Description:SAME AS UPLOADED , Claims:1. An encoder for encoding a picture (12) into a data stream (14), configured to

encode (108) a transform coefficient block (92) representing a block (84) of the picture (12) into the data stream (14) using a scan pattern (94) which sequentially traverses trans-form coefficients of the transform coefficient block (92) by

encoding into the data stream (14) data (96) representing a coded set (100 shown hatched) of transform coefficients (91) traversed by the scan pattern (94) [or scan path] from a first termination coefficient position (98) in a predetermined direction (102) to a second termination coefficient (104), the data (96) comprising quantization levels (106) of the transform coefficients in the coded set (100) of transform coefficients,

wherein the encoder is configured to entropy encode the quantization levels (106) con-text-adaptively using a first set (110) of contexts (112) for the quantization level of the transform coefficient at the first termination coefficient position (98) or at the second termination coefficient position (104) which is disjoint to a second set (110) of contexts (112) used for any other transform coefficient in the coded set (100) of transform coeffi-cients.

2. The encoder as claimed in claim 1, configured to

encode into the data stream (14) an indication (114) of a termination coefficient position at which a, when traversing the scan pattern (94) along a forward direction (116), last non-zero transform coefficient resides, wherein the predetermined direction (102) is a reverse direction (118) and the first termination coefficient position is the termination coefficient position indicated by the indication (114) and the second termination coeffi-cient position (104) is a coefficient position which is in the reverse direction (118) trav-ersed latest along the scan pattern (94).

3. The encoder as claimed in claim 2, configured to

use the first set of contexts for the transform coefficient at the first termination coefficient position (98).

4. The encoder as claimed in claim 3, wherein

the first set of contexts is disjoint to the second set (110) of contexts (112) used for any other transform coefficient in the coded set (100) of transform coefficients in-cluding the transform coefficient at the second termination coefficient position.

5. The encoder as claimed in claim 2, configured to

use the first set of contexts for the transform coefficient at the second ter-mination coefficient position.

6. The encoder as claimed in claim 5, wherein

the first set of contexts is disjoint to the second set (110) of contexts (112) used for any other transform coefficient in the coded set (100) of transform coefficients including the transform coefficient at the first termination co-efficient position.

7. The encoder as claimed in claim 2, configured to

use the first set of contexts for the transform coefficient at the first termi-nation coefficient position (98), and

use a third set of contexts, disjoint from the first set, for the transform co-efficient at the second termination coefficient position (98),

wherein the first and third sets are disjoint from the second sets of contexts used for any transform coefficient in the coded set of transform coeffi-cients lying, along the scan pattern, between the first and second termina-tion coefficient positions.

8. The encoder as claimed in any of claims 2 to 7,

wherein the first set is disjoint from the second set of contexts used for the transform coefficients at coefficient positions which are in the reverse di-rection (118) traversed along the scan pattern (94) immediately after the first termination coefficient position (98) and immediately before the sec-ond termination coefficient position (104).

9. The encoder as claimed in any of claims 2 to 8, wherein the second termination coefficient position (104) is a DC coefficient position.

10. The encoder as claimed in any of claims 1 to 9, wherein the disjointness is inde-pendent from the first termination coefficient position (98).

11. The encoder as claimed in claim 1 or 10, configured to

in entropy encoding (116) the quantization levels of the other transform coeffi-cients of the transform coefficient block (92) context-adaptively, use, for each partition (sub-block) of partitions (120) into which the transform coefficient block (92) is subdivided, a set of contexts which is disjoint to the first set.

12. The encoder as claimed in claim 11, wherein the partitions (120) into which the transform coefficient block is subdivided,

extend diagonally along a direction obliquely to a transform coefficient block’s (92) diagonal (122) running through the second termination coefficient position (e.g. DC position).

13. The encoder as claimed in any of claims 1 to 12, configured to

binarize the quantization levels (106) to obtain a binarization of the quantization levels of the transform coefficients and use the first set (110) of contexts (112) and the second set (110) of contexts (112) for at least one bin of the binarization.

14. The encoder as claimed in any of claims 1 to 12, configured to

binarize the quantization levels (106) to obtain a binarization of the quantization levels of the transform coefficients and use the first set (110) of contexts (112) and the second set (110) of contexts (112) for at least one bin of a prefix part of the binarization.

15. The encoder as claimed in any of claims 1 to 14, wherein configured to,

select a first actually used context out of the first set (110) of contexts (112) for the quantization level of the transform coefficient at the first termination coeffi-cient position (98) or at the second termination coefficient position (104) and a second actually used context out of the second set (110) of contexts (112) for the other transform coefficients in the coded set (100) of transform coefficients using previously encoded coefficients position at positions determined by a local tem-plate (132).

16. A decoder for decoding a picture (12) from a data stream (14), configured to

decode (108) a transform coefficient block (92) representing a block (84) of the picture (12) from the data stream (14) using a scan pattern (94) which sequentially traverses transform coefficients (91) of the transform coefficient block (92) by

decoding from the data stream (14) data (96) representing a coded set (100) of transform coefficients (91) traversed by the scan pattern (94) from a first termination coefficient position (98) in a predetermined direction (102) to a second termination coefficient position (104), the data (96) comprising quantization levels (106) of the transform coefficients in the coded set (100) of transform coefficients,

wherein the decoder is configured to entropy decode the quantization levels (106) context-adaptively using a first set (110) of contexts (112) for the quantization level of the transform coefficient at the first termination coefficient position (98) or at the second termination coefficient position (104) which is disjoint to a sec-ond set (110) of contexts (112) used for any other transform coefficient in the coded set (100) of transform coefficients.

17. The decoder as claimed in claim 16, configured to

decode from the data stream (14) an indication (114) of a termination coef-ficient position at which a, when traversing the scan pattern (94) along a forward direction (116), last non-zero transform coefficient resides, where-in the predetermined direction (102) is a reverse direction (118) and the first termination coefficient position is the termination coefficient position indicated by the indication (114) and the second termination coefficient position (104) is a coefficient position which is in the reverse direction (118) traversed latest along the scan pattern (94).

18. The decoder as claimed in claim 17, configured to

use the first set of contexts for the transform coefficient at the first termi-nation coefficient position (98).

19. The decoder as claimed in claim 18, wherein

the first set of contexts is disjoint to the second set (110) of contexts (112) used for any other transform coefficient in the coded set (100) of transform coefficients including the transform coefficient at the second termination coefficient position.

20. The decoder as claimed in claim 17, configured to

use the first set of contexts for the transform coefficient at the second ter-mination coefficient position.

21. The decoder as claimed in claim 20, wherein

the first set of contexts is disjoint to the second set (110) of contexts (112) used for any other transform coefficient in the coded set (100) of transform coefficients including the transform coefficient at the first termination co-efficient position.

22. The decoder as claimed in claim 17, configured to

use the first set of contexts for the transform coefficient at the first termi-nation coefficient position (98), and

use a third set of contexts, disjoint from the first set, for the transform co-efficient at the second termination coefficient position (98),

wherein the first and third sets are disjoint from the second sets of contexts used for any transform coefficient in the coded set of transform coeffi-cients lying, along the scan pattern, between the first and second termina-tion coefficient positions.

23. The decoder as claimed in any of claims 17 to 22, configured to

wherein the first set is disjoint from the second sets of contexts used for the transform coefficients at coefficient positions which are in the reverse direction (118) traversed along the scan pattern (94) immediately after the first termination coefficient position (98) and immediately before the sec-ond termination coefficient position (104).

24. The decoder as claimed in any of claims 17 to 23, wherein the second termination coefficient position (104) is a DC coefficient position.

25. The decoder as claimed in any of claims 16 to 24, wherein the disjointness is in-dependent from the first termination coefficient position (98).

26. The decoder as claimed in claim 16 or 25, configured to

in entropy decoding (116) the quantization levels of the other transform coeffi-cients of the transform coefficient block (92) context-adaptively, use, for each partition of partitions (120) into which the transform coefficient block (92) is subdivided, a set (110) of contexts which is disjoint to the first set.

27. The decoder as claimed in claim 26, wherein the partitions (120) into which the transform coefficient block is subdivided,

extend diagonally along a direction obliquely to a transform coefficient block’s (92) diagonal (122) running through the second termination coefficient position (104).

28. The decoder as claimed in any of claims 16 to 27, configured to

decode the quantization levels (106) in a manner binarized as claimed in a binari-zation of the quantization levels of the transform coefficients and use the first set (110) of contexts (112) and the second set (110) of contexts (112) for at least one bin of the binarization.

29. The decoder as claimed in any of claims 16 to 27, configured to

decode the quantization levels (106) in a manner binarized as claimed in a binari-zation of the quantization levels of the transform coefficients and use the first set (110) of contexts (112) and the second set (110) of contexts (112) for at least one bin of a prefix part (160) of the binarization (161).

30. The decoder as claimed in any of claims 16 to 29, wherein configured to,

select a first actually used context out of the first set (110) of contexts (112) for the quantization level of the transform coefficient at the first termination coeffi-cient position (98) or at the second termination coefficient position (104) and a second actually used context out of the second set (110) of contexts (112) for the other transform coefficients in the coded set (100) of transform coefficients using previously decoded coefficients position at positions determined by a local tem-plate (132).

31. An encoder for encoding a picture into a data stream, configured to

entropy encode a quantization level of a currently encoded transform coefficient of a transform coefficient block (92) representing a block (84) of the picture (12) context-adaptively by

use of a context which is determined based on

a sum of, and/or
a number of significant ones among,

one or more previously encoded transform coefficients located at positions determined by a local template (132) positioned at the currently encoded transform coefficient.

32. The encoder as claimed in claim 31, configured to

determine the context by forming a difference between a first value determined based on the sum and a second value determined based on the number of significant transform coefficient levels among the one or more previously encoded transform coeffi-cients located at the positions determined by the local template.

33. The encoder as claimed in claim 31 or 32, configured to

entropy encoding the quantization level using context-adaptive binary arithmetic coding of a binarization of an absolute value of the quantization level involving a unary code, wherein the context is used for bins of the unary code.

34. The encoder as claimed in claim 31 or 32, configured to

entropy encode the quantization level using context-adaptive binary arithmetic coding of a binarization of an absolute value of the quantization level involving a prefix part and a suffix part, wherein the context is used for one or more bins of the prefix part.

35. The encoder as claimed in any of claims 31 to 34, configured to

entropy encode bins of a binarization for quantization levels of transform coeffi-cients of the transform coefficient block (92) sequentially in a plurality of passes,

use the context for at least one bin of the binarization of the currently encoded transform coefficient, and

determine the context based on

a sum of an absolute value of coefficient level of the one or more previous-ly encoded transform coefficients located at the positions determined by the local template (132) positioned at the currently encoded transform co-efficient, which absolute value the coefficient level of the one or more pre-viously encoded transform coefficients minimally has as claimed in previ-ously encoded bins of the binarization of the absolute value of the coeffi-cient level of the one or more previously encoded transform coefficients.

36. The encoder as claimed in any of claims 31 to 35, configured to

entropy encode bins of a binarization for quantization levels of transform coeffi-cients of the transform coefficient block (92) sequentially in a plurality of passes,

use the context for at least one bin of the binarization of the currently encoded transform coefficient, and

determine the context based on

the number of significant ones among the one or more previously encoded transform coefficients located at the positions determined by the local template (132) positioned at the currently encoded transform coefficient.

37. The decoder for decoding a picture from a data stream, configured to

entropy decode a quantization level (106) of a currently decoded transform coeffi-cient (130) of a transform coefficient block (92) representing a block (84) of the picture (12) context-adaptively by

use of a context which is determined based on

a sum of, and/or
a number of significant ones among,

one or more previously decoded transform coefficients located at positions determined by a local template (132) positioned at the currently decoded transform coefficient.

38. The decoder as claimed in claim 37, configured to

determine the context by forming a difference between a first value determined based on the sum and a second value determined based on the number of significant transform coefficient levels among the one or more previously decoded transform coeffi-cients located at the positions determined by the local template.

39. The decoder as claimed in claim 37 or 38, configured to

entropy decoding the quantization level using context-adaptive binary arithmetic decoding of a binarization of an absolute value of the quantization level involving a unary code (160), wherein the context is used for bins of the unary code.

40. The decoder as claimed in claim 37 or 38, configured to

entropy decode the quantization level using context-adaptive binary arithmetic decoding of a binarization of an absolute value of the quantization level involving a prefix part (160) and a suffix part (162), wherein the context is used for one or more bins of the prefix part.

41. The decoder as claimed in any of claims 37 to 40, configured to

entropy decode bins of a binarization for quantization levels of transform coeffi-cients of the transform coefficient block (92) sequentially in a plurality of passes,

use the context for at least one bin of the binarization of the currently decoded transform coefficient (130), and

determine the context based on

a sum of an absolute value of coefficient level of the one or more previous-ly decoded transform coefficients located at the positions determined by the local template (132) positioned at the currently decoded transform co-efficient, which absolute value the coefficient level of the one or more pre-viously decoded transform coefficients minimally has as claimed in previ-ously decoded bins of the binarization (161) of the absolute value of the coefficient level of the one or more previously decoded transform coeffi-cients.

42. The decoder as claimed in any of claims 37 to 41, configured to

entropy decode bins of a binarization for quantization levels of transform coeffi-cients of the transform coefficient block (92) sequentially in a plurality of passes,

use the context for at least one bin of the binarization of the currently decoded transform coefficient (130), and

determine the context based on

the number of significant ones among the one or more previously decoded transform coefficients located at the positions determined by the local template (132) positioned at the currently decoded transform coefficient.

43. An encoder for encoding a picture into a data stream, configured to

encode a transform coefficient block (92) representing a block (84) of the picture (12) into the data stream by

encoding an absolute value of a quantization level of a currently encoded transform coefficient of the transform coefficient block in a manner bina-rized using a binarization (161) which is parameterized using a binariza-tion parameter (163),

setting of the binarization parameter based on

a sum of, and/or
a number of significant ones among,

one or more previously encoded transform coefficients located at positions determined by a local template (132) positioned at the currently encoded transform coefficient.

44. The encoder as claimed in claim 43, configured to

encode a first part of the binarization using context-adaptive entropy encoding, and

encode a second part of the binarization using an equi-probability bypass mode,

wherein the second part of the binarization comprises a prefix part and a suffix part and the binarization parameter determines a length of the prefix part.

45. The encoder as claimed in claim 43 or 44, wherein

the binarization comprises a prefix part and a suffix part and the binarization parameter determines a length of the prefix part.

46. The encoder as claimed in any of claims 43 to 45, wherein

the binarization parameter is an Exp Golomb order or a Rice parameter.

47. The encoder as claimed in any of claims 43 to 46, configured to

set the binarization parameter by mapping the sum of absolute values of quantization levels of the one or more previously encoded transform coefficients using a look-up table onto the binarization parameter.

48. The encoder as claimed in any of claims 43 to 46, configured to

encode a first part of the binarization using context-adaptive entropy encoding, and
encode a second part of the binarization using an equi-probability bypass mode,

entropy encode bins of the first part (160) of the binarization for quantization levels of transform coefficients of the transform coefficient block (92) sequentially in one or more passes, wherein the second part of the binarization (161) comprises a prefix part (162a) and a suffix part (162b) and the binarization parameter determines a length of the prefix part (162a),

determine the binarization parameter based on

a sum over an absolute value of a coefficient level of the one or more pre-viously encoded transform coefficients located at the positions determined by the local template (132) positioned at the currently encoded transform coefficient.

49. The encoder as claimed in any of claims 43 to 46, configured to

encode a first part of the binarization using context-adaptive entropy encoding, and
encode a second part of the binarization using an equi-probability bypass mode,

entropy encode bins of the first part (160) of the binarization for quantization levels of transform coefficients of the transform coefficient block (92) sequentially in one or more passes, wherein the second part of the binarization (161) comprises a prefix part (162a) and a suffix part (162b) and the binarization parameter determines a length of the prefix part (162a),

determine the binarization parameter based on

the number of significant ones among the one or more previously encoded transform coefficients located at the positions determined by the local template (132) positioned at the currently encoded transform coefficient.

