Signaling and use of chroma sample positioning information

• US 8,054,886 B2
• Filed: 06/29/2007
• Issued: 11/08/2011
• Est. Priority Date: 02/21/2007
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Srinivasan, Sridhar, Sullivan, Gary J., Regunathan, Shankar, Tu, Chengjie
• Primary Examiner(s): SIMITOSKI, MICHAEL J
• Application Number:
  US11/772,070
• Publication Number:
  US 20080198936A1
• Time in Patent Office: 1,593 Days
• Field of Search: 375/240.21, 348/450
• US Class Current: 375/240.21
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• 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 19/63 using sub-band based transform, e.g. wavelets
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards

Abstract

Rules for the signaling and interpretation of chroma position are described. One rule, called the short rule, defines fifteen discrete chroma centering positions and corresponding four-bit syntax element. Another rule, called the extended rule, defines 81 discrete chroma centering positions and corresponding seven-bit syntax elements. A described method includes receiving digital media data at a digital media encoder, determining chroma position information for the received digital media data, and representing the chroma position information with one or more syntax elements in an encoded bitstream. The one or more syntax elements are operable to communicate the chroma position information to a digital media decoder. The chroma position information facilitates an image rotation or flip.

Claims

1. A method comprising:

with a computing device,

receiving digital image data for an image, the digital image data comprising downsampled chroma information;

determining chroma position information for the downsampled chroma information according to a chroma position rule that maps the chroma position information to phase information in an X dimension and phase information in a Y dimension, and wherein the chroma position rule facilitates horizontal and vertical flipping or rotating of the image;

representing the chroma position information with one or more syntax elements included in an encoded bitstream; and

outputting the encoded bitstream.

2. The method of claim 1, wherein the chroma information is downsampled by a factor of two in one or more dimensions.

3. The method of claim 1, wherein the phase information in the X dimension comprises half-pixel-unit phase information.

4. The method of claim 1, wherein the phase information in the Y dimension or the X dimension comprises quarter-pixel-unit phase information.

5. The method of claim 1, wherein the chroma position rule maps the chroma position information to chroma centering phases that include X phase positions 0, 0.5 and 1, and Y phase positions 0, 0.25, 0.5, 0.75, and 1, where the phase positions are in pixel units.

6. The method of claim 1, wherein the one or more syntax elements comprises a single syntax element that represents both the phase information in the X dimension and the phase information in the Y dimension.

7. The method of claim 1, wherein the one or more syntax elements comprises a first syntax element that represents the phase information in the X dimension and a second syntax element that represents the phase information in the Y dimension.

8. The method of claim 1, wherein the digital image data comprises interlaced digital image data.

9. The method of claim 1, wherein the chroma position rule maps the chroma position information to chroma centering phases that include phase positions −

0.5, −

0.25, 0, 0.25, 0.5, 0.75, 1, 1.25 and 1.5, where the phase positions are in pixel units.

10. The method of claim 9, wherein the chroma position rule also facilitates translation of the image by an integer number of pixels.

11. The method of claim 1, further comprising using the chroma position information to upsample the downsampled chroma information.

12. A method comprising:

with a computing device,

receiving encoded digital image data for an image, the encoded digital image data comprising chroma information;

processing chroma position information for the chroma information, wherein the chroma position information indicates a position of the chroma information relative to luminance information in an X dimension and in a Y dimension and facilitates horizontal and vertical flipping or rotating of the image, and wherein the processing comprises processing one or more syntax elements of the encoded digital image data that signal the chroma position information; and

outputting a decoded bitstream.

13. The method of claim 12, wherein the chroma information is downsampled by a factor of two in one or more dimensions.

14. The method of claim 12, wherein the chroma position information indicates that chroma information is offset relative to the luminance information in the X dimension by a half pixel in luma pixel units.

15. The method of claim 12, wherein the chroma position information indicates that the chroma information is offset relative to the luminance information in the Y dimension or the X dimension by a quarter pixel in luma pixel units.

16. The method of claim 12, wherein the one or more syntax elements comprise a single syntax element that represents both the chroma position information in the X dimension and the chroma position information in the Y dimension.

17. The method of claim 12, wherein the one or more syntax elements comprise a first syntax element that represents the chroma position information in the X dimension and a second syntax element that represents the chroma position information in the Y dimension.

18. The method of claim 12, further comprising using the chroma position information to upsample the chroma information.

19. A method comprising:

using a computing device,

receiving compressed digital image data for a compressed image, the compressed digital image data comprising downsampled image channel information and one or more syntax elements indicating image channel position information;

decoding the one or more syntax elements to determine the image channel position information for the downsampled image channel information according to a first position rule of plural available position rules, each of the plural available position rules for mapping the image channel position information to phase information in an X dimension and phase information in a Y dimension to facilitate horizontal and vertical flipping or rotating of the image; and

using the image channel position information to perform a horizontal flip, vertical flip, or rotation of the compressed image.

