History-based rice parameter derivations for wavefront parallel processing in video coding
In some embodiments, a video decoder decodes a video from a bitstream of the video using a history-based Rice parameter derivation along with the wavefront parallel processing (WPP). The video decoder accesses a binary string representing a partition of the video and processes each coding tree unit (CTU) in the partition to generate decoded coefficient values in the CTU. The process includes prior to decoding the CTU, determining whether WPP is enabled and the CTU is the first CTU of a current CTU row in the partition, and if so, setting a history counter to an initial value. The process further includes decoding the CTU by calculating the Rice parameters for transform units (TUs) in the CTU based on the value of the history counter and decoding the binary string corresponding to the TUs in the CTU into coefficient values of the TUs based on the calculated Rice parameters.
1 . A method for decoding a video, the method comprising:
accessing a binary string representing a partition of the video, the partition comprising a plurality of coding tree units (CTUs) forming one or more CTU rows;
for each CTU of the plurality of CTUs in the partition,
prior to decoding the CTU, that the CTU is the first CTU of a current CTU row among the one or more CTU rows in the partition;
in response to determining that the CTU is the first CTU of the current CTU row in the partition,
setting a history counter for a color component for calculating Rice parameters to an initial value;
decoding the CTU, comprising:
calculating the Rice parameters for transform units (TUs) in the CTU based on the history counter;
decoding the binary string corresponding to the TUs in the CTU into coefficient values of the TUs based on the calculated Rice parameters; and
determining pixel values for the TUs in the CTU from the coefficient values; and
outputting a decoded partition of the video comprising the decoded plurality of CTUs in the partition,
wherein setting the history counter for a color component cIdx for calculating Rice parameters to an initial value comprises:
in response to determining that a history-based Rice parameter derivation is enabled, calculating the initial value by
StatCoeff[cIdx]=2*Floor(Log 2(BitDepth−10)),
wherein StatCoeff denotes the history counter, BitDepth specifies a bit depth of samples of luma and chroma arrays of the video, Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is base-2 logarithm of x.
2 . The method of claim 1 , wherein the partition is a frame, or a slice, or a tile.
3 . The method of claim 1 , wherein calculating the Rice parameters for the TUs in the CTU based on the history counter comprises:
determining a replacement variable HistValue based on the history counter;
calculating a local sum variable locSumAbs for a coefficient in a TU of the CTU using values of neighboring coefficients in a pre-determined neighborhood of the coefficient and the replacement variable Hist Value; and
deriving the Rice parameter for the TU based on the local sum variable locSum Abs.
4 . The method of claim 3 , wherein determining a replacement variable Hist Value based on the history counter comprises determining the replacement variable Hist Value for a color component cIdx by calculating:
HistValue
[
cIdx
]
=
1
≪
StatCoeff
[
cIdx
]
,
wherein StatCoeff denotes the history counter.
5 . The method of claim 3 , wherein calculating a local sum variable locSumAbs for a coefficient in a TU of the CTU comprises:
determining that a neighboring coefficient of a plurality of neighboring coefficients in the pre-determined neighborhood of the coefficient is outside the TU; and
using the replacement variable HistValue as a value of the neighboring coefficient outside the TU to calculate the local sum variable locSumAbs.
6 . The method of claim 1 , wherein decoding the CTU further comprises updating the history counter by:
in response to determining that the first, non-zero, Golomb-Rice coded transform coefficient in a TU is coded as abs_remainder, updating the history counter for a color component cIdx as:
StatCoeff[cIdx]=(StatCoeff[cIdx]+Floor(Log 2(abs_remainder[cIdx]))+2)>>1; and
in response to determining that the first, non-zero, Golomb-Rice coded transform coefficient in the TU is coded as dec_abs_level, updating the history counter for a color component cIdx as:
StatCoeff[cIdx]=(StatCoeff[cIdx]+Floor(Log 2(dec_abs_level[cIdx])))>>1,
wherein StatCoeff denotes the history counter, Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is a base-2 logarithm of x.
