LOCAL PICTURE IDENTIFIER AND COMPUTATION OF CO-LOCATED INFORMATION

• US 20100195721A1
• Filed: 02/02/2009
• Published: 08/05/2010
• Est. Priority Date: 02/02/2009
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Gan, Kim-chyan, Thumpudi, Naveen, Wu, Yongjun
• Granted Patent: US 8,189,666 B2
• Time in Patent Office: Days
• US Class Current: 375/240.12
• CPC Class Codes: H04N 19/102 characterised by the element, parameter or selection affected or controlled by the adaptive coding
• 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 19/44 Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
• CPC Class Codes: H04N 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/513 Processing of motion vectors
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards

Abstract

Video decoding innovations for using local picture identifiers and computing co-located information are described. In one aspect, a decoder identifies reference pictures in a reference picture list of a temporal direct prediction mode macroblock that match reference pictures used by a co-located macroblock using local picture identifiers. In another aspect, a decoder determines whether reference pictures used by blocks are the same by comparing local picture identifiers during calculation of boundary strength. In yet another aspect, a decoder determines a picture type of a picture and based on the picture type selectively skips or simplifies computation of co-located information for use in reconstructing direct prediction mode macroblocks outside the picture.

Claims

1. A computer-implemented method for transforming encoded video information using a video decoder, the method comprising:

receiving encoded video information in a bitstream; and

during decoding the encoded video information, wherein the decoding uses plural reference pictures identified with local picture identifiers;

identifying a temporal direct prediction mode macroblock, wherein the temporal direct prediction mode macroblock is associated with a reference picture list of one or more of the plural reference pictures;

identifying a co-located macroblock of the temporal direct prediction mode macroblock, wherein the co-located macroblock uses one or more reference pictures of the plural reference pictures;

identifying one or more reference pictures in the reference picture list that match the one or more reference pictures used by the co-located macroblock, wherein the identifying the one or more reference pictures in the reference picture list uses local picture identifiers; and

using the identified one or more reference pictures in reconstruction of the temporal direct prediction mode macroblock.

2. The method of claim 1 wherein the local picture identifiers are 8-bit local picture identifiers, and wherein the decoder sets the local picture identifiers independent of picture order count.

3. The method of claim 1 wherein the local picture identifiers are 5-bit local picture identifiers.

4. The method of claim 1 wherein the local picture identifiers are greater than or equal to 5-bits, and less than or equal to 32-bits, and wherein the decoder selectively reuses the local picture identifiers during decoding based on which of the local picture identifiers are in use, thereby controlling bit depth of the local picture identifiers and speeding up the identification of the one or more reference pictures in the reference picture list.

5. The method of claim 1 wherein the temporal direct prediction mode macroblock is in a B slice of the bitstream, and wherein the reference picture list is associated with the B slice.

6. The method of claim 1 further comprising, during decoding the encoded video information:

creating a table, wherein the table stores reference picture list index values of the reference picture list, and wherein the stored reference picture list index values are indexed in the table by the local picture identifiers;

wherein the identifying the one or more reference pictures in the reference picture list is performed by looking up one or more local picture identifiers of the one or more reference pictures used by the co-located macroblock in the table and retrieving one or more corresponding reference picture list index values, wherein the retrieved reference picture list index values identify the one or more reference pictures in the reference picture list that match the one or more reference pictures used by the co-located macroblock.

7. The method of claim 1 wherein the local picture identifiers are assigned to picture structures when allocated, and wherein the decoder reuses the local picture identifiers during the decoding based on availability of the local picture identifiers.

8. The method of claim 1 wherein the local picture identifiers are 8-bit local picture identifiers, and wherein an invalid picture identifier is assigned an 8-bit value of 255.

9. A computer-readable storage medium storing computer-executable instructions for causing a computer system programmed thereby to perform the method of claim 1.

10. A computer-implemented method for transforming encoded video information using a video decoder, the method comprising:

receiving encoded video information in a bitstream;

performing loop filtering during decoding the encoded video information, comprising;

calculating boundary strength values for plural blocks, wherein the calculating comprises determining whether reference pictures used by the plural blocks are the same by comparing local picture identifiers of the reference pictures; and

outputting the filtered macroblock.

11. The method of claim 10 wherein the local picture identifiers are 8-bit local picture identifiers, and wherein the decoder sets the local picture identifiers independent of picture order count.

12. The method of claim 10 wherein the local picture identifiers are 5-bit local picture identifiers.

13. The method of claim 10 wherein the local picture identifiers are greater than or equal to 5-bits, and less than or equal to 32-bits, and wherein the decoder selectively reuses the local picture identifiers during decoding based on which of the local picture identifiers are in use, thereby controlling bit depth of the local picture identifiers and speeding up the determination of whether reference pictures used by the plural blocks are the same during the loop filtering.

14. The method of claim 10 wherein the encoded video information is H.264 encoded video information.

15. A computer-implemented method for transforming encoded video information using a video decoder, the method comprising:

receiving encoded video information in a bitstream; and

during decoding the encoded video information;

determining a picture type for a picture based on slice type of one or more slices in the picture; and

based on the picture type of the picture, selectively skipping or simplifying computation of co-located information for use in reconstruction of one or more direct prediction mode macroblocks outside the picture.

16. The method of claim 15 wherein each of the one or more direct prediction mode macroblocks is a temporal direct prediction mode macroblock.

17. The method of claim 15 wherein each of the one or more direct prediction mode macroblocks is a spatial direct prediction mode macroblock.

18. The method of claim 15 wherein the determining the picture type of the picture comprises:

determining the picture type as an “

I picture”

if all slices in the picture are I slices;

determining the picture type as “

P picture”

if all slices in the picture are I or P slices, and there is at least one P slice in the picture; and

determining the picture type as “

B picture”

if at least one slice in the picture is a B slice.

19. The method of claim 15 wherein the one or more direct prediction mode macroblocks are in one or more B slices of the bitstream.

20. The method of claim 15 wherein if the picture type is “

I picture” and

a direct prediction mode macroblock of the one or more direct prediction mode macroblocks is a spatial direct prediction mode macroblock, the selectively skipping or simplifying computation of co-located information comprises, during reconstruction of the direct prediction mode macroblock;

retrieving information from list 0 of the picture; and

skipping retrieving information from list 1 of the picture.