History-based rice parameter derivations for video coding
View Patent ↗In some embodiments, a video decoder decodes a video from a bitstream of the video using a history-based Rice parameter derivation. 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 updating a history counter for a color component for calculating Rice parameters and prior to calculating a next Rice parameter, updating a replacement variable based on the updated history counter. The process further includes calculating the Rice parameters for transform units (TUs) in the CTU based on the value of the replacement variable 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);
decoding each CTU of the plurality of CTUs in the partition, decoding the CTU comprising:
updating a history counter StatCoeff for a color component for calculating Rice parameters;
prior to calculating a next Rice parameter, updating a replacement variable HistValue based on the updated history counter;
calculating the Rice parameters for transform units (TUs) in the CTU based on the updated replacement variable HistValue;
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.
2. The method of claim 1 , wherein updating the history counter StatCoeff comprises:
in response to determining that a first non-zero Golomb-Rice coded transform coefficient in a TU is coded as abs_remainder, updating the history counter StatCoeff for a color component cIdx as:
StatCoeff
[
cIdx
]
=
Floor
(
Log
2
(
abs_remainder
[
c
I
d
x
]
)
)
+
1
;
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
]
=
Floor
(
Log
2
(
dec_abs
_level
[
cIdx
]
)
)
,
wherein Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is base-2 logarithm of x.
3. The method of claim 1 , wherein the partition is a frame, a slice, or a tile.
4. The method of claim 1 , further comprising setting the history counter StatCoeff to an initial value based on a bit depth of samples of luma and chroma arrays of the video.
5. The method of claim 1 , wherein calculating the Rice parameters for the TUs in the CTU based on the history counter comprises:
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 HistValue; and
deriving the Rice parameter for the TU based on the local sum variable locSumAbs.
6. The method of claim 5 , 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.
7. The method of claim 1 , wherein updating a replacement variable HistValue based on the history counter comprises updating the replacement variable HistValue for a color component cIdx by calculating:
HistValue
[
c
I
d
x
]
=
1
<<
StatCoeff[cIdx]
,
wherein StatCoeff denotes the history counter.
8. A system comprising:
a processing device; and
a non-transitory computer-readable medium communicatively coupled to the processing device, wherein the processing device is configured to execute program code stored in the non-transitory computer-readable medium and thereby perform operations comprising:
accessing a binary string representing a partition of a video, the partition comprising a plurality of coding tree units (CTUs);
decoding each CTU of the plurality of CTUs in the partition, decoding the CTU comprising:
updating a history counter StatCoeff for a color component for calculating Rice parameters;
prior to calculating a next Rice parameter, updating a replacement variable HistValue based on the updated history counter;
calculating the Rice parameters for transform units (TUs) in the CTU based on the updated replacement variable HistValue;
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.
9. The system of claim 8 , wherein updating the history counter StatCoeff comprises:
in response to determining that a first non-zero Golomb-Rice coded transform coefficient in a TU is coded as abs_remainder, updating the history counter StatCoeff for a color component cIdx as:
StatCoeff
[
cIdx
]
=
Floor
(
Log
2
(
abs_remainder
[
c
I
d
x
]
)
)
+
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
]
=
Floor
(
Log
2
(
dec_abs
_level
[
cIdx
]
)
)
,
wherein Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is base-2 logarithm of x.
10. The system of claim 8 , further comprising setting the history counter StatCoeff to an initial value based on a bit depth of samples of luma and chroma arrays of the video.
11. The system of claim 8 , wherein calculating the Rice parameters for the TUs in the CTU based on the history counter comprises:
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 HistValue; and
deriving the Rice parameter for the TU based on the local sum variable locSumAbs.
12. The system of claim 11 , 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.
13. The system of claim 8 , wherein updating a replacement variable HistValue based on the history counter comprises updating the replacement variable HistValue for a color component cIdx by calculating:
HistValue
[
cI
d
x
]
=
1
<<
StatCoeff[cIdx]
,
wherein StatCoeff denotes the history counter.
14. 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);
processing the partition of the video to generate a binary representation of the partition, the processing comprising:
encoding each CTU of the plurality of CTUs in the partition, encoding the CTU comprising:
updating a history counter StatCoeff for a color component for calculating Rice parameters;
prior to calculating a next Rice parameter, updating a replacement variable HistValue based on the updated history counter;
calculating the Rice parameters for transform units (TUs) in the CTU based on the updated replacement variable HistValue; 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.
15. The method of claim 14 , wherein updating the history counter StatCoeff comprises:
in response to determining that a first non-zero Golomb-Rice coded transform coefficient in a TU is coded as abs_remainder, updating the history counter StatCoeff for a color component cIdx as:
StatCoeff
[
cIdx
]
=
Floor
(
Log
2
(
abs_remainder
[
c
I
d
x
]
)
)
+
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
]
=
Floor
(
Log
2
(
dec_abs
_level
[
cIdx
]
)
)
,
wherein Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is base-2 logarithm of x.
16. The method of claim 14 , wherein the partition is a frame, a slice, or a tile.
17. The method of claim 14 , further comprising setting the history counter StatCoeff to an initial value based on a bit depth of samples of luma and chroma arrays of the video.
18. The method of claim 14 , wherein calculating the Rice parameters for the TUs in the CTU based on the history counter comprises:
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 HistValue; and
deriving the Rice parameter for the TU based on the local sum variable locSumAbs.
19. The method of claim 18 , 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.
20. The method of claim 14 , wherein updating a replacement variable HistValue based on the history counter comprises updating the replacement variable HistValue for a color component cIdx by calculating:
HistValue
[
cId
x
]
=
1
<<
StatCoeff[cIdx]
,
wherein StatCoeff denotes the history counter.