SIGNALING COLOR VALUES FOR 3D LOOKUP TABLE FOR COLOR GAMUT SCALABILITY IN MULTI-LAYER VIDEO CODING

• US 20150172670A1
• Filed: 12/16/2014
• Published: 06/18/2015
• Est. Priority Date: 12/17/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Li, Xiang, Chen, Jianle, Karczewicz, Marta
• Granted Patent: US 9,756,337 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04N 19/105 Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/136 Incoming video signal characteristics or properties
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/30 using hierarchical techniques, e.g. scalability H04N19/63 takes precedence
• CPC Class Codes: H04N 19/42 characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation H04N19/635 takes precedence
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards

Abstract

Techniques are described for signaling information used to generate three-dimensional (3D) color lookup tables for color gamut scalability in multi-layer video coding. A lower layer of video data may include color data in a first color gamut and a higher layer of the video data may include color data in a second color gamut. To generate inter-layer reference pictures, a video encoder or video decoder performs color prediction using a 3D lookup table to convert the color data of a reference picture in the first color gamut to the second color gamut. According to the techniques, a video encoder may encode partition information and/or color values of a 3D lookup table generated for color gamut scalability. A video decoder may decode the partition information and/or color values to generate the 3D lookup table in order to perform color gamut scalability.

Claims

1. A method of decoding video data, the method comprising:

determining a number of octants for each of three color components of a three-dimensional (3D) lookup table for color gamut scalability;

for each of the octants for each of the color components, decoding color mapping coefficients for a linear color mapping function of color values in the 3D lookup table used to convert color data in a first color gamut for a lower layer of the video data to a second color gamut for a higher layer of the video data;

generating the 3D lookup table based on the number of octants for each of the color components and color values associated with the color mapping coefficients for each of the octants;

decoding residual data of video blocks of the video data; and

reconstructing the video blocks of the video data based on the decoded residual data and at least one reference picture generated using the 3D lookup table.

2. The method of claim 1, wherein color mapping coefficients comprise integer values that represent floating point values using a bit-depth based on at least one of an input bit-depth or an output bit-depth of the 3D lookup table.

3. The method of claim 1, wherein decoding the color mapping coefficients comprises, for a first one of the octants for each of the color components, decoding at least one coefficient of the color mapping coefficients based on a predicted value of the at least one coefficient of the color mapping coefficients.

4. The method of claim 3, wherein the predicted value of the at least one coefficient of the color mapping coefficients is a predefined fixed value.

5. The method of claim 3, wherein the at least one coefficient of the color mapping coefficients comprises a key coefficient that defines a weighting factor for the linear color mapping function between a same color component of the lower layer of the video data and the higher layer of the video data.

6. The method of claim 5, wherein decoding the color mapping coefficients further comprises, for the first one of the octants for each of the color components, decoding the key coefficient based on a predicted value equal to a predefined non-zero value, and decoding remaining coefficients of the color mapping coefficients based on a predicted value equal to zero.

7. The method of claim 3, wherein decoding the color mapping coefficients further comprises, for each remaining one of the octants for each of the color components, decoding the color mapping coefficients based on predicted values from at least one previously decoded octant.

8. The method of claim 1, further comprising determining a quantization value for residual values of the color mapping coefficients, wherein decoding the color mapping coefficients further comprises:

for each of the octants for each of the color components, decoding residual values of the color mapping coefficients;

inverse quantizing the residual values of the color mapping coefficients based on the determined quantization value; and

reconstructing the color mapping coefficients based on the decoded residual values and predicted values of the color mapping coefficients.

9. The method of claim 8 wherein determining the quantization value for residual values of the color mapping coefficients comprises decoding at least one syntax element indicating the quantization value.

10. The method of claim 1, further comprising restricting values of the color mapping coefficients to a range based on one of a predefined fixed value or a value dependent on at least one of an input bit-depth or an output bit-depth of the 3D lookup table.

11. The method of claim 1, wherein determining the number of octants for each of the color components comprises decoding at least one syntax element indicating the number of octants for at least one of the color components of the 3D lookup table.

12. The method of claim 1, further comprising:

performing color prediction using the 3D lookup table to convert color data of a reference picture in the first color gamut for the lower layer of the video data to the second color gamut for the higher layer of the video data; and

generating at least one inter-layer reference picture for the higher layer of the video data based on the converted color data,

wherein reconstructing the video blocks of the video data comprises reconstructing video blocks in a picture of the higher layer of the video data based on the decoded residual data and the at least one inter-layer reference picture generated using the 3D lookup table.

42. The device of claim 4, wherein the one or more processors are configured to, for the first one of the octants for each of the color components, encode the key coefficient based on a predicted value equal to a predefined non-zero value, and encode remaining coefficients of the color mapping coefficients based on a predicted value equal to zero.

13. A method of encoding video data, the method comprising:

generating a three-dimensional (3D) lookup table for color gamut scalability based on a number of octants for each of three color components and color values for each of the octants;

for each of the octants for each of the color components, encoding color mapping coefficients for a linear color mapping function of the color values in the 3D lookup table used to convert color data in a first color gamut for a lower layer of the video data to a second color gamut for a higher layer of the video data;

predicting video blocks of the video data based on at least one reference picture generated using the 3D lookup table; and

encoding residual data of the video blocks in a bitstream.

