Method of Block Vector Prediction for Intra Block Copy Mode Coding

• US 20170054996A1
• Filed: 05/05/2015
• Published: 02/23/2017
• Est. Priority Date: 05/06/2014
• Status: Active Grant

• Current Assignee: HFI Innovation, Inc. (MediaTek, Inc.)
• Original Assignee: Shan Liu, Tzu-Der Chuang, Xiaozhong Xu
• Inventors: XU, Xiaozhong, LIU, Shan, CHUANG, Tzu-Der
• Granted Patent: US 10,666,968 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/52 by predictive encoding
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques

Abstract

A method of block vector (BV) prediction for an IntraBC mode (Intra-block copy mode) coded block in a video coding system according to the present invention is disclosed. Multiple BV candidate lists are derived from neighboring blocks of the current block. A BV candidate list is selected as a BV predictor for the BV of the current block. The current block is coded based on an Intra reference block located according to the BV of the current block. In one embodiment, a left-bottom (LB) block of the current block is used to derive the first BV candidate list and an above-right (AR) block of the current block is used to derive the second BV candidate list. A 1-bit index code is signaled to select a BV predictor between the first BV candidate list and the second BV candidate list

Claims

1. A method of block vector (BV) prediction for an IntraBC mode (Intra-block copy mode) coded block in a video coding system, the method comprising:

receiving input data associated with a current block in a current picture;

determining a current BV for the current block to locate an Intra reference block in the current picture;

deriving multiple BV candidate lists from neighboring blocks of the current block;

selecting one BV candidate list as a BV predictor for the current block;

encoding the current BV based on the BV predictor;

signaling an index for identifying said one BV candidate list selected from the multiple BV candidate lists; and

encoding the current block using the Intra reference block as a predictor.

2. The method of claim 1, wherein said multiple BV candidate lists correspond to a first BV candidate list and a second BV candidate list.

3. The method of claim 2, wherein the first BV candidate list is generated from one or more first neighboring blocks in selected first positions according to a first position-related priority order, and the second BV candidate list is generated from one or more second neighboring blocks in selected second positions according to a second position-related priority order, and wherein the first BV candidate list is filled by a BV of a first IntraBC mode coded first neighboring block, and the second BV candidate list is filled by a BV of a first IntraBC mode coded second neighboring block.

4. The method of claim 3, wherein said one or more first neighboring blocks corresponds to a single first spatial neighboring block at a left-bottom (LB) position of the current block;

the first position-related priority order includes the LB position only;

said one or more second neighboring blocks corresponds to a single second spatial neighboring block at an above-right (AR) position of the current block; and

the second position-related priority order includes the AR position only.

5. A method of block vector (BV) decoding for an IntraBC-mode (Intra-block copy mode) coded block in a video decoder, the method comprising:

receiving a bitstream including coded data for a current picture;

deriving multiple BV candidate lists from IntraBC-mode-coded neighboring blocks of a current block;

determining an index from the bitstream for selecting a specific BV candidate list from the multiple BV candidate lists;

determining a coded BV from the bitstream;

decoding a current BV for the current block based on the coded BV and a BV predictor corresponding to said specific BV candidate list;

determining an Intra reference block in the current picture based on the current BV; and

decoding the current block using the Intra reference block.

6. The method of claim 5, wherein said multiple BV candidate lists correspond to a first BV candidate list and a second BV candidate list, and the index corresponds to a 1-bit code to select between the first BV candidate list and the second BV candidate list.

7. The method of claim 6, wherein the first BV candidate list is generated from one or more first neighboring blocks in selected first positions according to a first position-related priority order, and the second BV candidate list is generated from one or more second neighboring blocks in selected second positions according to a second position-related priority order, and wherein the first BV candidate list is filled by a BV of a first IntraBC mode coded first neighboring block, and the second BV candidate list is filled by a BV of a first IntraBC mode coded second neighboring block.

8. The method of claim 7, wherein said one or more first neighboring blocks corresponds to a single first spatial neighboring block at a left-bottom (LB) position of the current block;

the first position-related priority order includes the LB position only;

said one or more second neighboring blocks corresponds to a single second spatial neighboring block at an above-right (AR) position of the current block; and

the second position-related priority order includes the AR position only.

