Neighbor based signaling of intra prediction modes

Patent metadata

Field	Value
Publication number	US-2017332084-A1
Application number	US-201715590261-A
Country	US
Kind code	A1
Filing date	May 9, 2017
Priority date	May 13, 2016
Publication date	Nov 16, 2017
Grant date	—

Abstract

A device for coding video data is configured to determine that a current block of video data is coded using an intra prediction mode; add an intra prediction mode of a first neighboring block of the current block to a most probable mode candidate list for the current block; add an intra prediction mode for a second neighboring block of the current block to the most probable mode candidate list for the current block; add an intra prediction mode for a third neighboring block of the current block to the most probable mode candidate list for the current block; and code the current block of video data using an intra prediction mode.

First claim

What is claimed is:

1 . A method for decoding video data, the method comprising:
determining that a current block of video data is coded using an intra prediction mode; adding an intra prediction mode of a first neighboring block of the current block to a most probable mode candidate list for the current block; adding an intra prediction mode for a second neighboring block of the current block to the most probable mode candidate list for the current block; adding an intra prediction mode for a third neighboring block of the current block to the most probable mode candidate list for the current block; determining an intra prediction mode using the most probable mode candidate list; and decoding the current block of video data using the intra prediction mode.

2 . The method of claim 1 , wherein the first neighboring block, the second neighboring block, and the third neighboring block each correspond to one of a left neighbor block, an above neighbor block, a below left neighbor block, an above right neighbor block, or an above left neighbor block relative to the current block.

3 . The method of claim 1 , further comprising:
after adding the intra prediction modes of the first neighboring block and the second neighboring block to the most probable mode candidate list and before adding the intra prediction mode of the third neighboring block to the most probable mode candidate list, adding one or more default candidates to the most probable mode candidate list.

4 . The method of claim 3 , wherein the one or more defaults comprise one or both of a planar mode and a DC mode.

5 . The method of claim 1 , further comprising:
adding one or more derived intra prediction modes to the most probable mode candidate list.

6 . The method of claim 5 , further comprising:
determining the one or more derived intra prediction modes based on an intra prediction mode of a neighboring block.

7 . The method of claim 6 , wherein the one or more derived intra prediction modes comprise an intra prediction mode with a mode index of the intra prediction mode of the neighboring block plus an offset.

8 . The method of claim 7 , wherein the offset is equal to one of −2, −1, 1, or 2.

9 . The method of claim 5 , further comprising:
in response to two derived intra prediction modes being a same intra prediction mode, including only one instance of the two derived intra prediction modes in the most probable mode candidate list.

10 . The method of claim 1 , wherein determining the intra prediction mode comprises:
receiving an indication that the intra prediction mode is not an intra prediction mode included in the most probable mode candidate list; receiving additional syntax indicating the intra prediction mode.

11 . The method of claim 1 , wherein determining the intra prediction mode comprises:
receiving a context coded index value identifying an intra prediction mode included in the most probable mode candidate list; determining a context for decoding the context coded index value; context decoding the context coded index value using the determined context; and determining the intra prediction mode based on the index value.

12 . The method of claim 11 , further comprising:
based on the determined context, mapping the context coded index value to bins to determine a binarized codeword comprising the index value, wherein the binarized codeword corresponds to an intra prediction mode from the most probable mode candidate list.

13 . The method of claim 12 , wherein the binarized codeword comprises a truncated unary codeword.

14 . The method of claim 12 , wherein each bin of the binarized codeword is context coded.

15 . The method of claim 12 , wherein each bin of the binarized codeword corresponds to one of the most probable modes in the most probable mode candidate list.

16 . The method of claim 12 , further comprising:
determining the context for each bin based on a classification of the most probable mode corresponding to each bin.

17 . The method of claim 16 , further comprising:
for a first bin corresponding to a first most probable mode, determining a context for the first bin based on: whether the first most probable mode belongs to a horizontal set of modes; whether the first most probable mode belongs to a vertical set of modes; or whether the first most probable mode belongs to a non-angular set of modes.

18 . The method of claim 16 , further comprising:
for a first bin corresponding to a first most probable mode, determining a context for the first bin based on:
a distance from the first most probable mode to a horizontal mode; or
a distance from the first most probable mode to a vertical mode.

19 . The method of claim 1 , further comprising:
checking a group of neighboring blocks in a fixed order to determine if neighboring blocks from the group of neighboring blocks were intra coded, wherein the group of neighboring blocks comprises the first neighboring block, the second neighboring block, the third neighboring block, and at least one other neighboring block; and adding intra prediction modes used to encode neighboring blocks from the group of neighboring blocks into the most probable mode candidate list in the fixed order.

20 . The method of claim 19 , further comprising:
in response to two neighboring blocks from the group of neighboring blocks being coded using a same intra prediction mode, including only one instance of the same intra prediction mode in the most probable mode candidate list.

21 . The method of claim 19 , wherein checking the one or more neighboring blocks of the group of neighboring blocks comprises checking the one or more neighboring blocks using a same order used to check neighboring blocks for a merge mode.

22 . The method of claim 19 , further comprising:
in response to adding intra prediction modes used to encode neighboring blocks from the group of neighboring blocks into the most probable mode candidate list causing a number of intra prediction modes in the most probable mode candidate list to exceed a threshold number, terminating the checking of the one more checking one or more neighboring blocks of the group of neighboring blocks.

23 . A device for decoding video data, the device comprising:
a memory configured to store the video data; one or more processors configured to:
determine that a current block of the video data is coded using an intra prediction mode;
add an intra prediction mode of a first neighboring block of the current block to a most probable mode candidate list for the current block;
add an intra prediction mode for a second neighboring block of the current block to the most probable mode candidate list for the current block;
add an intra prediction mode for a third neighboring block of the current block to the most probable mode candidate list for the current block;
determine an intra prediction mode using the most probable mode candidate list; and
decode the current block using the intra prediction mode.

24 . The device of claim 23 , wherein the first neighboring block, the second neighboring block, and the third neighboring block each correspond to one of a left neighbor block, an above neighbor block, a below left neighbor block, an above right neighbor block, or an above left neighbor block relative to the current block.

25 . The device of claim 23 , wherein the one or more

Assignees

• Qualcomm Inc

Inventors

• Seregin Vadim
• Zhao Xin
• Said Amir
• Karczewicz Marta
• Hu Nan
• Chien Wei-Jung
• Thirumalai Vijayaraghavan

Classifications

• H04N19/91

  Entropy coding, e.g. variable length coding [VLC] or arithmetic coding · CPC title

• H04N19/11 Primary

  among a plurality of spatial predictive coding modes · CPC title

• H04N19/42

  characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation (H04N19/635 takes precedence) · CPC title

• H04N19/176 Primary

  the region being a block, e.g. a macroblock · CPC title

• H04N19/157

  Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter · CPC title