50. The encoder as claimed in any of claims 43 to 49, configured to

perform the setting the binarization parameter based on a sum of the one or more previ-ously encoded transform coefficients in a manner so that the binarization parameter is equal to or larger than binarization parameters set and used for absolute values of quanti-zation levels of previously encoded transform coefficients of the transform coefficient block.

51. A decoder for decoding a picture from a data stream, configured to

decode a transform coefficient block (92) representing a block (84) of the picture (12) from the data stream by

decoding an absolute value of a quantization level of a currently decoded transform coefficient of the transform coefficient block in a manner bina-rized using a binarization (161) which is parameterized using a binariza-tion parameter (163),

setting of the binarization parameter (163) based on

a sum of, and/or
a number of significant ones among,

one or more previously decoded transform coefficients located at positions determined by a local template (132) positioned at the currently decoded transform coefficient.

52. The decoder as claimed in claim 51, configured to

decode a first part (160) of the binarization using context-adaptive entropy decoding, and

decode a second part (162) of the binarization using an equi-probability bypass mode,

wherein the second part of the binarization (161) comprises a prefix part (162a) and a suffix part (162b) and the binarization parameter determines a length of the prefix part (162a).

53. The decoder as claimed in claim 51 or 52, wherein

the binarization (161) comprises a prefix part and a suffix part and the binarization pa-rameter determines a length of the prefix part.

54. The decoder as claimed in any of claims 51 to 53, wherein

the binarization parameter is an Exp Golomb order or a Rice parameter.

55. The decoder as claimed in any of claims 51 to 54, configured to

set the binarization parameter by mapping the sum of absolute values of quantization levels of the one or more previously encoded transform coefficients using a look-up table onto the binarization parameter.

56. The decoder as claimed in any of claims 51 to 55, configured to

decode a first part (160) of the binarization using context-adaptive entropy decoding, and
decode a second part (162) of the binarization using an equi-probability bypass mode,

entropy decode bins of the first part (160) of the binarization for quantization levels of transform coefficients of the transform coefficient block (92) sequentially in one or more passes, wherein the second part of the binarization (161) comprises a prefix part (162a) and a suffix part (162b) and the binarization parameter determines a length of the prefix part (162a),

determine the binarization parameter (164) based on

a sum over an absolute value of a coefficient level of the one or more pre-viously decoded transform coefficients located at the positions determined by the local template (132) positioned at the currently decoded transform coefficient.

57. The decoder as claimed in any of claims 51 to 56, configured to

decode a first part (160) of the binarization using context-adaptive entropy encoding, and
decode a second part (162) of the binarization using an equi-probability bypass mode,

entropy decode bins of the first part (160) of the binarization for quantization levels of transform coefficients of the transform coefficient block (92) sequentially in one or more passes, wherein the second part of the binarization (161) comprises a prefix part (162a) and a suffix part (162b) and the binarization parameter determines a length of the prefix part (162a)

determine the binarization parameter (164) based on

the number of significant ones among the one or more previously decoded transform coefficients located at the positions determined by the local template (132) positioned at the currently decoded transform coefficient.

58. The decoder as claimed in any of claims 51 to 57, configured to

perform the setting the binarization parameter based on a sum of the one or more previ-ously decoded transform coefficients in a manner so that the binarization parameter is equal to or larger than binarization parameters set and used for absolute values of quanti-zation levels of previously decoded transform coefficients of the transform coefficient block.

59. An encoder for encoding a picture into a data stream, configured to

encode the transform coefficient block (92) representing a block (84) of the pic-ture (12) into the data stream using a scan pattern (94) which sequentially travers-es transform coefficients of the transform coefficient block by

encoding an absolute value of quantization levels (106) of the transform coefficients of the transform coefficient block in a manner binarized using a binarization comprising a first binarization code (160) below a cutoff value (164) and a second binarization code (162), prefixed by a codeword of the first binarization code (160) for the cutoff value, above the cutoff value,

adaptively varying the cutoff value for the transform coefficients of the transform coefficient block depending on previously encoded transform coefficients.

60. The encoder as claimed in claim 59, configured to

adaptively vary the cutoff value in a manner so that the cutoff value monotonical-ly decreases during encoding the transform coefficient block (92) including a de-crease down to zero so that the binarization becomes the second binarization code without the first binarization code.

61. The encoder as claimed in any of claims 59 to 60,

wherein the transform coefficient block (92) is partitioned into partitions (120),

wherein the encoder is configured to encode bins (165) of the binarization (161) of the absolute value of the quantization level (106) of the transform coefficients of the trans-form coefficient block sequentially in passes along, in each pass, a coding order which traverses, for each partition (120), all transform coefficients consecutively without any transform coefficient of any other partition therebetween,

wherein the encoder is configured to encode bins of the first binarization code (160) prior to bins of the second binarization code (162),

wherein the encoder is configured to encode the bins of the first binarization code (160) using context-adaptive entropy encoding, and encode the bins of the second binarization code (162) using an equi-probability bypass mode,

wherein the encoder is configured to

set the cutoff value (164) for a currently encoded transform coefficient (130) de-pending on

a number of bins of the first binarization code, previously encoded using context-adaptive entropy encoding, within the transform coefficient block or within a partition in which the currently encoded transform coefficient is located.

62. A decoder for decoding a picture from a data stream, configured to

decode the transform coefficient block (92) representing a block (84) of the pic-ture (12) from the data stream using a scan pattern (94) which sequentially traverses transform coefficients of the transform coefficient block by

decoding an absolute value of quantization levels (106) of the transform coefficients of the transform coefficient block in a manner binarized using a binarization comprising a first binarization code (160) below a cutoff value (164) and a second binarization code (162), prefixed by a codeword of the first binarization code (160) for the cutoff value, above the cutoff value,

adaptively varying the cutoff value for the transform coefficients of the transform coefficient block depending on previously decoded transform coefficients.

63. The decoder as claimed in claim 62, configured to

adaptively vary the cutoff value in a manner so that the cutoff value monotonical-ly decreases during decoding the transform coefficient block (92) including a de-crease down to zero so that the binarization becomes the second binarization code without the first binarization code.

64. The decoder as claimed in any of claims 62 to 63,

wherein the transform coefficient block (92) is partitioned into partitions (120),

wherein the decoder is configured to decode bins (165) of the binarization (161) of the absolute value of the quantization level (106) of the transform coefficients of the trans-form coefficient block sequentially in passes along, in each pass, a coding order which traverses, for each partition (120), all transform coefficients consecutively without any transform coefficient of any other partition therebetween,

wherein the decoder is configured to decode bins of the first binarization code (160) prior to bins of the second binarization code (162),

wherein the decoder is configured to decode the bins of the first binarization code (160) using context-adaptive entropy decoding, and decode the bins of the second binarization code (162) using an equi-probability bypass mode,

wherein the decoder is configured to

set the cutoff value (164) for a currently decoded transform coefficient (130) de-pending on

a number of bins of the first binarization code, previously decoded using context-adaptive entropy encoding, within the transform coefficient block or within a partition in which the currently decoded transform coefficient is located.

65. A encoder for encoding a picture into a data stream, configured to

encode a transform coefficient block (92) representing a block (84) of the picture (12) into the data stream by

encoding an absolute value of a quantization level (106) of the transform coefficients of the transform coefficient block in a manner binarized using a binarization comprising a first binarization code (160) below a cutoff value [i.e. for absolute values below the cutoff value] and a second binari-zation code (162), prefixed by a codeword of the first binarization code (160) for the cutoff value, above the cutoff value,

setting the cutoff value (164) depending on one or more of

a size of the block (84),
a color component of the block (84),
a prediction mode underlying a prediction signal a prediction resid-ual of which the block (84) represents,
a transformation underlying the transform coefficient block (92),
a quantization parameter used to quantize the transform coefficient block (92),
a measure of an energy of previously encoded transform coeffi-cients, and
an evaluation of previously encoded transform coefficients.

66. The encoder as claimed in claim 65, wherein the previously encoded transform coefficients used for the evaluation are

located at positions determined by a local template (132) positioned at a currently encoded transform coefficient or

located at positions within a partition of the transform coef-ficient block (92) offset to a current partition the currently encoded transform coefficient is located in and preceding the current partition as claimed in a coding order used for encoding the absolute value of the quantization level (106) of the transform coefficients of the transform coefficient block defined by traversing the transform coefficients of the transform coefficient block along a scan pattern in a prede-termined direction (102).

67. The encoder as claimed in claim 65 or 66, configured to

adaptively vary the cutoff value for the transform coefficients of the transform coefficient block depending on previously encoded transform coefficients if the cutoff value is initially set to a value succeeding a predetermined threshold, and

keep constant the cutoff value (164) at least preliminarily [e.g. until reaching the last partition in order direction (102) if the cutoff value is initially set to a value exceeding the predetermined threshold.

68. The encoder as claimed in any of claims 65 to 67, configured to

adaptively vary the cutoff value for the currently encoded transform coef-ficient based on

a sum of, and/or
a number of significant ones among,

one or more previously encoded transform coefficients located at positions determined by the local template (132) positioned at the currently encoded transform coefficient.

69. The encoder of any claims 65 to 68, configured to

entropy encoding one or more bins of the first binarization context-adaptively using, for each partition of partitions into which the transform coeffi-cient block is subdivided, a set of contexts which is associated with the respective partition,

wherein the encoder is configured to perform the setting for a predetermined par-tition in a manner depending on

an evaluation of previously encoded transform coefficients located in a partition which is traversed by the coding order prior to the predetermined partition.

70. The encoder as claimed in any of claims 65 to 69, configured to

adaptively vary the cutoff value in a manner including setting the cutoff value to zero so that no first binarization exists if a measure of an energy of previously en-coded transform coefficients increases a certain threshold.

71. The encoder as claimed in any of claims 65 to 70,

wherein the transform coefficient block (92) is partitioned into partitions,

wherein the encoder is configured to encode bins of the binarization of the absolute value of the quantization level (106) of the transform coefficients of the transform coefficient block sequentially in passes along, in each pass, a coding order which traverses, for each partition, all transform coefficients consecutively without any transform coefficient of any other partition therebetween,

wherein the encoder is configured to encode bins of the first binarization code prior to bins of the second binarization code,

wherein the encoder is configured to encode the bins of the first binarization code using context-adaptive entropy encoding, and encode the bins of the second binarization code using an equi-probability bypass mode,

wherein the encoder is configured to

set the cutoff value (164) depending on

the measure of the energy of the previously encoded transform co-efficients within a partition in which a currently encoded transform coefficient is located.

72. The encoder as claimed in claim 71, configured to

Use a number of bins of the first binarization code, previously encoded using context-adaptive arithmetic encoding for the transform coefficients within the partition in which a currently encoded transform coefficient is located, as a measure for the energy.

73. The encoder as claimed in any of claims 65 to 70,

wherein the encoder is configured to encode bins of the binarization of the absolute value of the quantization level (106) of the transform coefficients of the transform coefficient block sequentially in passes,

wherein the encoder is configured to encode bins of the first binarization code prior to bins of the second binarization code,

wherein the encoder is configured to encode the bins of the first binarization code using context-adaptive entropy encoding, and encode the bins of the second binarization code using an equi-probability bypass mode,

wherein the encoder is configured to

set the cutoff value (164) depending on

the measure of the energy of the previously encoded transform co-efficients within the transform coefficient block.

74. The encoder as claimed in claim 73, configured to

Use a number of bins of the first binarization code, previously encoded using context-adaptive arithmetic encoding for the transform coefficients within the transform coeffi-cient block as a measure for the energy.

75. The encoder as claimed in any of claims 65 to 70,

wherein the transform coefficient block (92) is partitioned into partitions,

wherein the encoder is configured to encode bins of the binarization of the absolute value of the quantization level (106) of the transform coefficients of the transform coefficient block sequentially in passes along, in each pass, a coding order which traverses, for each partition, all transform coefficients consecutively without any transfer coefficient of any other partition therebetween,

wherein the encoder is configured to entropy encode bins of the first binarization code prior to bins of the second binarization code,

wherein the encoder is configured to encode the bins of the first binarization code using context-adaptive entropy encoding, and encode the bins of the second binarization code using an equi-probability bypass mode,

wherein the encoder is configured to

set the cutoff value (164) depending on

an evaluation of a number of bins of the first binarization code, previously encoded using context-adaptive entropy encoding for transform coefficients locat-ed at positions determined by a local template (132) positioned at a currently en-coded transform coefficient, with using a partition the current encoded transform coefficient is located in as the locale template.

76. A decoder for decoding a picture from a data stream, configured to

decode a transform coefficient block (92) representing a block (84) of the picture (12) from the data stream by

decoding an absolute value of a quantization level (106) of the transform coefficients of the transform coefficient block in a manner binarized using a binarization (161) comprising a first binarization code (160) below a cut-off value [i.e. for absolute values below the cutoff value] and a second bi-narization code (162), prefixed by a codeword of the first binarization code (160) for the cutoff value, above the cutoff value,

setting the cutoff value (164) depending on one or more of

a size of the block (84),
a color component of the block (84),
a prediction mode underlying a prediction signal a prediction resid-ual of which the block (84) represents,
a transformation underlying the transform coefficient block (92),
a quantization parameter used to quantize the transform coefficient block (92),
a measure of an energy of previously decoded transform coeffi-cients,
an evaluation of previously decoded transform coefficients.

77. The decoder as claimed in claim 76, wherein the previously decoded transform coefficients used for the evaluation are

located at positions determined by a local template (132) positioned at a currently decoded transform coefficient or

located at positions within a partition of the transform coef-ficient block (92) offset to a current partition the currently decoded transform coefficient is located in and preceding the current partition as claimed in a coding order used for decoding the absolute value of the quantization level (106) of the transform coefficients of the transform coefficient block defined by traversing the transform coefficients of the transform coefficient block along a scan pattern in a prede-termined direction (102).

78. The decoder as claimed in claim 76 or 77, configured to

adaptively vary the cutoff value for the transform coefficients of the transform coefficient block depending on previously decoded transform coefficients if the cutoff value is initially set to a value succeeding a predetermined threshold, and

keep constant the cutoff value (164) at least preliminarily [e.g. until reaching the last partition in order direction 102) if the cutoff value is initially set to a value exceeding the predetermined threshold.

79. The decoder as claimed in any of claims 76 to 78, configured to

adaptively vary the cutoff value for the currently encoded transform coef-ficient based on

a sum of, and/or
a number of significant ones among,

one or more previously encoded transform coefficients located at positions determined by the local template (132) positioned at the currently decoded transform coefficient.

80. The decoder of any claims 76 to 79, configured to

entropy decoding one or more bins of the binarization context-adaptively using, for each partition of partitions into which the transform coefficient block is subdivided, a set of contexts which is associated with the respective partition,

wherein the decoder is configured to perform the setting for a predetermined par-tition in a manner depending on
an evaluation of previously decoded transform coefficients located in a partition which is traversed by the coding order prior to the predetermined partition.

81. The decoder as claimed in any of claims 76 to 80, configured to

adaptively vary the cutoff value in a manner including setting the cutoff value to zero so that first binarization exists if a measure of an energy of previously de-coded transform coefficients increases a certain threshold.

82. The decoder as claimed in any of claims 76 to 81,

wherein the transform coefficient block (92) is partitioned into partitions,

wherein the decoder is configured to decode bins of the binarization of the absolute value of the quantization level (106) of the transform coefficients of the transform coefficient block sequentially in passes along, in each pass, a coding order which traverses, for each partition, all transform coefficients consecutively without any transform coefficient of any other partition therebetween,

wherein the decoder is configured to decode bins of the first binarization code prior to bins of the second binarization code,

wherein the decoder is configured to decode the bins of the first binarization code using context-adaptive entropy decoding, and decode the bins of the second binarization code using an equi-probability bypass mode,

wherein the decoder is configured to

set the cutoff value (164) depending on

the measure of the energy of the previously decoded transform co-efficients within a partition in which a currently decoded transform coefficient is located.