9. The method of claim 7, wherein said one or more first neighboring blocks correspond to two first spatial neighboring blocks at a left-bottom (LB) position and a lower-left (LL) position of the current block;

the first position-related priority order corresponds to the LB position->

the LL position;

said one or more second neighboring blocks correspond to three second neighboring blocks at an above-right (AR) position, an upper-right (UR) position and an upper-left (UL) position of the current block; and

the second position-related priority order corresponds to the AR position->

the UR position->

the UL position.

10. The method of claim 7, wherein the first BV candidate list is generated before the second BV candidate list is generated, and said one or more second neighboring blocks in the selected second positions are used to fill the first BV candidate list if the first BV candidate list is not filled from said one or more first neighboring blocks in the selected first positions.

11. The method of claim 10, wherein if no available BV candidate is found for the first BV candidate list from said one or more first neighboring blocks in the selected first positions or both said one or more first neighboring blocks in the selected first positions and said one or more second neighboring blocks in the selected second positions, a default BV is used for the first BV candidate list.

12. The method of claim 10, wherein if no available BV candidate is found for the second BV candidate list from said one or more second neighboring blocks in the selected second positions, a default BV is used for the second BV candidate list.

13. The method of claim 5, wherein each BV candidate list is generated from one or more neighboring blocks in selected positions according to a position-related priority order.

14. The method of claim 5, wherein if no neighboring block in selected positions associated with one BV candidate list is available to fill said one BV candidate list, a default BV is used for said one BV candidate list.

15. The method of claim 14, wherein the default BV is selected from a group including (0, 0), (−

2w,

     0), (−

w,

     0), (0, −

2w) and (0, −

w), wherein w corresponds to block width.

16. The method of claim 5, wherein if no neighboring block in selected positions associated with one BV candidate list is available to fill said one BV candidate list, a substitute BV corresponding to a previously IntraBC mode coded block is used for said one BV candidate list.

17. The method of claim 16, wherein each of said multiple BV candidate lists corresponds to a buffer used to store the substitute BV corresponding to the previously IntraBC mode coded block;

and a same BV value is not stored in both of different buffers corresponding to different BV candidate lists.

18. The method of claim 17, wherein said multiple BV candidate lists correspond to two BV candidate lists, and two buffers corresponding to said two BV candidate lists are initialized using two initial BV values corresponding to (−

2w,

     0) and (−

w,

     0), wherein w corresponds to block width.

19. The method of claim 5, wherein said multiple BV candidate lists include a temporal BV candidate list derived from one or more temporal neighboring blocks of the current block.

20. The method of claim 19, wherein said one or more temporal neighboring blocks corresponds to one or more co-located blocks selected from a group including a center (CTR) block, an outer bottom-right (BR) block, an upper-left (UL) block and an inner bottom-right (BR2) block in a co-located picture of the current picture.

21. The method of claim 5, wherein said multiple BV candidate lists include two or more BV candidate lists selected from a group consisting of one or more spatial BV candidate lists, one or more temporal BV candidate lists, and one or more stored BV candidate lists corresponding to one or more previously coded BVs.

22. The method of claim 21, wherein a BV predictor (BVP) list is constructed to derive said multiple BV candidate lists by adding one or more new BV candidate list to a previous BVP list.

23. The method of claim 22, wherein the BVP list is pruned to remove any redundant BV candidate list before or after said adding one or more new BV candidate list to the previous BVP list.

24. The method of claim 22, wherein if a size of final BVP list is larger than N, only N BV candidate lists are used in the final BVP list, wherein N is an integer greater than one.

25. The method of claim 22, wherein if a size of a final BVP list is less than N, one or more pre-defined BVs are added to the final BVP list, wherein N is an integer greater than one.

26. The method of claim 25, wherein said one or more pre-defined BVs correspond to one or more pre-defined values selected from a group including (0, 0), (−

2w,

     0), (−

w,

     0), (−

1.5w,

     0), (0, −

2w), (0, −

w) and (0, −

1.5w), wherein w corresponds to block width.