CODING OF TRANSFORM COEFFICIENTS FOR VIDEO CODING
This disclosure describes techniques for coding transform coefficients associated with a block of residual video data in a video coding process. Aspects of this disclosure include the selection of a scan order for both significance map coding and level coding, as well as the selection of contexts for entropy coding consistent with the selected scan order. This disclosure proposes a harmonization of the scan order to code both the significance map of the transform coefficients as well as to code the levels of the transform coefficient. It is proposed that the scan order for the significance map should be in the inverse direction (i.e., from the higher frequencies to the lower frequencies). This disclosure also proposes that transform coefficients be scanned in sub-sets as opposed to fixed sub-blocks. In particular, transform coefficients are scanned in a sub-set consisting of a number of consecutive coefficients according to the scan order.
1 . A method of coding transform coefficients associated with residual video data in a video coding process, the method comprising:
arranging a block of transform coefficients into one or more sub-sets of transform coefficients based on a scan order;
coding a first portion of levels of transform coefficients in each sub-set, wherein the first portion of levels includes at least a significance of the transform coefficients in each subset; and
coding a second portion of levels of transform coefficients in each sub-set.
2 . The method of claim 1 , wherein arranging a block of transform coefficients comprises arranging the block of transform coefficients into a single set of transform coefficients corresponding to an entire transform unit.
3 . The method of claim 1 , wherein the coding steps use context adaptive binary arithmetic coding (CABAC).
4 . The method of claim 1 , wherein coding the first portion of levels of transform coefficients comprises coding a significance of transform coefficients in each sub-set according to the scan order, and wherein coding the second portion of levels of transform coefficients levels comprises coding levels of transform coefficients according to the scan order.
5 . The method of claim 1 , wherein coding the first portion of levels of transform coefficients comprises coding significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set, and wherein coding the second portion of levels of transform coefficients comprises coding levels of transform coefficients in each sub-set in at least a second scan of transform coefficients in the respective sub-set.
6 . The method of claim 1 , wherein coding the first portion of levels of transform coefficients comprises coding significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set, and wherein coding the second portion of levels of transform coefficients comprises:
coding bin one of the levels of transform coefficients in each sub-set in a second scan of transform coefficients in the respective sub-set;
coding remaining bins of the levels of transform coefficients in each sub-set in a third scan of transform coefficients in the respective sub-set; and
coding a sign of the levels of transform coefficients in each sub-set in a fourth scan of transform coefficients in the respective sub-set.
7 . The method of claim 6 , further comprising coding the sign of the levels of transform coefficients before coding the remaining bins of the levels of transform coefficients.
8 . The method of claim 1 , wherein coding the first portion of levels of transform coefficients comprises coding significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set, and wherein coding the second portion of levels of transform coefficients comprises:
coding bin one of the levels of transform coefficients in each sub-set in a second scan of transform coefficients in the respective sub-set;
coding bin two of the levels of transform coefficients in each sub-set in a third scan of transform coefficients in the respective sub-set;
coding a sign of the levels of transform coefficients in each sub-set in a fourth scan of transform coefficients in the respective sub-set; and
coding remaining bins of the levels of transform coefficients in each sub-set in a fifth scan of transform coefficients in the respective sub-set.
9 . The method of claim 8 , wherein the first, second, third, fourth, and fifth scans are performed in any order.
10 . The method of claim 1 , wherein coding the first portion of levels of transform coefficients comprises coding levels in a regular mode of context adaptive binary arithmetic coding (CABAC), and wherein coding the second portion of levels of transform coefficients comprises coding levels in a bypass mode of CABAC.
11 . A system for coding transform coefficients associated with residual video data in a video coding process, the system comprising:
a video coding processor configured to arrange a block of transform coefficients into one or more sub-sets of transform coefficients based on a scan order, code a first portion of levels of transform coefficients in each sub-set, wherein the first portion of levels includes at least a significance of the transform coefficients in each subset, and code a second portion of levels of transform coefficients in each sub-set.