83. The decoder as claimed in claim82, configured to

Use a number of bins of the first binarization code, previously decoded using context-adaptive arithmetic decoding for the transform coefficients within the partition in which a currently decoded transform coefficient is located, as a measure for the energy.

84. The decoder as claimed in any of claims 76 to 81,

wherein the decoder is configured to deode bins of the binarization of the absolute value of the quantization level (106) of the transform coefficients of the transform coefficient block sequentially in passes,

wherein the decoder is configured to decode bins of the first binarization code prior to bins of the second binarization code,

wherein the decoder is configured to decode the bins of the first binarization code using context-adaptive entropy decoding, and decode the bins of the second binarization code using an equi-probability bypass mode,

wherein the decoder is configured to

set the cutoff value (164) depending on

the measure of the energy of the previously decoded transform co-efficients within the transform coefficient block.

85. The decoder as claimed in claim 84, configured to

Use a number of bins of the first binarization code, previously decoded using context-adaptive arithmetic decoding for the transform coefficients within the transform coeffi-cient block as a measure for the energy.

86. The decoder as claimed in any of claims 76 to 81,

wherein the transform coefficient block (92) is partitioned into partitions,

wherein the decoder is configured to decode bins of the binarization of the absolute value of the quantization level (106) of the transform coefficients of the transform coefficient block sequentially in passes along, in each pass, a coding order which traverses, for each partition, all transform coefficients consecutively without any transform coefficient of any other partition therebetween,

wherein the decoder is configured to decode bins of the first binarization code prior to bins of the second binarization code,

wherein the decoder is configured to decode the bins of the first binarization code using context-adaptive entropy decoding, and decode the bins of the second binarization code using an equi-probability bypass mode,

wherein the decoder is configured to

set the cutoff value (164) for a currently decoded transform coefficient depending on

an evaluation of a number of bins of the first binarization code, previously decoded using context-adaptive entropy decoding for transform coefficients locat-ed at positions determined by a local template (132) positioned at the currently decoded transform coefficient, with using a partition the current decoded trans-form coefficient is located in as the locale template.

87. An encoder for encoding a picture into a data stream, configured to

entropy encoding a quantization level of a currently encoded transform coefficient of a transform coefficient block (92) representing a block (84) of the picture (12) context-adaptively by

setting a shape of a local template (132) or disabling the local template (132) [so that the template-specific context dependency is disabled] de-pending on
previously encoded transform coefficients and/or
depending on one or more of
a size of the block (84),
a color component of the block (84),
a position of a termination coefficient position at which, when traversing the scan pattern along a forward direction (116), a last non-zero transform coefficient resides,
a transformation underlying the transform coefficient block (92),

use of a context which is

determined based on one or more previously encoded transform co-efficients located at positions determined by the local template (132) positioned at the currently encoded transform coefficient, or if the local template disabled, is independent from previously en-coded transform coefficients.

88. The encoder as claimed in claim 87, configured to

in setting a shape of, or disabling, the local template depending on the previously encoded transform coefficients,
set the shape of the local template depending on one or more previously encoded transform coefficients located at positions determined by a first local primitive template (170) positioned at the currently encoded trans-form coefficient.

89. The encoder as claimed in claim 88, configured to

in setting a shape of, or disabling, the local template depending on the previously encoded transform coefficients,
decide depending on one or more previously encoded transform coeffi-cients located at positions determined by a first local primitive template (170) positioned at the currently encoded transform coefficient, whether the shape of the local template (132) shall be
the first local primitive template (170) or
a second primitive template (172), wherein the second primitive template extends farther away from the currently encoded trans-form coefficient than the first second primitive template and in-cludes or not includes the positions determined by the first local primitive template.

90. The encoder as claimed in claim 89, configured to

Perform the decision depending on a sum of, or a number of significant ones among, the one or more previously encoded transform coefficients located at posi-tions determined by the first local primitive template (170) positioned at the cur-rently encoded transform coefficient.

91. The encoder as claimed in any of claims 87 to 90, configured to

disable the local template,
if an accumulative value derived based on previously encoded transform coefficients within the transform coefficient block or a count of previously encoded transform coefficients within the transform coefficient block be-ing greater than some threshold, exceeds a predetermined amount, and/or
disable the local template,
if a count of previously encoded transform coefficients within the trans-form coefficient block being insignificant, exceeds a predetermined amount.

92. The encoder as claimed in any of claims 87 to 91, configured to

determine the context based on a sum of, or a number of significant ones among, the one or more previously encoded transform coefficients located at the positions determined by the local template positioned at the currently encoded transform coefficient.

93. The encoder as claimed in any of claims 87 to 92, configured to

entropy encode the quantization level using context-adaptive binary arithmetic coding of a binarization of an absolute value of the quantization level involving a prefix part and a suffix part, wherein the context is used for one or more bins of the prefix part.

94. The encoder as claimed in any of claims 87 to 93, configured to

encode bins of a binarization for quantization levels of transform coefficients of the transform coefficient block (92) sequentially in a plurality of passes,

use the context for at least one bin of the binarization of the quantization level of currently encoded transform coefficient, and

determine the context based on previously encoded bins of the binarization of the absolute value of the coefficient level of the one or more previously encoded transform coefficients, or, if the local template disabled, independent from the previously encoded bins of the binarization of the absolute value of the coefficient level of the one or more previously encoded transform coefficients.

95. A decoder for decoding a picture from a data stream, configured to

entropy decoding a quantization level of a currently decoded transform coefficient of a transform coefficient block (92) representing a block (84) of the picture (12) context-adaptively by

setting a shape of a local template (132) or disabling the local template (132) [so that the template-specific context dependency is disabled] de-pending on
previously decoded transform coefficients and/or
depending on one or more of
a size of the block (84),
a position of a termination coefficient position at which, when traversing the scan pattern along a forward direction (116), a last non-zero transform coefficient resides,
a transformation underlying the transform coefficient block (92),

use of a context which is
determined based on one or more previously decoded transform co-efficients located at positions determined by the local template (130) positioned at the currently decoded transform coefficient, or
if the local template disabled, is independent from previously de-coded transform coefficients.

96. The decoder as claimed in claim 95, configured to

in setting a shape of, or disabling, the local template depending on the previously decoded transform coefficients,
set the shape of the local template depending on one or more previously decoded transform coefficients located at positions determined by a first local primitive template (170) positioned at the currently decoded trans-form coefficient (130).

97. The decoder as claimed in claim 96, configured to

in setting a shape of, or disabling, the local template depending on the previously decoded transform coefficients,
decide depending on one or more previously decoded transform coeffi-cients located at positions determined by a first local primitive template (170) positioned at the currently decoded transform coefficient, whether the shape of the local template (132) shall be
the first local primitive template (170) or
a second primitive template (172), wherein the second primitive template extends farther away from the currently decoded trans-form coefficient than the first second primitive template and in-cludes or not includes the positions determined by the first local primitive template.

98. The decoder as claimed in claim 97, configured to

Perform the decision depending on a sum of, or a number of significant ones among, the one or more previously decoded transform coefficients located at posi-tions determined by the first local primitive template (170) positioned at the cur-rently decoded transform coefficient.

99. The decoder as claimed in any of claims 95 to 98, configured to

disable the local template,
if an accumulative value derived based on previously decoded transform coefficients within the transform coefficient block or a count of previously decoded transform coefficients within the transform coefficient block be-ing greater than some threshold, exceeds a predetermined amount, and/or
disable the local template,
if a count of previously decoded transform coefficients within the trans-form coefficient block being insignificant, exceeds a predetermined amount.

100. The decoder as claimed in any of claims 95 to 99, configured to

determine the context based on a sum of, or a number of significant ones among, the one or more previously decoded transform coefficients located at the positions determined by the local template positioned at the currently decoded transform coefficient.

101. The decoder as claimed in any of claims 95 to 100, configured to

entropy decode the quantization level using context-adaptive binary arithmetic decoding of a binarization of an absolute value of the quantization level involving a prefix part and a suffix part, wherein the context is used for one or more bins of the prefix part.

102. The decoder as claimed in any of claims 95 to 101, configured to

decode bins of a binarization for quantization levels of transform coefficients of the transform coefficient block (92) sequentially in a plurality of passes,

use the context for at least one bin of the binarization of the quantization level of currently decoded transform coefficient, and

determine the context based on previously decoded bins of the binarization of the absolute value of the coefficient level of the one or more previously decoded transform coefficients, or, if the local template disabled, independent from the previously decoded bins of the binarization of the absolute value of the coefficient level of the one or more previously decoded transform coefficients.

103. An encoder for encoding a picture into a data stream, configured to

encode a transform coefficient (92) of a transform coefficient block (92) repre-senting a block (84) of the picture (12) by

entropy encoding quantization levels (106) of the transform coefficients of the transform coefficient block context-adaptively using, for each partition of partitions into which the transform coefficient block is subdivided, a set of contexts which is associated with the respective partition,

wherein the partitions into which the transform coefficient block is subdivided,

vary in shape and/or
are shaped depending on a scanning pattern along which the entropy encod-ing the quantization levels of the transform coefficients of the transform coefficient block is performed, and/or
are shaped depending on a size of the block (84), and/or
are shaped depending on explicit partition shaping information.

104. The encoder as claimed in claim 103, configured to

entropy encode the quantization levels of the transform coefficients of the trans-form coefficient block context-adaptively sequentially by following a scan pattern which sequentially traverses transform coefficients of the transform coefficient block in a manner traversing the partitions sequentially without interleaving trans-form coefficients of different partitions.

105. The encoder as claimed in claim 103 or 104, wherein the partitions into which the transform coefficient block is subdivided,

Extend diagonally along a direction obliquely to a normal direction through a DC transform coefficient of the transform coefficient block.

106. The encoder of any claims 103 to 105, configured to

encode a transform coefficient of a transform coefficient block (92) representing a block (84) of the picture (12) by

encoding for each partition of a set of partitions into which the transform coefficient block is subdivided an indication (150) whether all transform coefficients within the respective partition are encoded into the data stream, or whether the encoding of all transform coefficients within the re-spective partition is skipped and all transform coefficients within the re-spective partition are zero, and

entropy encoding, for each partition for which the indication indicates that all transform coefficients within the respective partition are encoded into the data stream, quantization levels of all transform coefficients of the re-spective partition context-adaptively using a set of contexts which is asso-ciated with the respective partition.

107. A decoder for decoding a picture from a data stream, configured to

decode a transform coefficient (92) of a transform coefficient block (92) repre-senting a block (84) of the picture (12) by

entropy decoding quantization levels (106) of the transform coefficients of the transform coefficient block context-adaptively using, for each partition of partitions into which the transform coefficient block is subdivided, a set of contexts which is associated with the respective partition,

wherein the partitions into which the transform coefficient block is subdivided,

vary in shape and/or
are shaped depending on a scanning pattern along which the entropy decod-ing the quantization levels of the transform coefficients of the transform coefficient block is performed, and/or
are shaped depending on a size of the block (84), and/or
are shaped depending on explicit partition shaping information.

108. The decoder as claimed in claim 107, configured to

entropy decode the quantization levels of the transform coefficients of the trans-form coefficient block context-adaptively sequentially by following a scan pattern which sequentially traverses transform coefficients of the transform coefficient block in a manner traversing the partitions sequentially without interleaving trans-form coefficients of different partitions.

109. The decoder as claimed in claim 107 or 108, wherein the partitions into which the transform coefficient block is subdivided,

Extend diagonally along a direction obliquely to a normal direction through a DC transform coefficient of the transform coefficient block.

110. The decoder of any claims 107 to 109, configured to

decode a transform coefficient of a transform coefficient block (92) representing a block (84) of the picture (12) by

decoding for each partition of a set of partitions into which the transform coefficient block is subdivided an indication (150) whether all transform coefficients within the respective partition are coded into the data stream, or whether the decoding of all transform coefficients within the respective partition is skipped and all transform coefficients within the respective partition are zero, and

entropy decoding, for each partition for which the indication indicates that all transform coefficients within the respective partition are coded into the data stream, quantization levels of all transform coefficients of the respec-tive partition context-adaptively using a set of contexts which is associated with the respective partition.

111. An encoder for encoding a picture into a data stream, configured to

encode a transform coefficient (92) of a transform coefficient block (92) repre-senting a block (84) of the picture (12) by

encoding for each partition of a set of partitions into which the transform coefficient block is subdivided an indication (150) whether all transform coefficients within the respective partition are zero, and

entropy encoding, for each partition for which the indication does not indi-cate that all transform coefficients within the respective partition are zero, quantization levels of transform coefficients within the respective parti-tion,

wherein the partitions into which the transform coefficient block is subdivided,

vary in shape and/or
are shaped depending on a scanning pattern along which the entropy encod-ing the quantization levels of the transform coefficients of the transform coefficient block is performed, and/or
are shaped depending on a size of the block (84), and/or
are shaped depending on explicit partition shaping information.

112. A decoder for decoding a picture from a data stream, configured to

decode a transform coefficient (92) of a transform coefficient block (92) repre-senting a block (84) of the picture (12) by

decoding for each partition of a set of partitions into which the transform coefficient block is subdivided an indication (150) whether all transform coefficients within the respective partition are zero, and

entropy decoding, for each partition for which the indication does not indi-cate that all transform coefficients within the respective partition are zero, quantization levels of transform coefficients within the respective parti-tion,

wherein the partitions into which the transform coefficient block is subdivided,

vary in shape and/or
are shaped depending on a scanning pattern along which the entropy decod-ing the quantization levels of the transform coefficients of the transform coefficient block is performed, and/or
are shaped depending on a size of the block (84), and/or
are shaped depending on explicit partition shaping information.

113. An encoder for encoding a picture into a data stream, configured to

encode a transform coefficient block (92) representing a block (84) of the picture (12) by

encoding for each partition of a set of partitions into which the transform coefficient block is subdivided an indication (150) whether all transform coefficients within the respective partition are encoded into the data stream, or whether the encoding of all transform coefficients within the re-spective partition is skipped and all transform coefficients within the re-spective partition are zero, and

entropy encoding, for each partition for which the indication indicates that all transform coefficients within the respective partition are encoded into the data stream, quantization levels of all transform coefficients of the re-spective partition.

114. The encoder as claimed in claim 113, configured to

entropy encode, for each partition for which the indication indicates that all trans-form coefficients within the respective partition are encoded into the data stream, the quantization levels of all transform coefficients of the respective partition by
entropy encoding, for a last transform coefficient of the respective parti-tion which is encoded last among the transform coefficients of the respec-tive partition, a flag indicating whether the last transform coefficient is ze-ro or not, irrespective of whether any of the previously encoded transform coefficients within the respective partition are all zero or not.

115. A decoder for decoding a picture from a data stream, configured to

decode a transform coefficient block (92) representing a block (84) of the picture (12) by

decoding for each partition of a set of partitions into which the transform coefficient block is subdivided an indication (150) whether all transform coefficients within the respective partition are coded into the data stream, or whether the decoding of all transform coefficients within the respective partition is skipped and all transform coefficients within the respective partition are zero, and

entropy decoding, for each partition for which the indication indicates that all transform coefficients within the respective partition are coded into the data stream, quantization levels of all transform coefficients of the respec-tive partition.

116. The decoder as claimed in claim 115, configured to

entropy decode, for each partition for which the indication indicates that all trans-form coefficients within the respective partition are coded into the data stream, the quantization levels of all transform coefficients of the respective partition by
entropy decoding, for a last transform coefficient of the of the respective partition which is decoded last among the transform coefficients of the re-spective partition, a flag indicating whether the last transform coefficient is zero or not, irrespective of whether any of the previously decoded trans-form coefficients within the respective partition are all zero or not.

117. An encoder for encoding a picture into a data stream, configured to

encoding a partitioning mode of a transform coefficient block (92) representing a block (84) of the picture (12) into the data stream,

encode the transform coefficient block by

if the partition mode is a first mode [e.g. partition into partitions 120 switched on], entropy encoding quantization levels of the transform coeffi-cients of the transform coefficient block context-adaptively using, for each partition of partitions into which the transform coefficient block is subdi-vided, a set of contexts which is associated with the respective partition, and

if the partition mode is a second mode [e.g. partition into partitions 120 switched off], entropy encoding the quantization levels of the transform coefficients of the transform coefficient block context-adaptively using a global set of contexts.

