prediction is performed in units of conventional 16 × 16 pixels, there may be a case where there is no region division within the macroblock 16 × 16 pixels. Therefore, the temporary region dividing unit 101, the first motion vector detecting unit 102, the second motion vector detecting unit 110, and the main region dividing / motion compensating unit 103 not only perform horizontal region division, but also perform vertical region division, It is necessary to perform motion detection for each of the regions without segmentation, and to determine the optimum motion vector and the region segmentation boundary.

  FIG. 14 is a flowchart showing three modes of motion detection and a process for obtaining an optimum value from motion vectors calculated in each mode. A motion vector is detected in each division mode in which the region is divided in the horizontal direction, the region is divided in the vertical direction, and no region is divided, and an optimum value is determined from the motion vectors calculated in each division mode.

  As indicated by the bold solid line, the processing of steps S201 and S202 is performed by the temporary region dividing unit 101, the processing of steps S203a and 203c is performed by the first motion vector detecting unit 102, and the processing of step S203b is performed by the second motion vector detecting unit. 110, and the region division / motion compensation unit 103 performs the processing of steps S204 to S209.

  In the horizontal division mode, the temporary area division unit 101 performs horizontal division temporary area detection (S201). The first motion vector detection unit 102, for the first temporary region that has the fewest sides adjacent to the encoded surrounding macroblock adjacent to the encoding target macroblock among the divided temporary regions, A first motion vector is detected (S203a). The second motion vector detection unit 110 detects the second motion vector for the second temporary area using the motion information of the surrounding macroblocks (S203b). Specifically, in the case of horizontal division, the motion vector of the immediately surrounding macroblock is set as the second motion vector of the second temporary area.

  Similarly, in the vertical division mode, the temporary area dividing unit 101 performs vertical division temporary area detection (S202). The first motion vector detection unit 102, for the first temporary region that has the fewest sides adjacent to the encoded surrounding macroblock adjacent to the encoding target macroblock among the divided temporary regions, A first motion vector is detected (S203a). The second motion vector detection unit 110 detects the second motion vector for the second temporary area using the motion information of the surrounding macroblocks (S203b). Specifically, in the case of vertical division, the motion vector of the left surrounding macroblock is set as the second motion vector of the second temporary area.

  In the case of no division, there is no division boundary in the macroblock, so motion detection is performed with the conventional 16 × 16 pixels. Since this process is equivalent to the case where the horizontal or vertical division position is the 0th pixel, the first motion vector detection unit 102 detects the first motion vector (S203c). In this case, since there is no region having the second motion vector, the second motion vector is not detected.

  The region segmentation / motion compensation unit 103 performs motion compensation prediction from the reference image stored in the memory 107 using the first motion vector and the second motion vector of each temporary region detected in each segment mode.

  In the horizontal division mode, the main region division / motion compensation unit 103 performs main division detection of the horizontal division (S204), and the first motion vector based on the first motion vector is detected in the horizontal main boundary. The synthesized motion compensated predicted image is generated by synthesizing the first motion compensated predicted image and the second motion compensated predicted image based on the second motion vector (S206). Since the second motion vector is determined based on the division direction in the first embodiment, in the horizontal division mode, the second motion compensated prediction image is generated using the second motion vector obtained by the horizontal division. . On the other hand, since the first motion compensated prediction image is generated using the first motion vector detected in each division mode, three types of first motion compensation prediction images are generated corresponding to the three division modes. Therefore, in the case of the horizontal division mode, three types of synthesized motion compensated predicted images are generated by synthesizing the second motion compensated predicted image with each of the three types of first motion compensated predicted images.

