Adaptive chroma quantization in video coding for multiple color imaging formats
AssigneeDolby Laboratories Licensing Corporation
InventorsTaoran Lu, Fangjun Pu, Peng Yin, Tao Chen
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Abstract
Methods to improve the quality of coding high-dynamic range (HDR) signals are presented. Instead of using a single chroma quantization table for all color formats, a video encoder may adaptively use separate tables for each one, and transmit the table's ID to a decoder. Examples for chroma quantization tables for video content encoded in the YCbCr (PQ) and ICtCp (PQ) color formats under a variety of color gamut containers are provided.
Claims7
In a video decoder, a method to decode a coded bitstream with a processor, the method comprising:
- receiving an input coded bitstream;
- extracting from the input coded bitstream a table identifier for selecting a chroma quantization table among two or more chroma quantization tables, wherein the two or more chroma quantization tables comprise a first table for the YCbCr (gamma) color format and a second table for the YCbCr (PQ) color format, wherein each chroma quantization table is associated with a different color format, and wherein in each chroma quantization table an input index quantization value (qPi) is mapped to an output chroma quantization value (QpC), wherein for input qPi values larger than a first value, the corresponding output QpC values for the first table are higher than the corresponding output QpC values for the second table;
- selecting a chroma quantization table using the table identifier;
- and
- generating a decoded output signal using the selected chroma quantization table and the input coded bitstream.
An apparatus comprising a processor and configured to decode a coded bitstream, wherein decoding comprises:
- receiving an input coded bitstream;
- extracting from the input coded bitstream a table identifier for selecting a chroma quantization table among two or more chroma quantization tables, wherein the two or more chroma quantization tables comprise a first table for the YCbCr (gamma) color format and a second table for the YCbCr (PQ) color format, wherein each chroma quantization table is associated with a different color format, and wherein in each chroma quantization table an input index quantization value (qPi) is mapped to an output chroma quantization value (QpC), wherein for input qPi values larger than a first value, the corresponding output QpC values for the first table are higher than the corresponding output QpC values for the second table;
- selecting a chroma quantization table using the table identifier;
- and
- generating a decoded output signal using the selected chroma quantization table and the input coded bitstream.
A non-transitory computer-readable storage medium having stored thereon computer-executable instructions for decoding a coded bitstream with one or more processors, wherein decoding comprises:
- receiving an input coded bitstream;
- extracting from the input coded bitstream a table identifier for selecting a chroma quantization table among two or more chroma quantization tables, wherein the two or more chroma quantization tables comprise a first table for the YCbCr (gamma) color format and a second table for the YCbCr (PQ) color format, wherein each chroma quantization table is associated with a different color format, and wherein in each chroma quantization table an input index quantization value (qPi) is mapped to an output chroma quantization value (QpC), wherein for input qPi values larger than a first value, the corresponding output QpC values for the first table are higher than the corresponding output QpC values for the second table;
- selecting a chroma quantization table using the table identifier;
- and
- generating a decoded output signal using the selected chroma quantization table and the input coded bitstream.
Dependencies are inferred from the claim text.