The objective of multiple description coding (MDC) is to encode a source in
to multiple bitstreams supporting multiple quality levels of decoding. In t
his paper, we only consider the two-description case, where the requirement
is that a high-quality reconstruction should be decodable from the two bit
streams together, while lower, but still acceptable, quality reconstruction
s should be decodable from either of the two individual bitstreams. This pa
per describes techniques for meeting MDC objectives in the framework of sta
ndard transform-based image coding through the design of pairwise correlati
ng transforms. The correlation introduced by the transform helps to reduce
the distortion when only a single description is received, but it also incr
eases the bit rate beyond that prescribed by the rate-distortion function o
f the source. We analyze the relation between the redundancy (i.e., the ext
ra bit rate) and the single description distortion using this transform-bas
ed framework. We also describe an image coder that incorporates the pairwis
e transform and show its redundancy-rate distortion performance for real im
ages.