JP7702228B2 - Image decoding device, image decoding method and program - Google Patents

Description

The present invention relates to an image decoding device, an image decoding method, and a program.

Non-Patent Document 1 and Non-Patent Document 2 disclose the geometric partitioning mode (GPM). GPM divides a rectangular block diagonally into two parts and motion compensates each part. Specifically, each divided small area is motion compensated by a motion vector and then combined by weighted averaging.

ITU-T H.266/VVC CE4:Summary report on Interprediction with geometric partitioning, JVET-Q0024

In Non-Patent Document 1 and Non-Patent Document 2, the motion vectors of the two divided small regions are specified by two indexes (cu_mv_idx0 and cu_mv_idx1) for one motion vector candidate list.

In this case, if the same motion vector were used, there would be no point in dividing the block, so there is a restriction that cu_mv_idx0 and cu_mv_idx1 cannot take the same value.

In order to improve the coding efficiency by taking advantage of such constraints, Non-Patent Documents 1 and 2 devise a method for shortening the code length representing cu_mv_idx1 when decoding cu_mv_idx1 by treating the value selected by cu_mv_idx0 as if it had disappeared from the motion vector candidate list.

However, when cu_mv_idx1 is smaller than cu_mv_idx0, there is no effect, so there is room for improvement in encoding performance. Therefore, the present invention has been made in consideration of the above-mentioned problems, and aims to provide an image decoding device, an image decoding method, and a program that can improve encoding efficiency in GPM.

The first feature of the present invention is an image decoding device, comprising: a decoding unit that decodes control information and a quantized value; an inverse quantization unit that inversely quantizes the quantized value to obtain a transform coefficient; an inverse transform unit that inversely transforms the transform coefficient to obtain a prediction residual; an intra prediction unit that generates a first predicted pixel based on a decoded pixel and the control information; a storage unit that stores the decoded pixel; an MV decoding unit that determines a motion vector to obtain motion information based on a plurality of indexes and a motion vector candidate list included in the control information; a motion compensation unit that generates a second predicted pixel based on the decoded pixel, the motion information, and the control information; a synthesis unit that generates a third predicted pixel based on the second predicted pixel and the control information; and an adder that adds one of the first to third predicted pixels and the prediction residual to obtain a decoded pixel, and the MV decoding unit reconstructs the plurality of indexes according to the magnitude relationship of the plurality of indexes.

The second feature of the present invention is an image decoding method comprising: step A of decoding control information and a quantized value; step B of inversely quantizing the quantized value to obtain a transform coefficient; step C of inversely transforming the transform coefficient to obtain a prediction residual; step D of generating a first predicted pixel based on a decoded pixel and the control information; step E of accumulating the decoded pixel; step F of determining a motion vector based on a plurality of indexes and a motion vector candidate list included in the control information to obtain motion information; step G of generating a second predicted pixel based on the decoded pixel, the motion information, and the control information; step H of generating a third predicted pixel based on the second predicted pixel and the control information; and step I of adding any one of the first to third predicted pixels and the prediction residual to obtain a decoded pixel, and the gist of the method is that in step F, the plurality of indexes are reconstructed according to the magnitude relationship of the plurality of indexes.

The third feature of the present invention is a program for making a computer function as an image decoding device, the image decoding device including a decoding unit that decodes control information and a quantized value, an inverse quantization unit that inversely quantizes the quantized value to obtain a transform coefficient, an inverse transform unit that inversely transforms the transform coefficient to obtain a prediction residual, an intra prediction unit that generates a first predicted pixel based on a decoded pixel and the control information, a storage unit that stores the decoded pixel, an MV decoding unit that determines a motion vector to obtain motion information based on a plurality of indexes and a motion vector candidate list included in the control information, a motion compensation unit that generates a second predicted pixel based on the decoded pixel, the motion information, and the control information, a synthesis unit that generates a third predicted pixel based on the second predicted pixel and the control information, and an adder that adds one of the first to third predicted pixels and the prediction residual to obtain a decoded pixel, and the MV decoding unit reconstructs the plurality of indexes according to the magnitude relationship of the plurality of indexes.