  In the case of the vertical division mode, the main region division / motion compensation unit 103 performs main division detection of the vertical division (S205), and the first motion vector based on the first motion vector is detected at the main boundary in the vertical direction. The synthesized motion compensated predicted image is generated by synthesizing the first motion compensated predicted image and the second motion compensated predicted image based on the second motion vector (S207). As in the case of the horizontal division mode, a second motion compensated prediction image is generated using the second motion vector obtained by the vertical division, and three types of first motion vectors are detected using the first motion vector detected in each division mode. A motion compensation predicted image is generated, and three types of synthesized motion compensated predicted images are generated by synthesizing the second motion compensated predicted image with each of the three types of first motion compensated predicted images.

  In the non-division mode, the region division / motion compensation unit 103 generates three types of motion compensated prediction images based only on the first motion vector in each division mode (S208).

  Since three types of combined motion compensated prediction images are generated in each of the horizontal division mode, the vertical division mode, and the no division mode, a total of nine types of combined motion compensated prediction images are generated.

  For the synthesized motion compensated prediction image generated in this way, the region segmentation / motion compensation unit 103 determines the presence / absence of region segmentation and the direction (if any), based on an evaluation value representing edge strength, which will be described later. The main boundary indicating the horizontal or vertical direction) and the region division position is determined (S209). The main region division / motion compensation unit 103 generates first and second motion compensated prediction images from the selected first and second motion vectors at the determined main boundary, and synthesizes them to perform final synthesis. A motion compensated prediction image is generated. The motion information such as the second motion vector determined by the region division / motion compensation unit 103 is stored in the memory 107 for use in the encoding process of the next macroblock.

  Here, the case has been described where the main boundary candidates are the three types of FIGS. 12A to 12C, but the main boundary candidates may be further increased. However, as described later, it is necessary to sufficiently consider the relationship with the orthogonal transform size of the orthogonal transform / quantization unit 104.

  Returning to FIG. 1, the subtraction unit 108 calculates a prediction residual component based on the difference between the original image to be encoded and the motion compensated prediction image calculated by the main region division / motion compensation unit 103, and generates an orthogonal transform / quantization unit. 104. The orthogonal transform / quantization unit 104 performs orthogonal transform / quantization of the prediction residual component.

  Here, the orthogonal transform / quantization unit 104 performs orthogonal transform using an orthogonal transform size corresponding to the size of motion compensation prediction. That is, when 16 × 4/16 × 8/16 × 12 (multiple of 4 in the vertical direction) is allowed as the size of motion compensation prediction, at least 16 × 4, 8 × 4, or 4 × 4 (vertical direction) An orthogonal transform size of a multiple of 4). As another example, when 16 × 2/16 × 4/16 × 6/16 × 8/16 × 10/16 × 12 (a multiple of 2 in the vertical direction) is allowed as the size of motion compensation prediction, at least An orthogonal transform size of 16 × 2 or 8 × 2 or 4 × 2 (a multiple of 2 in the vertical direction) can be used. As a result, when the prediction error of motion compensation prediction is orthogonally transformed, the motion compensation prediction boundary is not included in the prediction error set to be orthogonally transformed. As a result, it is possible to prevent a decrease in orthogonal transform efficiency caused by performing orthogonal transform together as a prediction error on pixels that straddle the boundary of motion compensation prediction, and the effect of further improving the coding efficiency is achieved.

  The variable length coding unit 105 performs variable length coding on the prediction residual component orthogonally transformed and quantized by the orthogonal transformation / quantization unit 104 and also selects the first motion selected by the region division / motion compensation unit 103. Variable-length encode the vector. Since the second motion vector detected by the second motion vector detection unit 110 is calculated with reference to an adjacent encoded macroblock, the same processing can be performed on the decoding side. Therefore, the second motion vector need not be encoded.

  The inverse quantization / inverse orthogonal transform unit 106 performs inverse orthogonal transform and inverse quantization on the prediction residual component orthogonally transformed / quantized by the orthogonal transform / quantization unit 104. Similar to the orthogonal transform / quantization unit 104, inverse orthogonal transform can be performed with a size corresponding to the size of motion compensation prediction.

