A novel weight-based URQ scheme for perceptual video coding of conversational video in HEVC

In this paper, we propose a novel weight-based unified rate-quantization (URQ) scheme for rate control in state-of-the-art HEVC standard, to improve its perceived visual quality for conversational videos. In conventional rate control of HEVC, a pixel-wise URQ scheme is proposed by introducing the concept of bit per pixel (bpp). This scheme is able to assign different amounts of bits to the blocks with various sizes, thus well suitable for flexible picture partition of HEVC. However, bpp does not reflect the visual importance of each pixel. Therefore, we propose a novel weight-based URQ scheme to take into account the visual importance for rate control in HEVC. In combination with the weight map acquired from a novel hierarchical perceptual model of face, such a scheme is capable of allocating more bits to the face and much more bits to the facial features, by using bit per weight (bpw) instead of bpp. As a result, the visual quality of face, especially facial features, can be improved such that perceptual video coding is achieved for HEVC. Finally, the experimental results validate such improvement.