14. The method of claim 13, further comprising, prior to encoding the color mapping coefficient, converting floating point values of the color mapping coefficients to integer values using a bit-depth based on at least one of an input bit-depth or an output bit-depth of the 3D lookup table.

15. The method of claim 13, wherein encoding the color mapping coefficients comprises, for a first one of the octants for each of the color components, encoding at least one coefficient of the color mapping coefficients based on a predicted value of the at least one coefficient of the color mapping coefficients.

16. The method of claim 15, wherein the predicted value of the at least one coefficient of the color mapping coefficients is a predefined fixed value.

17. The method of claim 15, wherein the at least one coefficient of the color mapping coefficients comprises a key coefficient that defines a weighting factor for the linear color mapping function between a same color component of the lower layer of the video data and the higher layer of the video data.

18. The method of claim 17, wherein encoding the color mapping coefficients further comprises, for the first one of the octants for each of the color components, encoding the key coefficient based on a predicted value equal to a predefined non-zero value, and encoding remaining coefficients of the color mapping coefficients based on a predicted value equal to zero.

19. The method of claim 15, wherein encoding the color mapping coefficients further comprises, for each remaining one of the octants for each of the color components, encoding the color mapping coefficients based on predicted values from at least one previously encoded octant.

20. The method of claim 13, further comprising determining a quantization value for residual values of the color mapping coefficients, wherein encoding the color mapping coefficients further comprises:

for each of the octants for each of the color components, calculating residual values of the color mapping coefficients based on original values of the color mapping coefficients and predicted values of the color mapping coefficients;

quantizing the residual values of the color mapping coefficients based on the determined quantization value; and

encoding the residual values of the color mapping coefficients.

21. The method of claim 20, further comprising encoding at least one syntax element indicating the determined quantization value for residual values of the color mapping coefficients.

22. The method of claim 13, further comprising restricting values of the color mapping coefficients to a range based on one of a predefined fixed value or a value dependent on at least one of an input bit-depth or an output bit--depth of the 3D lookup table.

23. The method of claim 13, further comprising encoding at least one syntax element indicating the number of octants for at least one of the color components of the 3D lookup table.

24. The method of claim 13, further comprising:

performing color prediction using the 3D lookup table to convert color data of a reference picture in the first color gamut for the lower layer of the video data to the second color gamut for the higher layer of the video data; and

generating at least one inter-layer reference picture for the higher layer of the video data based on the converted color data,

wherein predicting the video blocks of the video data comprises predicting video blocks in a picture of the higher layer of the video data based on the at least one inter-layer reference picture generated using the 3D lookup table.

25. A video decoding device comprising:

a memory configured to store video data; and

one or more processors in communication with the memory and configured to;

determine a number of octants for each of three color components of a three-dimensional (3D) lookup table for color gamut scalability of the video data,

for each of the octants for each of the color components, decode color mapping coefficients for a linear color mapping function of color values in the 3D lookup table used to convert color data in a first color gamut for a lower layer of the video data to a second color gamut for a higher layer of the video data,

generate the 3D lookup table based on the number of octants for each of the color components and color values associated with the color mapping coefficients for each of the octants,

decode residual data of video blocks of the video data, and

reconstruct the video blocks of the video data based on the decoded residual data and at least one reference picture generated using the 3D lookup table.

26. The device of claim 25, wherein the color mapping coefficients comprise integer values that represent floating point values using a bit-depth based on at least one of an input bit-depth or an output bit-depth of the 3D lookup table.

27. The device of claim 25, wherein the one or more processors are configured to, for a first one of the octants for each of the color components, decode at least one coefficient of the color mapping coefficients based on a predicted value of the at least one coefficient of the color mapping coefficients.

28. The device of claim 27, wherein the predicted value of the at least one coefficient of the color mapping coefficients is a predefined fixed value.

29. The device of claim 27, wherein the at least one coefficient of the color mapping coefficients comprises a key coefficient that defines a weighting factor for the linear color mapping function between a same color component of the lower layer of the video data and the higher la.yer of the video data,

30. The device of claim 29, wherein the one or more processors are configured to, for the first one of the octants for each of the color components, decode the key coefficient based on a predicted value equal to a predefined non-zero value, and decode remaining coefficients of the color mapping coefficients based on a predicted value equal to zero,

31. The device of claim 27, wherein the one or more processors are configured to, for each remaining one of the octants for each of the color components, decode the color mapping coefficients based on predicted values from at least one previously decoded octant.

32. The device of claim 25, wherein the one or more processors are configured to:

determine a quantization value for residual values of the color mapping coefficients;

for each of the octants for each of the color components, decode residual values of the color mapping coefficients;

inverse quantize the residual values of the color snapping coefficients based on the determined quantization value; and

reconstruct the color mapping coefficients used on the decoded residual values and predicted values of the color mapping coefficients.

33. The device of claim 32, wherein, to determine the quantization value for residual values of the color mapping coefficients, the one or more processors are configured to decode at least one syntax element indicating the quantization value.

