Variable coding resolution in video codec

• US 9,071,847 B2
• Filed: 10/06/2004
• Issued: 06/30/2015
• Est. Priority Date: 10/06/2004
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Holcomb, Thomas W., Lin, Chih-Lung, Srinivasan, Sridhar, Hsu, Pohsiang
• Primary Examiner(s): DIEP, NHON THANH
• Application Number:
  US10/960,356
• Publication Number:
  US 20060072672A1
• Time in Patent Office: 3,919 Days
• US Class Current: 1/1
• CPC Class Codes: H04N 19/107 between spatial and temporal predictive coding, e.g. picture refresh
• CPC Class Codes: H04N 19/136 Incoming video signal characteristics or properties
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/156 Availability of hardware or computational resources, e.g. encoding based on power-saving criteria
• CPC Class Codes: H04N 19/164 Feedback from the receiver or from the transmission channel
• 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 19/177 the unit being a group of pictures [GOP]
• CPC Class Codes: H04N 19/179 the unit being a scene or a shot
• 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 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards
• CPC Class Codes: H04N 19/80 Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation H04N19/635, H04N19/86 take precedence
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness

Abstract

A video codec provides for encoding and decoding pictures of a video sequence at various coded resolutions, such that pictures can be encoded at lower coded resolutions based on bit rate or other constraints while maintaining a consistent display resolution. The video codec employs a coding syntax where a maximum coded resolution is signaled at the sequence level of the syntax hierarchy, whereas a lower coded resolution is signaled at the entry point level for a segment of one or more intra-coded frames and frames predictively encoded based thereon. This allows the use of a separate out-of-loop resampler after the decoder to up-sample the pictures to the display resolution.

Claims

1. A method of decoding video coded using variable coded resolution, comprising, with a computing device that implements a video decoder:

receiving a video bit stream, where a sequence header is integral to the video bit stream, the video bit stream having a plurality of entry point segments representing separate sub-sequences of pictures of a video sequence;

decoding at least one syntax element from the sequence header, the least one syntax element from the sequence header specifying a maximum coded resolution for the video sequence;

for a given one of the entry point segments, determining whether to use the maximum coded resolution for the video sequence as coded resolution for pictures of the given entry point segment and, if not, determining the coded resolution for the pictures of the given entry point segment by decoding at least one syntax element of an entry point header for the given entry point segment, the at least one syntax element of the entry point header specifying the coded resolution for the pictures of the given entry point segment;

decoding said given entry point segment; and

reconstructing at least part of the video sequence with the decoded entry point segment.

2. The method of claim 1, wherein the at least one syntax element specifying the maximum coded resolution are maximum coded width and height values.

3. The method of claim 2, wherein the maximum coded width and height values are binary coded values relating to width and height of the maximum coded resolution, respectively.

4. The method of claim 1, wherein the determining whether to use the maximum coded resolution is based on a flag in the entry point header for the given entry point segment, the flag being indicative of whether the pictures in the given entry point segment are encoded at a coded resolution lower than the maximum coded resolution.

5. The method of claim 1, wherein the at least one syntax element of the entry point header specifying the coded resolution comprises coded width and height values.

6. The method of claim 5, wherein the coded width and height values are binary coded values relating to width and height of the coded resolution, respectively.

7. The method of claim 1 wherein the coded resolution for the given entry point segment is lower than the maximum coded resolution, and wherein the given entry point segment includes an I picture at the coded resolution and one or more P pictures encoded using motion compensation at the coded resolution, the method further comprising:

buffering the pictures of the decoded entry point segment at the coded resolution; and

up-sampling the pictures of the decoded entry point segment.

8. The method of claim 1 wherein the at least one syntax element of the sequence header include first and second sequence-layer syntax elements indicating maximum coded width and maximum coded height, respectively, for the video sequence, and wherein the entry point header for the given entry point segment includes:

a first entry point-layer syntax element indicating if the video bit stream includes the at least one syntax element specifying the coded resolution for the pictures of the given entry point segment; and

if so, as the at least one syntax element specifying the coded resolution for the pictures of the given entry point segment, second and third entry point-layer syntax elements indicating coded width and coded height, respectively, for the pictures of the given entry point segment.