  The adding unit 109 generates a reference image by adding the prediction residual component decoded by the inverse quantization / inverse orthogonal transform unit 106 and the motion compensated prediction image calculated by the region division / motion compensation unit 103. And stored in the memory 107.

  FIG. 2 is a block diagram illustrating a configuration of the moving picture decoding apparatus according to the first embodiment. The moving image decoding apparatus according to Embodiment 1 includes a variable length decoding unit 201, a main region division / motion compensation unit 203, an inverse quantization / inverse orthogonal transform unit 206, an addition unit 209, a memory 207, and a motion vector detection unit 210. Prepare.

  The variable length decoding unit 201 performs variable length decoding on the prediction residual component signal and the motion vector that have been orthogonally transformed and quantized. In the bit stream encoded by the moving image encoding device in FIG. 1, one motion vector is encoded for a macroblock, and a motion vector (“second” detected by a motion vector detection unit 210 described later is included. In order to avoid confusion with the “motion vector”), a motion vector decoded from the encoded stream is referred to as a “first motion vector”.

  The region segmentation / motion compensation unit 203 has the same function as the region segmentation / motion compensation unit 103 of the moving image encoding apparatus in FIG. 1, and the first motion vector and motion vector decoded by the variable length decoding unit 201. Using the second motion vector detected by the detection unit 210, motion compensation prediction is performed from the reference image stored in the memory 207. The region segmentation / motion compensation unit 203 performs a plurality of motion compensated prediction images generated from the motion vectors of each segment region in the same procedure as the region segmentation / motion compensation unit 103 of the video encoding device in FIG. A combined motion compensated prediction image is generated by combining.

  The inverse quantization / inverse orthogonal transform unit 206 has the same function as the inverse quantization / inverse orthogonal transform unit 106 of the moving image coding apparatus in FIG. 1, and uses the prediction residual component decoded by the variable length decoding unit 201. On the other hand, inverse orthogonal transform and inverse quantization are performed.

  The addition unit 209 adds the prediction residual component decoded by the inverse quantization / inverse orthogonal transformation unit 206 and the motion compensated prediction image calculated by the region division / motion compensation unit 203, thereby obtaining an image signal. Decrypt. The memory 207 is the same as the memory 107 of the moving image encoding apparatus in FIG. 1 and stores various information such as a decoded reference image and a decoded motion vector.

  The motion vector detection unit 210 has the same function as that of the second motion vector detection unit 110 of the moving picture encoding device in FIG. 1, and the motion information of the macroblock adjacent to the decoding target macroblock stored in the memory 207 The second motion vector is detected using this.

  Operations common to the moving image encoding apparatus and the moving image decoding apparatus having the above-described configuration, particularly operations of the region dividing / motion compensating unit 103 and the region dividing / motion compensating unit 203 will be described.

  The basic operation of the main region division / motion compensation unit 103 of the moving image encoding device and the main region division / motion compensation unit 203 of the moving image decoding device are the same, but the encoding device detects an optimal main division region. There is a first motion vector of each division mode that is a candidate for the operation, and the decoding apparatus is different in that only the first motion vector is decoded from the bit stream. For this reason, the encoding-side main region division / motion compensation unit 103 specifies a first motion vector obtained in each division mode for the decoding-side main region division / motion compensation unit 203, A storage unit for recording an evaluation value obtained from a motion compensated prediction image generated using one motion vector, a first motion vector of a division mode with the smallest evaluation value previously processed, and other information, and the above processing The difference is that a loop processing unit is provided for each division mode.

  Further, since the moving image decoding apparatus does not include the temporary area dividing unit 101 that performs the processes of steps S201 and S202 in FIG. 14, the motion vector detecting unit 210 of the moving image decoding apparatus is obtained by the main area dividing / motion compensating unit 203. The direction of the boundary candidate to be determined is determined, a block is selected from among the decoded blocks adjacent to the decoding target block according to the direction, a motion vector is detected using the motion information of the selected block, and Information on the determined boundary candidate direction is supplied to the region dividing / motion compensating unit 203, and the region dividing / motion compensating unit 203 finally determines the optimum boundary direction and position.

