Block size determination method, video encoding apparatus, and program
The computational complexity when a block configuration in an encoding target region is determined is reduced while the degradation of coding efficiency is suppressed. A video encoding apparatus includes a block selecting unit which selects each of blocks obtained by recursively dividing an encoding target block as a target block in a predetermined sequence, a block size acquiring unit which acquires the smallest block size in an adjacent block for the selected target block, an evaluation value calculating unit which calculates an evaluation value of the target block if a block size of the target block matches any one of the acquired block size, the block size one level higher than the acquired block size, and the block size one level lower than the acquired block size, and a block configuration determining unit which determines a combination of the blocks constituting the region within the encoding target block based on the evaluation value.
1. A video encoding apparatus which determines sizes of blocks constituting a region within an encoding target block for encoding target blocks into which an image region is divided in video encoding, the video encoding apparatus comprising:
a block selecting unit which selects each of blocks obtained by recursively dividing the encoding target block as a target block in a predetermined sequence;
a block size acquiring unit which acquires the smallest block size in an adjacent block for the selected target block;
an evaluation value calculating unit which calculates an evaluation value of the target block if a block size of the target block matches any one of the acquired block size, the block size one level higher than the acquired block size, and the block size one level lower than the acquired block size; and
a block configuration determining unit which determines a combination of the blocks constituting the region within the encoding target block based on the evaluation value.
2. The video encoding apparatus according to claim 1 ,
wherein the sequence is a sequence which starts from the largest block size in the encoding target block, and
the video encoding apparatus further comprises:
a sum calculating unit which calculates evaluation values of blocks into which the target block is divided and calculates a sum of the calculated evaluation values; and
a calculation target excluding unit which excludes blocks obtained by dividing the target block from calculation targets of the evaluation values if the evaluation value of the target block is less than the sum.
3. The video encoding apparatus according to claim 2 ,
wherein the sequence is a first sequence which starts from the largest block size in the encoding target block or a second sequence which starts from the smallest block size in the encoding target block, and
the block selecting unit determines which of the first sequence and the second sequence is to be used for selecting the target block based on the smallest block size in a block adjacent to the encoding target block.
4. The video encoding apparatus according to claim 2 ,
wherein the sequence is a first sequence which starts from the largest block size in the encoding target block or a second sequence which starts from the smallest block size in the encoding target block, and
the block selecting unit determines which of the first sequence and the second sequence is to be used for selecting the target block based on a picture type of the encoding target block.
5. The video encoding apparatus according to claim 1 ,
wherein the sequence is a sequence which starts from the smallest block size in the encoding target block, and
the video encoding apparatus further comprises:
a combination determining unit which determines a combination of blocks constituting a region within the target block based on the evaluation value; and
a calculation target excluding unit which excludes a block which includes the target block and is present in a layer higher than that of the target block from a calculation target of the evaluation value if the determined combination of the blocks within the target block is a combination of a plurality of blocks into which the target block is divided.
6. The video encoding apparatus according to claim 5 ,
wherein the sequence is a first sequence which starts from the largest block size in the encoding target block or a second sequence which starts from the smallest block size in the encoding target block, and
the block selecting unit determines which of the first sequence and the second sequence is to be used for selecting the target block based on the smallest block size in a block adjacent to the encoding target block.
7. The video encoding apparatus according to claim 5 ,
wherein the sequence is a first sequence which starts from the largest block size in the encoding target block or a second sequence which starts from the smallest block size in the encoding target block, and
the block selecting unit determines which of the first sequence and the second sequence is to be used for selecting the target block based on a picture type of the encoding target block.
8. The video encoding apparatus according to claim 1 ,
wherein the sequence is a first sequence which starts from the largest block size in the encoding target block or a second sequence which starts from the smallest block size in the encoding target block, and
the block selecting unit determines which of the first sequence and the second sequence is to be used for selecting the target block based on the smallest block size in a block adjacent to the encoding target block.
9. The video encoding apparatus according to claim 1 ,
wherein the sequence is a first sequence which starts from the largest block size in the encoding target block or a second sequence which starts from the smallest block size in the encoding target block, and
the block selecting unit determines which of the first sequence and the second sequence is to be used for selecting the target block based on a picture type of the encoding target block.
10. A block size determination method for determining sizes of blocks constituting a region within an encoding target block for encoding target blocks into which an image region is divided in video encoding, the block size determination method comprising:
a step of selecting each of blocks obtained by recursively dividing the encoding target block as a target block in a predetermined sequence;
a step of acquiring the smallest block size in an adjacent block for the selected target block;
a step of calculating an evaluation value of the target block if a block size of the target block matches any one of the acquired block size, the block size one level higher than the acquired block size, and the block size one level lower than the acquired block size; and
a step of determining a combination of the blocks constituting the region within the encoding target block based on the evaluation value.
11. A program for causing a computer to execute the block size determination method according to claim 10 .