7 . A processing device, comprising:
a memory configured to store a computer program; and
a processor:
wherein the processor is configured to execute the computer program stored on the memory to:
access a binary string representing a partition of a video, the partition comprising a plurality of coding tree units (CTUs) forming one or more CTU rows;
for each CTU of the plurality of CTUs in the partition,
prior to decoding the CTU, determine that the CTU is the first CTU of a current CTU row among the one or more CTU rows in the partition;
in response to determining that the CTU is the first CTU of the current CTU row in the partition, set a history counter for a color component for calculating Rice parameters to an initial value;
decode the CTU, comprising:
calculating the Rice parameters for transform units (TUs) in the CTU based on the history counter;
decoding the binary string corresponding to the TUs in the CTU into coefficient values of the TUs based on the calculated Rice parameters; and
determining pixel values for the TUs in the CTU from the coefficient values; and
output a decoded partition of the video comprising the decoded plurality of CTUs in the partition,
wherein the processor is further configured to, when setting the history counter for a color component cIdx for calculating Rice parameters to an initial value, execute the computer program to perform one or more of following operations:
in response to determining that a history-based Rice parameter derivation is enabled, calculating the initial value by
StatCoeff[cIdx]=2*Floor(Log 2(BitDepth−10),
wherein StatCoeff denotes the history counter, BitDepth specifies a bit depth of samples of luma and chroma arrays of the video, Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is base-2 logarithm of x.
8 . The processing device of claim 7 , wherein the partition is a frame, a slice, or a tile.
9 . The processing device of claim 7 , wherein the processor is further configured to:
determine a replacement variable HistValue based on the history counter;
calculate a local sum variable locSumAbs for a coefficient in a TU of the CTU using values of neighboring coefficients in a pre-determined neighborhood of the coefficient and the replacement variable HistValue; and
derive the Rice parameter for the TU based on the local sum variable locSumAbs.
10 . The processing device of claim 9 , wherein the processors is further configured to determine the replacement variable HistValue for a color component cIdx by calculating:
HistValue
[
cIdx
]
=
1
≪
StatCoeff
[
cIdx
]
,
wherein StatCoeff denotes the history counter.
11 . The processing device of claim 9 , wherein the processor is further configured to:
determine that a neighboring coefficient of a plurality of neighboring coefficients in the pre-determined neighborhood of the coefficient is outside the TU; and
use the replacement variable HistValue as a value of the neighboring coefficient outside the TU to calculate the local sum variable locSumAbs.
12 . The processing device of claim 7 , wherein the processor is further configured to update the history counter by:
in response to determining that the first, non-zero, Golomb-Rice coded transform coefficient in a TU is coded as abs remainder, updating the history counter for a color component cIdx as:
StatCoeff[cIdx]=(StatCoeff[cIdx]+Floor(Log 2(abs_remainder[cIdx]))+2)>>1; and
in response to determining that the first, non-zero, Golomb-Rice coded transform coefficient in the TU is coded as dec_abs_level, updating the history counter for a color component cIdx as:
StatCoeff[cIdx]=(StatCoeff[cIdx]+Floor(Log 2(dec_abs_level[cIdx])))>>1,
wherein StatCoeff denotes the history counter, Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is a base-2 logarithm of x.
13 . A method for encoding a video, the method comprising:
accessing a partition of the video, the partition comprising a plurality of coding tree units (CTUs) forming one or more CTU rows;
processing the partition of the video to generate a binary representation of the partition, the processing comprising:
for each CTU of the plurality of CTUs in the partition,
prior to encoding the CTU, determining that parallel coding is enabled and that the CTU is the first CTU of a current CTU row among the one or more CTU rows in the partition;
in response to determining that the parallel coding is enabled and that the CTU is the first CTU of the current CTU row in the partition, setting a history counter for a color component for calculating Rice parameters to an initial value; and
encoding the CTU, comprising:
calculating the Rice parameters for transform units (TUs) in the CTU based on the history counter, and
encoding coefficient values of the TUs into a binary representation corresponding to the TUs in the CTU based on the calculated Rice parameters; and
encoding the binary representation of the partition into a bitstream of the video,
wherein setting the history counter for a color component cIdx for calculating Rice parameters to an initial value comprises:
in response to determining that a history-based Rice parameter derivation is enabled, calculating the initial value by
StatCoeff[cIdx]=2*Floor(Log 2(BitDepth−10),
wherein StatCoeff denotes the history counter, BitDepth specifies a bit depth of samples of luma and chroma arrays of the video, Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is base-2 logarithm of x.
14 . The method of claim 13 , wherein the partition is a frame, or a slice, or a tile.
15 . The method of claim 13 , wherein calculating the Rice parameters for the TUs in the CTU based on the history counter comprises:
determining a replacement variable HistValue based on the history counter;
calculating a local sum variable locSumAbs for a coefficient in a TU of the CTU using values of neighboring coefficients in a pre-determined neighborhood of the coefficient and the replacement variable Hist Value; and
deriving the Rice parameter for the TU based on the local sum variable locSumAbs.
16 . The method of claim 15 , wherein determining a replacement variable Hist Value based on the history counter comprises determining the replacement variable Hist Value for a color component cIdx by calculating:
HistValue
[
cIdx
]
=
1
≪
StatCoeff
[
cIdx
]
,
wherein StatCoeff denotes the history counter.