118. The encoder as claimed in claim 117, configured to

if the partition mode is the first mode,

encode for each partition of a set of partitions an indication whether the quantization levels of the transform coefficients within the respective par-tition are encoded into the data stream, or whether the encoding of the quantization levels of the transform coefficients within the respective par-tition is skipped and all transform coefficients within the respective parti-tion are zero, and

skip, in entropy encoding the quantization levels of the transform coeffi-cients, the entropy encoding with respect to partitions for which the indica-tion indicates that the encoding of the quantization levels of the transform coefficients within the partitions is skipped and all transform coefficients within the partitions are zero.

119. A decoder for decoding a picture from a data stream, configured to

decoding a partitioning mode of a transform coefficient block (92) representing a block (84) of the picture (12) from the data stream,

decode the transform coefficient block by

if the partition mode is a first mode [e.g. partition into partitions 120 switched on], entropy decoding quantization levels of the transform coeffi-cients of the transform coefficient block context-adaptively using, for each partition of partitions into which the transform coefficient block is subdi-vided, a set of contexts which is associated with the respective partition, and

if the partition mode is a second mode [e.g. partition into partitions 120 switched off], entropy decoding the quantization levels of the transform coefficients of the transform coefficient block context-adaptively using a global set of contexts .

120. The decoder as claimed in claim 119, configured to

if the partition mode is the first mode,

decode for each partition of a set of partitions an indication whether the quantization levels of the transform coefficients within the respective par-tition are decoded into the data stream, or whether the decoding of the quantization levels of the transform coefficients within the respective par-tition is skipped and all transform coefficients within the respective parti-tion are zero, and

skip, in entropy decoding the quantization levels of the transform coeffi-cients, the entropy decoding with respect to partitions for which the indica-tion indicates that the decoding of the quantization levels of the transform coefficients within the partitions is skipped and all transform coefficients within the partitions are zero.

121. An encoder for encoding a picture into a data stream, configured to

encode a transform coefficient block (92) representing a block (84) of the picture (12) into the data stream (14) using a scan pattern (94’) which sequentially traverses transform coefficients (91) of the transform coefficient block by

entropy encoding quantization levels (106) of the transform coefficients of the transform coefficient block context-adaptively using, for each partition of partitions (120a,b,c) into which the transform coefficient block is subdi-vided, a set (110a,b,c) of contexts which is associated (126) with the re-spective partition (120),

wherein the scan pattern (94’) sequentially traverses the transform coefficients (91) of the transform coefficient block (92) in a manner so that at least one trans-form coefficient (such as the hatched ones 91’) of a first partition (e.g. 120a or 120c) is traversed between two transform coefficients of a second partition (e.g. 120b).

122. The encoder as claimed in claim 121, configured so that one set of contexts is commonly associated with the first partition and second partitions (e.g. 120a or 120c).

123. The encoder as claimed in claim 121 or 122, configured to

in entropy encoding the quantization levels of the transform coefficients of the transform coefficient block (92) context-adaptively,

determine for a currently encoded transform coefficient (130) a context out of the set (110) of contexts (112) associated with the partition (e.g. 120a) the currently encoded transform coefficient is located in, based on

one or more previously encoded transform coefficients located at positions determined by a local template (132) positioned at the currently encoded transform coefficient.

124. The encoder as claimed in claim 121 or 122, configured to

in entropy encoding the quantization levels of the transform coefficients of the transform coefficient block context-adaptively,

determine for a currently encoded transform coefficient a context out of the set of contexts associated with the partition the currently encoded transform coefficient is located in, based on
one or more previously encoded transform coefficients located at positions determined by a local template (132) positioned at the currently encoded transform coefficient, irrespective of whether the positions are within the partition the currently encoded transform coefficient is located in, and/or
a count (exemplarily 4 in the example figure) of previously encoded transform coefficients (e.g. hatched ones 140) located within the partition (e.g. 120a) the currently encoded transform coefficient (130) is located in, which exceed one or more certain thresholds.

125. The encoder as claimed in any of claims 121 to 123, configured to

encoding for each partition (120a,b,c) of a set of partitions into which the trans-form coefficient block (92) is subdivided an indication (150) whether the trans-form coefficients within the respective partition are encoded into the data stream, or whether the encoding of the transform coefficients within the respective parti-tion is skipped and all transform coefficients within the respective partition are zero, and skipping, in entropy encoding the quantization levels of the transform coefficients, the entropy encoding with respect to partitions for which the indica-tion indicates that the encoding of the transform coefficients within the partitions is skipped and all transform coefficients within the partitions are zero.

126. The encoder as claimed in claim 125, configured to

encoding the indication (150) into the data stream in between the quantization levels of transform coefficients within partitions for which the indication indi-cates that the transform coefficients within the respective partition are encoded in-to the data stream (e.g. for 1201 and 1203), in place of [in case of CBF being zero such as CBF2 in the example], or in front of [in case of CBF being one such as CBF3 in the example], a first encountered transform coefficient within the parti-tion the indication relates to.

127. A decoder for decoding a picture from a data stream, configured to

decode a transform coefficient block (92) representing a block (84) of the picture (12) from the data stream (14) using a scan pattern (94’) which sequentially traverses transform coefficients (91) of the transform coefficient block by

entropy decoding quantization levels (106) of the transform coefficients of the transform coefficient block context-adaptively using, for each partition of partitions into which the transform coefficient block is subdivided, a set (110a,b,c) of contexts which is associated (126) with the respective parti-tion (120),

wherein the scan pattern (94’) sequentially traverses the transform coefficients (91) of the transform coefficient block (92) in a manner so that at least one trans-form coefficient (such as the hatched ones 91’) of a first partition is traversed be-tween two transform coefficients of a second partition.

128. The decoder as claimed in claim 127, configured so that one set of contexts is commonly associated with the first partition and second partitions (e.g. 120a or 120c).

129. The decoder as claimed in claim 127 or 128, configured to

in entropy decoding the quantization levels of the transform coefficients of the transform coefficient block (92) context-adaptively,

determine for a currently encoded transform coefficient (130) a context out of the set (110) of contexts (112) associated with the partition (e.g. 120a) the currently decoded transform coefficient is located in, based on

one or more previously encoded transform coefficients located at positions determined by a local template (132) positioned at the currently decoded transform coefficient.

130. The decoder as claimed in claim 127 or 128, configured to

in entropy decoding the quantization levels of the transform coefficients of the transform coefficient block context-adaptively,

determine for a currently decoded transform coefficient a context out of the set of contexts associated with the partition the currently decoded transform coefficient is located in, based on
one or more previously decoded transform coefficients located at positions determined by a local template (132) positioned at the currently decoded transform coefficient, irrespective of whether the positions are within the partition the currently decoded transform coefficient is located in, and/or
a count (exemplarily 4 in the example figure) of previously decoded transform coefficients (e.g. hatched ones 140) located within the partition (e.g. 120a) the currently decoded transform coefficient (130) is located in, which exceed one or more certain thresholds.

131. The decoder as claimed in any of claims 127 to 129, configured to

decoding for each partition (120a,b,c) of a set of partitions into which the trans-form coefficient block (92) is subdivided an indication (150) whether the trans-form coefficients within the respective partition are decoded into the data stream, or whether the decoding of the transform coefficients within the respective parti-tion is skipped and all transform coefficients within the respective partition are zero, and skipping, in entropy decoding the quantization levels of the transform coefficients, the entropy decoding with respect to partitions for which the indica-tion indicates that the decoding of the transform coefficients within the partitions is skipped and all transform coefficients within the partitions are zero.

132. The decoder as claimed in claim 131, configured to

decoding the indication (150) from the data stream in between the quantization levels of transform coefficients within partitions for which the indication indicates that the transform coefficients within the respective partition are decoded into the data stream (e.g. for 1201 and 1203), in place of [in case of CBF being zero such as CBF2 in the exam-ple], or in front of [in case of CBF being one such as CBF3 in the example], a first en-countered transform coefficient within the partition the indication relates to.

133. A method for encoding a picture into a data stream, comprising:

subjecting a block of the picture separately for a first color component and a sec-ond color component to a transformation to obtain a first transform coefficient block and a second transform coefficient block, respectively,
entropy encoding the second transform coefficient block context-adaptively using a con-text which depends on the first transform coefficient block.

134. A method for decoding a picture from a data stream, comprising:

deriving a block (84) of the picture by, separately for a first color component and a second color component, a reverse transformation of a first transform coefficient block (921) and a second transform block (922), respectively,

entropy decoding the second transform coefficient block (922) context-adaptively using a context which depends on the first transform coefficient block.

135. A method for encoding a picture (12) into a data stream (14), comprising:

encoding (108) a transform coefficient block (92) representing a block (84) of the picture (12) into the data stream (14) using a scan pattern (94) which sequentially traverses trans-form coefficients of the transform coefficient block (92) by

encoding into the data stream (14) data (96) representing a coded set (100 shown hatched) of transform coefficients (91) traversed by the scan pattern (94) [or scan path] from a first termination coefficient position (98) in a predetermined direction (102) to a second termination coefficient (104), the data (96) comprising quantization levels (106) of the transform coefficients in the coded set (100) of transform coefficients,

wherein the method comprises entropy encoding the quantization levels (106) context-adaptively using a first set (110) of contexts (112) for the quantization level of the trans-form coefficient at the first termination coefficient position (98) or at the second termi-nation coefficient position (104) which is disjoint to a second set (110) of contexts (112) used for any other transform coefficient in the coded set (100) of transform coefficients.

136. The method for decoding a picture (12) from a data stream (14), comprising:

decoding (108) a transform coefficient block (92) representing a block (84) of the picture (12) from the data stream (14) using a scan pattern (94) which sequentially traverses transform coefficients (91) of the transform coefficient block (92) by

decoding from the data stream (14) data (96) representing a coded set (100) of transform coefficients (91) traversed by the scan pattern (94) from a first termination coefficient position (98) in a predetermined direction (102) to a second termination coef-ficient position (104), the data (96) comprising quantization levels (106) of the transform coefficients in the coded set (100) of transform coefficients,

wherein the method comprises entropy decoding the quantization levels (106) context-adaptively using a first set (110) of contexts (112) for the quantization level of the trans-form coefficient at the first termination coefficient position (98) or at the second termi-nation coefficient position (104) which is disjoint to a second set (110) of contexts (112) used for any other transform coefficient in the coded set (100) of transform coefficients.

137. A method for encoding a picture into a data stream, comprising

entropy encoding a quantization level of a currently encoded transform coefficient of a transform coefficient block (92) representing a block (84) of the picture (12) context-adaptively by

use of a context which is determined based on

a sum of, and/or
a number of significant ones among,

one or more previously encoded transform coefficients located at positions determined by a local template (132) positioned at the currently encoded transform coefficient.

138. A method for decoding a picture from a data stream, comprising:

entropy decoding a quantization level (106) of a currently decoded transform coefficient (130) of a transform coefficient block (92) representing a block (84) of the picture (12) context-adaptively by

use of a context which is determined based on

a sum of, and/or
a number of significant ones among,

one or more previously decoded transform coefficients located at positions determined by a local template (132) positioned at the currently decoded transform coefficient.

139. A method for encoding a picture into a data stream, comprising:

encoding a transform coefficient block (92) representing a block (84) of the picture (12) into the data stream by

encoding an absolute value of a quantization level of a currently encoded trans-form coefficient of the transform coefficient block in a manner binarized using a binari-zation (161) which is parameterized using a binarization parameter (163),

setting of the binarization parameter based on

a sum of, and/or
a number of significant ones among,

one or more previously encoded transform coefficients located at positions determined by a local template (132) positioned at the currently encoded transform coefficient.

140. A method for decoding a picture from a data stream, comprising:

decoding a transform coefficient block (92) representing a block (84) of the picture (12) from the data stream by

decoding an absolute value of a quantization level of a currently decoded trans-form coefficient of the transform coefficient block in a manner binarized using a binari-zation (161) which is parameterized using a binarization parameter (163),

setting of the binarization parameter (163) based on

a sum of, and/or
a number of significant ones among,

one or more previously decoded transform coefficients located at positions determined by a local template (132) positioned at the currently decoded transform coefficient.

141. A method for encoding a picture into a data stream, comprising:

encoding the transform coefficient block (92) representing a block (84) of the picture (12) into the data stream using a scan pattern (94) which sequentially traverses transform coefficients of the transform coefficient block by

encoding an absolute value of quantization levels (106) of the transform coeffi-cients of the transform coefficient block in a manner binarized using a binarization com-prising a first binarization code (160) below a cutoff value (164) and a second binariza-tion code (162), prefixed by a codeword of the first binarization code (160) for the cutoff value, above the cutoff value,

adaptively varying the cutoff value for the transform coefficients of the transform coeffi-cient block depending on previously encoded transform coefficients.

142. A method for decoding a picture from a data stream, comprising:

decoding the transform coefficient block (92) representing a block (84) of the picture (12) from the data stream using a scan pattern (94) which sequentially traverses trans-form coefficients of the transform coefficient block by

decoding an absolute value of quantization levels (106) of the transform coeffi-cients of the transform coefficient block in a manner binarized using a binarization com-prising a first binarization code (160) below a cutoff value (164) and a second binariza-tion code (162), prefixed by a codeword of the first binarization code (160) for the cutoff value, above the cutoff value,

adaptively varying the cutoff value for the transform coefficients of the transform coeffi-cient block depending on previously decoded transform coefficients.

143. A method for encoding a picture into a data stream, comprising:

encoding a transform coefficient block (92) representing a block (84) of the pic-ture (12) into the data stream by

encoding an absolute value of a quantization level (106) of the transform coefficients of the transform coefficient block in a manner binarized using a binarization comprising a first binarization code (160) below a cutoff value [i.e. for absolute values below the cutoff value] and a second binari-zation code (162), prefixed by a codeword of the first binarization code (160) for the cutoff value, above the cutoff value,

setting the cutoff value (164) depending on one or more of

a size of the block (84),
a color component of the block (84),
a prediction mode underlying a prediction signal a prediction resid-ual of which the block (84) represents,
a transformation underlying the transform coefficient block (92),
a quantization parameter used to quantize the transform coefficient block (92),
a measure of an energy of previously encoded transform coeffi-cients, and
an evaluation of previously encoded transform coefficients.

144. A method for decoding a picture from a data stream, comprising:

decoding a transform coefficient block (92) representing a block (84) of the pic-ture (12) from the data stream by

decoding an absolute value of a quantization level (106) of the transform coefficients of the transform coefficient block in a manner binarized using a binarization (161) comprising a first binarization code (160) below a cut-off value [i.e. for absolute values below the cutoff value] and a second bi-narization code (162), prefixed by a codeword of the first binarization code (160) for the cutoff value, above the cutoff value,

setting the cutoff value (164) depending on one or more of

a size of the block (84),
a color component of the block (84),
a prediction mode underlying a prediction signal a prediction resid-ual of which the block (84) represents,
a transformation underlying the transform coefficient block (92),
a quantization parameter used to quantize the transform coefficient block (92),
a measure of an energy of previously decoded transform coeffi-cients,
an evaluation of previously decoded transform coefficients.

145. A method for encoding a picture into a data stream, comprising:

entropy encoding a quantization level of a currently encoded transform coefficient of a transform coefficient block (92) representing a block (84) of the picture (12) context-adaptively by

setting a shape of a local template (132) or disabling the local template (132) [so that the template-specific context dependency is disabled] de-pending on
previously encoded transform coefficients and/or
depending on one or more of
a size of the block (84),
a color component of the block (84),
a position of a termination coefficient position at which, when traversing the scan pattern along a forward direction (116), a last non-zero transform coefficient resides,
a transformation underlying the transform coefficient block (92),

use of a context which is

determined based on one or more previously encoded transform co-efficients located at positions determined by the local template (132) positioned at the currently encoded transform coefficient, or if the local template disabled, is independent from previously en-coded transform coefficients.

