Method and appartus of adaptive loop filtering

• US 9,615,093 B2
• Filed: 08/10/2015
• Issued: 04/04/2017
• Est. Priority Date: 05/10/2010
• Status: Active Grant

• Current Assignee: HFI Innovation, Inc. (MediaTek, Inc.)
• Original Assignee: HFI Innovation, Inc. (MediaTek, Inc.)
• Inventors: Fu, Chih-Ming, Chen, Ching-Yeh, Tsai, Chia-Yang, Huang, Yu-Wen, Lei, Shaw-Min
• Primary Examiner(s): Aghevli, Reza
• Application Number:
  US14/822,026
• Publication Number:
  US 20150350648A1
• Time in Patent Office: 603 Days
• Field of Search: None
• CPC Class Codes: H04N 19/10 using adaptive coding
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• CPC Class Codes: H04N 19/129 Scanning of coding units, e.g. zig-zag scan of transform coefficients or flexible macroblock ordering [FMO]
• CPC Class Codes: H04N 19/134 characterised by the element, parameter or criterion affecting or controlling the adaptive coding
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/154 Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion use of rate-distortion criteria H04N19/147
• CPC Class Codes: H04N 19/157 Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/174 the region being a slice, e.g. a line of blocks or a group of blocks
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/196 being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters processing of motion vectors H04N19/513
• CPC Class Codes: H04N 19/439 using cascaded computational arrangements for performing a single operation, e.g. filtering
• CPC Class Codes: H04N 19/463 by compressing encoding parameters before transmission
• CPC Class Codes: H04N 19/82 involving filtering within a prediction loop
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness
• CPC Class Codes: H04N 19/96 Tree coding, e.g. quad-tree coding

Abstract

A method and apparatus receives input data for in-loop processing, where the input data corresponds to reconstructed or reconstructed-and-deblocked coding units of the picture. The input data is divided into multiple filter units and each filter unit includes one or more boundary-aligned reconstructed or reconstructed-and-deblocked coding units. A candidate filter is then selected from a candidate filter set for the in-loop processing. The candidate filter set comprises at least two candidate filters the said in-loop processing corresponding to adaptive loop filter (ALF), adaptive offset (AO), or adaptive clipping (AC). The in-loop processing is then applied to one of the filter units to generate a processed filter unit by using the candidate filter selected to all boundary-aligned reconstructed or reconstructed-and-deblocked coding units in said one of the filter units.

Claims

1. A method for processing video using in-loop processing, wherein a picture is partitioned into coding units for applying coding process to each coding unit, the method comprising:

receiving input data to said in-loop processing, wherein the input data corresponds to reconstructed or reconstructed-and-deblocked coding units of the picture;

dividing the input data into multiple filter units, wherein at least one filter unit includes two or more boundary-aligned reconstructed or reconstructed-and-deblocked coding units;

selecting a candidate filter from a candidate filter set for said in-loop processing, wherein the candidate filter set comprises at least two candidate filters for said in-loop processing corresponding to adaptive loop filter (ALF), adaptive offset (AO), or adaptive clipping (AC);

applying said in-loop processing to said at least one filter unit including said two or more boundary-aligned reconstructed or reconstructed-and-deblocked coding units using the candidate filter selected to generate a processed filter unit by using the candidate filter selected to all boundary-aligned reconstructed or reconstructed-and-deblocked coding units in said at least one filter unit; and

providing processed video data comprising the processed filter unit.

2. The method of claim 1, wherein boundaries of the filter units are also boundaries of the coding units.

3. The method of claim 1, wherein two or more of the filter units are merged as indicated by a merge index to share the candidate filter selected from the candidate filter set.

4. The method of claim 3, wherein said two or more of the filter units are spatially neighboring filter units, wherein said spatially neighboring filter units are formed by path scanning through the filter units using a scan pattern selected from a group consisting of horizontal scan, vertical scan, z-scan, snake scan, Hilbert scan, a pre-defined scan pattern, and a user-defined scan pattern.

5. The method of claim 4, wherein information associated with the scan pattern, a choice of whether to allow use of the merge index, or both are incorporated in a sequence level, a picture level, a slice level, a coding unit level, a filter unit level or a filter control unit level.

