Chroma quantization parameter adjustment in video encoding and decoding
A video coding system uses a value of a chroma quantization parameter table to quantize or de-quantize chroma values of a block of the video, the chroma quantization parameter table being directly coded in a set of parameters at the picture level or at the sequence level of the coded video stream. A corresponding encoding method, encoding device, decoding method, decoding device, and non-transitory readable medium are proposed.
1. A method for decoding video from a codec video stream comprising:
obtaining information representative of a chroma quantization parameter table; and
de-quantizing chroma values of a block of the video according to a value of the obtained chroma quantization parameter table,
wherein the chroma quantization parameter table is directly coded in a set of parameters at the picture level or at the sequence level of the coded video stream and is coded as a series of differential integer values, each a quantization parameter delta, a first quantization parameter delta being coded relatively to a base chroma quantization parameter while each of the following quantization parameter deltas that follow the first quantization parameter delta are coded differentially with a preceding quantization parameter delta.
2. The method of claim 1 , wherein the table is only coded for B slices of the video.
3. The method of claim 1 , wherein the chroma quantization parameter values are coded only for a limited range of input base chroma quantization parameter values.
4. The method of claim 1 , wherein the quantization parameter delta value is always positive.
5. The method of claim 4 , wherein no sign for the quantization parameter delta is encoded.
6. A non-transitory processor readable medium having stored therein instructions for causing a processor to perform the method of claim 1 .
7. An apparatus for decoding video from a codec video stream comprising:
a processor configured to:
obtain information representative of a chroma quantization parameter table; and
de-quantize chroma values of a block of the video according to a value of the obtained chroma quantization parameter table,
wherein the chroma quantization parameter table is directly coded in a set of parameters at the picture level or at the sequence level of the coded video stream and is coded as a series of differential integer values, each a quantization parameter delta, a first quantization parameter delta being coded relative to a base chroma quantization parameter while each of the following quantization parameter deltas that follow the first quantization parameter delta are coded differentially with a preceding quantization parameter delta.
8. The apparatus of claim 7 , wherein the table is only coded for B slices of the video.
9. The apparatus of claim 7 , wherein the chroma quantization parameter values are coded only for a limited range of input base chroma quantization parameter values.
10. The apparatus of claim 7 , wherein the quantization parameter delta value is always positive.
11. The apparatus of claim 10 , wherein no sign for the quantization parameter delta is encoded.
12. A method for encoding video comprising:
selecting a chroma quantization parameter table;
quantizing chroma values of a block of the video according to a value of the obtained chroma quantization parameter table; and
encoding the quantized value and high-level syntax information representative of the selected chroma quantization parameter table into a coded video stream,
wherein the table is directly coded in a set of parameters at the picture level or at the sequence level of the coded video stream and is coded under the form of a series of differential integer values, each a quantization parameter delta, a first quantization parameter delta being coded relative to a base chroma quantization parameter, while each of the following quantization parameter deltas that follows the first quantization parameter delta are coded differentially with a preceding quantization parameter delta.
13. The method of claim 12 , wherein the quantization parameter delta value is always positive.
14. The method of claim 13 , wherein no sign for the quantization parameter delta is encoded.
15. A non-transitory processor readable medium having stored therein instructions for causing a processor to perform the method of claim 12 .
16. An apparatus for encoding video comprising:
a processor configured to:
select a chroma quantization parameter table;
quantize chroma values of a block of the video according to a value of the obtained chroma quantization parameter table, and
encode the quantized value and high-level syntax information representative of the selected chroma quantization parameter table into a coded video stream,
wherein the table is directly coded in a set of parameters at the picture level or at the sequence level of the coded video stream and is coded under the form of a series of differential integer values, each a quantization parameter delta, a first quantization parameter delta being coded relative to a base chroma quantization parameter, while each of the following quantization parameter deltas that follows the first quantization parameter delta are coded differentially with a preceding quantization parameter delta.
17. The apparatus of claim 16 , wherein the quantization parameter delta value is always positive.
18. The apparatus of claim 17 , wherein no sign for the quantization parameter delta is encoded.