ADAPTIVE CODING OF VIDEO BLOCK PREDICTION MODE

• US 20080310507A1
• Filed: 06/04/2008
• Published: 12/18/2008
• Est. Priority Date: 06/15/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Karczewicz, Marta, Ye, Yan
• Granted Patent: US 8,428,133 B2
• Time in Patent Office: Days
• US Class Current: 375/240.12
• CPC Class Codes: H04N 19/103 Selection of coding mode or of prediction mode
• CPC Class Codes: H04N 19/11 among a plurality of spatial predictive coding modes
• CPC Class Codes: H04N 19/12 Selection from among a plurality of transforms or standards, e.g. selection between discrete cosine transform [DCT] and sub-band transform or selection between H.263 and H.264
• CPC Class Codes: H04N 19/122 Selection of transform size, e.g. 8x8 or 2x4x8 DCT; Selection of sub-band transforms of varying structure or type
• CPC Class Codes: H04N 19/129 Scanning of coding units, e.g. zig-zag scan of transform coefficients or flexible macroblock ordering [FMO]
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/147 according to rate distortion criteria rate-distortion as a criterion for motion estimation H04N19/567
• CPC Class Codes: H04N 19/157 Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/18 the unit being a set of transform coefficients
• 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 19/197 including determination of the initial value of an encoding parameter H04N19/56 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 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/463 by compressing encoding parameters before transmission
• CPC Class Codes: H04N 19/48 using compressed domain processing techniques other than decoding, e.g. modification of transform coefficients, variable length coding [VLC] data or run-length data motion estimation in a transform domain H04N19/547; processing of decoded motion vectors H04N19/513
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/625 using discrete cosine transform [DCT]
• CPC Class Codes: H04N 19/70 : characterised by syntax aspects related to video coding, e.g. related to compression standards

Abstract

This disclosure describes techniques for coding of header information of video blocks. In particular, the techniques of this disclosure select one of a plurality of prediction modes for use in generating a prediction block of a video block of a coding unit, the plurality of prediction modes including unidirectional prediction modes and multi-directional prediction modes that combine at least two unidirectional prediction modes. An encoding device encodes the prediction mode of the current video block based on prediction modes of one or more previously encoded video blocks of the coding unit. Likewise, a decoding unit receives encoded video data of a video block of a coding unit and decodes the encoded video data to identify one of a plurality of prediction modes for use in generating a prediction block of the video block based on prediction modes of one or more previously decoded video blocks of the coding unit.

Claims

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

selecting one of a plurality of prediction modes for use in generating a prediction block of a video block of a coding unit, wherein the prediction modes include unidirectional prediction modes and multi-directional prediction modes that combine at least two unidirectional prediction modes; and

encoding the prediction mode of the current video block based on prediction modes of one or more previously encoded video blocks of the coding unit.

2. The method of claim 1, further comprising selecting one of a plurality of coding contexts for use in encoding the prediction mode of the video block based on the prediction modes of the one or more previously encoded video blocks of the coding unit, wherein encoding comprises encoding according to the selected coding context.

3. The method of claim 2, wherein selecting one of the coding contexts comprises:

selecting a first coding context when the prediction modes of the one or more previously encoded video blocks are all unidirectional prediction modes;

selecting a second coding context when the prediction modes of the one or more previously encoded video blocks are all multi-directional prediction modes; and

selecting a third coding context when the prediction modes of the one or more previously encoded video blocks are neither all unidirectional nor all multi-directional.

4. The method of claim 1, further comprising:

subtracting the prediction block generated using the selected prediction mode from the video block to form a residual block;

selecting a transform to apply to the residual block based on the selected prediction mode; and

applying the selected transform to the residual block to generate residual transform coefficients.

5. The method of claim 4, wherein selecting the transform to apply to the residual block comprises:

selecting one of a discrete cosine transform (DCT) and an integer transform to apply to the residual block when the selected prediction mode exhibits limited directionality; and

selecting a directional transform to apply to the residual block when the selected prediction mode exhibits directionality.

6. The method of claim 5, wherein selecting one of the DCT and the integer transform comprises selecting one of the DCT and the integer transform to apply to the residual block when the selected prediction mode is either a DC unidirectional prediction mode or a multi-directional prediction mode that combines at least two prediction modes that point in substantially orthogonal directions.

7. The method of claim 5, further comprising storing a plurality of directional transforms, wherein each of the plurality of directional transforms corresponds with one of the prediction modes that exhibits directionality, wherein selecting the directional transform comprises selecting the one of the plurality of directional transforms corresponding to the selected prediction mode.