The present invention provides an image decoding device, an image decoding method, and a program that can improve the coding efficiency in GPM.

FIG. 1 is a diagram showing an example of functional blocks of an image decoding device 200 according to an embodiment. FIG. 2 is a diagram showing an example of a case in which a rectangular unit block is divided into two small regions A and B by a division boundary. FIG. 3 is a diagram showing an example of neighboring blocks of a current block to be decoded. FIG. 4 is a diagram for explaining an example of a method for reconstructing a motion vector candidate list by the MV decoding unit 205 of the image decoding device 200 according to an embodiment. FIG. 5 is a diagram showing examples of combinations that two indexes (cu_mv_idx0 and cu_mv_idx1) can take, and codes transmitted as control information for each combination. FIG. 6 is a diagram showing examples of combinations that two indexes (cu_mv_idx0 and cu_mv_idx1) can take, and codes transmitted as control information for each combination. FIG. 7 is a flowchart showing an example of the operation of the image decoding device 200 according to an embodiment. FIG. 8 is a flowchart showing an example of the operation of the image decoding device 200 according to an embodiment.

The following describes embodiments of the present invention with reference to the drawings. Note that the components in the following embodiments can be replaced with existing components as appropriate, and various variations, including combinations with other existing components, are possible. Therefore, the description of the following embodiments does not limit the content of the invention described in the claims.

First Embodiment
An image decoding device 200 according to this embodiment will be described below with reference to Figures 1 to 8. Figure 1 is a diagram showing an example of functional blocks of the image decoding device 200 according to this embodiment.

As shown in FIG. 1, the image decoding device 200 has a code input unit 210, a decoding unit 201, an inverse quantization unit 202, an inverse transform unit 203, an intra prediction unit 204, an MV decoding unit 205, an adder 206, an accumulation unit 207, a motion compensation unit 208, a synthesis unit 209, and an image output unit 220.

The code input unit 210 is configured to acquire code information encoded by the image encoding device.

The decoding unit 201 is configured to decode the control information and the quantization value from the code information input from the code input unit 210. For example, the decoding unit 201 is configured to output the control information and the quantization value by performing variable length decoding on the code information.

Here, the quantized value is sent to the inverse quantization unit 202, and the control information is sent to the intra prediction unit 204, the MV decoding unit 205, the motion compensation unit 208, and the synthesis unit 209. Note that such control information includes information necessary for controlling the intra prediction unit 204, the MV decoding unit 205, the motion compensation unit 208, and the synthesis unit 209, etc., and may include header information such as a sequence parameter set, a picture parameter set, a picture header, and a slice header.

The inverse quantization unit 202 is configured to inverse quantize the quantized values sent from the decoding unit 201 to obtain decoded transform coefficients. These transform coefficients are sent to the inverse transform unit 203.

The inverse transform unit 203 is configured to inverse transform the transform coefficients sent from the inverse quantization unit 202 to generate decoded prediction residuals. These prediction residuals are sent to the adder 206.

The intra prediction unit 204 is configured to generate a first predicted pixel based on the decoded pixel and the control information sent from the decoding unit 201. Here, the decoded pixel is obtained via the adder 206 and stored in the storage unit 207. The first predicted pixel is a predicted pixel that is an approximation of an input pixel in a small area set by the synthesis unit 207. The first predicted pixel is sent to the adder 206.

The storage unit 207 is configured to cumulatively store the decoded pixels sent from the adder 206. These decoded pixels are referenced by the motion compensation unit 208 via the storage unit 207.

The motion compensation unit 208 is configured to generate a second predicted pixel based on the decoded pixels stored in the storage unit 207 and the motion information sent from the MV decoding unit 205. Here, the second predicted pixel is a predicted pixel that is an approximation of an input pixel in a small area set by the synthesis unit 207. The second predicted pixel is sent to the synthesis unit 209.

