Author: Jianfei Cai

Publisher:

Published: 2002

Total Pages: 356

ISBN-13:

Visual communications plays an increasingly important role in information infrastructures. Despite a large number of standards and commercial products for applications of visual communications, providing high quality visual information over resource-limited wireless networks still remains a major challenge. This is because of the huge data size of visual information and the complicated characteristics of wireless channels. Due to the limited bandwidth of wireless channels, it is desired that visual information is compressed by highly efficient compression schemes while, due to the time-varying error prone environments of wireless channels, controlled redundancy is necessary to be added in the compressed bitstreams in order to ensure reliable transmissions. Therefore, there is a tradeoff between efficiency and reliability. The objective of this research is to find the optimal tradeoff between efficiency and reliability for image and video transmission over wireless channels. In this dissertation, several image and video transmission systems are developed based on robust error control and optimal bit allocation. For image transmission, two systems are developed, namely, TCQ-based error-resilient coding and robust joint source-channel coding (RJSCC). In the TCQ-based error-resilient coding, DCT-transformed blocks are classified and bits are optimally allocated among different classes and different coefficients according to their importance and sensitivity to the channel noise. In RJSCC, in addition to the bit allocation in source coding, we also consider the bit allocation between source coding and channel coding. We develop an end-to-end rate-distortion (R-D) function, which incorporates both transition probability and bit error rate of a bursty channel model. Based on the R-D function, bits can be allocated in such a way that we are able to achieve an optimum tradeoff between source coding accuracy and channel error protection under a fixed bandwidth limitation. As a result, RJSCC is among the best wireless image transmission systems reported in the literature. The study for wireless image transmission leads to our research in wireless video transmission. We propose a novel pre-interleaving scheme for video streaming over bursty loss channels. The pre-interleaving scheme is able to generate the desired error patterns for video source decoding while still preserving the features of the conventional combination of channel decoding and interleaving. The pre-interleaving scheme can be applied to any standard video codecs and to both wireless channels and packet-loss channels. Finally, we show the extensive study on the rate controls in wireless video streaming systems. The study includes three aspects: the rate control for off line video coding, the rate control for rate-reduction transcoding and the rate control for adaptive wireless video streaming. We propose a rate control scheme which is able to optimally allocate bits among video frames. We demonstrate that the proposed rate control scheme can provide better quality than that of the state-of-the-art H.263 standard.