8. The method of claim 4, further comprising storing a plurality of directional transforms that each correspond with one of the prediction modes, wherein each of the directional transforms comprises a column transform matrix of size N×

N and a row transform matrix of size N×

N, where N×

N is a dimension of the video block.

9. The method of claim 4, further comprising storing a plurality of directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of directional transforms comprises a transform matrix of size N2×

N², where N is a dimension of the video block.

10. The method of claim 1, wherein the plurality of prediction modes includes unidirectional prediction modes and a subset of possible bidirectional prediction modes, the subset of bidirectional prediction modes including at least one combination that includes each of the unidirectional prediction modes.

11. The method of claim 1, wherein encoding the prediction mode of the current video block based on prediction modes of one or more previously encoded video blocks of the coding unit comprises:

encoding a first bit representing the prediction mode to indicate that the prediction mode of the current block is the same as one of the prediction modes of the one or more previously encoded video blocks; and

encoding, when the prediction modes of the one or more previously encoded video blocks are not the same as one another, at least one additional bit representing the prediction mode to indicate which of the one or more previously encoded video blocks has the same prediction mode as the prediction mode of the video block.

12. The method of claim 1, wherein encoding the prediction mode of the current video block based on prediction modes of one or more previously encoded video blocks of the coding unit comprises:

encoding a first bit representing the prediction mode to indicate that the prediction mode of the current block is not the same as any of the prediction modes of the one or more previously encoded video blocks;

removing at least the prediction modes of the one or more previously encoded video blocks from the plurality of prediction modes;

removing at least one additional prediction mode that is not a prediction mode of the one or more previously encoded video blocks when two or more of the previously encoded video blocks of the coding unit have the same prediction mode;

temporarily rearranging prediction mode identifiers among the remaining prediction modes of the plurality of prediction modes; and

encoding a codeword that identifies the prediction mode identifier corresponding to the prediction mode of the current video block.

13. A device that encodes video data, the device comprising:

a prediction unit that selects one of a plurality of prediction modes for use in generating a prediction block of a video block of a coding unit, wherein the prediction modes include unidirectional prediction modes and multi-directional prediction modes that combine at least two unidirectional prediction modes; and

an entropy encoding unit that encodes the prediction mode of the current video block based on prediction modes of one or more previously encoded video blocks of the coding unit.

14. The device of claim 13, wherein the entropy encoding unit selects one of a plurality of coding contexts for use in encoding the prediction mode of the video block based on the prediction modes of the one or more previously encoded video blocks of the coding unit and encodesthe prediction mode according to the selected coding context.

15. The device of claim 14, wherein the entropy encoding unit selects a first coding context when the prediction modes of the one or more previously encoded video blocks are all unidirectional prediction modes, selects a second coding context when the prediction modes of the one or more previously encoded video blocks are all multi-directional prediction modes and selects a third coding context when the prediction modes of the one or more previously encoded video blocks are neither all unidirectional nor all multi-directional.

16. The device of claim 13, further comprising a transform unit that selects a transform to apply to a residual block based on the selected prediction mode and applies the selected transform to the residual block to generate residual transform coefficients, wherein the entropy encoding unit encodes the residual transform coefficients.

17. The device of claim 16, wherein the transform unit selects one of a discrete cosine transform (DCT) and an integer transform to apply to the residual block when the selected prediction mode exhibits limited directionality and selects a directional transform to apply to the residual block when the selected prediction mode exhibits directionality.

18. The device of claim 17, wherein the transform unit selects one of the DCT and the integer transform to apply to the residual block when the selected prediction mode is either a DC unidirectional prediction mode or a multi-directional prediction mode that combines at least two prediction modes that point in substantially orthogonal directions.

19. The device of claim 17, further comprising a memory that stores a plurality of directional transforms, wherein each of the plurality of directional transforms corresponds with one of the prediction modes that exhibits directionality, wherein the transform unit selects the one of the plurality of directional transforms corresponding to the selected prediction mode.

20. The device of claim 16, further comprising a memory that stores a plurality of directional transforms that each correspond with one of the prediction modes, wherein each of the directional transforms comprises a column transform matrix of size N×

N and a row transform matrix of size N×

N, where N×

N is a dimension of the video block.

21. The device of claim 16, further comprising a memory that stores a plurality of directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of directional transforms comprises a transform matrix of size N²×

N², where N is a dimension of the video block.