The adder 206 is configured to add one of the first to third predicted pixels generated from the decoded pixels, etc., to the prediction residual sent from the inverse transform unit 203 to obtain a decoded pixel. Such a decoded pixel is sent to the image output unit 220, the storage unit 207, and the intra prediction unit 204.

The synthesis unit 209 is configured to divide the block to be decoded into a plurality of shapes based on the second predicted pixels sent from the motion compensation unit 208 and the control information decoded by the decoding unit 201, synthesize the corresponding plurality of predicted pixels, and generate a third predicted pixel to be added to the prediction residual by the adder 206. The generated third predicted pixel is sent to the adder 206.

The synthesis unit 209 can use any method to divide and synthesize the block to be decoded into multiple shapes (small regions), but the following describes the use of the geometric partitioning mode (GPM) as an example.

The following describes how the MV decoding unit 205 reconstructs the indexes in the motion vector candidate list.

The MV decoding unit 205 is configured to determine a motion vector from the control information from the decoding unit 201 and send the motion vector to the motion compensation unit 208 as motion information.

Here, the MV decoding unit 205 is configured to determine a motion vector and use it as motion information based on multiple (in this embodiment, two) indexes (cu_mv_idx0 and cu_mv_idx1 described below) included in the control information and the motion vector candidate list (see Figure 4, etc.).

Specifically, the MV decoding unit 205 is configured to reconstruct the two indexes depending on the magnitude relationship between the two indexes, as described below.

The example in Figure 2 shows a case where unit blocks are distributed in a diagonal shape. In the example in Figure 2, a rectangular unit block (block to be decoded) is divided into two small regions A and B by a division boundary.

In each small area A/B, a second predicted pixel is generated by motion compensation. At this time, in order to reduce the amount of code for the motion vector itself used for motion compensation, a method of reusing the motion vector of a neighboring block of the block to be decoded can be used as a conventional method.

This method improves coding efficiency because the amount of code required to represent the motion vector itself using an index corresponding to the motion vector of the neighboring block being used is smaller than the amount of code required to represent the motion vector itself.

Specifically, as shown in Figure 3, since there are multiple neighboring blocks, such as above, to the left, and above left, a motion vector candidate list is constructed by listing the motion vectors of available neighboring blocks and eliminating similar motion vectors.

Then, only the index corresponding to the motion vector of the neighboring block used by the motion compensation unit 208 is decoded as control information, and the motion vector is determined based on this control information.

However, in the synthesis unit 209, since there are multiple small regions A/B and a motion vector is used in each small region A/B, two indexes (cu_mv_idx0 and cu_mv_idx1) are required.

In the following, in this embodiment, the index corresponding to the motion vector of the neighboring block selected for small area A is referred to as "cu_mv_idx0 (first index)," and the index corresponding to the motion vector of the neighboring block selected for small area B is referred to as "cu_mv_idx1 (second index)."

Here, if the multiple motion vectors used in the synthesis unit 209 (the motion vector of sub-region A and the motion vector of sub-region B) are the same, there is no point in dividing the sub-regions into A and B. Therefore, a constraint is imposed that the two indexes (cu_mv_idx0 and cu_mv_idx1) selected for sub-regions A and B must be different.

Conventionally, in order to reduce the code length representing cu_mv_idx1 of the two indexes, cu_mv_idx1 was coded after excluding the motion vector selected by cu_mv_idx0 from the motion vector candidate list.

Below, with reference to FIG. 4, an example of a method for reconstructing a motion vector candidate list in this embodiment is described.

As shown in FIG. 4, when the first motion vector in the motion vector candidate list is selected as cu_mv_idx0, the first motion vector is removed from the motion vector candidate list, and the second and subsequent motion vectors in the motion vector candidate list are moved up one by one.

Therefore, if the fourth motion vector before the exclusion of the first motion vector is selected as cu_mv_idx1, the index corresponding to the third motion vector can be encoded and decoded as the control information.

In other words, if cu_mv_idx0 is smaller than cu_mv_idx1, cu_mv_idx1 will be a number one smaller, and the amount of code for cu_mv_idx1 coded using variable length code will be reduced.

