Variable coding resolution in video codec

• US 20060072672A1
• Filed: 10/06/2004
• Published: 04/06/2006
• Est. Priority Date: 10/06/2004
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Lin, Chih-Lung, Srinivasan, Sridhar, Hsu, Pohsiang, Holcomb, Thomas W.
• Granted Patent: US 9,071,847 B2
• Time in Patent Office: Days
• US Class Current: 375/240.250
• 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 using variable coded resolution, comprising:

extracting a video bit stream from a carrying channel container, where a sequence header is integral to the video bit stream;

decoding at least one syntax element from a sequence header carried in the video bit stream specifying a maximum coded resolution;

decoding at least one syntax element specifying a coded resolution of a unit of the video bit stream; and

in a case where the coded resolution of the unit is less than the maximum coded resolution, up-sampling the unit to the maximum coded resolution for display of the video.

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 decoding the at least one syntax element specifying the coded resolution comprises:

decoding the at least one syntax element specifying the coded resolution from a header of a segment of the video comprising a group of at least one I-frame, and optionally one or more pictures predictively encoded based upon the at least one I-frame.

5. The method of claim 4, wherein the header of the segment is an entry point header.

6. The method of claim 4, wherein the at least one syntax element specifying the coded resolution comprises a flag indicative of whether pictures in the segment are encoded at a coded resolution lower than the maximum coded resolution.

7. The method of claim 4, wherein the at least one syntax element specifying the coded resolution comprises coded width and height values.

8. The method of claim 7, wherein the coded width and height values are binary coded values relating to width and height of the coded resolution, respectively.

9. The method of claim 4 further comprising:

buffering pictures of the segment at the coded resolution;

decoding any predictively encoded pictures of the segment with reference to the at least one I-frame buffered at the coded resolution; and

then, up-sampling pictures of the segment after decoding the any predictively encoded pictures.

10. A video decoder, comprising:

means for reading elements specifying a maximum coded resolution for a video sequence from a sequence header of the video sequence in a compressed video bit stream;

means for reading a flag indicative of whether at least one picture of a segment in the video sequence is encoded at a lower coded resolution;

means for reading elements specifying the lower coded resolution when indicated for the segment by the flag;

means for decoding the at least one picture of the segment; and

means for up-sampling the at least one picture of the segment from the lower coded resolution to the maximum coded resolution of the video sequence.

11. The video decoder of claim 10, wherein the elements specifying the maximum coded resolution are width and height values.

12. The video decoder of claim 10, wherein the elements specifying the lower coded resolution are width and height values.

13. The video decoder of claim 10, wherein the elements specifying the lower coded resolution are carried in an entry point header signaling an entry point of a sequence of at least one I-frame and possibly frames predictively encoded based on the at least one I-frame.

14. The video decoder of claim 13, further comprising:

means for buffering the at least one picture of the segment at the lower coded resolution for decoding any pictures predictively encoded from the at least one I-frame without resampling.

15. At least one computer-readable program carrying medium having a software module thereon that is executable by a processing unit to perform a method of decoding a video bit stream coded using variable coded resolution, the method comprising:

extracting a video bit stream from a carrying channel container, where a sequence header is integral to the video bit stream;

decoding at least one syntax element from a sequence header carried in the video bit stream specifying a maximum coded resolution;

decoding at least one syntax element specifying a coded resolution of a unit of the video bit stream; and

in a case where the coded resolution of the unit is less than the maximum coded resolution, up-sampling the unit to the maximum coded resolution for display of the video.

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

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

18. The at least one program carrying medium of claim 15, wherein said decoding the at least one syntax element specifying the coded resolution comprises:

decoding the at least one syntax element specifying the coded resolution from a header of a segment of the video comprising a group of at least one I-frame, and optionally one or more pictures predictively encoded based upon the at least one I-frame.

19. The at least one program carrying medium of claim 18, wherein the header of the segment is an entry point header.

20. The at least one program carrying medium of claim 18, wherein the at least one syntax element specifying the coded resolution comprises a flag indicative of whether pictures in the segment are encoded at a coded resolution lower than the maximum coded resolution.

21. The at least one program carrying medium of claim 18, wherein the at least one syntax element specifying the coded resolution comprises coded width and height values.

22. The at least one program carrying medium of claim 21, wherein the coded width and height values are binary coded values relating to width and height of the coded resolution, respectively.

23. The at least one program carrying medium of claim 18, wherein the method further comprises:

buffering pictures of the segment at the coded resolution;

decoding any predictively encoded pictures of the segment with reference to the at least one I-frame buffered at the coded resolution; and

then, up-sampling pictures of the segment after decoding the any predictively encoded pictures.