System for coding high dynamic range and wide color gamut sequences
A method of encoding a digital video data applies adaptive pre-processing to data representing high dynamic range (HDR) and/or wide color gamut (WCG) image data prior to encoding and complementary post-processing to the data after decoding in order to allow at least partial reproduction of the HDR and/or WCG data. The example methods apply one or more color space conversions, and a perceptual transfer functions to the data prior to quantization. The example methods apply inverse perceptual transfer functions and inverse color space conversions after decoding to recover the HDR and/or WCG data. The transfer functions are adaptive so that different transfer functions may be applied to video data sets including different groups of frames, frames or processing windows in a single frame. Information on the data set and information on the applied transfer function is passed as metadata from the encoder to the decoder.
1. A digital video decoding system for decoding a bit stream in a format that does not accommodate a digital video data set including high dynamic range (HDR) and wide color gamut (WCG) video data, to reconstruct an output digital video data set including at least one of HDR and WCG video data, the digital video decoding system comprising:
a decoder for decoding the bit stream to recover a digital video data set from the bit stream;
an intermediate color conversion process configured to:
extract intermediate color conversion metadata from the bit stream, the intermediate color conversion metadata identifying an input color space of the digital video data set extracted from the bit stream and an intermediate color space to which the digital video data set is to be converted;
convert the inverse transformed portion of the digital video data set from the input color space to the intermediate color space to produce intermediate color converted digital video data; and
an inverse compression transfer function process configured to extract compression metadata from the bit stream and to apply an inverse compression transfer function to the intermediate color converted video data to generate the digital video data set to be applied to the output color conversion process;
predictively decode the bit stream using one or more reference frames;
apply a color conversion process to the output digital video data set, the color conversion process being an inverse of the output color conversion process to generate a color converted video data set;
generate a perceptual transfer function process from the metadata identifying the inverse perceptual transfer function to be applied to the received video data;
apply the perceptual transfer function to the color converted video data set to generate a transformed video data set;
generate a perceptual normalization function using the metadata identifying the inverse perceptual normalization function;
apply the perceptual normalization function to the transformed video data set to generate a perceptually normalized video data set;
generate a further reference frame for use in predictively decoding the bit stream from the perceptually normalized video data set.
2. A digital video decoding system for decoding a bit stream in a format that does not accommodate a digital video data set including high dynamic range (HDR) and wide color gamut (WCG) video data, to reconstruct an output digital video data set including at least one of HDR and WCG video data, the digital video decoding system comprising:
a decoder for decoding the bit stream to recover a digital video data set from the bit stream;
an intermediate color conversion process configured to:
extract intermediate color conversion metadata from the bit stream, the intermediate color conversion metadata identifying an input color space of the digital video data set extracted from the bit stream and an intermediate color space to which the digital video data set is to be converted;
convert the inverse transformed portion of the digital video data set from the input color space to the intermediate color space to produce intermediate color converted digital video data; and
an inverse compression transfer function process configured to extract compression metadata from the bit stream and to apply an inverse compression transfer function to the intermediate color converted video data to generate the digital video data set to be applied to the output color conversion process;
receive video data corresponding to a portion of the digital video data set;
retrieve metadata from the bit stream identifying a transfer function to be applied to the received video data;
retrieve metadata from the bit stream identifying an inverse perceptual normalization function, including at least one of a gain factor or an offset, to be applied to the received video data;
generate an inverse perceptual transfer function based on the identified transfer function; and
apply the generated inverse perceptual transfer function and the inverse perceptual normalization function to the portion of the digital video data set to generate an inverse transformed portion of the digital video data set; an output color conversion process configured to process the inverse transformed portion of the digital video data set to reconstruct the output digital video data set including at least one of HDR and WCG video data.
3. The digital video decoding system of claim 1 , wherein the bit stream is a Main 10 High Efficiency Video Coder (HEVC) bit stream and the inverse perceptual transfer function process is configured to extract the metadata from supplemental enhancement information (SEI) data in the bit stream.
4. The digital video decoding system of claim 1 , wherein the inverse perceptual transfer function process is configured to receive the portion of the digital video data as one of a group of multiple video frames, a single video frame or a portion of a single video frame.
5. The digital video decoding system of claim 2 , wherein the bit stream is a Main 10 High Efficiency Video Coder (HEVC) bit stream and the inverse perceptual transfer function process is configured to extract the metadata from supplemental enhancement information (SEI) data in the bit stream.
6. The digital video decoding system of claim 2 wherein the inverse perceptual transfer function process is configured to receive the portion of the digital video data as one of a group of multiple video frames, a single video frame or a portion of a single video frame.