However, if cu_mv_idx0 is greater than cu_mv_idx1, removing cu_mv_idx0 from the motion vector candidate list does not affect cu_mv_idx1, so there is a problem in that the amount of code for cu_mv_idx1 is not reduced.

To solve this problem, in this embodiment, the MV decoding unit 205 may be configured to exclude the smaller of the two indexes from the motion vector candidate list, and then determine the motion vector corresponding to the larger of the two indexes.

Specifically, the image encoding device reconstructs the two indexes, i.e., cu_mv_idx0 and cu_mv_idx1, by comparing them and subtracting 1 from the larger index.

On the other hand, on the image decoding device 200 side, the MV decoding unit 205 is configured to reconstruct the two indexes, i.e., cu_mv_idx0 and cu_mv_idx1, by comparing the two indexes and adding 1 to the larger index.

In this case, if the difference between the indexes is 1 or -1 on the image encoding device side, subtracting 1 from the larger index will result in the two indexes having the same value, and the image decoding device 200 will not know to which of the two indexes to add 1.

Therefore, on the image encoding device side, a code representing an index for adding 1 (i.e., an index to which the addition process is applied) is assigned, and on the image decoding device 200 side, the MV decoding unit 205 is configured to decode the code representing the index for adding 1.

However, since the combination of "cu_mv_idx0=0" and "cu_mv_idx1=1" is most likely to be selected, in order to avoid an increase in the number of codes representing the indexes to which the addition process is applied, the MV decoding unit 205 sets the situation to decode the code representing the indexes to which the addition process is applied when the index combination is such that the difference between cu_mv_idx0 and cu_mv_idx1 is 1 or 2, rather than when the index combination is such that the difference between cu_mv_idx0 and cu_mv_idx1 is -1 or 1.

Specifically, on the image decoding device 200 side, when the difference obtained by subtracting cu_mv_idx1 from cu_mv_idx0 is 1 or 2, the MV decoding unit 205 decodes a 1-bit code representing the target to which the addition process is to be applied, determines the index to which the addition process is to be applied, and adds 1 to the determined index to determine two motion vectors.

Figure 5 shows possible combinations of two indexes (cu_mv_idx0 and cu_mv_idx1) and an example of the code transmitted as control information for each combination.

The numbers in the table shown in Figure 5 represent the control information when cu_mv_idx0 and cu_mv_idx1 each take a value between 0 and 9.

There are no diagonal elements that correspond to the cases where cu_mv_idx0 and cu_mv_idx1 are the same value, so such diagonal elements are marked with an x instead of a sign.

In the upper triangular matrix corresponding to the case where cu_mv_idx0 is smaller than cu_mv_idx1, the value of cu_mv_idx0 itself and the value obtained by subtracting 1 from cu_mv_idx1 are encoded as control information.

Conversely, in the lower triangular matrix corresponding to the case where cu_mv_idx0 is greater than cu_mv_idx1, the value obtained by subtracting 1 from cu_mv_idx0 and the value of cu_mv_idx1 itself are encoded as control information.

However, in the case of an index combination where "cu_mv_idx0-cu_mv_idx1=1" or "cu_mv_idx0-cu_mv_idx1=2", a code indicating the index to which the addition process is applied is added to the control information.

For example, in the case of an index combination where "cu_mv_idx0-cu_mv_idx1=1", "cu_mv_idx0-1", "cu_mv_idx1", and "0" are encoded as control information in the image encoding device.

In addition, in the case of an index combination where "cu_mv_idx0-cu_mv_idx1=2", "cu_mv_idx0", "cu_mv_idx1-1", and "1" are encoded as control information in the image encoding device.

Here, the image decoding device 200 performs processing that is the reverse of that performed by the image encoding device.

That is, when cu_mv_idx0 is equal to or less than cu_mv_idx1, the MV decoding unit 205 in the image decoding device 200 adds 1 to cu_mv_idx1 and determines the motion vector indicated by each index from the motion vector candidate list.