  In the following, a procedure for determining a main region that is a common part of the main region dividing / motion compensating unit 103 and the main region dividing / motion compensating unit 203 will be described.

  FIG. 15 is a flowchart for explaining the determination procedure of the main region by the main region division / motion compensation unit 103.

  First, a motion vector is detected for each of N (N ≧ 2) temporary regions divided by the temporary region dividing unit 101. Here, N = 2. Using the first motion vector detected by the first motion vector detection unit 102, motion compensation prediction is performed with the same size as the macroblock, and a first motion compensation predicted image is generated (S01). Using the second motion vector detected by the second motion vector detection unit 110, motion compensation prediction is performed with the same size as the macroblock, and a second motion compensation predicted image is generated (S02).

  Next, a candidate for this boundary, that is, a candidate for a position to divide the macroblock is set. In the case of horizontal division, 0-15th pixels below the left corner pixel of the macroblock are set as candidates for division positions, and in the case of vertical division, the 0-15th pixels rightward from the left corner pixels are set as candidates for division positions. To do.

  As a result of the boundary determination by horizontal or vertical region division, if this boundary coincides with the boundary with the adjacent surrounding macroblock, it is determined that there is no division. In this case, the division position corresponds to the 0th pixel. . When the division position is the 0th pixel, in order to determine the boundary with the adjacent surrounding macroblock, when calculating the difference between the pixels across the boundary in the following activity calculation steps (S004 to S007), Processing to acquire the pixel values of the surrounding macroblocks is necessary.

  The first to fourth activities shown in FIGS. 16A to 16D are calculated for each candidate of the set main boundary (S03 to S06). However, steps S03 to S06 can be performed in any order. Further, it is of course possible to calculate only the activity that is desired to be used for boundary evaluation without performing all of steps S03 to S06.

  First, as shown in FIG. 16A, a boundary activity (first activity) related to the boundary candidate is calculated for the first motion compensated prediction image (S03). Here, the absolute difference sum (SAD) between two pixels straddling the boundary candidate is used for the activity. Since the value of the first activity increases at the edge of the object, the prediction efficiency of the motion compensation prediction is improved by dividing the region at the corresponding boundary as the value increases. Similarly, as shown in FIG. 16B, a boundary activity (second activity) regarding the boundary candidate is calculated for the second motion compensated prediction image (S04). Similar to the first activity, the second activity improves the prediction efficiency of motion compensation prediction by dividing the region at the corresponding boundary as the value increases.

  Subsequently, as shown in FIG. 16C, motion compensation prediction is performed using the region above the main boundary candidate in the macroblock as the first motion compensated prediction image, and the region below the main boundary candidate is the second motion compensated prediction image. As for the synthesized motion compensated prediction image synthesized as follows, a boundary activity (third activity) related to this boundary candidate is calculated (S05). Since the third activity is the sum of absolute differences between two pixels straddling the boundary candidate, the absolute difference between the values of the pixels of the first motion compensated prediction image and the pixels of the second motion compensated prediction image located above and below the boundary candidate. The sum of Therefore, the smaller the value of the third activity, the smoother the boundary of the synthesized motion compensated prediction image, and the high frequency component is less likely to be generated in the prediction error signal, so that the prediction efficiency of motion compensation prediction is improved.

  Finally, as shown in FIG. 16D, a boundary activity (fourth activity) regarding the boundary candidate is calculated for the difference image between the first motion compensated predicted image and the second motion compensated predicted image (S06). Since the value of the fourth activity increases at the boundary of the object, the prediction efficiency of the motion compensation prediction is improved by dividing the region at the boundary as the value increases.