17 . The method of claim 15 , wherein calculating a local sum variable locSumAbs for a coefficient in a TU of the CTU comprises:
determining that a neighboring coefficient of a plurality of neighboring coefficients in the pre-determined neighborhood of the coefficient is outside the TU; and
using the replacement variable Hist Value as a value of the neighboring coefficient outside the TU to calculate the local sum variable locSumAbs.
18 . The method of claim 13 , wherein encoding the CTU further comprises updating the history counter by:
in response to determining that the first, non-zero, Golomb-Rice coded transform coefficient in a TU is coded as abs_remainder, updating the history counter for a color component cIdx as:
StatCoeff[cIdx]=(StatCoeff[cIdx]+Floor(Log 2(abs_remainder[cIdx]))+2)>>1; and
in response to determining that the first, non-zero, Golomb-Rice coded transform coefficient in the TU is coded as dec_abs_level, updating the history counter for a color component cIdx as:
StatCoeff
[
cIdx
]
=
(
StatCoeff
[
cIdx
]
+
Floor
(
Log
2
(
dec_abs
_level
[
cIdx
]
)
)
)
≫
1
,
wherein StatCoeff denotes the history counter, Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is a base-2 logarithm of x.
19 . A processing device, comprising:
a memory configured to store a computer program and a bitstream; and
a processor:
wherein the processor is configured to execute the computer program stored on the memory to perform the following steps for generating the bitstream:
accessing a partition of a video, the partition comprising a plurality of coding tree units (CTUs) forming one or more CTU rows;
processing the partition of the video to generate a binary representation of the partition, the processing comprising:
for each CTU of the plurality of CTUs in the partition,
prior to encoding the CTU, determining that parallel coding is enabled and that the CTU is the first CTU of a current CTU row among the one or more CTU rows in the partition;
in response to determining that the parallel coding is enabled and that the CTU is the first CTU of the current CTU row in the partition, setting a history counter for a color component for calculating Rice parameters to an initial value; and
encoding the CTU, comprising:
calculating the Rice parameters for transform units (TUs) in the CTU based on the history counter, and
encoding coefficient values of the TUs into a binary representation corresponding to the TUs in the CTU based on the calculated Rice parameters, and
encoding the binary representation of the partition into the bitstream,
wherein the processor is further configured to, when setting the history counter for a color component cIdx for calculating Rice parameters to an initial value, execute the computer program to perform the following steps for generating the bitstream;
in response to determining that a history-based Rice parameter derivation is enabled, calculating the initial value by
StatCoeff[cIdx]=2*Floor(Log 2)BitDepth−10)),
wherein StatCoeff denotes the history counter, BitDepth specifies a bit depth of samples of luma and chroma arrays of the video, Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is base-2 logarithm of x.
20 . The processing devicenon transitory computer readable medium of claim 19 , wherein the partition is a frame, or a slice, or a tile.
21 . The processing device of claim 19 , wherein the processor is further configured to perform the following steps for generating the bitstream:
determining a replacement variable HistValue based on the history counter;
calculating a local sum variable locSumAbs for a coefficient in a TU of the CTU using values of neighboring coefficients in a pre-determined neighborhood of the coefficient and the replacement variable Hist Value; and
deriving the Rice parameter for the TU based on the local sum variable locSumAbs.
22 . The processing device of claim 21 , wherein the processor is further configured to determine the replacement variable Hist Value for a color component cIdx by calculating:
HistValue
[
cIdx
]
=
1
≪
StatCoeff
[
cIdx
]
,
wherein StatCoeff denotes the history counter.
23 . The processing device of claim 21 , wherein the processor is further configured to perform the following steps for generating the bitstream:
determining that a neighboring coefficient of a plurality of neighboring coefficients in the pre-determined neighborhood of the coefficient is outside the TU; and
using the replacement variable HistValue as a value of the neighboring coefficient outside the TU to calculate the local sum variable locSumAbs.
24 . The processing device of claim 19 , wherein the processor is further configured to update the history counter by:
in response to determining that the first, non-zero, Golomb-Rice coded transform coefficient in a TU is coded as abs_remainder, updating the history counter for a color component cIdx as:
StatCoeff[cIdx]=(StatCoeff[cIdx]+Floor(Log 2(abs_remainder[cIdx]))+2)>>1; and
in response to determining that the first, non-zero, Golomb-Rice coded transform coefficient in the TU is coded as dec_abs_level, updating the history counter for a color component cIdx as:
StatCoeff[cIdx]=(StatCoeff[cIdx]+Floor(Log 2(dec_abs_level[cIdx])))>>1.
wherein StatCoeff denotes the history counter, Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is a base-2 logarithm of x.