In this paper, a new coding scheme is proposed for application in interactive image communication over low-bandwidth channels. The scheme combines progressive image transmission with transform codlag. The novel aspect of the scheme is to recode, or requantize, the residual errors caused by the quantizations of the transformed coefficients on a stage-by-stage basis. It is shown that theoretically the scheme is lossless. A computer simulation of progressive transmission is presented, where on the average 0.1 bits/pixel are transmitted per stage. It is shown that the first stage image already provides a useful approximation and that by the third stage the approximation is quite reasonable.
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