Multiple description coding using pairwise correlating transforms
The objective of multiple description coding (MDC) is to encode a source into multiple bitstreams supporting multiple quality levels of decoding. In this paper, we only consider the two-description case, where the requirement is that a high-quality reconstruction should be decodable from the two bitstreams together, while lower, but still acceptable, quality reconstructions should be decodable from either of the two individual bitstreams. This paper describes techniques for meeting MDC objectives in the framework of standard transform-based image coding through the design of pairwise correlating transforms. The correlation introduced by the transform helps to reduce the distortion when only a single description is received, but it also increases the bit rate beyond that prescribed by the rate-distortion function of the source. We analyze the relation between the redundancy (i.e., the extra bit rate) and the single description distortion using this transform-based framework. We also describe an image coder that incorporates the pairwise transform and show its redundancy-rate-distortion performance for real images.