| In today's world, demands of digital multimedia services are growing tremendously, together with the development of new communication technologies and investigation of new transmission media. Two common problems encountered in multimedia services are unreliable transmission channels and limited resources. This dissertation investigates advanced source coding and error control techniques, and is dedicated to designing joint source-channel coding schemes for robust image/video transmission. Error resilience properties of JPEG2000 codestreams are investigated first, and an LDPC-based joint iterative decoding scheme is proposed. Next, a progressive decoding method is presented for still and motion image transmission. The underlying channel codes are created using a Plotkin construction and offer the novel ability of using one long channel codeword to protect an entire image, yet still allowing progressive decoding. Progressive quality improvements occur in two ways: the first is the usual progressive refinement, where image quality is improved as more data are received; the second is that residual error rates of earlier received data are reduced as more data are received. Finally, multichannel systems are studied and an optimal rate allocation algorithm is proposed for parallel transmission of scalable images in 11 multichannel systems. The proposed algorithm selects a subchannel as well as a channel code rate for each packet, based on the signal-to-noise ratios (SNR) of the subchannels. The resulting scheme provides unequal error protection of source bits and significant gains are obtained over equal error protection (EEP) schemes. An application of the proposed algorithm to JPEG2000 transmission shows the advantages of exploiting differences in SNRs between subchannels. Multiplexing of multiple sources is also considered, and additional gains are achieved by exploiting information diversity among the sources. |