After all the activities used for the boundary evaluation are calculated, this boundary candidate is evaluated using a predefined evaluation value (S07). For example, the evaluation value is defined as follows.
Evaluation value = −A * ACT1-B * ACT2 + C * ACT3-D * ACT4
Here, ACT1 represents a first activity value, ACT2 represents a second activity value, ACT3 represents a third activity value, and ACT4 represents a fourth activity value. A, B, C, and D are constants of 0 or more.

  The evaluation value is calculated for all main boundary candidates, and the main boundary candidate having the minimum value is determined as the final main boundary (S08).

  Here, it is desirable that the main boundary and the temporary boundary are the same, but the determined main boundary is not necessarily the same as the temporary boundary. The temporary boundary for motion vector detection is a boundary for obtaining an optimal motion vector on the encoding side, and can be calculated using an original image to be encoded that can be used only on the encoding side. On the other hand, this boundary must be uniquely calculated on both the encoding side and the decoding side, and the calculated motion vector (transmitted on the decoding side) and its motion compensated prediction image (that is, the prediction residual component) Image before addition). For this reason, there is no mismatch between the encoding side and the decoding side even if the main boundary and the temporary boundary are not the same.

(Embodiment 2)
The moving picture coding apparatus according to the second embodiment has the same configuration as that of the moving picture coding apparatus according to the first embodiment shown in FIG. 1, but the second motion vector detecting unit 110 detects the second motion vector. Is different.

  FIGS. 17A and 17B are diagrams illustrating a second motion vector detection method performed by the second motion vector detection unit 110 of the video encoding device according to the second embodiment.

  As shown in FIG. 17 (a), three macroblocks MBA adjacent to the left, macroblock MBB immediately above, and macroblock MBC diagonally above right are three neighboring macroblocks adjacent to the macroblock to be encoded. Yes, the respective motion vectors are MVA, MVB and MVC.

  When encoding the motion vector of the macroblock to be encoded, the intermediate value vector PMV is determined from the motion vectors MVA, MVB and MVC of these three surrounding macroblocks MBA, MBB and MBC, and the macro to be encoded is determined. A difference value obtained by subtracting PMV from the motion vector of the block is calculated.

FIG. 17B is a diagram for explaining a method of obtaining the intermediate value vector PMV from the motion vectors MVA, MVB, and MVC of three surrounding macroblocks. The x component and y component of the motion vector of each surrounding macroblock are expressed as follows.
MVA = (MVAx, MVAy)
MVB = (MVBx, MVBy)
MVC = (MVCx, MVCy)

By taking the intermediate values of the X and Y components of the three motion vectors, the intermediate value vector PMV of the three surrounding macroblocks is expressed as follows in the case shown in FIG. The
PMV = med (MVA, MVB, MVC) = (MVAx, MVBy)
Here, the function med () is a function for calculating an intermediate value from the motion vector in parentheses.

  The determined intermediate value vector PMV is a value used to increase the encoding efficiency by taking the difference from the intermediate value vector PMV when encoding the motion vector of the macroblock to be encoded. It does not have a reference picture number for detection. Therefore, the intermediate value vector PMV cannot be used for generating a predicted image by motion compensation prediction like a normal motion vector.

Therefore, in Embodiment 2, a macroblock having a motion vector closest to the intermediate value vector PMV among the three surrounding macroblocks is determined, and the macroblock is set as a reference destination picture. For the determination, an absolute difference sum (SAD) of the intermediate value vector PMV and the motion vectors of the three surrounding macroblocks is obtained as in the following equation.
SADi = | MVix−PMVx | + | MViy−PMVy |
Here, the subscript i is one of the identifiers A, B, and C of the surrounding macro blocks MBA, MBB, and MBC, and PMVx and PMVy represent the x component and the y component of the intermediate value vector PMV.

