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Research And Improvement On Rate Distortion Optimization And Rate Control Algorithm For H.264

Posted on:2009-02-20Degree:MasterType:Thesis
Country:ChinaCandidate:Z G CuiFull Text:PDF
GTID:2178360272977165Subject:Computer application technology
Abstract/Summary:PDF Full Text Request
The main object of video encoding is to find the optimal equilibrium among the coding efficiency, reconstructed video qulity and encoding complexity. H.264 video coding standard only regulates the encoding syntax and the decoding method of video bitstream, it does not define the encoder's structure definitely, so there is a wide research field in the video encoder. In order to obtain better video image quality subject to a constraint channel bandwidth, computation complexity, delay-time and buffer consideration, H.264/AVC must take appropriate measures to control the encoder parameter, and regulate the encoder's output bit rate within a proper range.This paper analyses the rate distortion optimization scheme which has high encoding computation complexity and the foundation of rate control theory in the latest video coding standard, and probes into the main reasons of bit rate fluctuation, then summarize the latest research work about rate distortion and rate control algorithm. Based on the deep analysis of these research results, first we propose an improved quadratic rate distortion model which depicts the rate distortion characteristic of the signal source accurately. Then we introduce the notion of frame content encoding complexity to measure its spatial complexity, and acquire the current frame's complexity ratio among the whole GOP considering both frame temporal complexity and spatial complexity together. So we can allocate the frame target bit rate on the basis of its frame complexity ratio, and propose an improved frame layer rate control algorithm, we also put forward a new frame skipping scheme based on improved frame complexity and buffer fullness. The new proposed rate control algorithm and frame skipping scheme overcome the disadvantages in the rate control precision and encoding performance of former algorithm.Our new proposed algorithm was implemented on JM10.2 reference software platform, and the experimental results show that compared to the former rate control algorithm new scheme can accurately predict frame encoding complexity among the whole GOP, and reasonably allocate the frame layer target bit rate. The results also show the generated actual bit rate is more close to the predefined target bit rate, and acquire better reconstructed video image quality, achieve an average PSNR gain of about 0.28dB. Meanwhile effectively control the output bit rate fluctuation and, alleviate buffer and frame PSNR variation.
Keywords/Search Tags:H.264, Rate Distortion Optimization, Rate Control, Complexity, Linear Model, Quadratic Rate-Distortion Model
PDF Full Text Request
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