146. A method for decoding a picture from a data stream, comprising:

entropy decoding a quantization level of a currently decoded transform coefficient of a transform coefficient block (92) representing a block (84) of the picture (12) context-adaptively by

setting a shape of a local template (132) or disabling the local template (132) [so that the template-specific context dependency is disabled] de-pending on
previously decoded transform coefficients and/or
depending on one or more of
a size of the block (84),
a position of a termination coefficient position at which, when traversing the scan pattern along a forward direction (116), a last non-zero transform coefficient resides,
a transformation underlying the transform coefficient block (92),

use of a context which is
determined based on one or more previously decoded transform co-efficients located at positions determined by the local template (130) positioned at the currently decoded transform coefficient, or
if the local template disabled, is independent from previously de-coded transform coefficients.

147. A method for encoding a picture into a data stream, comprising:

encoding a transform coefficient (92) of a transform coefficient block (92) repre-senting a block (84) of the picture (12) by

entropy encoding quantization levels (106) of the transform coefficients of the transform coefficient block context-adaptively using, for each partition of partitions into which the transform coefficient block is subdivided, a set of contexts which is associated with the respective partition,

wherein the partitions into which the transform coefficient block is subdivided,

vary in shape and/or
are shaped depending on a scanning pattern along which the entropy encod-ing the quantization levels of the transform coefficients of the transform coefficient block is performed, and/or
are shaped depending on a size of the block (84), and/or
are shaped depending on explicit partition shaping information.

148. A method for decoding a picture from a data stream, comprising:

decoding a transform coefficient (92) of a transform coefficient block (92) repre-senting a block (84) of the picture (12) by

entropy decoding quantization levels (106) of the transform coefficients of the transform coefficient block context-adaptively using, for each partition of partitions into which the transform coefficient block is subdivided, a set of contexts which is associated with the respective partition,

wherein the partitions into which the transform coefficient block is subdivided,

vary in shape and/or
are shaped depending on a scanning pattern along which the entropy decod-ing the quantization levels of the transform coefficients of the transform coefficient block is performed, and/or
are shaped depending on a size of the block (84), and/or
are shaped depending on explicit partition shaping information.

149. A method for encoding a picture into a data stream, comprising

encode a transform coefficient (92) of a transform coefficient block (92) repre-senting a block (84) of the picture (12) by

encoding for each partition of a set of partitions into which the transform coefficient block is subdivided an indication (150) whether all transform coefficients within the respective partition are zero, and

entropy encoding, for each partition for which the indication does not indi-cate that all transform coefficients within the respective partition are zero, quantization levels of transform coefficients within the respective parti-tion,

wherein the partitions into which the transform coefficient block is subdivided,

vary in shape and/or
are shaped depending on a scanning pattern along which the entropy encod-ing the quantization levels of the transform coefficients of the transform coefficient block is performed, and/or
are shaped depending on a size of the block (84), and/or
are shaped depending on explicit partition shaping information.

150. A method for decoding a picture from a data stream, comprising

decode a transform coefficient (92) of a transform coefficient block (92) repre-senting a block (84) of the picture (12) by

decoding for each partition of a set of partitions into which the transform coefficient block is subdivided an indication (150) whether all transform coefficients within the respective partition are zero, and

entropy decoding, for each partition for which the indication does not indi-cate that all transform coefficients within the respective partition are zero, quantization levels of transform coefficients within the respective parti-tion,

wherein the partitions into which the transform coefficient block is subdivided,

vary in shape and/or
are shaped depending on a scanning pattern along which the entropy decod-ing the quantization levels of the transform coefficients of the transform coefficient block is performed, and/or
are shaped depending on a size of the block (84), and/or
are shaped depending on explicit partition shaping information.

151. A method for encoding a picture into a data stream, comprising:

encoding a transform coefficient block (92) representing a block (84) of the pic-ture (12) by

encoding for each partition of a set of partitions into which the transform coefficient block is subdivided an indication (150) whether all transform coefficients within the respective partition are encoded into the data stream, or whether the encoding of all transform coefficients within the re-spective partition is skipped and all transform coefficients within the re-spective partition are zero, and

entropy encoding, for each partition for which the indication indicates that all transform coefficients within the respective partition are encoded into the data stream, quantization levels of all transform coefficients of the re-spective partition.

152. A method for decoding a picture from a data stream, comprising:

decoding a transform coefficient block (92) representing a block (84) of the pic-ture (12) by

decoding for each partition of a set of partitions into which the transform coefficient block is subdivided an indication (150) whether all transform coefficients within the respective partition are decoded into the data stream, or whether the decoding of all transform coefficients within the re-spective partition is skipped and all transform coefficients within the re-spective partition are zero, and

entropy decoding, for each partition for which the indication indicates that all transform coefficients within the respective partition are decoded into the data stream, quantization levels of all transform coefficients of the re-spective partition.

153. A method for encoding a picture into a data stream, comprising:

encoding a partitioning mode of a transform coefficient block (92) representing a block (84) of the picture (12) into the data stream,

encoding the transform coefficient block by

if the partition mode is a first mode [e.g. partition into partitions 120 switched on], entropy encoding quantization levels of the transform coeffi-cients of the transform coefficient block context-adaptively using, for each partition of partitions into which the transform coefficient block is subdi-vided, a set of contexts which is associated with the respective partition, and

if the partition mode is a second mode [e.g. partition into partitions 120 switched off], entropy encoding the quantization levels of the transform coefficients of the transform coefficient block context-adaptively using a global set of contexts.

154. A method for decoding a picture from a data stream, comprising:

decoding a partitioning mode of a transform coefficient block (92) representing a block (84) of the picture (12) from the data stream,

decoding the transform coefficient block by

if the partition mode is a first mode [e.g. partition into partitions 120 switched on], entropy decoding quantization levels of the transform coeffi-cients of the transform coefficient block context-adaptively using, for each partition of partitions into which the transform coefficient block is subdi-vided, a set of contexts which is associated with the respective partition, and

if the partition mode is a second mode [e.g. partition into partitions 120 switched off], entropy decoding the quantization levels of the transform coefficients of the transform coefficient block context-adaptively using a global set of contexts .

155. A method for encoding a picture into a data stream, comprising:

encoding a transform coefficient block (92) representing a block (84) of the pic-ture (12) into the data stream (14) using a scan pattern (94’) which sequentially traverses transform coefficients (91) of the transform coefficient block by

entropy encoding quantization levels (106) of the transform coefficients of the transform coefficient block context-adaptively using, for each partition of partitions (120a,b,c) into which the transform coefficient block is subdivided, a set (110a,b,c) of contexts which is associated (126) with the respective partition (120),

wherein the scan pattern (94’) sequentially traverses the transform coefficients (91) of the transform coefficient block (92) in a manner so that at least one transform coefficient (such as the hatched ones 91’) of a first partition (e.g. 120a or 120c) is traversed between two transform coefficients of a second partition (e.g. 120b).

156. A method for decoding a picture from a data stream, comprising:

decoding a transform coefficient block (92) representing a block (84) of the picture (12) from the data stream (14) using a scan pattern (94’) which sequentially traverses trans-form coefficients (91) of the transform coefficient block by

entropy decoding quantization levels (106) of the transform coefficients of the transform coefficient block context-adaptively using, for each partition of partitions into which the transform coefficient block is subdivided, a set (110a,b,c) of contexts which is associated (126) with the respective partition (120),

wherein the scan pattern (94’) sequentially traverses the transform coefficients (91) of the transform coefficient block (92) in a manner so that at least one transform coefficient (such as the hatched ones 91’) of a first partition is traversed between two transform co-efficients of a second partition.

FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS (AMENDMENT) RULES, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
Transform Coefficient Block Coding
2. APPLICANT:
a) Name
b) Nationality
c) Address Fraunhofer-Gesellschaft Zur Förderung Der Angewandten Forschung :
E.V.
: DE
: Hansastraße 27c, 80686 München (DE)
3. PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Description
The present application is concerned with the coding of pictures and videos using trans-form coefficient block coding.
In other words, the present application to the field of digital signal processing and, in par-ticular, to methods and devices for image and video decoders and encoders.
It is the object of the present invention to provide concepts for more efficiently coding a picture and/or a video a data stream.
This object is achieved by the subject-matter of the independent claims of the present application.
In accordance with a first aspect of the present application, a coding efficiency increase in picture coding is achieved by using a context or context model for entropy encod-ing/decoding a certain transform coefficient block of a certain color component which de-pends on the transform coefficient block of a different color component. That is, a block of a picture is separately subject to a transformation for a first color component and a second color component, respectively, so as to obtain a first transform coefficient block for the first color component and second transform coefficient block for the second color component, and an entropy encoding/decoding the second transform coefficient block context-adaptively, the context used is selected dependent on the first transform coefficient block. Both transformations might relate to a prediction residual determined for the block for each color component, but this is merely optional. In any case, rendering the context used for entropy encoding/decoding the second transform coefficient block dependent on the first transform coefficient block improves the probability estimation underlying the entropy encoding/decoding and, accordingly, increases the coding efficiency. In accordance with an embodiment, the context dependency on the first transform coefficient block is used, or applied for, an indication coded into the data stream for the first and second transform coefficient blocks, which indicates whether the transform coefficients within the respective transform coefficient block are encoded into the data stream, or whether the encoding of
the transform coefficients of the respective transform coefficient block is skipped and all transform coefficients within the respective transform coefficient block are zero. This indi-cation might be a flag signaled for both transform coefficient blocks in the data stream. Thus, in accordance with this embodiment, encoding/decoding of the indication for the second transform coefficient block is performed using context-adaptive entropy encod-ing/decoding using a context which depends on the first transform coefficient block such as depending on the indication signaled in the data stream for the first transform coeffi¬cient block or quantization levels of transform coefficients of the first transform coefficient block.
In accordance with a second aspect of the present application picture coding using trans-form coefficient block entropy coding is rendered more efficient by spending a separate set of contexts for entropy coding a quantization level of certain transform coefficients. In particular, a transform coefficient block which represents a block of the picture is assumed to be coded into the data stream using a scan pattern which sequentially traverses the transform coefficients of the transform coefficient block. Accordingly, encoding/decoding data representing a coding set of transform coefficients traversed by the scan pattern from a first termination coefficient position onwards in a predetermined direction to a second termination coefficient position is done using entropy encoding/decoding. The data com-prises quantization levels of the transform coefficients in the coded set of transform coeffi-cients. The encoding/decoding the quantization levels is done context-adaptively using a first set of contexts for the quantization level of the transform coefficient at the first termi-nation coefficient position or at the second termination coefficient position, wherein this first set of contexts is disjoined to a second set of contexts used for any other transform coefficient in the coded set of transform coefficients. For instance, a separate context set is used for the DC transform coefficient of the transform coefficient block or, differently, speaking, the transform coefficient at the upper left-hand side, with the predetermined direction leading to this DC transform coefficient which represents the second termination coefficient position, though. For instance, the transform coefficients' quantization levels may be coded using context-adaptive binary entropy coding/decoding by using a binariza-tion of the quantization levels of the transform coefficients and the disjoined set of con¬texts may apply to, or be used for, one or more bins of the binarization such as a prefix part of the binarization.
In accordance with a third aspect of the present application, a coding efficiency improve-ment in encoding a picture using entropy coding of a transform coefficient block is
achieved by determining a context for entropy encoding/decoding a quantization level of a currently encoded transform coefficient of the transform coefficient block based on a sum of and/or a number of significant ones among, one or more previously encoded transform coefficients located at positions determined by a local template positioned at the currently encoded/decoded transform coefficient. That is, a local template is used in order to exam-ine transform coefficients located nearby in the transform coefficient block as far as the quantization level of the one or more transform coefficients thus examined is revealed by a previous portion of the data stream. For instance, the entropy encoding/decoding of the quantization levels of the transform coefficients of the transform coefficient block may be done on a binary basis by sequentially entropy encoding/decoding bins of a binarization of the quantization levels of the transform coefficient in a plurality of passes and the context for at least bin of the binarization of the currently encoded/traversed transform coefficient may, thus, be determined based on the just-mentioned sum and/or the just-mentioned number of significant ones among the transform coefficients located at the local template. For instance, the sum may be a sum of an absolute value of the coefficient level of the one or more previous transform coefficients located at the local template, which absolute value this coefficient level of the one or more previous transform coefficients minimally has according to previously encoded/decoded bins of the binarization of the coefficient level of the one or more previous transform coefficients. Additionally or alternatively, the context may be determined based on the number of significant ones among the one or more previous transform coefficients located at the local template with the significance being determined based on the previously encoded/decoded bins.
A further aspect of the present application relates to coding transform coefficients of a transform coefficient block using binarization of absolute values of the quantization levels of the transform coefficients. In accordance with this aspect of the present application, a coding efficiency increase is achieved by setting a binarization parameter for parameteriz-ing the binarization of a currently encoded/decoded transform coefficient based on a sum of, and/or a number of significant ones among, one or more previously encoded/decoded transform coefficients located at positions determined by a local template positioned at the currently encoded/decoded transform coefficient. For instance, a first part of the binariza-tion of the transform coefficients might be coded using context-adaptive entropy encod-ing/decoding while a second part of the binarization is encoded/decoded using an equi-probability bypass mode. That is, the second part is written into the data stream, and read therefrom, at a code rate of one. The second part might comprise a prefix part and a suffix part and the binarization parameter may determine the length of the prefix part. The length
might, for instance, be an Exp-Golomb order or Rice parameter. Similar statements as made above might be true with respect to the possibility of coding the transform coeffi-cients of the transform coefficient block, or the coefficient levels thereof, in several passes and with respect to the consideration of this circumstance in forming this sum and/or de-termining the number of significant coefficients.
A further aspect of the present application also relates to the binarization used to code absolute values of quantization levels of the transform coefficients of a transform coeffi-cient block. In particular, in accordance with this aspect, picture coding is made more effi-cient by adaptively varying a cutoff value associated with a binarization. The binarization comprises a first binarization code below a cutoff value and a second binarization code, prefixed by a codeword of the first binarization code for the cutoff value, above the cutoff value. The adaptive variation of the cutoff value is performed dependent on previously encoded/decoded transform coefficients. For instance, the adaptation may be done in a manner also resulting in setting the cutoff value to zero whereupon the binarization merely comprises the second binarization code. The coding may be done in a manner so that bins of the first binarization code are coded context-adaptively, whereas bins of the sec¬ond binarization code are coded in bypass mode.
A further aspect of the present application also relates to the cutoff value and aims at in-creasing the coding efficiency by setting the cutoff value depending on one or more of a size of the block, a color component of the block, a prediction mode underlying a predic¬tion signal a prediction residual of which the block represents, a transformation underlying the transform coefficient block, a quantization parameter used to quantize the transform coefficient block, a measure of an energy of previously encoded/decoded transform coef-ficients, wherein the latter may be located at positions determined by a local template po-sitioned at a currently encoded/decoded transform coefficient or located at positions within a partition of the transform coefficient block offset to a current partition, the currently en-coded/decoded transform coefficient is located in and preceding the current partition ac-cording to a coding order used for encoding/decoding the absolute value of the quantiza¬tion level of the transform coefficients of the transform coefficient block defined by travers¬ing the transform coefficients of the transform coefficient block along a scan pattern in a predetermined direction.
An even further aspect of the present application aims at increasing the coding efficiency of picture coding using transform coefficient block coding by an intelligent way of setting
the shape of the local template or disabling the local template used for context-adaptively entropy encoding quantization levels of transform coefficients of the transform coefficient block. In particular, the dependency may involve one or more of a size of the block, a col¬or component of the block, a position of a termination coefficient position at which, when traversing the scan pattern along a forward direction, a last non-zero transform coefficient results, and a transformation underlying the transform coefficient block. The context may then be determined based on one or more previously encoded/decoded transform coeffi-cients located at positions determined by the local template positioned at the currently encoded/decoded transform coefficient or, if the local template is disabled, independent from these transform coefficients. In this manner, the context managing complexity, the number of context and the context efficiency in terms of probability estimation accuracy may be better determined, or adapted to, on the actual needs. In this regard, one should know that the usage of too many contexts does not increase the coding efficiency inevita-bly. Rather, the selection of contexts needs to take into account that contexts should be, preferably, used sufficiently frequently in order to, by way of context updates, attain good probability estimations. Thus, this aspect sees to adapt the context managing characteris¬tic to the needs in order to improve the coding efficiency.
In accordance with a further aspect of the present application, the transform coefficient block is partitioned into patterns for sake of using separate sets of contexts for the various partitions. A coding efficiency increase is aimed at by varying the partitions in shape, so that they are not conformed to each other within the transform coefficient block, and/or by shaping the partitions depending on a scanning pattern along which the entropy encod-ing/decoding the quantization levels of the transform coefficient block is performed, and/or by shaping the partitions depending on a size of the block and/or by shaping the partitions depending on an explicit partition shaping information. Again, the idea behind this aspect relates to the necessity to adapt the context management complexity to the actual needs. Thereby, the coding efficiency is increased.
A further aspect of the present application relates to the partitioning of a transform coeffi-cient block into partitions in terms of signaling in the data stream for each partition an indi-cation whether all transform coefficients within the respective partition are coded into the data stream or whether the coding of all transform coefficients within the respective parti-tion is skipped and all transform coefficients within the respective partition are zero. In particular, in accordance with this aspect of the present application, the indication is inter-preted in a way indicating whether all coefficients are coded or none. Each of these parti-
tions may have a set of contexts associated therewith using which the transform coeffi-cients within the respective partition are encoded if so indicated by the indication. In other words, here the partition wise indication of zeroness is indicative, if so set, that all trans¬form coefficients within a certain partition are coded and this circumstance needs not to be questioned anymore.
A further aspect of the present application also relates to an aspect of spending partition-specific context sets for encoding the quantization levels of transform coefficients within the various partitions and aims at improving the coding efficiency by signaling by way of a partition mode for the transform coefficient block in the data stream, whether partitioning is used, or whether such partitioning is disabled and this one set of context is used globally for the transform coefficient block instead.
Finally, a further aspect of the present application also deals with the partition-specific context set usage and suggests improving the coding efficiency by decoupling the scan pattern along which the transform coefficients of the transform coefficient block are se-quentially coded, from the partitioning in that the scan pattern sequentially traverses the transform coefficients of the transform coefficient block in a manner so that at least one transform coefficient of a first partition is traversed between two transform coefficients of a second partition. In this manner, it is feasible to traverse the transform coefficients in a manner so that the "knowledge increase" during scanning the transform coefficients in-creases more rapidly so as to gain improved coding history for the context selec-tion/adaptation, but with concurrently being able to appropriately associated individual context sets to various partitions of the transform block.
Advantageous implementations of the embodiments and aspects described above are the subject of dependent claims. Preferred embodiments of the present application are de-scribed below with respect to the figures among which:
Fig. 1 shows a schematic block diagram of a block-based predictive decoder us-
ing transform-based residual coding, which serves as an example for pos-sible implementations of the embodiments of the present application de-scribed herein;
Fig. 2 shows a schematic block diagram of a block-based predictive video decod-
er fitting to the encoder of Fig. 1, which serves as an example for possible implementations of the embodiments for a decoder described herein;
Fig. 3 shows an example for a partitioning of a picture into coding blocks encoded
using intra-prediction and inter-prediction, respectively, and a partition of the same picture into residual blocks for the sake of transform-based resid¬ual coding of the prediction residual with concurrently schematically illus¬trating the prediction correction on the basis of the residual by way of addi¬tion of the prediction signal and the residual signal, respectively;
Fig. 4 shows a schematic diagram illustrating the transform-based residual coding
of a residual block by de-encoding the transform coefficient block 92 asso-ciated with the residual block via a certain transformation;
Fig. 5 shows a schematic diagram illustrating the coding of a coded set of trans-
form coefficients of a transform coefficient block by defining the coded set via an indication indicating a last non-zero transform coefficient when scan-ning the transform coefficients from a specific firstly scanned transform co-efficient such as a DC coefficient to a coefficient farthest away from this first coefficient, so that the coded set comprises all coefficients between the last non-zero coefficient and the transform coefficient at the first coefficient po¬sition;
Fig. 6 shows a schematic diagram illustrating the possibility of coding transform
coefficients using a binarization composed of a first binarization code and a second binarization code with switching from the binarization merely com-prising the first binarization code to a state where the binarization compris¬es the codeword of the first binarization code for the cutoff value followed by the second binarization code;
Fig. 7 shows a schematic diagram illustrating a possibility for having a binarization
with a prefix part and a suffix part when such a binarization may underlie, for instance, the second binarization code of Fig. 6;
Fig. 8 exemplarily illustrates a partitioning of a transform coefficient block into
partitions, here a regular partitioning into rows and columns of partitions, each partition, accordingly, being composed of an array of coefficients, wherein the partitioning may be used for a context set association to the transform coefficients and/or zeroness indication of the transform coeffi-cients as described herein below;
Fig. 9 shows a schematic diagram illustrating the usage of partitions for the sake
of context set association;
Fig. 10 shows schematically a transform coefficient block and the usage of a local
template for a currently encoded/decoded transform coefficient block for the sake of selecting one context for this currently entropy-encoded/decoded transform coefficient;
Fig. 11a shows a schematic diagram illustrating the coding of a residual block with
respect to a decomposition of this block into more than one color compo-nent;
Fig. 11b schematically illustrates the data 96 of coding the transform coefficient
block 92 into a data stream 14 as including a global zeroness indication 190 indicating whether all transform coefficients of that block 92 are zero, in which case the quantization levels of the transformation coefficients may not have to be coded but infer to be zero at the decoder side;
Fig. 11c schematically illustrates the usage of partitioning of a transform coefficient
block into partitions for the sake of indicating, in units of partitions, the zeroness of transform coefficients by way of coded sub-block flags CBFs;
Fig. 11 d illustrates that the data 96 into which a transform coefficient block is coded
may comprise a last position indication 114 indicating the last coefficient position of a non-zero transform coefficient as shown in Fig. 5;
Fig. 11 e exemplarily shows the entropy de/encoding of quantization levels of trans-
form coefficients in a context-adaptive manner using a certain context out of a context set;
Fig. 11 f schematically illustrates the fact that the data into which a transform coeffi-
cient block is coded may comprise a sequential coding of the transform co-efficients' quantization levels in a coding order 102 in the data stream which corresponds to traversing the scan part of Fig. 5 from the last coefficient position to the first coefficient position;
Fig. 12 shows a schematic diagram illustrating a first embodiment of the present
application of performing context selection for one color component de-pendent on the transform coefficient block of the same residual block for another color component;
Fig. 13 shows a schematic diagram illustrating a partitioning of a transform coeffi-
cient block into partitions which do not coincide in shape as shown in Fig. 8;
Fig. 14 shows a schematic diagram illustrating a possibility of varying shapes of a
local template used for context selection as taught in Fig. 10, or even disa-bling same;
Fig. 15 shows a schematic diagram illustrating a transform coefficient block parti-
tioned into partitions with the scan part for sequentially encoding the trans-form coefficients traversing the transform coefficients in a manner so that transform coefficients of the partitions are interleaved with each other.
Fig. 16 shows a schematic diagram illustrating a transform coefficient block and its
coding using an interleaving scan part as shown in Fig. 15 with exemplarily illustrating a currently entropy-encoded/decoded transform coefficient and previously encoded transform coefficients exceeding certain thresholds, with a count thereof being used, for example, for context selection for the currently entropy-encoded/decoded transform coefficient;
Fig. 17 shows a schematic diagram illustrating a coding sequence of the quantiza-
tion level of coefficients on the one hand and zeroness indications of coded sub-block flags on the other hand, resulting from coding a transform coeffi-cient block with an interleaving scan part exemplarily shown in Fig. 18;
Fig. 18 also shows a transform coefficient block with a scan part which interleaves
transform coefficients of different partitions as shown in Figs. 15 and 16, with illustrating using hatching of the non-zero coefficients;
Fig. 19 illustrates a partition-wise scanning example of transform examples of a
transform coefficient block;
Fig. 20 illustrates a pseudocode for coding a transform coefficient block;
Fig. 21 illustrates a pseudocode for binarizing an absolute value of a quantization
level of a transform coefficient;
Fig. 22 illustrates an example for binarizing an absolute value of a quantization
level of a transform coefficient;
Fig. 23 illustrates a pseudocode for coding transform coefficients of a transform
coefficient block;
Fig. 24 illustrates a pseudocode for coding transform coefficients of a transform
coefficient block; and
Fig. 25 illustrates different examples for a partitioning of a transform coefficient
block into partitions.
The following description of the figures starts with a presentation of a description of video encoder and video decoder of a block-based predictive codec for coding pictures of a vid-eo in order to form an example for a coding framework into which embodiments described herein may be built. The video encoder and video decoder are described with respect to Figs 1 to 3. Thereinafter the description of further embodiments of the present application are presented with respect to figures. Same are numbered and in the above section a reference is made which portions above refer to which embodiment described and claimed below. All these embodiments could be built into the video encoder and decoder of Figs. 1 and 2, respectively, although the embodiments described herein such as those described with respect to the subsequent Figs, may also be used to form video encoder and video decoders not operating according to the coding framework underlying the video encoder and video decoder of Figs. 1 and 2.
Fig. 1 shows an apparatus for predictively coding a video 11 composed of a sequence of pictures 12 into a data stream 14. Block-wise predictive coding is used to this end. Fur¬ther, transform-based residual coding is exemplarily used. The apparatus, or encoder, is indicated using reference sign 10. Fig. 2 shows a corresponding decoder 20, i.e. an appa-ratus 20 configured to predictively decode the video 11' composed of pictures 12' in pic¬ture blocks from the data stream 14, also here exemplarily using transform-based residual decoding, wherein the apostrophe has been used to indicate that the pictures 12' and vid¬eo 11', respectively, as reconstructed by decoder 20 deviate from pictures 12 originally encoded by apparatus 10 in terms of coding loss introduced by a quantization of the pre-diction residual signal. Fig. 1 and Fig. 2 exemplarily use transform based prediction resid¬ual coding, although embodiments of the present application are not restricted to this kind of prediction residual coding. This is true for other details described with respect to Fig. 1 and 2, too, as will be outlined hereinafter.
The encoder 10 is configured to subject the prediction residual signal to spatial-to-spectral transformation and to encode the prediction residual signal, thus obtained, into the data stream 14. Likewise, the decoder 20 is configured to decode the prediction residual signal from the data stream 14 and subject the prediction residual signal thus obtained to spec-tral-to-spatial transformation.
Internally, the encoder 10 may comprise a prediction residual signal former 22 which gen-erates a prediction residual 24 so as to measure a deviation of a prediction signal 26 from the original signal, i.e. video 11 or a current picture 12. The prediction residual signal for¬mer 22 may, for instance, be a subtracter which subtracts the prediction signal from the original signal, i.e. current picture 12. The encoder 10 then further comprises a transform¬er 28 which subjects the prediction residual signal 24 to a spatial-to-spectral transfor¬mation to obtain a spectral-domain prediction residual signal 24' which is then subject to quantization by a quantizer 32, also comprised by encoder 10. The thus quantized predic¬tion residual signal 24" is coded into bitstream 14. To this end, encoder 10 may optionally comprise an entropy coder 34 which entropy codes the prediction residual signal as trans¬formed and quantized into data stream 14. The prediction residual 26 is generated by a prediction stage 36 of encoder 10 on the basis of the prediction residual signal 24" de¬coded into, and decodable from, data stream 14. To this end, the prediction stage 36 may internally, as is shown in Fig. 1, comprise a dequantizer 38 which dequantizes prediction residual signal 24" so as to gain spectral-domain prediction residual signal 24'", which
corresponds to signal 24' except for quantization loss, followed by an inverse transformer 40 which subjects the latter prediction residual signal 24'" to an inverse transformation, i.e. a spectral-to-spatial transformation, to obtain prediction residual signal 24"", which corresponds to the original prediction residual signal 24 except for quantization loss. A combiner 42 of the prediction stage 36 then recombines, such as by addition, the predic¬tion signal 26 and the prediction residual signal 24"" so as to obtain a reconstructed signal 46, i.e. a reconstruction of the original signal 12. Reconstructed signal 46 may correspond to signal 12'.
A prediction module 44 of prediction stage 36 then generates the prediction signal 26 on the basis of signal 46 by using, for instance, spatial prediction, i.e. intra prediction, and/or temporal prediction, i.e. inter prediction. Details in this regard are described in the follow¬ing.
Likewise, decoder 20 may be internally composed of components corresponding to, and interconnected in a manner corresponding to, prediction stage 36. In particular, entropy decoder 50 of decoder 20 may entropy decode the quantized spectral-domain prediction residual signal 24" from the data stream, whereupon dequantizer 52, inverse transformer 54, combiner 56 and prediction module 58, interconnected and cooperating in the manner described above with respect to the modules of prediction stage 36, recover the recon-structed signal on the basis of prediction residual signal 24" so that, as shown in Fig. 2, the output of combiner 56 results in the reconstructed signal, namely the video 11'or a current picture 12' thereof.
Although not specifically described above, it is readily clear that the encoder 10 may set some coding parameters including, for instance, prediction modes, motion parameters and the like, according to some optimization scheme such as, for instance, in a manner optimizing some rate and distortion related criterion, i.e. coding cost, and/or using some rate control. As described in more details below, encoder 10 and decoder 20 and the cor-responding modules 44, 58, respectively, support different prediction modes such as intra-coding modes and inter-coding modes or modes where the former modes form a kind of set or pool of primitive prediction modes based on which the predictions of picture blocks are composed. The granularity at which encoder and decoder switch between these pre-diction compositions may correspond to a subdivision of the pictures 12 and 12', respec-tively, into blocks. Note that some of these blocks may be blocks being solely intra-coded and some blocks may be blocks solely being inter-coded and, optionally, even further
blocks may be blocks obtained using both intra-coding and inter-coding, but details are set-out hereinafter. According to intra-coding mode, a prediction signal for a block is ob-tained on the basis of a spatial, already coded/decoded neighborhood of the respective block. Several intra-coding sub-modes may exist the selection among which, quasi, repre-sents a kind of intra prediction parameter. There may be directional or angular intra-coding sub-modes according to which the prediction signal for the respective block is filled by extrapolating the sample values of the neighborhood along a certain direction which is specific for the respective directional intra-coding sub-mode, into the respective block. The intra-coding sub-modes may, for instance, also comprise one or more further sub-modes such as a DC coding mode, according to which the prediction signal for the respective block assigns a DC value to all samples within the respective block, and/or a planar intra-coding mode according to which the prediction signal of the respective block is approxi¬mated or determined to be a spatial distribution of sample values described by a two-dimensional linear function over the sample positions of the respective block with deriving tilt and offset of the plane defined by the two-dimensional linear function on the basis of the neighboring samples. Compared thereto, according to inter-prediction mode, a predic¬tion signal for a block may be obtained, for instance, by temporally predicting the block inner. For parametrization of an inter-prediction mode, motion vectors may be signaled within the data stream, the motion vectors indicating the spatial displacement of the por¬tion of a previously coded picture of the video 11 at which the previously coded/decoded picture is sampled in order to obtain the prediction signal for the respective block. This means, in addition to the residual signal coding comprised by data stream 14, such as the entropy-coded transform coefficient levels representing the quantized spectral-domain prediction residual signal 24", data stream 14 may have encoded thereinto prediction re¬lated parameters for assigning to the blocks prediction modes, prediction parameters for the assigned prediction modes, such as motion parameters for inter-prediction modes, and, optionally, further parameters which control a composition of the final prediction sig¬nal for the blocks using the assigned prediction modes and prediction parameters as will be outlined in more detail below. Additionally, the data stream may comprise parameters controlling and signaling the subdivision of picture 12 and 12', respectively, into the blocks. The decoder 20 uses these parameters to subdivide the picture in the same man¬ner as the encoder did, to assign the same prediction modes and parameters to the blocks, and to perform the same prediction to result in the same prediction signal.
Fig. 3 illustrates the relationship between the reconstructed signal, i.e. the reconstructed picture 12', on the one hand, and the combination of the prediction residual signal 24"" as

