OPTIMAL BLOCK COSINE TRANSFORM IMAGE CODING FOR NOISY CHANNELS.

The two-dimensional block transform coding scheme based on the discrete cosine transform has been studied extensively for image coding applications. While this scheme has proven to be efficient in the absence of channel errors, its performance degrades rapidly over noisy channels. In this paper we present a method for the joint source-channel coding optimization of a scheme based on the 2-D block cosine transform when the output of the encoder is to be transmitted via a memoryless binary symmetric channel. Our approach involves an iterative algorithm for the design of the quantizers (in the presence of channel errors) used for encoding the transform coefficients. It is shown that substantial performance improvements can be obtained by using this scheme. Furthermore, theoretically predicted results for an assumed 2-D image model are provided.