PICTURE CODING USING ADAPTIVE COLOR SPACE TRANSFORMATION

• US 20090168894A1
• Filed: 02/13/2006
• Published: 07/02/2009
• Est. Priority Date: 01/13/2006
• Status: Active Grant

• Current Assignee: GE Video Compression, LLC (General Electric Company)
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Kauff, Peter, Wiegand, Thomas, Marpe, Detlev
• Granted Patent: US 8,446,960 B2
• Time in Patent Office: Days
• US Class Current: 375/240.240
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/154 Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion use of rate-distortion criteria H04N19/147
• CPC Class Codes: H04N 19/19 using optimisation based on Lagrange multipliers
• CPC Class Codes: H04N 19/196 being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters processing of motion vectors H04N19/513
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 9/67 for matrixing camera processing pipelines for matrixing of colour signals H04N23/85

Abstract

The present invention is based on the finding that pictures or a picture stream can be encoded highly efficient when a representation of pictures is chosen that is having different picture blocks, wherein each picture block is carrying picture information for picture areas smaller than the full area of the picture and when the different picture blocks are carrying the picture information either in a first color-space representation or in a second color-space-representation. Since different color-space-representations have individual inherent properties with respect to their describing parameters, choosing an appropriate color-space-representation individually for the picture blocks results in an encoded representation of pictures that is having a better quality at a given size or bit rate.

Claims

1-25. -25. (canceled)

26. A decoder for reconstructing a picture represented in an entropy encoded representation having a first and a second picture block, the picture blocks carrying picture information for picture areas smaller than the area of the picture, wherein the first picture block is carrying the picture information in a first color-space representation and the second picture block is carrying the picture information in a second color-space representation, the decoder comprising:

an entropy decoder for deriving the first and second picture blocks using an entropy decoding rule; and

a color-space transformer for transforming either the color-space representation of the first picture block to the second color-space representation or the color-space representation of the second picture block to the first color-space representation.

27. The decoder in accordance with claim 26, in which the color-space transformer is further operative to process transformation indication information indicating a desired transformation for a picture block;

and

in which the decoder is further having a flag receiver for receiving the transformation indication information.

28. The decoder in accordance with claim 26, in which the color-space transformer is operative to process the RGB-color-space and a second color-space representation comprising one luma-parameter indicating a brightness and two chroma parameters indicating a chromatic composition of a signal.

29. The decoder in accordance with claim 28, in which the color-space transformer is operative to perform the color-space transformation between the RGB-color-space described by parameters R, G, and B and the second color-space representation described by the luma parameter Y and the chroma parameters Cg and Co according to the following formulas:

Co=R−

B  

t=Y−

(Cg>

>

1)

t=B+(Co>

>

1)  

G=Cg+t

Cg=G−

t B=t−

(Co>

>

1)

Y=t+(Cg>

>

1)  

R=B+Co.

30. The decoder in accordance with claim 26, in which the color-space transformer is operative to perform the transformation based on a parametric representation of the picture information within the picture blocks, the parametric representation describing the picture information in a transform domain.

31. The decoder in accordance with claim 30, in which the color-space transformer is operative to perform the transformation based on a parameter representation describing the picture information in a frequency domain.

32. The decoder in accordance with claim 26, in which the entropy decoder further comprises a requantizer for deriving t the first and the second picture block from a quantized representation of entropy decoded picture information.

33. The decoder in accordance with claim 26, in which the entropy decoder is operative to use an entropy decoding rule comprising the use of a Variable-length-codebook.

34. The decoder in accordance with claim 26, in which the entropy decoder is operative to use an entropy decoding rule comprising the use of a binary arithmetic coding algorithm.

35. The decoder in accordance with claim 26, in which the entropy decoder is operative to use a decoding rule having one or more sub-rules chosen depending on a decoding context.

36. The decoder in accordance with claim 26, in which the decoder is operative to reconstruct the picture using information from reference pictures of a picture stream, which are temporarily preceding or following the picture within the picture stream and that are represented using related picture blocks corresponding to the picture blocks of the picture, the related picture blocks having picture information on the same picture content as the picture blocks, wherein a positional change between the picture blocks and the corresponding picture blocks of the reference pictures with respect to a fixed location of the given picture blocks can be described by motion vectors.

37. The decoder in accordance with claim 36, in which the decoder is operative to reconstruct the picture blocks using the corresponding picture blocks and differential picture blocks predicting a change in picture information of the picture blocks with respect to the corresponding picture blocks.