22. The device of claim 13, wherein the plurality of prediction modes includes unidirectional prediction modes and a subset of possible bidirectional prediction modes, the subset of bidirectional prediction modes including at least one combination that includes each of the unidirectional prediction modes.

23. The device of claim 13, wherein the entropy encoding unit:

encodes a first bit representing the prediction mode to indicate that the prediction mode of the current block is the same as one of the prediction modes of the one or more previously encoded video blocks; and

encodes at least one additional bit when the prediction modes of the one or more previously encoded video blocks are not the same as one another, the at least one additional bit indicating which of the one or more previously encoded video blocks has the same prediction mode as the prediction mode of the video block.

24. The device of claim 13, wherein

the prediction unit:

removes at least the prediction modes of the one or more previously encoded video blocks from the plurality of prediction modes,

removes at least one additional prediction mode that is not a prediction mode of the one or more previously encoded video blocks when two or more of the previously encoded video blocks of the coding unit have the same prediction mode, and

temporarily rearranges prediction mode identifiers among the remaining prediction modes of the plurality of prediction modes, and the entropy encoding unit;

encodes a first bit representing the prediction mode to indicate that the prediction mode of the current block is not the same as any of the prediction modes of the one or more previously encoded video blocks, and

encodes a codeword that identifies the prediction mode identifier corresponding to the prediction mode of the current video block.

25. The device of claim 13, wherein the device comprises a wireless communication device.

26. The device of claim 13, wherein the device comprises an integrated circuit device.

27. A computer-readable medium comprising instructions that upon execution in a video coding device cause the device to code video blocks, wherein the instructions cause the device to:

select one of a plurality of prediction modes for use in generating a prediction block of a video block of a coding unit, wherein the prediction modes include unidirectional prediction modes and multi-directional prediction modes that combine at least two unidirectional prediction modes; and

encode the prediction mode of the current video block based on prediction modes of one or more previously encoded video blocks of the coding unit.

28. The computer-readable medium of claim 27, further comprising instructions that cause the device to select one of a plurality of coding contexts for use in encoding the prediction mode of the video block based on the prediction modes of the one or more previously encoded video blocks of the coding unit, wherein encoding comprises encoding according to the selected coding context.

29. The computer-readable medium of claim 28, wherein the instructions cause the device to:

select a first coding context when the prediction modes of the one or more previously encoded video blocks are all unidirectional prediction modes;

select a second coding context when the prediction modes of the one or more previously encoded video blocks are all multi-directional prediction modes; and

select a third coding context when the prediction modes of the one or more previously encoded video blocks are neither all unidirectional nor all multi-directional.

30. The computer-readable medium of claim 27, further comprising instructions to cause the device to:

subtracting the prediction block generated using the selected prediction mode from the video block to form a residual block;

select a transform to apply to the residual block based on the selected prediction mode; and

apply the selected transform to the residual block to generate residual transform coefficients.

31. The computer-readable medium of claim 30, wherein the instructions cause the device to:

select one of a discrete cosine transform (DCT) and an integer transform to apply to the residual block when the selected prediction mode exhibits limited directionality; and

select a directional transform to apply to the residual block when the selected prediction mode exhibits directionality.

32. The computer-readable medium of claim 31, wherein the instructions cause the device to select one of the DCT and the integer transform to apply to the residual block when the selected prediction mode is either a DC unidirectional prediction mode or a multi-directional prediction mode that combines at least two prediction modes that point in substantially orthogonal directions.

33. The computer-readable medium of claim 31, further comprising instructions that cause the device to store a plurality of directional transforms, wherein each of the plurality of directional transforms corresponds with one of the prediction modes that exhibits directionality, wherein selecting the directional transform comprises selecting the one of the plurality of directional transforms corresponding to the selected prediction mode.

34. The computer-readable medium of claim 30, further comprising instructions that cause the device to store a plurality of directional transforms that each correspond with one of the prediction modes, wherein each of the directional transforms comprises a column transform matrix of size N×

N and a row transform matrix of size N×

N, where N×

N is a dimension of the video block.

35. The computer-readable medium of claim 30, further comprising instructions that cause the device to storing a plurality of directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of directional transforms comprises a transform matrix of size N²×

N², where N is a dimension of the video block.

36. The computer-readable medium of claim 27, wherein the plurality of prediction modes includes unidirectional prediction modes and a subset of possible bidirectional prediction modes, the subset of bidirectional prediction modes including at least one combination that includes each of the unidirectional prediction modes.