34. The device of claim 25, wherein the one or more processors are configured to restrict values of the color mapping coefficients to a range based on one of a predefined fixed value or a value dependent on at least one of an input bit-depth or an output bit-depth of the 3D lookup table.

35. The device of claim 25, wherein, to determine the number of octants for each of the color components, the one or more processors are configured to decode at least one syntax element indicating the number of octants for at least one of the color components of the 3D lookup table.

36. The device of claim 25, wherein the one or more processors are configured to:

perform color prediction using the 3D lookup table to convert color data of a reference picture in the first color gamut for the lower layer of the video data to the second color gamut for the higher layer of the video data;

generate at least one inter-layer reference picture for the higher layer of the video Lta based on the converted color data; and

reconstruct video blocks in a picture of the higher layer of the video data based on the decoded residual data and the at least one inter--layer reference picture generated using the 3D lookup table.

37. A video encoding device comprising:

a memory configured to store video data; and

one or More processors in communication with the memory and configured to;

generate a three-dimensional (3D) lookup table for color gamut scalability of the video data based on a number of octants for each of three color components and color values for each of the octants,

for each of the octants for each of the color components, encode color mapping coefficients for a linear color mapping function of the color values in the 3D lookup table used to convert color data in a first color gamut for a lower layer of the video data to a second color gamut for a higher layer of the video data,

predict video blocks of the video data bas at least one reference picture generated using the 3D lookup table, and

encode residual data of the video blocks in a bitstream.

38. The device of claim 37, wherein the one or more processors are configured to, prior to encoding the color mapping coefficients, convert floating point values of the color mapping coefficients to integer values using a bit-depth based on at least one of an input hit-depth or an output hit-depth of the 3D lookup table,

39. The device of claim 37, wherein the one or more processors are configured to, for a first one of the octants for each of the color components, encode at least one coefficient of the color mapping coefficients based on a predicted value of the at least one coefficient of the color flapping coefficients.

40. The device of claim 39, wherein the predicted value of the at least one coefficient of the color mapping coefficients is a predefined fixed value.

41. The device of claim 39, wherein the at least one coefficient of the color mapping coefficients comprises a key coefficient that defines a weighting factor for the linear color mapping function between a same color component of the lower layer of the video data and the higher layer of the video data.

43. The device of claim 39, wherein the one or more processors are configured to, for each remaining one of the octants for each of the color components, encode the color mapping coefficients based on predicted values from at least one previously encoded octant.

44. The device of claim 37, wherein the one or more processors are configured

determine a quantization value for residual values of the color mapping coefficients;

for each of the octants for each of the color components, calculate residual values of the color mapping coefficients based on original values of the color mapping coefficients and predicted values of the color mapping coefficients;

quantize the residual values of the color mapping coefficients based on the determined quantization value; and

encode the residual values of the color wrapping coefficients.

45. The device of claim 44, wherein the one or more processors are configured to encode at least one syntax element indicating the determined quantization value.

46. The device of claim 37, wherein the one or more processors are configured to restrict values of the color mapping coefficients to a range based on one of a predefined fixed value or a value dependent on at least one of an input bit-depth or an output bit-depth of the 3D lookup table.

47. The device of claim 37, wherein the one or more processors are configured to encode at least one syntax element indicating the number of octants for at least one of the color components of the 3D lookup table.

48. The device of claim 37, wherein the one or more processors are configured to:

perform color prediction using the 3D lookup table to convert color data of a reference picture in the first color gamut for the lower layer of the video data to the second color gamut for the higher layer of the video data;

generate at least one inter-layer reference picture for the higher layer of the video data based on the converted color data; and

predict video blocks in a picture of the higher layer of the video data based on the at least one inter-layer reference picture generated using the 3D lookup table.

49. A video decoding device comprising:

means for determining a number of octants for each of three color components of a three-dimensional (3D) lookup table for color gamut scalability;

means for decoding, for each of the octants for each of the color components, color mapping coefficients for a linear color mapping function of color values in the 3D lookup table used to convert color data in a first color gamut for a lower layer of the video data to a second color gamut for a higher layer of the video data;

means for generating the 3D lookup table based on the number of octants for each of the color components and color values associated with the color mapping coefficients for each of the octants;

means for decoding residual data of video blocks of the video data; and

means for reconstructing the video blocks of the video data based on the decoded residual data and at least one reference picture generated using the 3D lookup table.

50. A computer-readable storage medium storing instructions for decoding video data that, when executed, cause one or more processors to:

determine a number of octants for each of three color components of a three-dimensional (3D) lookup table for color gamut scalability;

for each of the octants for each of the color components, decode color mapping coefficients for a linear color mapping function of color values in the 3D lookup table used to convert color data in a first color gamut for a lower layer of the video data to a second color gamut for a higher layer of the video data;

generate the 3D lookup table based on the number of octants for each of the color components and color values associated with the color mapping coefficients for each of the octants;

decode residual data of video blocks of the video data; and

reconstruct the video blocks of the video data based on the decoded residual data and at least one reference picture generated using the 3D lookup table.