  The motion vector of the surrounding macro block that minimizes the absolute difference sum SADi is selected by the above equation. For example, in the case shown in FIG. 17B, the absolute difference sum SADi with the intermediate value vector PMV is the minimum for the motion vector MBV of the macroblock MBB, and the second motion vector detection unit 110 This motion vector MBV is detected as the second motion vector for the upper region of the macroblock to be encoded.

  Here, the absolute difference sum (SAD) between the intermediate value vector PMV and the motion vectors of the surrounding macroblocks is used as the evaluation value for determination, but the absolute square sum of the intermediate value vector PMV and the motion vectors of the surrounding macroblocks ( SSD) may be used, and is not particularly limited as long as it is a scale for measuring the similarity between the intermediate value vector PMV and the motion vectors of surrounding macroblocks.

  Next, the syntax of a moving image bit stream encoded by the moving image encoding apparatuses according to Embodiments 1 and 2 will be described.

  FIG. 18 shows a first syntax pattern based on the MPEG-4 AVC syntax. As shown in FIG. 18A, first, a first flag (use_auto_mc_size) indicating whether or not the shape of motion compensated prediction is automatically determined on the decoding side using the feature amount of the predicted image in units of slices is transmitted. When the first flag use_auto_mc_size is OFF, the macroblock is fixedly divided based on the macroblock type mb_type shown in FIG. 18B as before, and motion compensation prediction is performed. When the first flag use_auto_mc_size is ON, motion compensated prediction is performed by automatically determining the shape of motion compensated prediction on the decoding side using the feature amount of the predicted image. In the macro block unit, as in MPEG-4 AVC, mb_type is transmitted to determine the shape of motion compensation prediction.

  FIG. 19 shows a second syntax pattern for transmitting a second flag (auto_mc_size_enable) indicating whether the shape of motion compensated prediction is automatically determined on the decoding side not only at the slice level but also in macroblock units. When the second flag auto_mc_size_enable is OFF, as in the case where the first flag use_auto_mc_size is OFF at the slice level, the macroblock is fixedly divided based on the macroblock type mb_type as before, and motion compensation prediction is performed. When the second flag auto_mc_size_enable is ON, motion compensated prediction is performed by automatically determining the shape of motion compensated prediction on the decoding side using the feature amount of the predicted image. When the second syntax is used, it is possible to prevent the prediction efficiency from being lowered by automatically determining the main boundary of the macroblock.

  FIG. 20 shows a third syntax pattern for switching an algorithm for automatically determining the shape of motion compensation prediction at the slice level on the decoding side. When the first flag use_auto_mc_size is ON for each slice, a third flag auto_mc_algorithm indicating the algorithm type for automatically determining the shape of motion compensated prediction on the decoding side is transmitted. For example, when the third flag auto_mc_algorithm = 0, the shape of the motion compensation prediction is determined based on the evaluation value using all of the first to fourth activities ACT1 to ACT4. When the algorithm type auto_mc_algorithm = 1, the shape of the motion compensation prediction is determined based on the evaluation value using only the first to third activities ACT1 to ACT3 excluding the fourth activity ACT4. In this way, by associating the type of activity used with the value of the third flag auto_mc_algorithm, the algorithm for determining the shape of the motion compensation prediction can be switched. When the third syntax is used, it is possible to determine an optimal algorithm type on the encoding side and to perform automatic segmentation on the decoding side, thereby further improving the encoding efficiency.

  FIG. 21 shows a fourth syntax pattern for transmitting a fourth flag boundary_direc_mode indicating whether or not the decoding side automatically determines the presence / absence and the direction of region division for each macroblock. There are two methods as the syntax of the fourth flag boundary_direc_mode. The first method fixes the code amount of the fourth flag boundary_direc_mode, and presets the presence / absence and direction of region division for the value of the fourth flag boundary_direc_mode. The second method is to change the meaning of the fourth flag boundary_direc_mode and the code amount according to the state of the decoded surrounding macroblock adjacent to the macroblock to be decoded on the decoding side. It is to encode.

