High Dynamic Range (HDR) and Wider Color Gamut (WCG) content represents a greater range of luminance levels and
a more complete reproduction of colors found in real-world scenes. The characteristics of HDR/WCG content are very
different from the SDR content. It poses a challenge to the compression system which is originally designed for SDR
content. Recently in MPEG/VCEG, two directions have been taken to improve compression performances for
HDR/WCG video using HEVC Main10 codec. The first direction is to improve HDR-10 using encoder optimization.
The second direction is to modify the video signal in pre/post processing to better fit compression system. The process
therefore is out of coding loop and does not involve changes to the HEVC specification. Among many proposals in the
second direction, reshaper is identified to be the key component. In this paper, a novel luma reshaper is presented which
re-allocates the codewords to help codec improve subjective quality. In addition, encoder optimization can be performed
jointly with reshaping. Experiments are conducted with ICtCp color difference signal. Simulation results show that if
both joint optimization of reshaper and encoder are carried out, there is evidence that improvement over the HDR-10
anchor can be achieved.
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