On the other hand, if cu_mv_idx0 is greater than cu_mv_idx1, the MV decoding unit 205 first calculates the difference between cu_mv_idx0 and cu_mv_idx1.

Next, if the difference between cu_mv_idx0 and cu_mv_idx1 is 1, the MV decoding unit 205 decodes an additional bit (a code representing the index to which the addition process is applied) from the control information, and if the additional bit is 0, it uses cu_mv_idx0 and cu_mv_idx1 as is and determines the motion vector indicated by each index from the motion vector candidate list.

In addition, if the difference between cu_mv_idx0 and cu_mv_idx1 is 1 and the above-mentioned 1 bit is 1, or if the difference between cu_mv_idx0 and cu_mv_idx1 is 2 or more, the MV decoding unit 205 adds 1 to cu_mv_idx0 and determines the motion vector indicated by each index from the motion vector candidate list.

However, even if cu_mv_idx0 is greater than cu_mv_idx1 and the difference between cu_mv_idx0 and cu_mv_idx1 is 1, if cu_mv_idx0 contains the maximum index value ("9" in the example of FIG. 5), the MV decoding unit 205 does not need to decode the above-mentioned 1 bit and uses cu_mv_idx0 and cu_mv_idx1 as is to determine the motion vector indicated by each index from the motion vector candidate list.

As another example, as shown in FIG. 6, when cu_mv_idx0 and cu_mv_idx1 contain the value of "maximum value - 1 ("8" in the example of FIG. 6)", the MV decoding unit 205 may be configured to decode the above-mentioned 1 bit (a code representing the index to which the addition process is applied) from the control information.

With this configuration, when cu_mv_idx0 and cu_mv_idx1 contain the maximum index value ("9" in the example of FIG. 6), the image encoding device can intentionally add one bit to reduce the maximum values of cu_mv_idx0 and cu_mv_idx1 by one.

In other words, if cu_mv_idx0, cu_mv_idx1, and "maximum value - 1 ("8" in the example of FIG. 6)" all match, the MV decoding unit 205 decodes an additional bit from the control information, and if that bit is 1, it adds 1 to cu_mv_idx0 and determines the motion vector indicated by each index from the motion vector candidate list.

On the other hand, if cu_mv_idx0, cu_mv_idx1, and "maximum value - 1 ("8" in the example of Figure 6)" all match, and the above-mentioned 1 bit is 0, the MV decoding unit 205 adds 1 to cu_mv_idx1 and determines the motion vector indicated by each index from the motion vector candidate list.

In both the examples of Figures 5 and 6, the amount of code can be adaptively reduced according to the magnitude relationship between cu_mv_idx0 and cu_mv_idx1, and the coding efficiency can be improved by avoiding additional bits for index combinations with high selection rates.

Below, an example of the operation of the image decoding device 200 according to this embodiment will be described with reference to Figures 7 and 8.

Specifically, we will explain the motion vector decoding method and the control information to be decoded by the decoding unit 201 and the MV decoding unit 205 of the image decoding device 200 according to this embodiment.

The coding information input to the decoding unit 201 may include a sequence parameter set (SPS) that summarizes control information on a per-sequence basis. The coding information may also include a picture parameter set (PPS) or a picture header (PH) that summarizes control information on a per-picture basis. The coding information may also include a slice header (SH) that summarizes control information on a per-slice basis.

First, we will explain an example of the operation of the image decoding device 200 according to this embodiment shown in Figure 7.

As shown in FIG. 7, in step S101, the decoding unit 201 determines whether any of sps_div_enabled_flag, pps_div_enabled_flag, and sh_div_enabled_flag is 1.

If neither is 1, the operation proceeds to step S102 and ends without applying the technology of this embodiment.

If either is 1, in step S101, the decoding unit 201 determines whether the block to be decoded is in split mode.

If the block to be decoded is not in split mode, the operation proceeds to step S102 and ends without applying the technology according to this embodiment.

