Luma to chroma quantization parameter table signaling
AssigneeInterDigital CE Patent Holdings, SAS
InventorsPhilippe De Lagrange, Edouard Francois, Franck Hiron, Christophe Chevance
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Abstract
Compression technology comprises deriving chroma quantization parameter (Qpc) based on luma Qp using luma-to-chroma Qp mapping table. Such a table may be shared by the encoder and the decoder. However, in some cases, signaling such a table in the data stream instead of having it fixed by a standard may be advantageous. The syntax used to encode, signal and decode this table has a cost in terms of bitrate. The present principles propose to signaling of a luma-to-chroma mapping table in the data stream according to different embodiments.
Claims20
A method of decoding video data, the method comprising:
- decoding, from a data stream, a starting luma quantization parameter (QP) value;
- determining a first pivot point for a luma-to-chroma QP mapping table by setting an output chroma QP value of the first pivot point to be equal to an input luma QP value of the first pivot point, wherein the input luma QP value is derived from the decoded starting luma QP value;
- decoding, from the data stream, one or more delta values for defining one or more subsequent pivot points of the luma-to-chroma QP mapping table;
- determining the luma-to-chroma QP mapping table based on the first pivot point and the one or more subsequent pivot points;
- and
- decoding a block of an image using the determined luma-to-chroma QP mapping table.
A device comprising a processor configured for:
- decoding, from a data stream, a starting luma quantization parameter (QP) value;
- determining a first pivot point for a luma-to-chroma QP mapping table by setting an output chroma QP value of the first pivot point to be equal to an input luma QP value of the first pivot point, wherein the input luma QP value is derived from the decoded starting luma QP value;
- decoding, from the data stream, one or more delta values for defining one or more subsequent pivot points of the luma-to-chroma QP mapping table;
- determining the luma-to-chroma QP mapping table based on the first pivot point and the one or more subsequent pivot points;
- and
- decoding a block of an image using the determined luma-to-chroma QP mapping table.
A method for encoding video data into a data stream, the method comprising:
- obtaining a luma-to-chroma QP mapping table having a plurality of pivot points, wherein for a first pivot point of the table, an output chroma QP value is equal to an input luma QP value;
- encoding, into the data stream, a starting luma quantization parameter (QP) value representing the input luma QP value of the first pivot point;
- determining one or more delta values for defining one or more subsequent pivot points of the luma-to-chroma QP mapping table;
- encoding, into the data stream, the determined one or more delta values;
- and
- encoding a block of an image by quantizing transform coefficients of the block using the obtained luma-to-chroma QP mapping table.
A device comprising a processor configured for:
- obtaining a luma-to-chroma QP mapping table having a plurality of pivot points, wherein for a first pivot point of the table, an output chroma QP value is equal to an input luma QP value;
- encoding, into the data stream, a starting luma quantization parameter (QP) value representing the input luma QP value of the first pivot point;
- determining one or more delta values for defining one or more subsequent pivot points of the luma-to-chroma QP mapping table;
- encoding, into the data stream, the determined one or more delta values;
- and
- encoding a block of an image by quantizing transform coefficients of the block using the obtained luma-to-chroma QP mapping table.
Dependencies are inferred from the claim text.