Weighted Chroma Downsampling and Luma-Referenced Chroma Upsampling for HDR/WCG Video Coding

High dynamic range (HDR) and wide color gamut (WCG) video coding adopt chroma downsampling and upsampling for coding efficiency, which causes degradation in visual quality. In this paper, we propose weighted chroma downsampling and luma-referenced chroma upsampling for HDR/WCG video coding. We adopt ICtCp color space for HDR/WCG video coding instead of Y’CbCr color space due to its advantage in the chroma data processing. We perform weighted chroma downsampling prior to encoding based on the difference between neighboring pixels. Moreover, we take advantage of the full resolution luma data to generate weights for chroma upsampling by exploring the correlation between luma and chroma data after decoding. The experimental results show that the proposed method reconstructs high quality HDR videos with better image details and less color distortion, and outperforms HDR Anchor in terms of both objective and subjective evaluations.