37. The computer-readable medium of claim 27, wherein the instructions cause the device to:

encode a first bit representing the prediction mode to indicate that the prediction mode of the current block is the same as one of the prediction modes of the one or more previously encoded video blocks; and

encode, when the prediction modes of the one or more previously encoded video blocks are not the same as one another, at least one additional bit representing the prediction mode to indicate which of the one or more previously encoded video blocks has the same prediction mode as the prediction mode of the video block.

38. The computer-readable medium of claim 27, wherein the instructions cause the device to:

encode a first bit representing the prediction mode to indicate that the prediction mode of the current block is not the same as any of the prediction modes of the one or more previously encoded video blocks;

remove at least the prediction modes of the one or more previously encoded video blocks from the plurality of prediction modes;

remove at least one additional prediction mode that is not a prediction mode of the one or more previously encoded video blocks when two or more of the previously encoded video blocks of the coding unit have the same prediction mode;

temporarily rearrange prediction mode identifiers among the remaining prediction modes of the plurality of prediction modes; and

encode a codeword that identifies the prediction mode identifier corresponding to the prediction mode of the current video block.

39. A device that encodes video data, the device comprising:

means for selecting one of a plurality of prediction modes for use in generating a prediction block of a video block of a coding unit, wherein the prediction modes include unidirectional prediction modes and multi-directional prediction modes that combine at least two unidirectional prediction modes; and

means for encoding the prediction mode of the current video block based on prediction modes of one or more previously encoded video blocks of the coding unit.

40. The device of claim 39, further comprising means for selecting one of a plurality of coding contexts for use in encoding the prediction mode of the video block based on the prediction modes of the one or more previously encoded video blocks of the coding unit, wherein encoding comprises encoding according to the selected coding context.

41. The device of claim 40, wherein the selecting means selects a first coding context when the prediction modes of the one or more previously encoded video blocks are all unidirectional prediction modes, selects a second coding context when the prediction modes of the one or more previously encoded video blocks are all multi-directional prediction modes, and selects a third coding context when the prediction modes of the one or more previously encoded video blocks are neither all unidirectional nor all multi-directional.

42. The device of claim 39, further comprising:

means for subtracting the prediction block generated using the selected prediction mode from the video block to form a residual block;

means for selecting a transform to apply to residual block based on the selected prediction mode; and

means for applying the selected transform to the residual block to generate residual transform coefficients.

43. The device of claim 42, wherein the transform selecting means selects one of a discrete cosine transform (DCT) and an integer transform to apply to the residual block when the selected prediction mode exhibits limited directionality and selects a directional transform to apply to the residual block when the selected prediction mode exhibits directionality.

44. The device of claim 43, wherein the transform selecting means selects one of the DCT and the integer transform to apply to the residual block when the selected prediction mode is either a DC unidirectional prediction mode or a multi-directional prediction mode that combines at least two prediction modes that point in substantially orthogonal directions.

45. The device of claim 43, further comprising means for storing a plurality of directional transforms, wherein each of the plurality of directional transforms corresponds with one of the prediction modes that exhibits directionality, wherein the transform selecting means selects the one of the plurality of directional transforms corresponding to the selected prediction mode.

46. The device of claim 42, further comprising means for storing a plurality of directional transforms that each correspond with one of the prediction modes, wherein each of the directional transforms comprises a column transform matrix of size N×

N and a row transform matrix of size N×

N, where N×

N is a dimension of the video block.

47. The device of claim 42, further comprising storing a plurality of directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of directional transforms comprises a transform matrix of size N²×

N², where N is a dimension of the video block.

48. The device of claim 39, wherein the plurality of prediction modes includes unidirectional prediction modes and a subset of possible bidirectional prediction modes, the subset of bidirectional prediction modes including at least one combination that includes each of the unidirectional prediction modes.

49. The device of claim 39, wherein the encoding means encodes a first bit representing the prediction mode to indicate that the prediction mode of the current block is the same as one of the prediction modes of the one or more previously encoded video blocks and encodes, when the prediction modes of the one or more previously encoded video blocks are not the same as one another, at least one additional bit representing the prediction mode to indicate which of the one or more previously encoded video blocks has the same prediction mode as the prediction mode of the video block.

50. The device of claim 39, wherein

the prediction mode selecting means:

removes at least the prediction modes of the one or more previously encoded video blocks from the plurality of prediction modes,

removes at least one additional prediction mode that is not a prediction mode of the one or more previously encoded video blocks when two or more of the previously encoded video blocks of the coding unit have the same prediction mode, and

temporarily rearranges prediction mode identifiers among the remaining prediction modes of the plurality of prediction modes, and the encoding means;

encodes a first bit representing the prediction mode to indicate that the prediction mode of the current block is not the same as any of the prediction modes of the one or more previously encoded video blocks, and

encodes a codeword that identifies the prediction mode identifier corresponding to the prediction mode of the current video block.