If the block to be decoded is in the split mode, in step S103, the decoding unit 201 determines whether the small area split from the block to be decoded is in intra prediction or MMVD (Merge mode with Motion Vector Difference) in which a discrete difference motion vector is added to a motion vector derived from a motion vector candidate list disclosed in Non-Patent Document 1.

If the answer is yes, the operation proceeds to step S102 and ends without applying the technology of this embodiment.

The reason is that if either of the above small regions is intra prediction, the above index comparison is not necessary.

In addition, if at least one of the above small regions is MMVD, even if the indexes point to the same motion vector candidate, the MMVD adds a discrete differential motion vector to the motion vector, so the motion vectors of each small region will no longer match, making it unnecessary to compare the indexes.

If the answer is No, in step S104, the MV decoding unit 205 decodes cu_mv_idx0, which is a signal that specifies an index of the motion vector candidate list, from the control information.

In step S105, the MV decoding unit 205 determines whether the maximum number of motion vector candidate lists (MaxNumGpmMergeCand) is greater than 2.

If it is 2 or less, the operation proceeds to step S102 and ends without applying the technology of this embodiment.

If it is greater than 2, in step S106, the MV decoding unit 205 decodes cu_mv_idx1, which is a signal that specifies the index of the motion vector candidate list, from the control information.

In step S107, the MV decoding unit 205 determines whether cu_mv_idx0 is less than or equal to cu_mv_idx1.

If the answer is Yes, the operation proceeds to step S114; if the answer is No, the operation proceeds to step S108.

In step S114, the MV decoding unit 205 adds 1 to cu_mv_idx1, determines the motion vectors indicated by cu_mv_idx0 and cu_mv_idx1 from the motion vector candidate list, and ends this operation.

In step S108, the MV decoding unit 205 determines whether the difference between cu_mv_idx0 and cu_mv_idx1 is 1.

If the answer is Yes, the operation proceeds to step S110; if the answer is No, the operation proceeds to step S109.

In step S109, the MV decoding unit 205 adds 1 to cu_mv_idx0, determines the motion vectors indicated by cu_mv_idx0 and cu_mv_idx1 from the motion vector candidate list, and ends this operation.

In step S110, the MV decoding unit 205 determines whether cu_mv_idx0 matches MAX_IDX, which indicates the maximum index value (the number of motion vector candidate lists minus 1).

If the answer is Yes, the operation proceeds to step S113; if the answer is No, the operation proceeds to step S111.

In step S113, the MV decoding unit 205 determines the motion vectors indicated by cu_mv_idx0 and cu_mv_idx1 from the motion vector candidate list, and then ends this operation.

In step S111, the MV decoding unit 205 decodes cu_add_idx, which is a signal that specifies whether or not to add 1 (a code that represents the index to which the addition process is applied).

In step S112, the MV decoding unit 205 determines whether cu_add_idx is 1 or not.

If the answer is Yes (if the answer is 1), the operation proceeds to step S113; if the answer is No (if the answer is 0), the operation proceeds to step S109.

Note that the condition separation in step S112 may be omitted by regarding cu_add_idx as taking the value of 0 or 1 and being added to cu_mv_idx0. In this case, the condition formula is as follows:
if (cu_mv_idx0 <= cu_mv_idx1){
cu_mv_idx1 += 1
} else {
if (cu_mv_idx0 - cu_mv_idx1 != 1){
cu_mv_idx0 += 1
} else {
if (cu_mv_idx0 != MAX_IDX) {
Decode cu_add_idx
cu_mv_idx0 += cu_add_idx
}
}

Secondly, an example of the operation of the image decoding device 200 according to this embodiment shown in FIG. 8 will be described, focusing on the differences from the operation of the image decoding device 200 according to this embodiment shown in FIG. 7 above.

Steps S201 to S206 shown in FIG. 8 are the same as steps S101 to S106 shown in FIG. 7.

As shown in FIG. 8, in step S207, the MV decoding unit 205 determines whether cu_mv_idx0 and cu_mv_idx1 match "MAX_IDX-1".

