Given an achievable quadruple (R/sub 1/, R/sub 2/, D/sub 1/, D/sub 2/) for progressive transmission, the rate loss at step i is defined as L/sub i/=R/sub i/-R(D/sub i/). Let D/sub 1/ and D/sub 2/ be any two desired distortion levels (D/sub 2/<D/sub 1/). It is shown that for an i.i.d. source and for squared error, an achievable quadruple can be found for which L/sub i//spl les/1/2 bit/sample (a similar statement is proved for situations in which more than two steps are required). Moreover, an achievable quadruple can be found with L/sub 2/ arbitrarily small and L/sub 1//spl les/1/2 bit/sample if D/sub 2/ is small enough. If an information-efficient description at D/sub 1/ is required (i.e., L/sub 1/=0), then there exists an achievable quadruple with L/sub 2//spl les/1 bit/sample. The results are independent of both the source and the particular D/sub 1/, D/sub 2/ requirements and extend to any difference distortion measure. The techniques employed parallel Zamir's bounding of the rate loss in the Wyner-Ziv problem. Bounds for the rate loss in other multiterminal source coding problems also are given.
['Luis A. Lastras', 'Toby Berger']
All sources are nearly successively refinable