Research Of Rate Control Scheme Based On H.264/AVC

H.264/AVC is the latest international video coding standard developed by ITU-T and ISO/IEC. H.264 has enormous advantages: high compress efficiency, better image quality and excellent network performance, which caters to various applications, attracting much attention from research institution and multimedia industry. Rate control is an important technology in video coding, which should be researched further. It aims to achieve high video quality by allocating bit-rate fairly.This paper analyses the practical application of rate control firstly, and proposes some efficient methods to improve the video quality, especially the subjective quality. Besides, we research the fast video bitstream generation technology and incorporate it into H.264. The main contributions are:MB type Judgment algorithmSince the active regions are more sensitive to HVS, it is reasonable to give more importance to the regions. This paper uses the concept"direct MAD", defines five MB types and proposes judge arithmetic of MB types, which could accurately extract the ROI regions in advance.Adaptive MAD prediction modelLinear prediction model performs poorly when scene changes happen; this paper presents an adaptive MAD prediction model based on direct MAD, which could predict the MAD value of the current frame or MB, especially the video with scene change and high motion.Optimal bit allocation schemeJVT-G012 rate control scheme allocates the bits to the frames averagely, which always impair the reconstructed quality of those frames with high complexity. Our scheme estimates their coding complexity and allocates bits adaptively, which prevent the video quality shaking acutely.Initial QP determination modelH.264 selects the initial QP among 4 predefined QPs. Based on extensive experiments, we develop an initial QP determination model related to bit-rate, frame rate, frame difference complexity. An appropriate initial QP can be selected by this model to improve the visual quality.