20. The method of claim 19, wherein the downsampled image channel information comprises downsampled chroma information, and wherein the image channel position information comprises chroma position information.

21. A method comprising:

using a computing device,

receiving encoded digital image data for an image, the encoded digital image data comprising chroma information;

decoding chroma position information for downsampled chroma information by decoding one or more syntax elements in the encoded digital image data that indicate the chroma position information, the chroma position information indicating a position of the chroma information relative to luminance information in an X dimension and in a Y dimension; and

re-encoding at least part of the received digital image data under a transformation, wherein the transformation is a horizontal flip, vertical flip, rotation or crop;

wherein the re-encoding comprises modifying the chroma position information to reflect the transformation.

22. The method of claim 21 wherein the re-encoding comprises lossless encoding.

23. The method of claim 21 wherein the re-encoding comprises lossy encoding.

24. The method of claim 21 wherein the re-encoding comprises transform domain encoding.

25. One or more computer-readable storage devices storing computer-executable instructions which when executed by a computer cause the computer to perform a method, the method comprising:

receiving digital image data for an image, the digital image data comprising downsampled chroma information;

determining chroma position information for the downsampled chroma information according to a chroma position rule that maps the chroma position information to phase information in an X dimension and phase information in a Y dimension, and wherein the chroma position rule facilitates horizontal and vertical flipping or rotating of the image;

representing the chroma position information with one or more syntax elements included in an encoded bitstream; and

outputting the encoded bitstream.

26. The one or more computer-readable storage devices of claim 25, wherein the chroma information is downsampled by a factor of two in one or more dimensions.

27. The one or more computer-readable storage devices of claim 25, wherein the phase information in the X dimension comprises half-pixel-unit phase information.

28. The one or more computer-readable storage devices of claim 25, wherein the phase information in the Y dimension or the X dimension comprises quarter-pixel-unit phase information.

29. The one or more computer-readable storage devices of claim 25, wherein the chroma position rule maps the chroma position information to chroma centering phases that include X phase positions 0, 0.5 and 1, and Y phase positions 0, 0.25, 0.5, 0.75, and 1, where the phase positions are in pixel units.

30. The one or more computer-readable storage devices of claim 25, wherein the one or more syntax elements comprises a single syntax element that represents both the phase information in the X dimension and the phase information in the Y dimension.

31. The one or more computer-readable storage devices of claim 25, wherein the one or more syntax elements comprises a first syntax element that represents the phase information in the X dimension and a second syntax element that represents the phase information in the Y dimension.

32. The one or more computer-readable storage devices of claim 25, wherein the digital image data comprises interlaced digital image data.

33. The one or more computer-readable storage devices of claim 25, wherein the chroma position rule maps the chroma position information to chroma centering phases that include phase positions −

0.5, −

0.25, 0, 0.25, 0.5, 0.75, 1, 1.25 and 1.5, where the phase positions are in pixel units.

34. The one or more computer-readable storage devices of claim 33, wherein the chroma position rule also facilitates translation of the image by an integer number of pixels.

35. The one or more computer-readable storage devices of claim 25, further comprising using the chroma position information to upsample the downsampled chroma information.

36. One or more computer-readable storage devices storing computer-executable instructions which when executed by a computer cause the computer to perform a method, the method comprising:

receiving encoded digital image data for an image, the encoded digital image data comprising chroma information;

processing chroma position information for the chroma information, wherein the chroma position information indicates a position of the chroma information relative to luminance information in an X dimension and in a Y dimension and facilitates horizontal and vertical flipping or rotating of the image, and wherein the processing comprises processing one or more syntax elements of the encoded digital image data that signal the chroma position information; and

outputting a decoded bitstream.

37. The one or more computer-readable storage devices of claim 36, wherein the chroma information is downsampled by a factor of two in one or more dimensions.

38. The one or more computer-readable storage devices of claim 36, wherein the chroma position information indicates that the chroma information is offset relative to the luminance information in the X dimension by a half pixel in luma pixel units.

39. The one or more computer-readable storage devices of claim 36, wherein the chroma position information indicates that the chroma information is offset relative to the luminance information in the Y dimension or the X dimension comprises by a quarter pixel in luma pixel units.

40. The one or more computer-readable storage devices of claim 36, wherein the one or more syntax elements comprise a single syntax element that represents both the chroma position information in the X dimension and the chroma position information in the Y dimension.

41. The one or more computer-readable storage devices of claim 36, wherein the one or more syntax elements comprise a first syntax element that represents the chroma position information in the X dimension and a second syntax element that represents the chroma position information in the Y dimension.

42. The one or more computer-readable storage devices of claim 36, further comprising using the chroma position information to upsample the chroma information.