If the answer is Yes, the operation proceeds to step S214; if the answer is No, the operation proceeds to step S208.

In step S208, the MV decoding unit 205 determines whether cu_mv_idx0 is greater than cu_mv_idx1.

If the answer is Yes, the operation proceeds to step S210; if the answer is No, the operation proceeds to step S209.

In step S209, the MV decoding unit 205 adds 1 to cu_mv_idx1, determines the motion vectors indicated by cu_mv_idx0 and cu_mv_idx1 from the motion vector candidate list, and ends this operation.

In step S210, the MV decoding unit 205 determines whether the difference between cu_mv_idx0 and cu_mv_idx1 is 1.

If the answer is Yes, the operation proceeds to step S212; if the answer is No, the operation proceeds to step S211.

In step S211, the MV decoding unit 205 adds 1 to cu_mv_idx0, determines the motion vectors indicated by cu_mv_idx0 and cu_mv_idx1 from the motion vector candidate list, and ends this operation.

In step S212, the MV decoding unit 205 decodes cu_add_idx, which is a signal that specifies whether or not to add 1 (a code that represents the index to which the addition process is applied).

In step S213, the MV decoding unit 205 adds cu_add_idx (0 or 1) to cu_mv_idx0, determines the motion vectors indicated by cu_mv_idx0 and cu_mv_idx1 from the motion vector candidate list, and ends this operation.

In step S214, the MV decoding unit 205 decodes cu_add_idx.

In step S215, the MV decoding unit 205 determines whether cu_add_idx is 1 or not.

If the answer is Yes (if the answer is 1), the operation proceeds to step S217; if the answer is No (if the answer is 0), the operation proceeds to step S216.

In step S216, the MV decoding unit 205 adds 1 to cu_mv_idx1, determines the motion vectors indicated by cu_mv_idx0 and cu_mv_idx1 from the motion vector candidate list, and ends this operation.

In step S217, the MV decoding unit 205 adds 1 to cu_mv_idx0, determines the motion vectors indicated by cu_mv_idx0 and cu_mv_idx1 from the motion vector candidate list, and ends this operation.

Note that the condition separation in step S112 may be omitted by regarding cu_add_idx as taking the value of 0 or 1 and being added to cu_mv_idx0. In this case, the condition formula is as follows:
if (cu_mv_idx0 == MAX_IDX-1 && cu_mv_idx1 == MAX_IDX-1){
Decode cu_add_idx
if (cu_add_idx) {
cu_mv_idx0 += 1
} else {
cu_mv_idx1 += 1
}
} else {
if (cu_mv_idx0 > cu1_mv_idx1){
if (cu_mv_idx0 - cu_mv_idx1 == 1){
Decode cu_add_idx
cu_mv_idx0 += cu_add_idx
} else {
cu_mv_idx0 += 1
}
} else {
cu_mv_idx1 += 1
}
}

The image decoding device 200 according to this embodiment can improve coding efficiency by adaptively dividing blocks and decoding motion vectors according to the division shape.

The image decoding device 200 described above may be realized as a program that causes a computer to execute each function (each process).

In addition, according to this embodiment, for example, it is possible to realize an improvement in the overall service quality in video communication, which makes it possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, which is to "build resilient infrastructure, promote sustainable industrialization and foster innovation."

200... Image decoding device 201... Decoding unit 202... Inverse quantization unit 203... Inverse transform unit 204... Intra prediction unit 205... MV decoding unit 206... Adder 207... Storage unit 208... Motion compensation unit 209... Combining unit 210... Code input unit 220... Image output unit

Claims (13)

