The Coding Methods And Rate Control Of Compressed Video Communication

The first IPTV license has been granted by China government, it indicates the application of digital TV and stream media opens the way to great development, in addition the coming 3G period, the multimedia communication becomes people's hottest expect. Because of the tremendous market, the researchers in companies try their best on the communication of multimedia information on Internet and wireless condition, especially the compressed video communication, which is the most important kernel part of multimedia communication. The thesis focuses on several key techniques such as video communication coding methods on low-rate and rate control algorithms on low-delay condition, and brings forward two improvements.On aspect of video coding with low-rate, the thesis improves the chessboard-sample which is opposite to the traditional sample which is adopted by the spatial scalability coding. The specialty of huge data stream limits the application of compressed digital video on Internet and wireless, on the other hand the Internet and wireless channel are short of the guarantee of QoS, and the bandwidth isfluctuating over a broad range, so the communication of compressed video becomes a real puzzle. A lot of coding methods have been put forward to solve this problem. Traditional digital video encoder is based on memory, it compressed the video data into several stream on several fixation rate. But because of the heterogeneity of Internet, traditional encoder does not work well. Recently, lots of coding techniques such as FGS are put forward and work well on Internet because of their character of fine granularity scalability. The thesis analyses several video coding methods which are based on communication, and puts forward a chessboard sampled fine granularity scalable coding.To solve the problem of skip frame on the low-delay condition of a rate control model, the thesis reworks the scheme, and performs much better than the former. In real time, two-way video communications, the end-to-end delay must be controlled rigorously, how to minimize the delay for transmitting video data is very important. On the condition of controlling the delay produced by bits in the encoder buffer rigorously, we must avoid the frame-skip to the best of our abilities, because the frame-skip will produce the undesirable motion discontinuity, so a good rate control algorithm is very important to avoid buffer underflow. The thesis analyses the scheme of normal rate control model and introduces several famous rate control algorithms, including TM5 and SRC and fluid flow traffic model, which used by the newest compression standard H.264. After analysis the problem on fluid control model, an improved encoder scheme is brought forward; it solves the bad skip-frame performance of H.264 rate control and enhances the PSNR of some sequences.