MIXED MODE FOR FRAME BUFFER COMPRESSION

• US 20140219558A1
• Filed: 01/31/2014
• Published: 08/07/2014
• Est. Priority Date: 02/04/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Teng, Chia-Yuan, Jacobson, Natan Haim
• Granted Patent: US 9,177,393 B2
• Time in Patent Office: Days
• US Class Current: 382/166
• CPC Class Codes: G06T 9/00 Image coding bandwidth or redundancy reduction for static pictures H04N1/41; coding or decoding of static colour picture signals H04N1/64; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00
• CPC Class Codes: H04N 19/11 among a plurality of spatial predictive coding modes
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• 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 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards

Abstract

Certain aspects relate to systems and techniques for compressing image data using mixed mode compression schemes. A mixed mode compression scheme can reduce the amount of data stored in a frame buffer to reduce power costs of an image display system. In some implementations, mixed mode compression can be suitable for compression of pixel blocks having one or two color channels exhibiting a relatively low variation in pixel intensity with the remaining channel or channels exhibiting a relatively high variation. The pixel values in each color channel of an RGB or YC_oC_g image can be analyzed to determine how many channels are a smooth component and how many channels are a variant component, and mixed mode compression can be selected and implemented based on the color channel analysis to adaptively and individually compress the color channels.

Claims

1. A system in an electronic device for compressing image data, the system comprising:

a channel analysis module configured to

receive a pixel block comprising a plurality of components, at least some of the plurality of components corresponding to a color channel of the pixel block;

determine whether the pixel block is a mixed block by comparing values associated with each of the plurality of components to at least one threshold and assigning a classification of either smooth or variant to at least some of the plurality of components based on the at least one threshold, a mixed block being a pixel block having;

at least one component assigned the smooth classification, and

all of the plurality of components in the mixed block assigned the classification of either smooth or variant; and

a mixed mode compression module configured to compress the pixel block using mixed encoding based at least partly on the assigned component classifications.

2. The system of claim 1, wherein the values associated with each of the plurality of components are sum of absolute difference values indicating a level of color variance of the component.

3. The system of claim 1, wherein the channel analysis module does not assign the classification of smooth or variant to a component if the value associated with the component is between a low threshold and a high threshold.

4. The system of claim 1, wherein the mixed block further comprises at least one component assigned the variant classification.

5. The system of claim 4, wherein the mixed mode compression module implements different compression modes for the at least one component assigned the smooth classification and the at least one component assigned the variant classification.

6. The system of claim 5, wherein the mixed mode compression module implements pulse code modulation to code the at least one component assigned the variant classification.

7. The system of claim 5, wherein the mixed mode compression module implements prediction to code the at least one component assigned the smooth classification.

8. The system of claim 1, wherein a bitstream coded by mixed encoding comprises a first bit representing a color space of the pixel block, a plurality of subsequent bits representing the classification of each of the plurality of components, and at least one coded component field including the coded bitstream of a corresponding one of the plurality of components.

9. The system of claim 8, wherein the at least one coded component field corresponds to the at least one component assigned the variant classification.

10. The system of claim 8, wherein the at least one coded component field includes a value of each of a plurality of pixels in the pixel block.

11. The system of claim 8, the mixed block having two components assigned the classification of variant, the bitstream comprising two coded component fields corresponding to the two components assigned the classification of variant.

12. The system of claim 1, further comprising a mixed mode decision module configured to enable mixed mode compression if the pixel block is a mixed block.

13. The system of claim 1, further comprising a mixed mode decision module configured to disable mixed mode compression if the pixel block is not a mixed block.

14. The system of claim 1, further comprising a coding parameter module configured to set a quantization parameter based on a number of components assigned the classification of variant.

15. A method for compressing image data in an electronic device, the method comprising:

receiving a pixel block comprising a plurality of components, at least some of the plurality of components corresponding to a color channel of the pixel block;

comparing values associated with each of the plurality of components to at least one of a high threshold and a low threshold to determine a level of color variance in each of the plurality of components;

assigning a classification of smooth to at least one smooth component of the plurality of components, the value associated with the at least one smooth component being less than the low threshold;

assigning a classification of variant to at least one variant component of the plurality of components;

the value of associated with the at least one variant component being higher than the high threshold; and

determining whether the pixel block is a mixed block based on the assigned classifications.

16. The method of claim 15, further comprising compressing the pixel block using mixed encoding based at least partly on the assigned component classifications.

17. The method of claim 15, wherein the values associated with each of the plurality of components are sum of absolute difference values indicating a level of color variance of the component.

18. The method of claim 17, further comprising calculating the sum of absolute difference values for each of the plurality of components.

19. The method of claim 17, further comprising determining a color space of the pixel block based at least partly on the sum of absolute difference values.

20. The method of claim 15, further comprising implementing different compression modes for the at least one component assigned the smooth classification and the at least one component assigned the variant classification.

21. The method of claim 20, further comprising coding the at least one variant component using prediction.

22. The method of claim 20, further comprising coding the at least one smooth component using pulse code modulation.

23. An apparatus for compressing image data in an electronic device, the apparatus comprising:

means for determining level of color variance in each of a plurality of components of a pixel block by comparing values associated with each of the plurality of components to at least one of a high threshold and a low threshold;

means for assigning a classification of smooth to at least one smooth component of the plurality of components and assigning a classification of variant to at least one variant component, the value associated with the at least one smooth component being less than the low threshold and the value associated with the at least one variant component being greater than the high threshold; and

means for determining whether the pixel block is a mixed block based on the assigned classifications.

24. The apparatus of claim 23, further comprising means for implementing different compression modes for at least one component assigned the smooth classification and at least one component assigned the variant classification.

25. The apparatus of claim 23, further comprising means for calculating sum of absolute difference values for each of the plurality of components.

26. The apparatus of claim 23, further comprising means for determining a color space of the pixel block.

27. The apparatus of claim 23, further comprising means for setting set a quantization parameter based on a number of components assigned the classification of variant.

28. A non-transitory computer-readable medium storing instructions that, when executed, cause at least one physical computer processor to perform a method of compressing image data, the method comprising:

determining level of color variance in each of a plurality of components of a pixel block by comparing values associated with each of the plurality of components to at least one of a high threshold and a low threshold;

assigning a classification of either smooth or variant to at least some of the plurality of components based on the compared values;

determining whether the pixel block is a mixed block based on the assigned classifications; and

implementing different compression modes for at least one component assigned the smooth classification and at least one component assigned the variant classification.

29. The non-transitory computer-readable medium of claim 28, further comprising coding the at least one component assigned the variant classification using prediction.

30. The non-transitory computer-readable medium of claim 28, further comprising coding the at least one component assigned the smooth classification using pulse code modulation.