Error Control In Low Bit Rate Video Communications

This thesis presents the results of an investigataion into the error control in low bit rate video communications. Due to the limitation of bandwidth and the effect of channel noise, data error or loss is almost inevitable. ARQ (Auto Repeat on reQuest) is used in data communication to garauntee error-free transmission, but it is not suitable for video communication because video communication has stringent delay requirement and limitless retransmission is not allowed. However, video communication can tolerate some kind of data error or loss and different parts of video bitstream have unequal error sensitivities. So we need new error control methods designed especially for video communicaton. Error control can be done in any step such as prediction, transform, quantization, VLC, bitstream syntax structure, channel coding, decoding and etc. This thesis reviews the research on error control in detail and proposes a novel error control method for Internet video communication. At the same time, this thesis analyzes the optimal resourse allocation problem in video coding and reviews recent advances in rate-distortorn optimized video coding. The main points are as follows:First, current video applications are classified by their communication modes, the network parameters are discussed in detail which affect the quality of video communications and the performance of typical networks are described.Second, the international standards for video coding are briefly described including H.26x and MPEG. Particularly, the encoding and decoding algorithm and bitstream syntax of H.263 are introduced in detail.Third, the state of arts of error control in video communications is investigated, including transport-level error control, error resilient coding, error concealment, and encoder and decoder interactive error control. The core idea and performance of every technique are discussed.Forth, a novel error control method for Internet video communication is proposed, named adaptive intra update. This method can effectively enhance packet loss resilience and improve the quality of decoded video.Last, the basic rate-distortion theory and two optimization tools are introduced, and their applications in mode selection, joint source-channel coding and rate control are discussed in detail.