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

receiving encoded video data of a video block of a coding unit; and

decoding the encoded video data to identify one of a plurality of prediction modes for use in generating a prediction block of the video block based on prediction modes of one or more previously decoded video blocks of the coding unit, wherein the prediction modes include unidirectional prediction modes and multi-directional prediction modes that combine at least two unidirectional prediction modes.

52. The method of claim 51, further comprising selecting one of a plurality of coding contexts for use in decoding the prediction mode of the video block based on the prediction modes of the one or more previously decoded video blocks of the coding unit, wherein decoding comprises decoding according to the selected coding context.

53. The method of claim 52, wherein selecting one of the plurality of coding contexts comprises:

selecting a first coding context when the prediction modes of the one or more previously decoded video blocks are all unidirectional prediction modes;

selecting a second coding context when the prediction modes of the one or more previously decoded video blocks are all multi-directional prediction modes; and

selecting a third coding context when the prediction modes of the one or more previously decoded video blocks are neither all unidirectional or all multi-directional.

54. The method of claim 51, further comprising:

selecting an inverse transform to apply to residual transform coefficients of the video block based on the identified prediction mode; and

applying the selected inverse transform to the residual transform coefficients of the video block to generate residual data.

55. The method of claim 54, wherein selecting the inverse transform to apply to the transformed residual coefficients comprises:

selecting one of an inverse discrete cosine transform (DCT) and an inverse integer transform to apply to the residual transform coefficients of the video block when the identified prediction mode exhibits limited directionality; and

selecting an inverse directional transform to apply to the residual transform coefficients of the video block when the identified prediction mode exhibits directionality.

56. The method of claim 55, wherein selecting one of the inverse DCT and the inverse integer transform comprises selecting one of the inverse DCT and inverse integer transform to apply to the residual transform coefficients of the video block when the identified prediction mode is either a DC unidirectional prediction mode or a multi-directional prediction mode that combines at least two prediction modes that point in substantially orthogonal directions.

57. The method of claim 55, further comprising storing a plurality of inverse directional transforms that each corresponds with one of the prediction modes that exhibits directionality, wherein selecting the inverse directional transform comprises selecting the one of the plurality of inverse directional transforms corresponding to the identified prediction mode.

58. The method of claim 54, further comprising storing a plurality of inverse directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of inverse directional transforms comprises a column transform matrix of size N×

N and a row transform matrix of size N×

N, where N×

N is a dimension of the video block.

59. The method of claim 54, further comprising storing a plurality of inverse directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of inverse directional transforms comprises a transform matrix of size N²×

N², where N×

N is a dimension of the video block.

60. The method of claim 51, wherein the plurality of prediction modes includes unidirectional prediction modes and a subset of possible bidirectional prediction modes, the subset of bidirectional prediction modes including at least one combination that includes each of the unidirectional prediction modes.

61. The method of claim 51, wherein decoding the encoded video data to identify one of the plurality of prediction modes for use in generating a prediction block of the video block based on prediction modes of one or more previously decoded video blocks of the coding unit comprises:

identifying the prediction mode for use in generating the prediction block of the video block as one of the prediction modes of the one or more previously decoded video blocks based on a first encoded bit representing the prediction mode; and

selecting the prediction mode of any of the one or more previously decoded video blocks when the prediction modes of the one or more previously decoded video blocks are the same.

62. The method of claim 61, further comprising:

identifying, when the prediction mode of the one or more previously decoded video blocks are not the same, which of the one or more previously decoded video blocks has the same prediction mode as the prediction mode for use in generating the prediction block of the video block based on at least one additional encoded bit representing the prediction mode; and

selecting the prediction mode of the identified previously decoded video block.

63. The method of claim 51, wherein decoding the encoded video data to identify one of the plurality of prediction modes for use in generating a prediction block of the video block based on prediction modes of one or more previously decoded video blocks of the coding unit comprises:

identifying the prediction mode for use in generating the prediction block of the video block as not being any of the prediction modes of the one or more previously decoded video blocks based on a first encoded bit representing the prediction mode;

removing at least the prediction modes of the one or more previously decoded video blocks from the plurality of prediction modes;

removing at least one additional prediction mode that is not the prediction mode of the one or more previously encoded video blocks when two or more of the previously encoded video blocks of the coding unit have the same prediction mode;

temporarily rearranging prediction mode identifiers among the remaining prediction modes of the plurality of prediction modes; and

decoding a codeword to identify the prediction mode identifier corresponding to the prediction mode for use in generating a prediction block of the current video block.

