Adaptive PQ: Adaptive perceptual quantizer for HEVC main 10 profile-based HDR video coding

Although high dynamic range (HDR) videos are a very fascinating media to represent real-world scenes, they need a huge amount of memory to store and transmit due to the high bit-depth. Thus, it is a major challenge for HDR video coding to efficiently compress them without sacrificing perceptual quality. Perceptual Quantizer (PQ) provides a solution to this problem, which is used as Anchor based on the HEVC Main 10 coding. However, PQ is not adaptive to HDR contents because of using a fixed mapping function from floating-point luminance to 10bit quantized luma. In this paper, we propose an adaptive transfer function based on PQ for HEVC Main 10 Profile-based HDR video coding, called adaptive PQ. Different from PQ, the proposed transfer function adaptively maps luminance to luma according to HDR contents. Thus, adaptive PQ is able to efficiently utilize the quantization interval. Moreover, adaptive PQ has better perceptual uniformity in the luminance range than PQ because of adaptively using the luminance range. Experimental results demonstrate that adaptive PQ achieves a significant performance improvement in HDR video coding over PQ in terms of visual quality and bit-rate.