  In the first method, the fourth flag boundary_direc_mode is represented by a combination of a total of 2 bits, that is, a first bit indicating the presence or absence of area division and a second bit indicating the division direction. FIG. 22 is a table showing an example of the meaning of the value of the fourth flag boundary_direc_mode. The value of the fourth flag boundary_direc_mode is represented by a decimal number, and the value in parentheses is represented by a binary number. Of the 2-bit signal of the fourth flag boundary_direc_mode, the upper bit is configured as a first bit indicating the presence / absence of region division, and the lower bit is configured as a second bit indicating the division direction.

  When the fourth flag boundary_direc_mode is “0”, it is the same as when the first flag use_auto_mc_size is turned OFF at the slice level, and motion compensation prediction is performed without segmentation. When the second flag auto_mc_size_enable is ON, it is limited to horizontal or vertical region division according to the value of the fourth flag boundary_direc_mode, performs motion compensation prediction, and uses the feature amount of the predicted image to change the shape of motion compensation prediction. Automatically determined on the decryption side.

  In the second method, the meaning of the fourth flag boundary_direc_mode is changed according to the decoding information held by the decoded surrounding macroblock adjacent to the decoding target macroblock. Here, the state of surrounding macroblocks determined as reference destinations of motion vectors in Embodiment 1 will be described as an example. The code length and the meaning of the code that the fourth flag boundary_direc_mode can take are changed according to the state of the macroblock immediately above and the macroblock on the left adjacent to the macroblock to be decoded. When both the macroblock immediately above and the macroblock on the left are valid, that is, with motion information, there are three possibilities for area division: no division, horizontal division, and vertical division. Each state is expressed by 2 bits. For example, “0” indicates no division, “1” indicates horizontal division, and “2” indicates vertical division.

  If either the macroblock immediately above or the macroblock on the left is valid, that is, it has motion information, it is possible to grasp the valid macroblock as a reference destination, the division direction is uniquely determined, and the region The division is limited to two states with no division or with division. In this case, the two states are represented by 1 bit, for example, “0” indicates no division and “1” indicates that there is division.

  If the macroblock directly above and the macroblock on the left are both invalid, for example, if the type of both macroblocks is the intra-frame coding mode (intra mode) and there is no motion information, the region division process may not be performed. Determined uniquely. In this case, the fourth flag boundary_direc_mode is not transmitted, and is the same as when the first flag use_auto_mc_size is turned OFF at the slice level, and motion compensation prediction is performed without segmentation.

  When the fourth syntax is used, it is possible to improve the efficiency of the process of automatically determining the main boundary on the decoding side and to prevent the decoding side from erroneously determining the main boundary.

  As described above, according to the embodiment of the present invention, region division is performed on a macroblock to be encoded, and motion compensation prediction is performed using motion information of surrounding macroblocks that have been encoded. As a result, the amount of code required for transmission of motion information is suppressed, and appropriate motion compensation is performed in each divided region, so that prediction errors can be reduced, and encoding efficiency and image quality are improved. .

  In the embodiment, unidirectional prediction used in MPEG P pictures and the like has been described, but the present invention is also applied to bidirectional prediction (usually forward prediction and backward prediction) used in B pictures and the like. Is possible.

  In the embodiment, in the second motion vector detection unit 110 of the encoding device and the motion vector detection unit 210 of the decoding device, neighboring macroblocks referred to by the macroblock to be encoded are adjacent to each other in the same picture. However, it may be selected from pictures that are close in time. For example, a method of detecting the second motion vector using the motion information of a macroblock of a picture close in time that is at the same position as the macroblock to be encoded can be considered.

  The above processing relating to encoding and decoding can be realized as a transmission, storage, and reception device using hardware, and is stored in a ROM (Read Only Memory), a flash memory, or the like. It can also be realized by firmware or software such as a computer. The firmware program and software program can be recorded 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. .