signaled in the data stream, and the prediction signal 26, on the other hand. As already denoted above, the combination may be an addition. The prediction signal 26 is illustrated in Fig. 3 as a subdivision of the picture area into blocks 80 of varying size, although this is merely an example. The subdivision may be any subdivision, such as a regular subdivi¬sion of the picture area into rows and columns of blocks, or a multi-tree subdivision of pic¬ture 12 into leaf blocks of varying size, such as a quadtree subdivision or the like, wherein a mixture thereof is illustrated in Fig. 3 where the picture area is firstly subdivided into rows and columns of tree-root blocks which are then further subdivided in accordance with a recursive multi-tree subdivisioning to result into blocks 80.
The prediction residual signal 24"" in Fig. 3 is also illustrated as a subdivision of the pic¬ture area into blocks 84. These blocks might be called transform or residual blocks in or¬der to distinguish same from the coding blocks 80. In effect, Fig. 3 illustrates that encoder 10 and decoder 20 may use two different subdivisions of picture 12 and picture 12', re¬spectively, into blocks, namely one subdivisioning into coding blocks 80 and another sub¬division into blocks 84. Both subdivisions might be the same, i.e. each block 80, may con¬currently form a transform block 84 and vice versa, but Fig. 3 illustrates the case where, for instance, a subdivision into transform blocks 84 forms an extension of the subdivision into blocks 80 so that any border between two blocks 80 overlays a border between two blocks 84, or alternatively speaking each block 80 either coincides with one of the trans¬form blocks 84 or coincides with a cluster of transform blocks 84. However, the subdivi¬sions may also be determined or selected independent from each other so that transform blocks 84 could alternatively cross block borders between blocks 80. As far as the subdi¬vision into transform blocks 84 is concerned, similar statements are thus true as those brought forward with respect to the subdivision into blocks 80, i.e. the blocks 84 may be the result of a regular subdivision of picture area into blocks, arranged in rows and col¬umns, the result of a recursive multi-tree subdivisioning of the picture area, or a combina¬tion thereof or any other sort of segmentation. Just as an aside, it is noted that blocks 80 and 84 are not restricted to being quadratic, rectangular or any other shape. Further, the subdivision of a current picture 12 into blocks 80 at which the prediction signal is formed, and the subdivision of a current picture 12 into blocks 84 at which the prediction residual is coded, may not the only subdivision used for coding/decoding. These subdivision from a granularity at which prediction signal determination and residual coding is performed, but firstly, the residual coding may alternatively be done without subdivisioning, and sec¬ondly, at other granularities than these subdivisions, encoder and decoder may set certain
coding parameters which might include some of the aforementioned parameters such as prediction parameters, prediction signal composition control signals and the like.
Fig. 3 illustrates that the combination of the prediction signal 26 and the prediction residu¬al signal 24"" directly results in the reconstructed signal 12'. However, it should be noted that more than one prediction signal 26 may be combined with the prediction residual sig¬nal 24"" to result into picture 12' in accordance with alternative embodiments such as prediction signals obtained from other views or from other coding layers which are cod¬ed/decoded in a separate prediction loop with separate DPB, for instance.
In Fig. 3, the transform blocks 84 shall have the following significance. Transformer 28 and inverse transformer 54 perform their transformations in units of these transform blocks 84. For instance, many codecs use some sort of DST or DCT for all transform blocks 84. Some codecs allow for skipping the transformation so that, for some of the transform blocks 84, the prediction residual signal is coded in in the spatial domain direct¬ly. However, in accordance with embodiments described below, encoder 10 and decoder 20 are configured in such a manner that they support several transforms. For example, the transforms supported by encoder 10 and decoder 20 could comprise:
o DCT-II (or DCT-III), where DCT stands for Discrete Cosine Transform
o DST-IV, where DST stands for Discrete Sine Transform
o DCT-IV
o DST-VII
o Identity Transformation (IT)
Naturally, while transformer 28 would support all of the forward transform versions of these transforms, the decoder 20 or inverse transformer 54 would support the correspond¬ing backward or inverse versions thereof:
o Inverse DCT-II (or inverse DCT-III)
o Inverse DST-IV
o Inverse DCT-IV
o Inverse DST-VII
o Identity Transformation (IT)
In any case, it should be noted that the set of supported transforms may comprise merely one transform such as one spectral-to-spatial or spatial-to-spectral transform.
As already outlined above, Figs. 1 - 3 have been presented as an example where the concepts described further below may be implemented in order to form specific examples for video encoders and decoders according to the present application. Insofar, the video encoder and decoder of Figs. 1 and 2, respectively, represent possible implementations of the video encoders and decoders described herein below.
The embodiments of the various aspects of the present application that will be described later on sometimes make use of common underlying concepts which are presented be-forehand. That is, encoders and decoders of embodiments described later on, do not have to, as just-outlined, correspond, in implementation, to the details set out above with re¬spect to Figs. 1-3, but they may correspond to one or more of the following technical de¬tails and these technical details help or assist in understanding the embodiments de¬scribed later on. For instance, let's start with Fig. 4. The embodiments described later on coincide in that they are concerned with picture coding. The picture might be part of a vid¬eo and the decoders and encoders described below may be video encoders and video decoders, respectively, but still picture coding may apply as well. Thus, Fig. 4 schemati¬cally illustrates the general behavior or task of encoders and decoders for which embodi¬ments are described below.
Fig. 4 shows the picture to be coded. The same reference signs as used in Figs. 1-3 are used in order to help in understanding as to how the details set forth herein below could be used to implement the example of Fig. 1-3 in a manner so as to arrive at an embodi¬ment of the present application. Further, Fig. 4 shows a block 84 of picture 12. It is a cur¬rently coded block or currently decoded block. The usage of the reference sign 84 reveals that the transform coding outlined herein below, may relate to a prediction residual as it has been outlined above with respect to Figs. 1 to 3, but this is, in principle, a circum¬stance which could be left off in alternative embodiments. That is, for all the embodiments set out herein below, it may be that the transform coefficient block mentioned therein rep¬resents the transform of a prediction residual within block 84 such as the residual with respect to an intra-picture prediction or inter-picture prediction. Block 84 is related to the transform coefficient block 92 by way of transform 90. Examples of the transform have been set out above with respect to Figs. 1-3 and they shall apply for all embodiments. One transform is selected for block 84. Alternatively, the transform may be fixed. In case
of selection, the selection may be signaled in the data stream. Among the transform, one may be the identity transform. While it might be that the transform of the transform coeffi-cient block 92 has a dimension or size coinciding with the size of block 84, i.e., the num¬ber of coefficients of block 92 may coincide with the number of samples in block 84, this needs not to apply to all transformations supported or may, in case of merely one trans¬formation 90 being used, not apply. Both, encoder and decoder may use the inverse transformation so as to reconstruct the inner of block 84 such as the prediction residual, in spatial domain, the decoder for sake of presentation, the encoder for sake of feeding the decoded picture buffer. The embodiments described subsequently, concentrate on the task 108 of de/encoding the transform coefficient block 92 into/from data stream 14.
As illustrated in Fig. 4, the transform coefficient block 92 may be composed of transform coefficients 91 which are arranged in a rectangular array. That is, the transform coefficient block 92 may be a rectangular block.
The aim of the transformation 90 is to aim at a redundancy reduction and to gather non¬zero coefficients towards a smaller number of the coefficients 91. See, for instance, Fig. 5, which shows a transform coefficient block 92. The transform coefficient at transform coef-ficient position 104, namely the upper left coefficient position, may be a DC coefficient and towards this coefficient position 104 the probability of a certain coefficient to be quantized to a quantization level not being zero increases, for instance. In order to exploit this cir-cumstance, the coding of the transform coefficient block 92 may involve the signalization of an indication in the data stream which indicates a transform coefficient position 98 which is furthest away from coefficient position 104 when sequentially scanning the trans¬form coefficients starting from coefficient position 104 along a scanning path 94 in a man¬ner generally leading away from coefficient position 104. The indication of this termination position 98 shall serve as an indication that the data stream 14 has encoded thereinto only a coded set 100 of transform coefficients 91, namely the hatched ones in Fig. 5, which coded set 100 includes all transform coefficients, and including, termination coeffi¬cient position 98 to, and including, termination coefficient 104. The other coefficients, non-hatched in Fig. 5, are then known to be zero at decoder side.
It might be useful, and as used in accordance with some embodiments of the present ap-plication, when the coded set of transform coefficients 91 is coded into the data stream 14 along the reverse direction 118, i.e., not the forward direction along scanning path 94
generally leading away from termination coefficient position 104, but the opposite direction thereof which leads to termination coefficient position 104.
Although not specifically discussed with respect to some embodiments described later on, it might even apply for the latter embodiments (optionally) that a quantization levels of the transform coefficients 91 are coded into the data stream 14 using binarization. That is, a quantization level of a certain transform coefficient 91 is, as illustrated in Fig. 6, by way of the binarization mapped onto a bin string or codeword 161. The binarization may be com-posed of a first binarization code 160 which serves as a kind of prefix, and a second bina-rization code 162. To be more precise, let's say 106 in Fig. 6 is the quantization level. If the quantization level 106 is above a certain cutoff value 164, the quantization level 106 is binarized to a bin string 161 composed of a part 162 stemming from the second binariza¬tion code, prefixed by a codeword of the first binarization code which corresponds to the cutoff value 164. If, however, the quantization level 106 is not above the cutoff value, then the quantization level 106 is mapped onto a bin string composed of the first binarization code 160 only. In some embodiments, the cutoff value 164 may become zero for certain transform coefficients in which case the binarization 161 merely comprises the second binarization code 162.
Although it might be that the one or more bins forming the binarization 161 of a certain transform coefficient may be coded into the data stream, and decoded therefrom, respec-tively, coefficient by coefficient along the scanning path 94, some embodiments described later on make use of several passes which traverse the coefficients. This means, in turn, that whenever a "previously encoded/decoded transform coefficients" are mentioned be-low, the binarization thereof might not have been encoded/decoded completely. Rather, at least one bin has been encoded/decoded for such a previous transform coefficient. The binarization 161 may be formed in such a manner that a length of the first binarization code, the length of the second binarization code as well as the overall binarization length of binarization 161 monotonically increases with respect to the quantization level 106 or, to be more precise, the magnitude value thereof. That is, the more leading bins of the bi¬narization 161 have been read for a certain quantization level 106, the more probable it becomes that, firstly, the binarization 161 is completely read and, secondly, the larger an absolute value is which the quantization level 106 may not fall below or which the quanti¬zation level minimally has in case there are bins of the binarization 161 following these leading bins and not yet having been read.
As a concrete example, for instance, it might be that the bins of the first binarization code
160 are coded/decoded first in one or more passes with then attending to the cod-ing/decoding of the second binarization code. While the bins of the first binarization code 160 might be coded using context-adaptive entropy coding, the bins of the second binari-zation code 162 might be coded using an equi-probability bypass mode, i.e., using a code rate of one.
As illustrated in Fig. 7, the second binarization code itself might be composed binarization code comprising a prefix part 162a and a suffix part 162b. A binarization parameter 163 might adjust a length of the prefix part 162a. For instance, the binarization parameter 163 might be an Exp-Gofomb order or a Rice parameter.
Again, the bins 165 of the binarization 161 belonging to the first binarization code might be coded using context-adaptive binary coding. Same are illustrated are us¬ing hatching in Fig. 6. The other bins 165 belonging to the second binarization code 162 might be coded using the bypass mode and are illustrated in Figs. 6 and 7 without hatching. Many embodiments described subsequently relate to context selection. This context selection may then, as a specific implementation, be used for context-adaptively coding one or more of the bins 165, for instance. Further details are set out hereinbelow.
Before starting with the description of the embodiments of the present application, further concepts which are sometimes commonly used by some of the embodi¬ments described later on shall be presented. In particular, in accordance with some embodiments, the transform coefficient block 92 is partitioned into partitions 120 as illustrated using dashed lines in Fig. 8, for sake of signaling that all trans¬form coefficients within a certain partition 120 are zero and accordingly, may be skipped when coding the transform coefficients 91. If such partitioning for sake of zeroness signalization is used, an indication is signaled in the data stream 14 on a partition by partition basis in order to signal for a certain partition whether the transform coefficients 91 therein are all zero, or whether this is not the case and the transform coefficients 91 therein are coded into the data stream. If not taught to the contrary during the description of the various embodiments of the present application, one possible applying to all the subsequently applied embodiments is
that the scanning part 94 may be selected in a way so that the transform coeffi-cients 91 are traversed by the scanning path 94 in a manner so that all transform coefficients 91 of a certain partition 120 are scanned or traversed by the scan path 94 before the transform coefficient of any other partition. When combining the lat-ter possibility with the multiple pass alternatives mentioned above with respect to Figs. 6 and 7, it may be that the transform coefficients 91 within one partition 120 are coded completely, i.e., the bins of the bin string 161 are coded completely, before the coded/decoding proceeds with transform coefficients of any other parti-tion. That is, one or more passes are used to traverse an encode/decode the transform coefficients 91 of a certain partition 120 along scan path 94, before the coding/decoding proceeds in one or more passes with the encoding/decoding of transform coefficients of the next partition along the scan path 94 in scan order such as scan order 118.
Another concept using partitions is illustrated with respect to Fig. 9. A few embod-iments described later on make use of this concept. Here, the transform coefficient block 92 is partitioned into partitions 120 for sake of context usage. Context sets 110a to 110c are depicted at the right hand side of Fig. 9. A set 110a-c of contexts comprises one or more contexts indicated by "P#". Each "context" may alternatively be denoted as a context model and indicates the probability estimation underlying the entropy coding using this context. For instance, in case of binary entropy cod¬ing, i.e., the entropy coding of a bin, a context indicates the probability estimation for one of the bin values, for instance, and, accordingly, automatically also the probability estimation for the other bin value. Each of the partitions 120 has one of the context sets 110a-c associated therewith. For instance, transform coefficients 91 within a certain partition 120 are entropy coded/decoded using a selected one out of the context set 110 associated with that partition 120 with the selection out of this set being done, for instance, on the basis of an evaluation of coefficients in the neighborhood of the current coefficient 91.
The latter circumstance is, for instance, depicted in Fig. 10. A currently encod-ed/decoded transform coefficient is highlighted herein using a cross 130. Currently encoded/decoded may, when using the multi-pass approach mentioned above,
mean that one bin of this coefficient 130 is currently encoded/decoded. Reference sign 132 indicates a local template positioned at/around coefficient 130 and coeffi-cients positioned within or at this local template 132 be evaluated or used in order to determine the context to be used for encoding coefficients 130 or its currently encoded/decoded bin. Again, some embodiments directly mention the usage of the local template 132, Embodiments described later on, which do not specifically mention the use of the local template 132 for sake of determining the context used for coding a currently encoded / decoded coefficient 130 may, however, in fact be modified so as to also make use of this way of selecting the context. The selection for coefficient 130 may, in accordance with the embodiment of Fig. 9, be done out of the set associated with the partition 120a the current coefficient 130 is located in. However, the usage of portioning for sake of partition-specific deign of context sets is merely an example and may not be used by all embodiments.
Another aspect which some of the embodiments described later on directly relate to, and which may also be used to modify or extend other embodiments, relates to the content of block 84 relating to multiple components, namely multiple color components. Examples for color components are, for instance, a luma/coma rep-resentation according to which the content of block 84 is spatially sampled ones for luma L and for two coma components C1 and C2, but other examples may exist as well. Block 84 would, thus, be composed of a sample array 841 for the first color component, a sample array 842 for the second color component, a sample array for a third color component 843. The aspect here is that each component may be treated separately. That is, for each component, the respective sample array of block 84 may represent a prediction residual with respect to a respective compo-nent of a predictor. Each sample array is subject to the transformation 90, prefera-bly the same one, and yields a corresponding transform coefficient block 921 to 923. It should be noted here, however, that the sample resolution of the various color components may differ from each other and so the sizes among the sample arrays and the sizes among the transform coefficient blocks may vary likewise. Each transform coefficient block 921 to 923 is subject to de/encoding 108 into/from data stream 14, with each transform coefficient block 921 to 923 being subject to the measures and steps and processes described with respect to Figs. 3 to 9.
While the multicomponent concept described in Fig. 11a may be applied onto sub-sequently explained embodiments which do not further mention any color compo-nent aspect, it should be noted that the subsequently explained embodiments may likewise be used for cases or implementations where merely one component ex¬ists.
Another aspect not yet having been described above is the fact that the coding of a certain transform coefficient block 92 and, accordingly, the decoding thereof, may start with an indication 190 whether any of the transform coefficients 91 of that transform coefficient block 92 is non-zero anyway. If not, the transform coeffi-cient block is known to the decoder to be zero globally. Merely if this indication 190 which is illustrated in Fig. 11b indicates that at least one non-zero coefficient 91 exists, any combination of the above-outlined concepts is used to code the trans-form coefficient block. In a similar manner, Fig. 11c illustrates the similar indica-tions 150 for partitions 120, i.e. they indicate zeroness within an associated parti-tion 120. Fig. 11 d illustrates the last position indication 114 which might indicate the position 98. Fig. 11e illustrates the individual context currently used for entropy encoding/decoding 116 a current coefficient's quantization level 106, selected out of an associated context set 110, and Fig. 11f illustrates the coding order 102 at which the quantization levels 106 are coded into the data stream, namely an order resulting from traversing path 94 in the direction 118, for instance.
The reader should now be prepared to understand and follow the embodiments of the present application subsequently described. An embodiment which relates to a first aspect of the present application is described with respect to Fig. 12. Here, encoder and decoder encode/decode a picture 12 into data stream 14 in a manner special in terms of performing the entropy coding of different transform coefficient blocks of different color components of one block 84. Fig. 12 shows block 84 as being composed of two color components, thereby being composed of sample arrays 841 and 842, although it is clear that the composition may encompass three color components as explained with respect to Fig. 11a. As explained with respect to Fig. 11a, the encoder subjects block 84 of the picture 12 separately for the first color component and the second color component to transformation 90 to obtain a

