Weight-based R-λ rate control for perceptual HEVC coding on conversational videos

• Our work is based on the latest R-λ rate control scheme.
• Besides face regions, the regions inside the faces are treated with unequal importance.
• We conduct eye tracking experiments to learn the importance weights of different regions from training videos.
• The bits are perceptually allocated according to the term of bit per weight (bpw).
• We introduce the objective and subjective quality assessments together to make experimental results more reasonable.

This paper proposes a novel weight-based R-λ scheme for rate control in HEVC, to improve the perceived visual quality of conversational videos. For rate control in HEVC, the conventional R-λ scheme is based on bit per pixel (bpp) to allocate bits. However, bpp does not reflect the visual importance variation of pixels. Therefore, we propose a novel weight-based R-λ scheme to consider this visual importance for rate control in HEVC. We first conducted an eye-tracking experiment on training videos to figure out different importance of background, face, and facial features, thus generating weight maps of encoding videos. Upon the weight maps, our scheme is capable of allocating more bits to the face (especially facial features), using a new term bit per weight. Consequently, the visual quality of face and facial features can be improved such that perceptual video coding is achieved for HEVC, as verified by our experimental results.