6. The method of claim 1, wherein each of the filter units is further partitioned into third blocks corresponding to filter control units, and a filter control flag is associated with each of the filter control units to select one filter from the candidate filter set for applying said in-loop processing.

7. The method of claim 6, wherein each of filter units is partitioned into filter control units using quadtree partitioning, bock partitioning, prediction unit synchronized partitioning, or transform unit synchronized partitioning.

8. The method of claim 7, wherein the filter control flag is used to indicate filter ON/OFF control when one filter is selected for the filter unit or the filter control flag is used to indicate one of multiple filters when more than one filter are selected for the filter unit.

9. The method of claim 1, wherein the input data corresponds to a first reconstructed or constructed-and-deblocked color component and a second reconstructed or constructed-and-deblocked color component, and the first reconstructed or constructed-and-deblocked color component and the second reconstructed or constructed-and-deblocked color component share filter information associated with said in-loop processing, and the filter information shared corresponds to filter control unit partitioning, filter selection, filter control flag, filter shape, filter coefficients, or a combination of the above.

10. The method of claim 9, wherein whether to share the filter information associated with said in-loop processing by the first reconstructed or constructed-and-deblocked color component and the second reconstructed or constructed-and-deblocked color component is enabled or disable according to a sharing switch.

11. The method of claim 10, wherein information associated with the sharing switch is incorporated in a sequence level, a picture level, a slice level, a coding unit level, a filter unit level or a filter control unit level.

12. The method of claim 10, wherein the filter information associated with said in-loop processing for the second reconstructed or constructed-and-deblocked color component is derived from the filter information associated with said in-loop processing for the first reconstructed or constructed-and-deblocked color component.

13. The method of claim 1, wherein filter information associated with said in-loop processing is explicitly incorporated in a bitstream or is derived implicitly based on the input data according to a selection method.

14. The method of claim 13, wherein the selection method is indicated by a syntax element in a sequence level, a picture level, a slice level, a coding unit level, a filter unit level or a filter control unit level.

15. The method of claim 14, wherein the input data is classified into multiple categories using classification, and one filter is selected from the candidate filter set for each of the categories, the classification is based on a first characteristic derived from the input data, wherein the first characteristic is selected from a first group consisting of pixel intensity, edge activity, edge orientation, edge intensity, mode information, quantization parameter, residual energy, regional feature, motion information, and a combination of the above.

16. The method of claim 15, wherein more than one first characteristics are adaptively selected for the classification according to a classifier indicator, wherein the classifier indicator is incorporated in a sequence level, a picture level, a slice level, a coding unit level, a filter unit level or a filter control unit level.

17. The method of claim 15, wherein said multiple categories are further classified using a second characteristic derived from the input data, wherein the second characteristic is selected from a second group consisting of pixel intensity, edge activity, edge orientation, edge intensity, mode information, quantization parameter, residual energy, regional feature, motion information, and a combination of the above, and wherein the second characteristic is different from the first characteristic.

18. The method of claim 15, wherein the regional feature is derived according to the characteristics for the filter unit, the coding unit or a pixel location.

19. An apparatus for processing video using in-loop processing, wherein a picture is partitioned into coding units for applying coding process to each coding unit, the apparatus comprising one or more electronic devices configured to:

receive input data to said in-loop processing, wherein the input data corresponds to reconstructed or reconstructed-and-deblocked coding units of the picture;

divide the input data into multiple filter units, wherein at least one filter unit includes two or more boundary-aligned reconstructed or reconstructed-and-deblocked coding units;

select a candidate filter from a candidate filter set for said in-loop processing, wherein the candidate filter set comprises at least two candidate filters for said in-loop processing corresponding to adaptive loop filter (ALF), adaptive offset (AO), or adaptive clipping (AC);

apply said in-loop processing to said at least one filter unit including said two or more boundary-aligned reconstructed or reconstructed-and-deblocked coding units using the candidate filter selected to generate a processed filter unit by using the candidate filter selected to all boundary-aligned reconstructed or reconstructed-and-deblocked coding units at least one filter unit in said at least one filter unit; and

provide processed video data comprising the processed filter unit.