Design Of Low Bit Rate Software Codec Based On H.264 For Video Conferencing

In recent years, with the rapid construction of communication network infrastruc -ture, video conferencing system has developed rapidly because of which can provide various kinds of information (such as providing video and audio for the participants at different places), cost saving, and improve work efficiency. Because of more bit-stream saving, inherent anti-packet loss, anti-BER capacity, and network adaptability, which enables H.264 to be more suitable for the transmission of IP, H.264 is expected to become the preferred standard in the video conferencing system.This paper initially on the H.264 standard, summary the main features and highlights of H.264 . Then, I designed and realized the "PC-based software Low Bit Rate Codec" based on H.264. In this process, research was focused on the intra prediction mode selection algorithm, and design of coding table in entropy coding.Intra prediction can reduce the redundancy of frequency domain and space domain and obtain higher compression efficiency, which is the most important and the longest time-consuming part of coding process .This paper introduces some prediction algorithms, and improves the prediction algorithm based on the features of PC-based video conferencing system.In CAVLC, H.264 uses a number of VLC code table, and different code table corresponding to different probability model .When the motion compensation and anti-4×4 transform have got the appropriate optimization, the time occupied by code table lookup appears not to be ignored. In this paper, by improving code table structure and using the binary tree search algorithm, further reduces the search time and improves the encoding efficiency.As part of work, put the encoder for Desktop Video Conference System, under the conditions of 256Kbps ADSL lines and four part meeting, get satisfied results.