| Multiple description coding (MDC) has been widely employed for multimedia delivery over unreliable communication networks. In this dissertation, we present MD-SPIHT, a simple and efficient scheme for using the Set Partitioning in Hierarchical Trees (SPIHT) image coding algorithm in an MDC framework. To combat packet loss, controlled amounts of redundancy are added to the original data during the compression process. Unequal loss protection is implemented by varying the amount of redundancy with the importance of data. The redundancy allocation is optimized for expected channel conditions. In addition, we present a method for protecting a region of interest (ROI) in an image sent across lossy communication networks. To increase the probability that the ROI is received with high quality, we add more redundancy to the ROI than to other parts of the image. In both cases, redundancy is added using the proposed Overcomplete Wavelet Representations based on the shift variance of the Discrete Wavelet Transform. The MD-SPIHT algorithm achieves graceful degradation of image quality in the presence of increasing description loss; high image quality is obtained when over half of the descriptions are lost. |
