Method of Intra Block Copy with Flipping for Image and Video Coding

• US 20170195677A1
• Filed: 05/22/2015
• Published: 07/06/2017
• Est. Priority Date: 05/22/2014
• Status: Abandoned Application

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: YE, Jing, LIU, Shan, XU, Xiaozhong
• Application Number:
  US15/308,722
• Publication Number:
  US 20170195677A1
• Time in Patent Office: Days
• CPC Class Codes: H04N 19/11 among a plurality of spatial predictive coding modes
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/34 Scalability techniques involving progressive bit-plane based encoding of the enhancement layer, e.g. fine granular scalability [FGS]
• CPC Class Codes: H04N 19/463 by compressing encoding parameters before transmission
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards
• CPC Class Codes: H04N 19/96 Tree coding, e.g. quad-tree coding

Abstract

A method and apparatus for video coding including an IntraBC (Intra-block copy) mode with flipping for prediction unit (PU) with a non-2N×2N partition size is disclosed. An IntraBC mode is selected from a mode group comprising a normal IntraBC mode and a flipping mode for a current PU with a current PU size belonging to a size group including at least one PU size selected from 2N×N, N×2N and N×N and N is a positive integer. When the IntraBC mode is used for the current PU, a flipping flag is signaled in a current PU-level syntax to indicate whether the current PU is coded using the flipping mode. Furthermore, when the current PU is coded using the flipping mode, a flip-direction flag is signaled in the current PU-level syntax to indicate a flipping direction of a corresponding flipped reference block.

Claims

1. A method of video coding including an IntraBC (Intra-block copy) mode for a picture, the method comprising:

receiving input data associated with a current CU (coding unit) in a current picture, wherein the current CU is partitioned into one or more PUs (prediction units) and each PU is associated with a PU size;

selecting an IntraBC mode from a mode group comprising a normal IntraBC mode and a flipping mode for a current PU with a current PU size belonging to a size group including at least one PU size selected from 2N×

N, N×

2N and N×

N and N is a positive integer, wherein the flipping mode uses a flipped reference block as an IntraBC predictor; and

encoding or decoding the current PU using the IntraBC mode selected.

2. The method of claim 1, wherein when the IntraBC mode is used for the current PU, a flipping flag is signaled in a current PU-level syntax to indicate whether the current PU is coded using the flipping mode.

3. The method of claim 2, wherein when the current PU is coded using the flipping mode, a flip-direction flag is signaled in the current PU-level syntax to indicate a flipping direction of a corresponding flipped reference block.

7. The method of claim 2, wherein a flip-direction flag to indicate a flipping direction of a corresponding flipped reference block is inferred based on a partition mode for the current PU and no flip-direction flag is signaled for the current PU.

12. The method of claim 1, wherein when the current CU is partitioned into multiple PUs using a partition mode, and a flipping flag is signaled for the current CU when the current CU is coded by the IntraBC mode, at least one of said multiple PUs is predicted by another PU of said multiple PUs according to the flipping mode.

13. The method of claim 12, wherein if the partition mode corresponds to 2N×

N, a top 2N×

N PU of the current CU is coded using the normal IntraBC mode and a bottom 2N×

N PU of the current CU is coded using the flipping mode with a vertical direction based on the top 2N×

N PU.

14. The method of claim 12, wherein if the partition mode corresponds to N×

2N, a left N×

2N PU of the current CU is coded using the normal IntraBC mode and a right N×

2N PU of the current CU is coded using the flipping mode with a horizontal direction based on the left N×

2N PU.

15. The method of claim 12, wherein if the partition mode corresponds to N×

N, a top-left N×

N PU of the current CU is coded using the normal IntraBC mode and a top-right N×

N PU of the current CU is coded using the flipping mode with a horizontal direction based on the top-left N×

N PU, and a bottom-left N×

N PU and a bottom-right N×

N PU of the current CU is coded using the flipping mode with a vertical direction based on the top-left N×

N PU and the top-right N×

N PU respectively.

16. The method of claim 1, wherein when the current CU is partitioned into a top 2N×

N PU and a bottom 2N×

N PU, a flipping flag is only signaled for the bottom 2N×

N PU, and if the flipping flag is True, the bottom 2N×

N PU is coded using the flipping mode with a vertical direction based on the top 2N×

N PU.

