Size dependent inter coding

1. A method for video processing, comprising:

determining, for a conversion between a current block of a video and a bitstream of the video, whether multiple flags of the current block are presented in the bitstream based on whether a same dimension condition associated with a size of the current block is satisfied; and

performing the conversion based on the determining,

wherein whether a skip flag indicating whether a skip mode is used for the current block and a flag indicating whether an inter prediction mode is used for the current block are presented in the bitstream are both based on the same dimension condition that a width of the current block is equal to 4 and a height of the current block is equal to 4;

wherein a context increasement used for coding an inter prediction direction flag is equal to a fixed integer number that is not a function of a width or a function of a height of the current block in response to a sum of the width and the height of the current block being 12, and

wherein in response to the size of the current block being 8×4 or 4×8, a weight index is set to 0 for the current block, and wherein the weight index is used to find weights from a weight set to generate a weighted sum from prediction samples of list 0 and list 1.

2. The method of claim 1 , wherein in response to a value of the skip flag being 1, a merge data syntax structure is not included in the bitstream.

3. The method of claim 1 , wherein the multiple flags comprise an intra block copy flag indicating whether an intra block copy mode is used for the current block, and whether the intra block copy flag is presented in the bitstream is also based on the same dimension condition.

4. The method of claim 3 , wherein in response to the same dimension condition being satisfied and a value of the skip flag being 1, the intra block copy flag is not presented in the bitstream.

5. The method of claim 4 , wherein the intra block copy flag is pred_mode_ibc_flag which is a coding unit level flag.

6. The method of claim 1 , wherein in response to the same dimension condition being satisfied and a value of a video sequence level flag indicating that an intra block copy mode is not allowed for an entire video sequence, the skip flag is not presented in the bitstream.

7. The method of claim 6 , wherein the video sequence level flag is sps_ibc_enabled_flag.

8. The method of claim 1 , wherein the multiple flags comprise a flag related with whether a triangle mode is used for the current block.

9. The method of claim 1 , wherein the inter prediction direction flag is used to indicate whether list0, list1, or bi-prediction is used for the current block.

10. The method of claim 9 , wherein in response to the size of the current block being 8×4 or 4×8, the bi-prediction is not used for the current block.

11. The method of claim 1 , wherein the conversion includes encoding the current block into the bitstream.

12. The method of claim 1 , wherein the conversion includes decoding the current block from the bitstream.

13. An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:

determine, for a conversion between a current block of a video and a bitstream of the video, whether multiple flags of the current block are presented in the bitstream based on whether a same dimension condition associated with a size of the current block is satisfied; and

perform the conversion based on the determining,

wherein whether a skip flag indicating whether a skip mode is used for the current block and a flag indicating whether an inter prediction mode is used for the current block are presented in the bitstream are both based on the same dimension condition that a width of the current block is equal to 4 and a height of the current block is equal to 4;

wherein a context increasement used for coding an inter prediction direction flag is equal to a fixed integer number that is not a function of a width or a function of a height of the current block in response to a sum of the width and the height of the current block being 12, and

wherein in response to the size of the current block being 8×4 or 4×8, a weight index is set to 0 for the current block, and wherein the weight index is used to find weights from a weight set to generate a weighted sum from prediction samples of list 0 and list 1.

14. The apparatus of claim 13 , wherein in response to a value of the skip flag being 1, a merge data syntax structure is not included in the bitstream.

15. The apparatus of claim 13 , wherein the multiple flags comprise an intra block copy flag indicating whether an intra block copy mode is used for the current block, and whether the intra block copy flag is presented in the bitstream is also based on the same dimension condition.

16. The apparatus of claim 15 , wherein in response to the same dimension condition being satisfied and a value of the skip flag being 1, the intra block copy flag is not represented in the bitstream.

17. A non-transitory computer-readable storage medium storing instructions that cause a processor to:

determine, for a conversion between a current block of a video and a bitstream of the video, whether multiple flags of the current block are presented in the bitstream based on whether a same dimension condition associated with a size of the current block is satisfied; and

perform the conversion based on the determining,

wherein whether a skip flag indicating whether a skip mode is used for the current block and a flag indicating whether an inter prediction mode is used for the current block are presented in the bitstream are both based on the same dimension condition that a width of the current block is equal to 4 and a height of the current block is equal to 4;

wherein a context increasement used for coding an inter prediction direction flag is equal to a fixed integer number that is not a function of a width or a function of a height of the current block in response to a sum of the width and the height of the current block being 12, and

wherein in response to the size of the current block being 8×4 or 4×8, a weight index is set to 0 for the current block, and wherein the weight index is used to find weights from a weight set to generate a weighted sum from prediction samples of list 0 and list 1.

18. A method for generating and storing a bitstream of a video, comprising:

determining, for a current block of a video, whether multiple flags of the current block are presented in the bitstream based on whether a same dimension condition associated with a size of the current block is satisfied;

generating the bitstream based on the determining, and

storing the bitstream to a non-transitory computer-readable recording medium;

wherein whether a skip flag indicating whether a skip mode is used for the current block and a flag indicating whether an inter prediction mode is used for the current block are presented in the bitstream are both based on the same dimension condition that a width of the current block is equal to 4 and a height of the current block is equal to 4;

wherein a context increasement used for coding an inter prediction direction flag is equal to a fixed integer number that is not a function of a width or a function of a height of the current block in response to a sum of the width and the height of the current block being 12, and

wherein in response to the size of the current block being 8×4 or 4×8, a weight index is set to 0 for the current block, and wherein the weight index is used to find weights from a weight set to generate a weighted sum from prediction samples of list 0 and list 1.

19. The apparatus of claim 16 , wherein the intra block copy flag is pred_mode_ibc_flag which is a coding unit level flag.

20. The apparatus of claim 13 , wherein in response to the same dimension condition being satisfied and a value of a video sequence level flag indicating that an intra block copy mode is not allowed for an entire video sequence, the skip flag is not presented in the bitstream.