Methods and devices for quantization and de-quantization design in video coding
A method for video encoding is provided. The method may be applied in an encoder and includes: determining, for a first coding block, a quantization parameter and a quantized level; deriving a scale value by scaling the quantization parameter by a scale factor, determining a plurality of parameters associated with a coding unit (CU); obtaining a plurality of bit-shifts by bit-shifting the plurality of parameters; and obtaining a plurality of coefficients associated with the CU based on the quantized level, the scale value, and the plurality of bit-shifts.
1. A method for video encoding, comprising:
partitioning a video frame into a plurality of video blocks;
determining, for a first coding block in the plurality of video blocks, a quantization parameter and a quantized level;
deriving a scale value by looking up a scale level table based on the quantization parameter; and
in response to determining that the first coding block is coded in a transform skip mode, obtaining a residual sample for a sample in the first coding block based on the quantized level, the scale value and a plurality of bit-shifts by applying a first de-quantization operation,
wherein the first de-quantization operation is also applied to obtain a reconstructed sample for an escape sample in a second coding block coded in a palette mode in the plurality of video blocks; and
wherein a block size of the first coding block or the second coding block is not used for determining parameters of the first de-quantization operation.
2. The method of claim 1 , further comprising:
in response to determining that a third coding block in the plurality of video blocks is coded in a regular transform mode, obtaining a residual sample for a sample in the third coding block by applying a second de-quantization operation different from the first de-quantization operation;
wherein the block size of the third coding block is used for determining parameters of the second de-quantization operation.
3. The method of claim 1 , wherein the scale level table is levelScale [k]={40, 45, 51, 57, 64, 72}, wherein k is an integer between 0 and 5 inclusive.
4. The method of claim 1 , further comprising:
generating an escape flag to indicate if the escape sample is present in the second coding block.
5. The method of claim 1 , wherein the plurality of bit-shifts comprise a left shift of QP/6 bits and a right shift of 6 bits, wherein QP is the quantization parameter.
6. The method of claim 1 , wherein the first de-quantization operation is applied using following equation:
pSample
=
pLevel
×
decScale
[
QP
%6
]
×
2
(
QP
/
6
)
2
6
wherein pLevel is a quantized level, pSample corresponds to a reconstructed value of a residual sample in the transform skip mode or an escape sample in the palette mode, decScale [ ] is a scale value, OP is a quantization parameter, % denotes a modulo operation, QP % 6 represents an operation of OP modulo 6.
7. A computing device, comprising:
one or more processors;
a non-transitory storage coupled to the one or more processors; and
a plurality of programs stored in the non-transitory storage that, when executed by the one or more processors, cause the one or more processors to perform acts comprising:
partitioning a video frame into a plurality of video blocks;
determining, for a first coding block in the plurality of video blocks, a quantization parameter and a quantized level;
deriving a scale value by looking up a scale level table based on the quantization parameter; and
in response to determining that the first coding block is coded in a transform skip mode, obtaining a residual sample for a sample in the first coding block based on the quantized level, the scale value and a plurality of bit-shifts by applying a first de-quantization operation,
wherein the first de-quantization operation is also applied to obtain a reconstructed sample for an escape sample in a second coding block coded in a palette mode in the plurality of video blocks; and
wherein a block size of the first coding block or the second coding block is not used for determining parameters of the first de-quantization operation.
8. The computing device of claim 7 , wherein the plurality of programs, when executed by the one or more processors, cause the one or more processors to further perform acts comprising:
in response to determining that a third coding block in the plurality of video blocks is coded in a regular transform mode, obtaining a residual sample for a sample in the third coding block by applying a second de-quantization operation different from the first de-quantization operation;
wherein the block size of the third coding block is used for determining parameters of the second de-quantization operation.
9. The computing device of claim 7 , wherein the scale level table is levelScale [k] ={40, 45, 51, 57, 64, 72}, wherein k is an integer between 0 and 5 inclusive.
10. The computing device of claim 7 , wherein the plurality of programs, when executed by the one or more processors, cause the one or more processors to further perform acts comprising:
generating an escape flag to indicate if the escape sample is present in the second coding block.
11. The computing device of claim 7 , wherein the plurality of bit-shifts comprise a left shift of QP/6 bits and a right shift of 6 bits, wherein QP is the quantization parameter.
12. The computing device of claim 7 , wherein the first de-quantization operation is applied using following equation:
pSample
=
pLevel
×
decScale
[
QP
%6
]
×
2
(
QP
/
6
)
2
6
wherein pLevel is a quantized level, pSample corresponds to a reconstructed value of a residual sample in the transform skip mode or an escape sample in the palette mode, decScale [ ] is a scale value, OP is a quantization parameter, % denotes a modulo operation, QP % 6 represents an operation of OP modulo 6.
13. A non-transitory computer readable storage medium storing a bitstream generated by a method for video encoding, executed by a processor, comprising:
partitioning a video frame into a plurality of video blocks;
determining, for a first coding block in the plurality of video blocks, a quantization parameter and a quantized level;
deriving a scale value by looking up a scale level table based on the quantization parameter; and
in response to determining that the first coding block is coded in a transform skip mode, obtaining a residual sample for a sample in the first coding block based on the quantized level, the scale value and a plurality of bit-shifts by applying a first de-quantization operation,
wherein the first de-quantization operation is also applied to obtain a reconstructed sample for an escape sample in a second coding block coded in a palette mode in the plurality of video blocks; and
wherein a block size of the first coding block or the second coding block is not used for determining parameters of the first de-quantization operation.
14. The non-transitory computer readable storage medium of claim 13 , wherein the method further comprises:
in response to determining that a third coding block in the plurality of video blocks is coded in a regular transform mode, obtaining a residual sample for a sample in the third coding block by applying a second de-quantization operation different from the first de-quantization operation;
wherein the block size of the third coding block is used for determining parameters of the second de-quantization operation.
15. The non-transitory computer readable storage medium of claim 13 , wherein the scale level table is levelScale [k]={40, 45, 51, 57, 64, 72}, wherein k is an integer between 0 and 5 inclusive.
16. The non-transitory computer readable storage medium of claim 13 , wherein the method further comprises:
generating an escape flag to indicate if the escape sample is present in the second coding block.
17. The non-transitory computer readable storage medium of claim 13 , wherein the plurality of bit-shifts comprise a left shift of QP/6 bits and a right shift of 6 bits, wherein QP is the quantization parameter.
18. The non-transitory computer readable storage medium of claim 13 , wherein the first de-quantization operation is applied using following equation:
pSample
=
pLevel
×
decScale
[
QP
%6
]
×
2
(
QP
/
6
)
2
6
wherein pLevel is a quantized level, pSample corresponds to a reconstructed value of a residual sample in the transform skip mode or an escape sample in the palette mode, decScale [ ] is a scale value, OP is a quantization parameter, % denotes a modulo operation, QP % 6 represents an operation of OP modulo 6.