An image decoding device, comprising:
a decoding unit for decoding the control information and the quantization value;
an inverse quantization unit that inversely quantizes the quantized values to generate transform coefficients;
an inverse transform unit that inversely transforms the transform coefficients to generate prediction residuals;
an intra prediction unit that generates a first predicted pixel based on a decoded pixel and the control information;
a storage unit that stores the decoded pixels;
an MV decoding unit that determines a motion vector based on a plurality of indexes and a motion vector candidate list included in the control information, and sets the motion vector as motion information;
a motion compensation unit that generates a second predicted pixel based on the decoded pixel, the motion information, and the control information;
a synthesis unit that generates a third predicted pixel based on the second predicted pixel and the control information;
an adder that adds any one of the first to third predicted pixels and the prediction residual to obtain a decoded pixel,
The image decoding device according to claim 1, wherein the MV decoding unit reconstructs the plurality of indexes in accordance with a magnitude relationship between the plurality of indexes. the plurality of indexes are two indexes,
2. The image decoding device according to claim 1, wherein the MV decoding unit excludes the smaller of the two indexes from the motion vector candidate list, and then determines the motion vector corresponding to the larger of the two indexes. the plurality of indexes are two indexes,
2. The image decoding device according to claim 1, wherein the MV decoding section adds 1 to the larger of the two indexes. The image decoding device according to claim 1, characterized in that the MV decoding unit decodes a code representing an index to which the addition process is applied from the control information. the plurality of indexes includes a first index and a second index,
The image decoding device according to claim 4, characterized in that the MV decoding unit decodes a code representing an index to which an addition process is to be applied from the control information when the first index is greater than the second index and when the difference between the first index and the second index is 1. the plurality of indexes includes a first index and a second index,
The image decoding device according to claim 1 , wherein the MV decoding unit adds 1 to the second index when the first index is equal to or smaller than the second index. The image decoding device according to claim 5 , wherein the MV decoding unit uses the first index and the second index as they are when a code representing an index to which the addition process is applied is 0. The image decoding device according to claim 5 , wherein the MV decoding unit adds 1 to the first index when a code representing the index to which the addition process is applied is 1. The image decoding device according to claim 2, characterized in that the MV decoding unit adds 1 to the larger of the two indexes when the difference between the two indexes is 2 or more. the plurality of indexes includes a first index and a second index,
2 . The image decoding device according to claim 1 , wherein the MV decoding unit uses the first index and the second index as they are when the first index matches a maximum value. The image decoding device according to claim 4, characterized in that the MV decoding unit decodes, from the control information, a code representing an index to which the addition process is applied when the first index and the second index include a value of maximum value -1. 1. An image decoding method, comprising:
a step A of decoding control information and quantization values;
A step B of dequantizing the quantized values to obtain transform coefficients;
a step C of inversely transforming the transform coefficients to obtain prediction residuals;
a step D of generating a first predicted pixel based on the decoded pixel and the control information;
a step E of storing said decoded pixels;
a step F of determining a motion vector based on a plurality of indexes and a motion vector candidate list included in the control information, and setting the motion vector as motion information;
a step G of generating a second predicted pixel based on the decoded pixel, the motion information and the control information;
a step H of generating a third predicted pixel based on the second predicted pixel and the control information;
a step I of adding any one of the first to third predicted pixels and the prediction residual to obtain a decoded pixel,
The image decoding method according to claim 1, wherein in the step F, the plurality of indexes are reconstructed in accordance with a magnitude relationship between the plurality of indexes. A program for causing a computer to function as an image decoding device,
The image decoding device comprises:
a decoding unit for decoding the control information and the quantization value;
an inverse quantization unit that inversely quantizes the quantized values to generate transform coefficients;
an inverse transform unit that inversely transforms the transform coefficients to generate prediction residuals;
an intra prediction unit that generates a first predicted pixel based on a decoded pixel and the control information;
a storage unit that stores the decoded pixels;
an MV decoding unit that determines a motion vector based on a plurality of indexes and a motion vector candidate list included in the control information, and sets the motion vector as motion information;
a motion compensation unit that generates a second predicted pixel based on the decoded pixel, the motion information, and the control information;
a synthesis unit that generates a third predicted pixel based on the second predicted pixel and the control information;
an adder that adds any one of the first to third predicted pixels and the prediction residual to obtain a decoded pixel,
The program, wherein the MV decoding unit reconstructs the plurality of indexes in accordance with a magnitude relationship between the plurality of indexes.

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