  101 Temporary region dividing unit, 102 First motion vector detecting unit, 103 Region dividing / motion compensating unit, 104 Orthogonal transformation / quantization unit, 105 Variable length coding unit, 106 Inverse quantization / inverse orthogonal transformation unit, 107 Memory , 108 subtraction unit, 109 addition unit, 110 second motion vector detection unit, 201 variable length decoding unit, 203 area division / motion compensation unit, 206 inverse quantization / inverse orthogonal transform unit, 207 memory, 209 addition unit, 210 Motion vector detection unit.

Claims (6)

A temporary area dividing unit that divides the encoding target block into a plurality of temporary areas at a predetermined temporary boundary;
A first motion vector detection unit that detects a motion vector of a first temporary region that has a minimum portion in contact with an encoded block adjacent to the encoding target block by motion estimation between images;
A second motion vector detection unit that detects a motion vector using motion information of an encoded block adjacent to the encoding target block for each of the temporary regions other than the first temporary region;
A plurality of prediction blocks corresponding to the coding target block is generated from a reference image using a motion vector of each temporary region, a main boundary is determined based on activities of the plurality of prediction blocks, and each prediction block is A motion compensation unit that generates a combined prediction block by combining regions obtained by dividing the boundary between the prediction blocks;
A moving picture encoding apparatus comprising: a prediction difference block obtained by subtracting the combined prediction block from the encoding target block; and an encoding unit that encodes a motion vector of a first temporary area.   The second motion vector detection unit selects a block from encoded blocks adjacent to the encoding target block according to a division direction of the encoding target block divided by the temporary region dividing unit. The moving picture coding apparatus according to claim 1, wherein a motion vector is detected using the motion information of the selected block.   The second motion vector detection unit generates an intermediate value vector from a motion vector of an encoded block adjacent to the encoding target block, and selects the intermediate vector from the encoded blocks adjacent to the encoding target block. The moving picture coding apparatus according to claim 1, wherein a block having a motion vector closest to a value vector is selected, and a motion vector is detected using motion information of the selected block.   The activity of the prediction block is a boundary activity obtained by evaluating a pixel value of each pixel adjacent through a main boundary into which the prediction block is divided. Video encoding device. Dividing the block to be encoded into a plurality of temporary regions at a predetermined temporary boundary;
Detecting a motion vector of a first provisional region having a minimum portion in contact with an encoded block adjacent to the encoding target block by motion estimation between images;
Detecting a motion vector using motion information of an encoded block adjacent to the encoding target block for each of the temporary regions other than the first temporary region;
A plurality of prediction blocks corresponding to the coding target block is generated from a reference image using a motion vector of each temporary region, a main boundary is determined based on activities of the plurality of prediction blocks, and each prediction block is Generating a synthesized prediction block by combining regions obtained by dividing at the boundary between the prediction blocks;
A moving picture coding method comprising: a prediction difference block obtained by subtracting the combined prediction block from the coding target block; and a step of coding a motion vector of a first temporary area. A function of dividing the block to be encoded into a plurality of temporary areas at a predetermined temporary boundary;
A function of detecting a motion vector of a first temporary region with a minimum portion in contact with an encoded block adjacent to the encoding target block by motion estimation between images;
A function for detecting a motion vector using motion information of an encoded block adjacent to the encoding target block for each of the temporary regions other than the first temporary region;
A plurality of prediction blocks corresponding to the coding target block is generated from a reference image using a motion vector of each temporary region, a main boundary is determined based on activities of the plurality of prediction blocks, and each prediction block is A function of generating a combined prediction block by combining regions obtained by dividing at the boundary between the prediction blocks;
A moving picture coding program that causes a computer to realize a prediction difference block obtained by subtracting the synthesized prediction block from the coding target block and a motion vector of a first temporary area.