17. The method of claim 1, wherein when the current CU is partitioned into a left N×

2N PU and a right N×

2N PU, a flipping flag is only signaled for the right N×

2N PU, and if the flipping flag is True, the right N×

2N PU is coded using the flipping mode with a horizontal direction based on the left N×

2N PU.

18. The method of claim 1, wherein when the current CU is partitioned into a top-left N×

N PU, a top-right N×

N PU, a bottom-left N×

N PU and a bottom-right N×

N PU, wherein a first flipping flag is signaled for the top-right N×

N PU, and if the first flipping flag is True, the top-right N×

N PU is coded using the flipping mode with a horizontal direction based on the top-left N×

N PU, and wherein a second flipping flag is signaled for the bottom-left N×

N PU or the bottom-right N×

N PU, and if the second flipping flag is True, the bottom-left N×

N PU or the bottom-right N×

N PU is coded using the flipping mode with a vertical direction based on the top-left N×

N PU or the top-right N×

N PU respectively.

19. The method of claim 1, wherein when the current CU is partitioned into a top 2N×

N PU and a bottom 2N×

N PU, a first flipping flag is signaled for the top 2N×

N PU and a second flipping flag is signaled for the bottom 2N×

N PU, wherein if the first flipping flag is True, the top 2N×

N PU is coded using the flipping mode with a vertical direction based on an immediate above 2N×

N block, and wherein if the second flipping flag is True, the bottom 2N×

N PU is coded using the flipping mode with the vertical direction based on the top 2N×

N PU.

20. The method of claim 1, wherein when the current CU is partitioned into a left N×

2N PU and a right N×

2N PU, a first flipping flag is signaled for the left N×

2N PU and a second flipping flag is signaled for the right N×

2N PU, wherein if the first flipping flag is True, the left N×

2N PU is coded using the flipping mode with a horizontal direction based on an immediate left N×

2N block, and wherein if the second flipping flag is True, the right N×

2N PU is coded using the flipping mode with the horizontal direction based on the left N×

2N PU.

21. The method of claim 1, wherein when the current CU is partitioned into a top-left N×

N PU, a top-right N×

N PU, a bottom-left N×

N PU and a bottom-right N×

N PU, wherein a first flipping flag is signaled for the top-left N×

N PU, and if the first flipping flag is True, the top-left N×

N PU is either coded using the flipping mode with a horizontal direction based on an immediate left N×

N block or coded using the flipping mode with a vertical direction based on an immediate top N×

N block, and wherein the top-right N×

N PU, the bottom-left N×

N PU and the bottom-right N×

N PU are coded using the flipping mode based on a previous coded N×

N PU in the current CU if a corresponding flipping flag is True.

31. The method of claim 1, wherein the mode group further comprises a mask mode, wherein a masked area within a corresponding reference block is generated by substituting mask samples in the masked area with a single sample value and the masked area has a mask width.

32. The method of claim 31, wherein when the IntraBC mode is used for the current PU, a mask flag is signaled before a flipping flag in a current PU-level syntax, wherein the flipping flag indicates whether the current PU is coded using the flipping mode and the mask flag indicates whether the current PU is coded using the mask mode.

33. The method of claim 31, wherein when the IntraBC mode is used for the current PU, a mask flag is signaled after a flipping flag in a current PU-level syntax, wherein the flipping flag indicates whether the current PU is coded using the flipping mode and the mask flag indicates whether the current PU is coded using the mask mode.

34. The method of claim 31, wherein the mode group further comprises a combined mask and flipping mode.

35. The method of claim 34, wherein the mode group includes four IntraBC modes corresponding to the normal IntraBC mode, the flipping mode, the mask mode and the combined mask and flipping mode, and wherein said selecting the IntraBC mode from the mode group is according to a variable-length binary decision tree consisting of the four IntraBC modes.

4. -6. (canceled)

8. -11. (canceled)

22. -30. (canceled)

36. -43. (canceled)

44. An apparatus of video coding including an IntraBC (Intra-block copy) mode for a picture, the apparatus comprising one or more electronic circuits configured to:

receive input data associated with a current CU (coding unit) in a current picture, wherein the current CU is partitioned into one or more PUs (prediction units) and each PU is associated with a PU size;

select an IntraBC mode from a mode group comprising a normal IntraBC mode and a flipping mode for a current PU with a current PU size belonging to a size group including at least one PU size selected from 2N×

N, N×

2N and N×

N and N is a positive integer, wherein the flipping mode uses a flipped reference block as an IntraBC predictor; and

encode or decode the current PU using the IntraBC mode selected.