102. The device of claim 60, wherein the decoding means:

identifies the prediction mode for use in generating the prediction block of the video block as one of the prediction modes of the one or more previously decoded video blocks based on a first encoded bit representing the prediction mode; and

selects the prediction mode of any of the one or more previously decoded video blocks when the prediction modes of the one or more previously decoded video blocks are the same.

103. The device of claim 102, wherein the decoding means:

identifies, when the prediction mode of the one or more previously decoded video blocks are not the same, which of the one or more previously decoded video blocks has the same prediction mode as the prediction mode for use in generating the prediction block of the video block based on at least one additional encoded bit representing the prediction mode; and

selects the prediction mode of the identified previously decoded video block.

64. A device for decoding video data, the device comprising:

an entropy decoding unit that decodes encoded video data of a video block of a coding unit to identify one of a plurality of prediction modes for use in generating a prediction block of the video block based on prediction modes of one or more previously decoded video blocks of the coding unit, wherein the prediction modes include unidirectional prediction modes and multi-directional prediction modes that combine at least two unidirectional prediction modes; and

a prediction unit that generates the prediction block using the decoded prediction mode.

65. The device of claim 64, wherein the entropy decoding unit selects one of a plurality of coding contexts for use in decoding the prediction mode of the video block based on the prediction modes of the one or more previously decoded video blocks of the coding unit, wherein decoding comprises decoding according to the selected coding context.

66. The device of claim 65, wherein the entropy decoding unit:

selects a first coding context when the prediction modes of the one or more previously decoded video blocks are all unidirectional prediction modes;

selects a second coding context when the prediction modes of the one or more previously decoded video blocks are all multi-directional prediction modes; and

selects a third coding context when the prediction modes of the one or more previously decoded video blocks are neither all unidirectional or all multi-directional.

67. The device of claim 64, further comprising an inverse transform unit that:

selects an inverse transform to apply to residual transform coefficients of the video block based on the identified prediction mode; and

applies the selected inverse transform to the residual transform coefficients of the video block to generate a residual data.

68. The device of claim 67, wherein the inverse transform unit:

selects one of an inverse discrete cosine transform (DCT) and an inverse integer transform to apply to the residual transform coefficients of the video block when the identified prediction mode exhibits limited directionality; and

selects an inverse directional transform to apply to the residual transform coefficients of the video block when the identified prediction mode exhibits directionality.

69. The device of claim 68, wherein the inverse transform unit selects one of the inverse DCT and inverse integer transform to apply to the residual transform coefficients of the video block when the identified prediction mode is either a DC unidirectional prediction mode or a multi-directional prediction mode that combines at least two prediction modes that point in substantially orthogonal directions.

70. The device of claim 68, wherein the inverse transform unit stores a plurality of inverse directional transforms that each corresponds with one of the prediction modes that exhibits directionality and selects the one of the plurality of inverse directional transforms corresponding to the identified prediction mode.

71. The device of claim 67, wherein the inverse transform unit stores a plurality of inverse directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of inverse directional transforms comprises a column transform matrix of size N×

N and a row transform matrix of size N×

N, where N×

N is a dimension of the video block.

72. The device of claim 67, wherein the inverse transform unit stores a plurality of inverse directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of inverse directional transforms comprises a transform matrix of size N²×

N², where N×

N is a dimension of the video block.

73. The device of claim 64, wherein the plurality of prediction modes includes unidirectional prediction modes and a subset of possible bidirectional prediction modes, the subset of bidirectional prediction modes including at least one combination that includes each of the unidirectional prediction modes.

74. The device of claim 64, wherein the decoding unit:

identifies the prediction mode for use in generating the prediction block of the video block as one of the prediction modes of the one or more previously decoded video blocks based on a first encoded bit representing the prediction mode; and

selects the prediction mode of any of the one or more previously decoded video blocks when the prediction modes of the one or more previously decoded video blocks are the same.

75. The device of claim 74, wherein the decoding unit:

identifies, when the prediction mode of the one or more previously decoded video blocks are not the same, which of the one or more previously decoded video blocks has the same prediction mode as the prediction mode for use in generating the prediction block of the video block based on at least one additional encoded bit representing the prediction mode; and

selects the prediction mode of the identified previously decoded video block.