12 . The system of claim 11 , wherein the video coding processor is configured to arrange the block of transform coefficients into a single set of transform coefficients corresponding to an entire transform unit.
13 . The system of claim 11 , wherein the video coding processor is configured to code the first portion and the second portion using context adaptive binary arithmetic coding (CABAC).
14 . The system of claim 11 , wherein the video coding processor is configured to code significance of transform coefficients in each sub-set according to the scan order, and wherein the video coding unit is configured to code levels of transform coefficients according to the scan order.
15 . The system of claim 11 , wherein the video coding processor is configured to code significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set, and wherein the video coding unit is configured to code levels of transform coefficients in each sub-set in at least a second scan of transform coefficients in the respective sub-set.
16 . The system of claim 11 , wherein the video coding processor is configured to:
code significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set;
code bin one of the levels of transform coefficients in each sub-set in a second scan of transform coefficients in the respective sub-set;
code remaining bins of the levels of transform coefficients in each sub-set in a third scan of transform coefficients in the respective sub-set; and
code a sign of the levels of transform coefficients in each sub-set in a fourth scan of transform coefficients in the respective sub-set.
17 . The system of claim 16 , wherein the video coding processor is configured to code the sign of the levels of transform coefficients before coding the remaining bins of the levels of transform coefficients.
18 . The system of claim 11 , wherein the video coding processor is further configured to:
code a significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set;
code bin one of the levels of transform coefficients in each sub-set in a second scan of transform coefficients in the respective sub-set;
code bin two of the levels of transform coefficients in each sub-set in a third scan of transform coefficients in the respective sub-set;
code a sign of the levels of transform coefficients in each sub-set in a fourth scan of transform coefficients in the respective sub-set; and
code remaining bins of the levels of transform coefficients in each sub-set in a fifth scan of transform coefficients in the respective sub-set.
19 . The system of claim 18 , wherein the first, second, third, fourth, and fifth scans are performed in any order.
20 . The system of claim 11 , wherein the video coding processor is further configured to code the first portion of levels of transform coefficients in a regular mode of context adaptive binary arithmetic coding (CABAC), and wherein the video coding unit is further configured to code the second portion of levels of transform coefficients in a bypass mode of CABAC.
21 . A system for coding transform coefficients associated with residual video data in a video coding process, the system comprising:
means for arranging a block of transform coefficients into one or more sub-sets of transform coefficients based on a scan order;
means for coding a first portion of levels of transform coefficients in each sub-set, wherein the first portion of levels includes at least a significance of the transform coefficients in each subset; and
means for coding a second portion of levels of transform coefficients in each sub-set.
22 . The system of claim 21 , wherein the means for arranging a block of transform coefficients comprises means for arranging the block of transform coefficients into a single set of transform coefficients corresponding to an entire transform unit.
23 . The system of claim 21 , wherein the means for coding the first portion and the means for coding the second portion use context adaptive binary arithmetic coding (CABAC).
24 . The system of claim 21 , wherein the means for coding the first portion of levels of transform coefficients comprises means for coding significance of transform coefficients in each sub-set according to the scan order, and wherein the means for coding the second portion of levels of transform coefficients levels comprises means for coding levels of transform coefficients according to the scan order.
25 . The system of claim 21 , wherein the means for coding the first portion of levels of transform coefficients comprises means for coding significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set, and wherein the means for coding the second portion of levels of transform coefficients comprises means for coding levels of transform coefficients in each sub-set in at least a second scan of transform coefficients in the respective sub-set.
26 . The system of claim 21 , wherein the means for coding the first portion of levels of transform coefficients comprises means for coding significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set, and wherein the means for coding the second portion of levels of transform coefficients comprises:
means for coding bin one of the levels of transform coefficients in each sub-set in a second scan of transform coefficients in the respective sub-set;
means for coding remaining bins of the levels of transform coefficients in each sub-set in a third scan of transform coefficients in the respective sub-set; and
means for coding a sign of the levels of transform coefficients in each sub-set in a fourth scan of transform coefficients in the respective sub-set.
