A 4K/60p HEVC Real-Time Encoding System With High Quality HDR Color Representations

This paper describes a 4K/60p high efficiency video coding (HEVC, the latest coding standard) real-time encoding system with high quality high dynamic range (HDR) color representations. The HDR technology provides attractive video contents with a wider dynamic range of luminance, which can make shadows and brighter details appear clearly without any blown out highlights or blocked up shadows. We propose a new rate control method for HDR video coding. The method consists of two algorithms for improving perceptual quality by reducing degradation of HDR-specific color artifacts. The first one, adaptive block size and prediction mode decision, is conducted to suppress perceptual degradation due to prediction error in high chroma areas. The second, local quantization parameter control, is carried out to improve the visual quality with appropriate bit allocation in low chroma areas. The method was implemented in an HEVC real-time encoding system and its performance was assessed by measuring the color difference metrics by 3.86% at the most degraded frame, while peak signal-to-noise ratio remained almost the same. The subjective quality of the decoded HDR images was improved by reducing color artifacts.