Rate control for HEVC intra-coding with a CTU-dependent distortion model

Abstract

Rate control is used to regulate the coded bits for valid video storage or transmissions. For the novel high-efficiency video coding (HEVC) encoder, a new the R–λ-based rate control model is incorporated to further make a trade-off between video quality and bandwidth utilization. However, the intra-coding distortion, which is drifted from the coding tree units (CTUs) to subsequent CTUs and thus affects the performance of rate control, is not fully considered in R–λ model. To address this issue, an intra-CTU rate control scheme is developed in this paper for further improving the visual quality. First the 35 intra-modes are segmented into 5 categories, and then the distortion drift of each category is studied in terms of intra-prediction principle. Afterwards the SAD-based distortion formulation is derived and utilized into R–λ model. Finally, the modified R–λ model is added in HEVC rate control for quantization calculation. The experimental results show that the proposed method significantly increases the encoding performance while well accepting computational complexity.

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