Inherited motion information for decoding a current coding unit in a video coding system

1. A method of video decoding at a decoder, comprising:

receiving a bitstream including encoded data of a picture;

decoding a plurality of coding units (CUs) in the picture based on motion information stored in a history-based motion vector prediction (HMVP) table without updating the HMVP table; and

updating the HMVP table with motion information of all or a part of the plurality of CUs after the plurality of CUs are decoded based on the motion information stored in the HMVP table.

2. The method of claim 1 , further comprising:

decoding every P CUs in the picture based on motion information stored in the HMVP table without updating the HMVP table, P being an integer greater than 1; and

updating the HMVP table with motion information of all or a part of every P CUs after every P CUs are decoded.

3. The method of claim 2 , further comprising:

receiving a syntax element indicating a value of P in the bitstream.

4. The method of claim 1 , wherein

the decoding includes:

decoding CUs within a merge sharing region based on the motion information stored in the HMVP table, wherein the plurality of CUs are the CUs within the merge sharing region that are decoded based on the motion information stored in the HMVP table, and

the updating includes:

after the merge sharing region is decoded, updating the HMVP table with the motion information of all or the part of the CUs within the merge sharing region that are decoded based on the motion information stored in the HMVP table.

5. The method of claim 4 , wherein the CUs within the merge sharing regions are coded with a current picture reference (CPR) mode based on the HMVP table.

6. The method of claim 1 , wherein the plurality of CUs are decoded in parallel.

7. The method of claim 1 , wherein the updating includes one of:

updating the HMVP table with the motion information of the last Q of the plurality of CUs, Q being an integer greater than 0,

updating the HMVP table with the last Q motion information of the remaining motion information of the plurality of CUs resulting from a pruning operation,

updating the HMVP table with the motion information of the first W of the plurality of CUs, W being an integer greater than 0, or

updating the HMVP table with the first W motion information of the remaining motion information of the plurality of CUs resulting from a pruning operation.

8. The method of claim 1 , further comprising:

resetting the HMVP table for every N coding tree unit (CTU) rows, N being an integer greater than 0.

9. The method of claim 8 , wherein the N CTU rows are CTU rows in a slice or a tile of the picture.

10. The method of claim 1 , further comprising:

resetting the HMVP table for every CTU row in a slice or a tile of the picture.

11. The method of claim 1 , further comprising:

resetting the HMVP table after processing N CTUs, N being an integer greater than 0.

12. The method of claim 1 , further comprising:

resetting the HMVP table after processing a region having a predefined size.

13. The method of claim 1 , further comprising:

resetting the HMVP table at a beginning of a tile in the picture.

14. The method of claim 1 , further comprising:

initializing the HMVP table at a beginning of a current CTU row with motion information of a CU in a CTU row processed prior to the current CTU row in the picture.

15. The method of claim 1 , further comprising:

storing motion information of last CUs in a CTU row processed prior to a current CTU row in a buffer,

wherein the decoding includes:

decoding the plurality of CUs in the current CTU row based on the motion information stored in the HMVP table and the buffer.

16. The method of claim 1 , wherein the updating includes:

performing a pruning process over a subset of HMVP candidates stored in the HMVP table, wherein the subset of HMVP candidates is fewer than all the HMVP candidates in the HMVP table, and the motion information for updating the HMVP table is not added to the HMVP table when an HMVP candidate in the HMVP table identical or similar to the respective motion information for updating the HMVP table is found.

17. An apparatus of video decoding, comprising circuitry configured to:

receive a bitstream including encoded data of a picture;

decode a plurality of coding units (CUs) in the picture based on motion information stored in a history-based motion vector prediction (HMVP) table without updating the HMVP table; and

update the HMVP table with motion information of all or a part of the plurality of CUs after the plurality of CUs are decoded based on the motion information stored in the HMVP table.

18. The apparatus of claim 17 , wherein the circuitry is configured to:

decode CUs within a merge sharing region based on the motion information stored in the HMVP table, wherein the plurality of CUs are the CUs within the merge sharing region that are decoded based on the motion information stored in the HMVP table, and

after the merge sharing region is decoded, update the HMVP table with the motion information of all or the part of the CUs within the merge sharing region that are decoded based on the motion information stored in the HMVP table.

19. The apparatus of claim 17 , wherein the circuitry is configured to:

reset the HMVP table for every CTU row in a slice or a tile of the picture.

20. A non-transitory computer-readable medium storing a program that, when executed by a processor, causes the processor to perform a method of video decoding, the method comprising:

receiving a bitstream including encoded data of a picture;

decoding a plurality of coding units (CUs) in the picture based on motion information stored in a history-based motion vector prediction (HMVP) table without updating the HMVP table; and

updating the HMVP table with motion information of all or a part of the plurality of CUs after the plurality of CUs are decoded based on the motion information stored in the HMVP table.