RATE-DISTORTION PERFORMANCE IN CODING BAND-LIMITED SOURCES BY SAMPLING AND DITHERED QUANTIZATION

The rate distortion characteristics of a scheme for encoding continuou s-time band limited stationary sources, with a prescribed band, is con sidered. In this coding procedure the input is sampled at Nyquist's ra te or faster, the samples undergo. dithered uniform or lattice quantiz ation, using subtractive dither, and the quantizer output is entropy-c oded. The rate-distortion performance, and the tradeoff between the sa mpling rate and the quantization accuracy is investigated, utilizing t he observation that the coding scheme is equivalent to an additive noi se channel. It is shown that the mean-square error of the scheme is fi xed as long as the product of the sampling period and the quantizer se cond moment is kept constant, while for a fixed distortion the coding rate generally increases when the sampling rate exceeds the Nyquist ra te. Finally, as the lattice quantizer dimension becomes large, the equ ivalent additive noise channel of the scheme tends to be white Gaussia n, and both the rate and the distortion performance become invariant t o the sampling rate.