9. A computer system comprising a processor and memory, wherein the computer system implements a video player comprising:

a demultiplexer configured to extract a video bit stream, where a sequence header is integral to the video bit stream;

a video decoder configured to;

read elements specifying a maximum coded resolution for a video sequence from the sequence header, the video sequence having a plurality of entry point segments for separate sub-sequences of pictures of the video sequence, each of the entry point segments being marked by a separate entry point and having at least one picture;

read a flag of an entry point header for a given one of the entry point segments in the video sequence, the flag indicating whether the at least one picture of the given entry point segment is encoded at a lower coded resolution;

read, from the entry point header for the given entry point segment, elements specifying the lower coded resolution for the at least one picture of the given entry point segment when indicated for the given entry point segment by the flag;

decode the at least one picture of the given entry point segment; and

up-sample the at least one picture of the given entry point segment from the lower coded resolution to the maximum coded resolution for the video sequence.

10. The computer system of claim 9, wherein the elements specifying the maximum coded resolution are width and height values.

11. The computer system of claim 9, wherein the elements specifying the lower coded resolution are width and height values.

12. The computer system of claim 9, further comprising:

a buffer, in the decoder, configured to buffer the at least one picture of the given entry point segment at the lower coded resolution for decoding any motion-compensated pictures without resampling of the buffered at least one picture.

13. The computer system of claim 9 wherein the elements of the sequence header include first and second sequence-layer syntax elements indicating maximum coded width and maximum coded height, respectively, for the video sequence, and wherein the elements of the entry point header for the given entry point segment include first and second entry point-layer syntax elements indicating coded width and coded height, respectively, for the pictures of the given entry point segment.

14. At least one computer-readable medium having a computer-executable instructions stored thereon that are executable by a processing unit to perform decoding of a video bit stream coded using variable coded resolution, the at least one computer-readable medium being selected from the group consisting of volatile memory, non-volatile memory, and magnetic disk, the decoding of the video bit stream comprising:

receiving a video bit stream, where a sequence header is integral to the video bit stream, the video bit stream having a plurality of entry point segments representing separate sub-sequences of pictures of a video sequence;

decoding at least one syntax element from the sequence header, the at least one syntax element from the sequence header specifying a maximum coded resolution for the video sequence;

for a given one of the entry point segments, determining whether to use the maximum coded resolution for the video sequence as coded resolution for pictures of the given entry point segment and, if not, determining the coded resolution for the pictures of the given entry point segment by decoding at least one syntax element of an entry point header for the given entry point segment, the at least one syntax element of the entry point header specifying the coded resolution for the pictures of the given entry point segment;

decoding said given entry point segment; and

in a case where the coded resolution for the pictures of the given entry point segment is lower than the maximum coded resolution, up-sampling the pictures of the given entry point segment to the maximum coded resolution for display of the video.

15. The at least one computer-readable medium of claim 14, wherein the at least one syntax element specifying the maximum coded resolution are maximum coded width and height values.

16. The at least one computer-readable medium of claim 15, wherein the maximum coded width and height values are binary coded values relating to width and height of the maximum coded resolution, respectively.

17. The at least one computer-readable medium of claim 14, wherein the determining whether to use the maximum coded resolution is based on a flag in the entry point header for the given entry point segment, the flag being indicative of whether the pictures in the given entry point segment are encoded at a coded resolution lower than the maximum coded resolution.

18. The at least one computer-readable medium of claim 14, wherein the at least one syntax element of the entry point header specifying the coded resolution comprises coded width and height values.

19. The at least one computer-readable medium of claim 18, wherein the coded width and height values are binary coded values relating to width and height of the coded resolution, respectively.

20. The at least one computer-readable medium of claim 14, wherein the coded resolution for the given entry point segment is lower than the maximum coded resolution, wherein the given entry point segment includes an I picture at the coded resolution and one or more P pictures encoded using motion compensation at the coded resolution, and wherein the decoding of the video bit stream further comprises:

buffering the pictures of the decoded entry point segment at the coded resolution.

21. The at least one computer-readable medium of claim 14 wherein the at least one syntax element of the sequence header include first and second sequence-layer syntax elements indicating maximum coded width and maximum coded height, respectively, for the video sequence, and wherein the entry point header for the given entry point segment includes:

a first entry point-layer syntax element indicating if the video bit stream includes the at least one syntax element specifying the coded resolution for the pictures of the given entry point segment; and

if so, as the at least one syntax element specifying the coded resolution for the pictures of the given entry point segment, second and third entry point-layer syntax elements indicating coded width and coded height, respectively, for the pictures of the given entry point segment.