Research And Implementation Of Video Encoder For Video Conference Applications Based On The H.264 Standard

Video conference system, a synthetic application of multimedia communication technology, is developing dramatically and will also have wider market demand in the near future. As video coding is the core and critical technology that affects the whole performance of video conference system, researching and software implementation of the real-time video encoder based on the H. 264 standard and reference JM (Joint Model) source code will be provided in this thesis.The Motion Estimation (ME) technology with the highest computing complexity and the most obvious impact on the encoding efficiency is researched firstly. By analyzing the recommended ME algorithm of the H. 264 standard, comparing the performances of a large number of typically fast ME algorithms and merging the relevant theoretical assumptions, the executive speed of the recommended ME algorithm of the standard is greatly improved. More over, the static background of the video contents can be roughly separated from the foreground by adopting the Video Objects Segmentation technology, which also furthers the reduction of the running time of the ME module.Besides of the considerable improvement of ME module, three more time-consuming modules such as, the SAD calculation module, the transform coding module and the 1/4 pixel interpolation module, are selected based on the quantitative analyze of the statistic data from Intel VTune Analyzer and optimized by using the SSE2 instructions to rewrite the source code of them. The post-optimized coding speed of the encoder can basically satisfy the real-time requirement of video conference applications.At last, an adaptive algorithm for computing complexity adjustment is proposed to overcome the deficiency, using the same setting of coding parameters in different frame rate requirements and in different system, in most encoder products. Based on the study of the Rate-Distortion Optimization (RDO) and Rate Control (RC) technology of the H. 264 standard, researching the precise proportional relations between the important coding parameters and the computing complexity and the characteristics of relativity among the coding parameters, the full solution of the adaptive algorithm is designed and realized, which can adaptively adjust the coding parameters to guarantee the frame rate requirement set by the video conference system without visible quality deterioration.The video encoder researched and implemented in this thesis is proved to be efficient and effective by testing data in different stages in the developing process. It can well satisfy the real-time requirement of video conference systems with drastic improvement of video quality comparing to the MPEG-4 encoder (using Simple Profile settings) under the same bandwidth environment. It is also equipped with the adaptive adjustment function of computing complexity and has great practical value for the developing video conference applications.