76. The device of claim 64, wherein the decoding unit:

identifies the prediction mode for use in generating the prediction block of the video block as not being any of the prediction modes of the one or more previously decoded video blocks based on a first encoded bit representing the prediction mode;

removes at least the prediction modes of the one or more previously decoded video blocks from the plurality of prediction modes;

removes at least one additional prediction mode that is not the prediction mode of the one or more previously encoded video blocks when two or more of the previously encoded video blocks of the coding unit have the same prediction mode;

temporarily rearranges prediction mode identifiers among the remaining prediction modes of the plurality of prediction modes; and

decodes a codeword to identify the prediction mode identifier corresponding to the prediction mode for use in generating a prediction block of the current video block.

77. The device of claim 64, wherein the device comprises a wireless communication device.

78. The device of claim 64, wherein the device comprises an integrated circuit device.

79. A computer-readable medium comprising instructions that upon execution in a video coding device cause the device to code video blocks, wherein the instructions cause the device to:

receive encoded video data of a video block of a coding unit; and

decode the encoded video data to identify one of a plurality of prediction modes for use in generating a prediction block of the video block based on prediction modes of one or more previously decoded video blocks of the coding unit, wherein the prediction modes include unidirectional prediction modes and multi-directional prediction modes that combine at least two unidirectional prediction modes.

80. The computer-readable medium of claim 79, further comprising instructions that cause the device to select one of a plurality of coding contexts for use in decoding the prediction mode of the video block based on the prediction modes of the one or more previously decoded video blocks of the coding unit, wherein decoding comprises decoding according to the selected coding context.

81. The computer-readable medium of claim 80, wherein the instructions cause the device to:

select a first coding context when the prediction modes of the one or more previously decoded video blocks are all unidirectional prediction modes;

select a second coding context when the prediction modes of the one or more previously decoded video blocks are all multi-directional prediction modes; and

select a third coding context when the prediction modes of the one or more previously decoded video blocks are neither all unidirectional or all multi-directional.

82. The computer-readable medium of claim 79, further comprising instructions that cause the device to:

select an inverse transform to apply to residual transform coefficients of the video block based on the identified prediction mode; and

apply the selected inverse transform to the residual transform coefficients of the video block to generate residual data.

83. The computer-readable medium of claim 82, wherein the instructions cause the device to:

select one of an inverse discrete cosine transform (DCT) and an inverse integer transform to apply to the residual transform coefficients of the video block when the identified prediction mode exhibits limited directionality; and

select an inverse directional transform to apply to the residual transform coefficients of the video block when the identified prediction mode exhibits directionality.

84. The computer-readable medium of claim 83, wherein the instructions cause the device to select one of the inverse DCT and inverse integer transform to apply to the residual transform coefficients of the video block when the identified prediction mode is either a DC unidirectional prediction mode or a multi-directional prediction mode that combines at least two prediction modes that point in substantially orthogonal directions.

85. The computer-readable medium of claim 83, further comprising instructions that cause the device to store a plurality of inverse directional transforms that each corresponds with one of the prediction modes that exhibits directionality, wherein selecting the inverse directional transform comprises selecting the one of the plurality of inverse directional transforms corresponding to the identified prediction mode.

86. The computer-readable medium of claim 82, further comprising instructions that cause the device to store a plurality of inverse directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of inverse directional transforms comprises a column transform matrix of size N×

N and a row transform matrix of size N×

N, where N×

N is a dimension of the video block.

87. The computer-readable medium of claim 82, further comprising instructions that cause the device to store a plurality of inverse directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of inverse directional transforms comprises a transform matrix of size N²×

N², where N×

N is a dimension of the video block.

88. The computer-readable medium of claim 79, wherein the plurality of prediction modes includes unidirectional prediction modes and a subset of possible bidirectional prediction modes, the subset of bidirectional prediction modes including at least one combination that includes each of the unidirectional prediction modes.

89. The computer-readable medium of claim 79, wherein the instructions cause the device to:

identify the prediction mode for use in generating the prediction block of the video block as one of the prediction modes of the one or more previously decoded video blocks based on a first encoded bit representing the prediction mode; and

select the prediction mode of any of the one or more previously decoded video blocks when the prediction modes of the one or more previously decoded video blocks are the same.