38. The decoder in accordance with claim 36, further comprising an input interface for receiving a bit stream representation of the picture stream having the information of the single pictures of the picture stream.

39. The decoder in accordance with claim 26, further having a picture composer for reconstructing the picture using the first and the second picture block.

40. The decoder in accordance with claim 26, in which the color-space transformer is further operative to process bypass information indicating a sequence of picture blocks and to switch off color-space transformation for the sequence of picture blocks indicated by the bypass information.

41. An encoder for generating a representation of a picture having a first and a second picture block, the picture blocks carrying picture information for picture areas smaller than the area of the picture in a first color-space representation, the encoder comprising:

a color-space transformer for deriving transformed picture blocks, the color-space transformer adapted to transform the picture information of one of the first and the second picture blocks to a second color-space representation; and

an entropy encoder for deriving an entropy encoded representation of the transformed picture blocks according to an entropy encoding rule.

42. The encoder in accordance with claim 41, in which the color-space transformer is operative to transform the first or the second picture block for optimizing a rate-distortion ratio of the entropy encoded representations of the transformed picture blocks using a cost function.

43. The encoder in accordance with claim 41, in which the color-space transformer is operative to process a transformation information indicating a picture block to be transformed;

and

further comprising a transformation decider for generating the transformation information using a decision rule.

44. The encoder in accordance with claim 43, in which the transformation decider is operative to use a decision rule that is selecting the picture block requiring less information units when transformed to the second color-space representation.

45. The encoder in accordance with claim 44, in which the transformation decider is operative to use a decision rule that is selecting the picture block in a rate-distortion optimal way.

46. The encoder in accordance with claim 42, further comprising an output interface for outputting a bit stream having the picture information including the entropy encoded representations of the transformed first and the second picture blocks.

47. The encoder in accordance with claim 41, further comprising a motion estimator adapted to derive motion vectors indicating a positional change between related picture blocks and the picture blocks, the related picture blocks being contained within reference pictures of a picture stream and having picture information on the same picture content as the picture blocks, wherein the reference pictures temporarily precede or follow the picture within the picture stream.

48. A method of decoding a picture represented in an entropy encoded representation having a first and a second picture block, the picture blocks carrying picture information for picture areas smaller than the area of the picture, wherein the first picture block is carrying the picture information in a first color-space representation and the second picture block is carrying the picture information in a second color-space representation, the method comprising:

entropy decoding the entropy encoded representation for deriving the first and second picture blocks using an entropy decoding rule; and

transformation of either the color-space representation of the first picture block to the second color-space representation or the color-space representation of the second picture block to the first color-space representation.

49. A method of generating a representation of a picture having a first and a second picture block, the picture blocks carrying picture information for picture areas smaller than the area of the picture in a first color-space representation, the method comprising:

transformation of the picture information of the first or of the second picture block to a second color-space representation to derive transformed picture blocks; and

entropy encoding the transformed picture blocks for deriving an entropy encoded representation of the transformed picture blocks according to an entropy encoding rule.

50. A parameter bit stream having an entropy encoded representation of a picture having a first picture block and a second picture block, the picture blocks carrying picture information for picture areas smaller than the area of the picture, wherein the first picture block is carrying the picture information in a first color-space representation and the second picture block is carrying the picture information in a second color-space representation.

51. A computer readable medium storing a computer program for performing, when run on a computer, the method of decoding a picture represented in an entropy encoded representation having a first and a second picture block, the picture blocks carrying picture information for picture areas smaller than the area of the picture, wherein the first picture block is carrying the picture information in a first color-space representation and the second picture block is carrying the picture information in a second color-space representation, the method comprising:

entropy decoding the entropy encoded representation for deriving the first and second picture blocks using an entropy decoding rule; and

transformation of either the color-space representation of the first picture block to the second color-space representation or the color-space representation of the second picture block to the first color-space representation.

52. A computer readable medium storing a computer program for performing, when run on a computer, the method of generating a representation of a picture having a first and a second picture block, the picture blocks carrying picture information for picture areas smaller than the area of the picture in a first color-space representation, the method comprising:

transformation of the picture information of the first or of the second picture block to a second color-space representation to derive transformed picture blocks; and

entropy encoding the transformed picture blocks for deriving an entropy encoded representation of the transformed picture blocks according to an entropy encoding rule.