27 . The system of claim 26 , further comprising means for coding the sign of the levels of transform coefficients before coding the remaining bins of the levels of transform coefficients.
28 . The system of claim 21 , wherein the means for coding the first portion of levels of transform coefficients comprises means for coding significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set, and wherein the means for coding the second portion of levels of transform coefficients comprises:
means for coding bin one of the levels of transform coefficients in each sub-set in a second scan of transform coefficients in the respective sub-set;
means for coding bin two of the levels of transform coefficients in each sub-set in a third scan of transform coefficients in the respective sub-set;
means for coding a sign of the levels of transform coefficients in each sub-set in a fourth scan of transform coefficients in the respective sub-set; and
means for coding remaining bins of the levels of transform coefficients in each sub-set in a fifth scan of transform coefficients in the respective sub-set.
29 . The system of claim 28 , wherein the first, second, third, fourth, and fifth scans are performed in any order.
30 . The system of claim 21 , wherein the means for coding the first portion of levels of transform coefficients comprises means for coding levels in a regular mode of context adaptive binary arithmetic coding (CABAC), and wherein the means for coding the second portion of levels of transform coefficients comprises means for coding levels in a bypass mode of CABAC.
31 . A computer program product comprising a computer-readable storage medium having stored thereon instructions that, when executed, cause a processor of a device for coding transform coefficients associated with residual video data in a video coding process to:
arrange a block of transform coefficients into one or more sub-sets of transform coefficients based on a scan order;
code a first portion of levels of transform coefficients in each sub-set, wherein the first portion of levels includes at least a significance of the transform coefficients in each subset; and
code a second portion of levels of transform coefficients in each sub-set.
32 . The computer program product of claim 31 , further causing a processor to arrange the block of transform coefficients into a single set of transform coefficients corresponding to an entire transform unit.
33 . The computer program product of claim 31 , wherein the processor is configured to code the first portion and to code the second portion using context adaptive binary arithmetic coding (CABAC).
34 . The computer program product of claim 31 , further causing a processor to code significance of transform coefficients in each sub-set according to the scan order, and to code levels of transform coefficients according to the scan order.
35 . The computer program product of claim 31 , further causing a processor to code significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set, and to code levels of transform coefficients in each sub-set in at least a second scan of transform coefficients in the respective sub-set.
36 . The computer program product of claim 31 , further causing a processor to:
code significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set;
code bin one of the levels of transform coefficients in each sub-set in a second scan of transform coefficients in the respective sub-set;
code remaining bins of the levels of transform coefficients in each sub-set in a third scan of transform coefficients in the respective sub-set; and
code a sign of the levels of transform coefficients in each sub-set in a fourth scan of transform coefficients in the respective sub-set.
37 . The computer program product of claim 36 , further causing a processor to code the sign of the levels of transform coefficients before coding the remaining bins of the levels of transform coefficients.
38 . The computer program product of claim 31 , further causing a processor to:
code a significance of transform coefficients in each sub-set in a first scan of transform coefficients in the respective sub-set;
code bin one of the levels of transform coefficients in each sub-set in a second scan of transform coefficients in the respective sub-set;
code bin two of the levels of transform coefficients in each sub-set in a third scan of transform coefficients in the respective sub-set;
code a sign of the levels of transform coefficients in each sub-set in a fourth scan of transform coefficients in the respective sub-set; and
code remaining bins of the levels of transform coefficients in each sub-set in a fifth scan of transform coefficients in the respective sub-set.
39 . The computer program product of claim 38 , wherein the first, second, third, fourth, and fifth scans are performed in any order.
40 . The computer program product of claim 31 , further causing a processor to:
code the first portion of levels of transform coefficients in a regular mode of context adaptive binary arithmetic coding (CABAC); and
code the second portion of levels of transform coefficients in a bypass mode of CABAC.