Encoder, decoder, encoding method, and decoding method

1. A system, comprising:

an encoder that encodes a block of an image, the encoder comprising:

a processor; and

memory connected to the processor,

wherein, using the memory, the processor:

determines prediction mode information;

determines a set of partition modes in accordance with the prediction mode information;

selects a partition mode from the determined set of partition modes;

writes a parameter into a bitstream;

partitions a block into a plurality of sub blocks using the selected partition mode; and

encodes a sub block included in the plurality of sub blocks in an encoding process,

wherein the processor:

sets the parameter to a first value in response to partitioning the block into three sub blocks, each of a width and a height of each of the three sub blocks being a power of two; and

sets the parameter to a second value in response to partitioning the block into an even number of sub blocks, the second value being different from the first value, each of the even number of sub blocks having a same size; and

a decoder, which, in operation, decodes image blocks in a decoding process.

2. The system according to claim 1 , wherein the processor, in operation:

determines a first set of partition modes in response to the prediction information indicating inter prediction mode; and

determines a second set of partition modes in response to the prediction information indicating intra prediction mode, a partition mode included in the second set of partition modes producing smaller sub blocks than all of sub blocks produced by the first set of partition modes.

3. The system according to claim 1 wherein the decoder, in operation, decodes the block of the image encoded by the encoder.

4. The system according to claim 3 wherein the encoding process includes generating a bitstream and the bitstream is transmitted to the decoder.

5. The system of claim 3 wherein the decoding process of the block of the image comprises:

partitioning the block into three sub blocks in response to the parameter indicating the first value, each of a width and a height of each of the three sub blocks being a power of two; and

partitioning the block into an even number of sub blocks in response to the parameter indicating the second value, the second value being different from the first value, each of the even number of sub blocks having a same size.

6. A system, comprising:

a decoder that decodes a block of an image, the decoder comprising:

a processor; and

memory connected to the processor,

wherein, using the memory, the processor:

determines prediction mode information;

determines a set of partition modes in accordance with the prediction mode information;

parses a parameter from the bitstream;

selects a partition mode from the set of partition modes in accordance with the parameter;

partitions a block into a plurality of sub blocks using the selected partition mode; and

decodes a sub block included in the plurality of sub blocks in a decoding process,

wherein the processor:

partitions the block into three sub blocks in response to the parameter indicating a first value, each of a width and a height of each of the three sub blocks being a power of two; and

partitions the block into an even number of sub blocks in response to the parameter indicating a second value, the second value being different from the first value, each of the even number of sub blocks having a same size; and

an encoder, which, in operation, encodes image blocks in an encoding process.

7. The system according to claim 6 , wherein the processor, in operation:

determines a first set of partition modes in response to the prediction information indicating inter prediction mode; and

determines a second set of partition modes in response to the prediction information indicating intra prediction mode, a partition mode included in the second set of partition modes producing smaller sub blocks than all of sub blocks produced by the first set of partition modes.

8. The system according to claim 7 wherein the encoder, in operation, encodes the block of the image decoded by the decoder.

9. The system according to claim 8 wherein the decoding process includes receiving a bitstream generated by the encoder.

10. A method, comprising:

encoding a block of an image, the encoding comprising:

determining prediction mode information;

determining a set of prediction modes in accordance with the prediction mode information;

selecting a partition mode from the determined set of partition modes;

writing a parameter into a bitstream;

partitioning a block into a plurality of sub blocks using the selected partition mode; and

encoding a sub block included in the plurality of sub blocks in an encoding process,

wherein the encoding comprises:

setting the parameter to a first value in response to partitioning the block into three sub blocks, each of a width and a height of each of the three sub blocks being a power of two; and

setting the parameter to a second value in response to partitioning the block into an even number of sub blocks, the second value being different from the first value, each of the even number of sub blocks having a same size; and

decoding image blocks in a decoding process.

11. The method according to claim 10 , wherein the encoding comprises:

determining a first set of partition modes in response to the prediction information indicating inter prediction mode; and

determining a second set of partition modes in response to the prediction information indicating intra prediction mode, a partition mode included in the second set of partition modes producing smaller sub blocks than all of sub blocks produced by the first set of partition modes.

12. The method according to claim 10 wherein the decoding process includes decoding the encoded block of the image.

13. The method according to claim 12 , comprising:

generating a bitstream including the encoded block; and

transmitting the bitstream to a decoder.

14. The method of claim 13 wherein the decoding process of the block of the image comprises:

partitioning the block into three sub blocks in response to the parameter indicating the first value, each of a width and a height of each of the three sub blocks being a power of two; and

partitioning the block into an even number of sub blocks in response to the parameter indicating the second value, the second value being different from the first value, each of the even number of sub blocks having a same size.

15. A method, comprising:

decoding a block of an image, the decoding comprising:

determining prediction mode information;

determining a set of partition modes in accordance with the prediction mode information;

parsing a parameter from the bitstream;

selecting a partition mode from the set of partition modes in accordance with the parameter;

partitioning a block into a plurality of sub blocks using the selected partition mode; and

decoding a sub block included in the plurality of sub blocks in a decoding process,

wherein the decoding comprises:

partitioning the block into three sub blocks in response to the parameter indicating a first value, each of a width and a height of each of the three sub blocks being a power of two; and

partitioning the block into an even number of sub blocks in response to the parameter indicating a second value, the second value being different from the first value, each of the even number of blocks having a same size; and

encoding image blocks in an encoding process.

16. The method according to claim 15 , wherein the decoding comprises:

determining a first set of partition modes in response to the prediction information indicating inter prediction mode; and

determining a second set of partition modes in response to the prediction information indicating intra prediction mode, a partition mode included in the second set of partition modes producing smaller sub blocks than all of sub blocks produced by the first set of partition modes.

17. The method according to claim 15 , wherein the encoding process includes encoding the decoded block of the image.

18. The method according to claim 15 , comprising receiving a bitstream generated including the block of the image.