Intra-Prediction With Multiple Reference Lines

Patent metadata

Field	Value
Publication number	US-2018332284-A1
Application number	US-201815972870-A
Country	US
Kind code	A1
Filing date	May 7, 2018
Priority date	May 9, 2017
Publication date	Nov 15, 2018
Grant date	—

Abstract

A video coding device receives a bitstream including video data. The device determines an intra-prediction mode subset. The intra-prediction mode subset include intra-prediction modes that correlate to a plurality of reference lines for a current image block and excludes intra-prediction modes that correlate to a primary reference line for the current image block. When a first intra-prediction mode is included in the intra-prediction mode subset, the device decodes the first intra-prediction mode by an alternative intra-prediction mode index. When the first intra-prediction mode is not included in the intra-prediction mode subset, the device decodes the first intra-prediction mode by an intra-prediction mode index. The device presents video data including an image block decoded based on the first intra-prediction mode.

First claim

What is claimed is:

1 . A video coding device comprising:
a receiver configured to receive a bitstream; a processor coupled to the receiver and configured to:
determine an intra-prediction mode subset, the intra-prediction mode subset including intra-prediction modes that correlate to a plurality of reference lines for a current image block and excluding intra-prediction modes that correlate to a primary reference line for the current image block;
when a first intra-prediction mode is included in the intra-prediction mode subset, decode the first intra-prediction mode by an alternative intra-prediction mode index; and
a display coupled to the processor, the display to present video data including an image block decoded based on the first intra-prediction mode.

2 . The video coding device of claim 1 , wherein the processor is further configured to:
decode a reference line index when the first intra-prediction mode is included in the intra-prediction mode subset, the reference line index indicating a first reference line from the plurality of reference lines for the first intra-prediction mode; and decode no reference line index when the first intra-prediction mode is not included in the intra-prediction mode subset.

3 . The video coding device of claim 2 , wherein the reference line index is positioned after the first intra-prediction mode in the bitstream.

4 . The video coding device of claim 1 , wherein the intra-prediction mode subset includes a starting directional intra-prediction mode (DirS), an ending directional intra-prediction mode (DirE), and every Nth directional intra-prediction mode between DirS and DirE, where N is a predetermined integer value.

5 . The video coding device of claim 1 , wherein the intra-prediction mode subset further includes planar prediction mode and Direct Current (DC) prediction mode.

6 . The video coding device of claim 1 , wherein the intra-prediction mode subset includes a starting directional intra-prediction mode (DirS), an ending directional intra-prediction mode (DirE), a middle directional intra-prediction mode (DirD), a horizontal directional intra-prediction mode (DirH), a vertical directional intra-prediction mode (DirV), and valid directional intra-prediction modes at directions of plus or minus N of DirS, DirE, DirD, DirH, and DirV, where N is a predetermined integer value.

7 . The video coding device of claim 6 , wherein the intra-prediction mode subset further includes planar prediction mode and Direct Current (DC) prediction mode.

8 . The video coding device of claim 1 , wherein the intra-prediction mode subset includes intra-prediction modes selected for decoded neighbor blocks, the decoded neighbor blocks positioned at a predetermined adjacency to the current image block.

9 . The video coding device of claim 1 , wherein the intra-prediction mode subset includes modes associated with a most probable mode (MPM) list for the current image block.

10 . A method comprising:
storing, in a memory, a bitstream including image blocks coded as prediction blocks; obtaining, by a processor coupled to the memory, a current prediction block encoded by a Direct Current (DC) intra-prediction mode; determining a DC prediction value to approximate a current image block corresponding to the current prediction block by averaging all reference samples in at least two of a plurality of reference lines associated with the current prediction block; reconstructing, by the processor, the current image block based on the DC prediction value; and displaying, on a display, a video frame including the current image block.

11 . The method of claim 10 , wherein determining the DC prediction value includes averaging all reference samples in N adjacent reference lines to the current prediction block, where N is a predetermined integer.

12 . The method of claim 10 , wherein determining the DC prediction value includes averaging of all reference samples in a selected reference line and a corresponding reference line.

13 . The method of claim 10 , wherein determining the DC prediction value includes averaging all reference samples in a primary reference line and a selected reference line.

14 . A non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to:
receive, via a receiver, a bitstream; decode, by the processor, an intra-prediction mode from the bitstream, the intra-prediction mode indicating a relationship between a current block and a selected reference line, the current block associated with a plurality of reference lines including the selected reference line; decode, by the processor, the selected reference line based on a selected code word indicating the selected reference line, the selected code word including a length based on a selection probability of the selected reference line; and present, on a display, video data including an image block decoded based on the intra-prediction mode and the selected reference line.

15 . The non-transitory computer readable medium of claim 14 , wherein the plurality of reference lines are indicated by a plurality of code words, and a reference line farthest from the current block is indicated by the code word with a second shortest length.

16 . The non-transitory computer readable medium of claim 14 , wherein the plurality of reference lines are indicated by a plurality of code words, and a reference line second farthest from the current block is indicated by the code word with a second shortest length.

17 . The non-transitory computer readable medium of claim 14 , wherein the plurality of reference lines are indicated by a plurality of code words, and a predefined reference line other than an adjacent reference line is indicated by the code word with a second shortest length.

18 . The non-transitory computer readable medium of claim 14 , wherein the plurality of reference lines are indicated by a plurality of code words, the plurality of code words sorted into a class A group and a class B group, the class A group including code words with shorter lengths than lengths of the code words in the class B group.

19 . The non-transitory computer readable medium of claim 14 , wherein the plurality of reference lines include reference rows and reference columns, and a number of reference rows stored for the current block is half a number of reference columns stored for the current block.

20 . The non-transitory computer readable medium of claim 14 , wherein the plurality of reference lines include reference rows and reference columns, and a number of reference rows stored for the current block is equal to a number of reference columns stored for the current block minus one.

21 . The non-transitory computer readable medium of claim 14 , wherein the plurality of reference lines include reference rows, and a number of reference rows stored for the current block is selected based on a number of reference rows employed by a deblocking filter operation.

Assignees

• Futurewei Technologies Inc

Inventors

• Liu Shan
• Ma Xiang

Classifications

• H04N19/13

  Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC] · CPC title

• H04N19/105

  Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction · CPC title

• H04N19/70

  characterised by syntax aspects related to video coding, e.g. related to compression standards · CPC title

• H04N19/139

  Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability · CPC title

• H04N19/11 Primary

  among a plurality of spatial predictive coding modes · CPC title