90. The computer-readable medium of claim 89, further comprising instructions that cause the device to:

identify, when the prediction mode of the one or more previously decoded video blocks are not the same, which of the one or more previously decoded video blocks has the same prediction mode as the prediction mode for use in generating the prediction block of the video block based on at least one additional encoded bit representing the prediction mode; and

select the prediction mode of the identified previously decoded video block.

91. The computer-readable medium of claim 79, wherein the instructions cause the device to:

identify the prediction mode for use in generating the prediction block of the video block as not being any of the prediction modes of the one or more previously decoded video blocks based on a first encoded bit representing the prediction mode;

remove at least the prediction modes of the one or more previously decoded video blocks from the plurality of prediction modes;

remove at least one additional prediction mode that is not the prediction mode of the one or more previously encoded video blocks when two or more of the previously encoded video blocks of the coding unit have the same prediction mode;

temporarily rearrange prediction mode identifiers among the remaining prediction modes of the plurality of prediction modes; and

decode a codeword to identify the prediction mode identifier corresponding to the prediction mode for use in generating a prediction block of the current video block.

92. A device for decoding video data, the device comprising:

means for receiving encoded video data of a video block of a coding unit; and

means for decoding the encoded video data to identify one of a plurality of prediction modes for use in generating a prediction block of the video block based on prediction modes of one or more previously decoded video blocks of the coding unit, wherein the prediction modes include unidirectional prediction modes and multi-directional prediction modes that combine at least two unidirectional prediction modes.

93. The device of claim 92, wherein the decoding means selects one of a plurality of coding contexts for use in decoding the prediction mode of the video block based on the prediction modes of the one or more previously decoded video blocks of the coding unit, wherein decoding comprises decoding according to the selected coding context.

94. The device of claim 93, wherein the decoding means:

selects a first coding context when the prediction modes of the one or more previously decoded video blocks are all unidirectional prediction modes;

selects a second coding context when the prediction modes of the one or more previously decoded video blocks are all multi-directional prediction modes; and

selects a third coding context when the prediction modes of the one or more previously decoded video blocks are neither all unidirectional or all multi-directional.

95. The device of claim 92, further comprising means for transforming residual transform coefficients, wherein the transforming means:

selects an inverse transform to apply to residual transform coefficients of the video block based on the identified prediction mode; and

applies the selected inverse transform to the residual transform coefficients of the video block to generate residual data.

96. The device of claim 95, wherein the transforming means:

selects one of an inverse discrete cosine transform (DCT) and an inverse integer transform to apply to the residual transform coefficients of the video block when the identified prediction mode exhibits limited directionality; and

selects an inverse directional transform to apply to the residual transform coefficients of the video block when the identified prediction mode exhibits directionality.

97. The device of claim 96, wherein the transforming means selects one of the inverse DCT and inverse integer transform to apply to the residual transform coefficients of the video block when the identified prediction mode is either a DC unidirectional prediction mode or a multi-directional prediction mode that combines at least two prediction modes that point in substantially orthogonal directions.

98. The device of claim 96, further comprising means for storing a plurality of inverse directional transforms that each corresponds with one of the prediction modes that exhibits directionality, wherein transforming means selects the one of the plurality of inverse directional transforms corresponding to the identified prediction mode.

99. The device of claim 95, further comprising means for storing a plurality of inverse directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of inverse directional transforms comprises a column transform matrix of size N×

N and a row transform matrix of size N×

N, where N×

N is a dimension of the video block.

100. The device of claim 95, further comprising means for storing a plurality of inverse directional transforms that each corresponds with one of the prediction modes, wherein each of the plurality of inverse directional transforms comprises a transform matrix of size N²×

N², where N×

N is a dimension of the video block.

101. The device of claim 92, wherein the plurality of prediction modes includes unidirectional prediction modes and a subset of possible bidirectional prediction modes, the subset of bidirectional prediction modes including at least one combination that includes each of the unidirectional prediction modes.

104. The device of claim 92, wherein the decoding means:

identifies the prediction mode for use in generating the prediction block of the video block as not being any of the prediction modes of the one or more previously decoded video blocks based on a first encoded bit representing the prediction mode;

removes at least the prediction modes of the one or more previously decoded video blocks from the plurality of prediction modes;

removes at least one additional prediction mode that is not the prediction mode of the one or more previously encoded video blocks when two or more of the previously encoded video blocks of the coding unit have the same prediction mode;

temporarily rearranges prediction mode identifiers among the remaining prediction modes of the plurality of prediction modes; and

decodes a codeword to identify the prediction mode identifier corresponding to the prediction mode for use in generating a prediction block of the current video block.