first transformation coefficient block 921 and a second transform coefficient block 922, respectively and likewise, the decoder derives the block 84 of the picture by separately performing a reverse transformation on the first transformation coeffi-cient block 92-] and the second transform coefficient block 922, respectively. With respect to the entropy encoding and entropy decoding of the second transform coefficient block 922 into/from data stream 14, encoder and decoder operate con-text-adaptively using a context which depends on the first transform coefficient block 921. The dependency is illustrated in Fig. 12 by way of an arrow 300.
For example, the context determined using dependency 300 on the first transform coefficient block may relate to the partition-specific indications explained above with respect to Fig. 8, indicating whether transform coefficients 91 in a certain par-tition 120 are all zero or contain at least one non-zero coefficient in which case the quantization levels of the transformation coefficients 91 inside that partition are entropy encoded/decoded into/from data stream 14 whereas this entropy encod-ing/decoding is skipped for the other partitions indicating all-zeroness. Such an indication for a partition 120 could be a flag and could be called a coded sub-block flag. The context chosen for such a coded sub-block flag for a certain parti-tion/sub-block 120 could, for instance, be chosen dependent on the coded sub-block flag (further indication) coded for the collocated sub-block (partition) in the first transform coefficient block. The selection could, thus, be made among two available contexts: a first available context is used if the flag for the collocated par-tition in the first transform coefficient block 921 is one and the second available context is used for the flag of a certain partition in the second transform coefficient block 922 if the flag for the collocated partition in the first transform coefficient block 921 is zero. The dependency 300 for a certain indication of a certain partition 120 of the second transform coefficient block 922 could, however, alternatively be implemented in a different manner. For instance, the context chosen for a certain indication of zeroness with respect to a certain partition 120 of the second trans-form coefficient block 922 could depend on the quantization levels of the transform coefficients of the first transform coefficient block such as those within the collo-cated partition.
That is, without having been explicitly stated above, we may assume that the two transform coefficient blocks 921 and 922 may be of equal shape and size or may be of equal aspect ratio with respect to horizontal and vertical dimension and the partitioning into partitions 120 may be equal for these blocks 921 and 922 or coin-cide when scaling one transform coefficient block 921 onto the other.
Alternatively or additionally, the dependency 300 may relate to the global indica-tion of transform coefficient zeroness explained above. That is, the indication cod-ed into or decoded from data stream 14 with respect to transform coefficient block 922 would then, via dependency 300, depend on, with respect to the context used, on the first transform coefficient block 921. If this indication indicates that the trans-form coefficients 91 of the second transform coefficient block 921 comprise at least one non-zero coefficient, the quantization levels of the transform coefficients 91 of block 922 are entropy encoded into and entropy decoded from data stream 14, but if the indication indicates that all transform coefficients within the second transform coefficient block are zero, the coding/decoding of the second transform coefficient block 922 is done with the decoder inferring that all transform coefficients 91 of that block 922 are zero. For instance, the dependency 300 may, in that case, render the context used for the indication of zeroness for the second transform coefficient block 922 dependent on the corresponding indication coded/decoded for the first transform coefficient block 921. Alternatively, the dependency 300 may render the context used for the indication of zeroness of transform coefficient block 922 de¬pendent on the quantization levels of the transform coefficients of the first trans¬form coefficient block 921 For instance, a first context could be chosen for the in¬dication for the second transform coefficient block if the indication for the first transform coefficient block 921 indicates the non-zeroness of at least one trans¬form coefficient of the first transform coefficient block 921 and a second context could be chosen for the zeroness indication of the second transform coefficient block 922 if the corresponding zeroness indication of the first transform coefficient block 921 indicates all-zeroness of the transform coefficients of the first transform coefficient block 921.
Additionally or alternatively, the dependency 300 could relate to the position indi-cation of the termination coefficient position 98. Different possibilities exist to sig-nal this position indication in data stream 14. For instance, the position indication could be signaled in the data stream as a one-dimensional address or rank indicat¬ing the position 98 as an address or rank of position 98 among all coefficient posi¬tions when measured along the scan path 94 in the forward direction 116. Alterna¬tively, the position indication could indicate position indicate position 98 within the respective transform coefficient block by way of two coordinates which indicate position 98 in terms of its horizontal and vertical position within transform coeffi¬cient block 921 and 922, respectively. Now, in addition to, or alternatively to the possibilities of implementing the dependency 300 already discussed above, the dependency 300 may affect the last position indication of position 98 for the sec¬ond transform coefficient block 922. In particular, the context used to encode this indication may depend on the first transform coefficient block such as the last posi¬tion indication of position 98 for the first transform coefficient block 921 or an eval¬uation of the position or distribution of significant transform coefficients 91 within the first transform coefficient block 921|.The way the last position indications of blocks 921 and 922 are encoded may also involve a binarization into a binarization code and the context the dependency of which involves the dependency 300 may be used for one or more bins such as the first bin of the binarization code of the last position indication.
Additionally or alternatively, one or more bins such as the first bin of the binariza-tion 161 of the transform coefficients 91 within the second transform coefficient block 922 may be subject to the dependency 130, i.e., the context used to encode the one or more bins of binarization 161 may depend on the first transform coeffi-cient block 921 such as the corresponding bin of the binarization of the collocated transform coefficient of the first transform coefficient block 921.
In finalizing the description of the embodiment(s) of Fig. 12 it should be noted that the two color components shown in Fig. 12 may be coma components and in par-
icular, the color component of the second transform coefficient block may be Cr while the color component of the first transform coefficient block 921 may be Cb.
The next embodiment for an encoder for encoding a picture into, and a decoder for decoding the picture from a data stream relates to a further aspect of the present application, namely one aiming at a coding efficiency increase by providing a spe¬cific context set 110 for specific transform coefficient positions, namely the trans¬form coefficient position 104 which may be, as outlined above, a DC coefficient position. While the embodiment is presented in the following with respect to exact¬ly this transform coefficient position 104, it should be noted that the provision of a specific, coefficient individual context set may alternatively or additionally be ap¬plied to coefficient position 98, i.e., the non-zero coefficient's position farthest away from coefficient position 104 measured along scan path 94. "Context individ¬ual" shall denote the fact that the context set is not used for any other coefficient 91 of the same transform coefficient block or even that none of the contexts con¬tained in the context set of the transform coefficient position in question, here 104, is used for coding any other transform coefficient within the same transform coeffi¬cient block.
The embodiment may be illustrated on the basis of Fig. 5. Encoder and decoder are configured to encode/decode the transform coefficient block 92 into/from the data stream using the scan pattern 94 by encoding/decoding into/from the data stream the data 96 (compare Fig. 4) which represents the coded set 100 of trans-form coefficients 91 traverse by the scan pattern 94 from the first termination coef-ficient position 98 in a predetermined direction 102 to the second termination coef-ficient 104, the data 96 comprising quantization levels of non-zero transform coef-ficients in the coded set 100 of transform coefficients, i.e., at least the quantization levels of the non-zero transform coefficients along with the locations thereof or the quantization levels of all transform coefficients of coded set 100. It should be un-derstood that the signaling of the position indication of position 98 described above with respect to Fig. 5 shall be understood for the presently described embodiment merely as an example and the signaling of this position indication could be left off alternatively in the present embodiment with, for instance, the coded set 100 cov-
ering all transform coefficients 91 of transform coefficient block 92 inevitably or otherwise synchronizing encoder and decoder in determining the coded set 100.
In any case, in accordance with a present embodiment, encoder and decoder are configured to entropy encode/entropy decode the quantization levels context-adaptively with using a specific (first) set of contexts, 110, for the termination coef¬ficient position 104 which may be a DC coefficient position, and this coefficient set 110 used for the coefficient at position 104 is disjoined to the one or more sets of contexts used for any other transform coefficient 91 in the coded set 100 of trans¬form coefficients. In accordance with a specific example, for instance, one context set 110 is used for entropy encoding the quantization level of the DC transform coefficient at position 104, while another/different context set 110 is used for en¬tropy encoding/decoding the quantization levels of all other transform coefficients 91 of block 92 wherein the "difference" between the context sets may involve that none of the contexts contained in the context set of the coefficient at position 104 is contained within the context set of the other transform coefficients and vice ver¬sa.
In accordance with the above-mentioned alternative where the position specific context set is used for the transform coefficient quantization level at position 98, all other transform coefficients 91 could use the same context set which is then dif¬ferent from the context set used for transform coefficient at position 98. And in case of the further alternative also mentioned above, position specific context sets could be used for both the transform coefficients at position 104 as well as the one at position 98 and they could be mutually different to each other as well as to the context set which would then, for example, be jointly used for entropy encod-ing/decoding the coefficients 91 contained in the coded set 100 and being be-tween positions 104 and 98 along scan path 94.
The position specific context set thus individually provided for one coefficient posi¬tion, namely here coefficient position 104, could be used, for instance, for encod¬ing one or more bins of the binarization 161 of the transform coefficient as position 104. This one or more bin 165 could be one or more bins 165 of the first binariza-
tion code 160. It could, for instance, be the first bin in bin order of binarization 161 with this bin, for instance, indicated whether the transform coefficient at the corre-sponding position is significant, i.e., non-zero, or not. Likewise, the disjoined set of contexts used for the other transform coefficients would be used for the corre-sponding one or more bins of the binarization 161 of these other transform coeffi-cients.
it should be recalled that the context sets just-mentioned with respect to Fig. 5 may then serve as a reservoir out of which a specific context is then used for a currently encoded/decoded transform coefficient. That is, the position specific con-text set 110 for the transform coefficient at position 104 would serve as a basis of reservoir out of which the context actually to be used for entropy encod-ing/decoding the one or more bins of the binarization 161 of the coefficient level of the transform coefficient at position 104 is selected using a local template 132 shown in Fig. 10. The local template 132 shown in Fig. 10 comprises five trans-form coefficient positions in the neighborhood of the currently entropy encod-ed/decoded transform coefficient 130 namely the coefficient positions to the right of, below, diagonally to the right and bottom of the currently entropy encod-ed/decoded transform coefficient 130 as well as the next but nearest position to the right and the next but nearest position below coefficient 130. However, this is merely an example and the number and location of the positions covered by the local template 132 could be chosen differently.
For completeness, it is noted that the just-described embodiments where a con-text-specific context set is used for one or two specific coefficient positions 104 and/or 98, may be combined with the possibility discussed with respect to Fig. 8 according to which for the remaining transform coefficients, partition specific coef-ficient sets 110 may be used for partitions 120 into which the transform coefficient block 92 is partitioned. For instance, Fig. 13 shows position 104 and shows that the transform coefficient block 92 is partitioned into several partitions, namely here four partitions 120. In accordance with the present embodiment, a position-specific context set would be used for entropy encoding/decoding the quantization level of the coefficient at position 104, while for all the other transform coefficients 91 of
block 92 the context set to be used would be determined to be the one associated with the partition the respective transform coefficient 91 is located in and these context sets may be mutually disjoined as well as disjoined to the context set pro-vided specifically for position 104.
In the example, of Fig. 13, the partitions extend diagonally along a direction obliquely to a transform coefficient block's diagonal 122 which runs through the termination coefficient position 104 such as the DC coefficient position, and the opposite corner of the transform coefficient block, i.e., the coefficient position at the bottom right hand side of the coefficient block 92 which, thus, may correspond to the highest frequency in both horizontal and vertical direction.
It is clear that the embodiment just-described with respect to Figs. 5 and 13 may readily be combined with the embodiment described with respect to Fig. 12.
The embodiments described next relate to a further aspect of the present applica-tion for an encoder for encoding a picture into a data stream and a decoder for decoding the picture from the data stream, with the aspect being specific with re-spect to a context selection or a context determination for a currently encod-ed/decoded transform coefficient. The embodiment(s) may be best understood and described with respect to Fig. 10. Specifically, encoder and decoder are con¬figured to entropy encode/decode a quantization level of the currently encod¬ed/decoded transform coefficient 130 of transform coefficient block 92 context-adaptively by use of a context which is determined based of a sum of and/or a number of significant ones among the one or more previously encoded/decoded transform coefficients located at positions determined by the local template 132 which template is positioned at the currently encoded/decoded transform coeffi¬cient 130. It should be recalled that, while it would be possible in accordance with the present embodiment(s) that the transform coefficients or, to be more precise, their quantization levels are entropy coded/decoded one after the other, i.e. com¬pletely before proceeding with the entropy encoding/decoding the next transform coefficient 91, the concept discussed above could be applied as well according to which the entropy encoding/decoding the quantization levels of the transformation
coefficients takes place using context-adapted binary entropy coding of bins of a binarization of quantization levels in multiple passes. The context-adaptivity may be restricted to the first binarization code 160 as discussed above. That is, on the one hand, it is noted that the context selected/determined using the local template 132 and forming the sum and/or counting the number of significant ones among the one or more transform coefficients within the local template 132 could be ap-plied to one or more bins of the first binarization code 160. Additionally, multiple pass coding could be used. That is, the currently entropy encoded/decoded trans-form coefficient 130 could be the transform coefficient whose bin is currently en-tropy encoded/decoded. Further, as the bins 165 of the binarization 161 of the transform coefficients 91 of block 92 are coded sequentially in a plurality of pass-es, the bins 165 or the binarization 161 of the transform coefficients 91 encom-passed by the local template 132 could have been entropy encoded/decoded in-completely so far. Accordingly, with respect to the determination of the context for coefficient 130 or, to be more precise, its currently encoded/decoded bin, the sum could be computed as follows. In particular, the sum of coefficients 91 within local template 132 could be computed as the sum of predetermined absolute value of the coefficient level of the one or more transform coefficients located within the local template 132, which predetermined absolute value the coefficient level of the respective coefficient inside local template 132 minimally has to have according to the bins of the binarization of that coefficient level of that transform coefficient which have been encoded/decoded so far in the multiple pass bin encod-ing/decoding process. As a specific example, you may imagine that the binariza-tion 161 comprises the following bins: the first bin of the first binarization code 160 may, as already mentioned above, indicate whether the quantization level of the transform coefficient to which the binarization 161 relates, is significant, i.e. non-zero, or not. A second bin in bin order of the binarization 160 could also belong to the first