Design and performance of residual quantizers

This paper shows that tree search encoders are ineffective when used to determine the closest code vector in residual quantizer (RQ) alphabets. In particular, the equivalent cell boundaries are poorly chosen and the labelling of equivalent code vectors produced by the decoder and by a tree-structured encoder are inconsistent. This problem does not arise when two-level RQ alphabets are used in trellis coded vector quantizers. Trellis-coded RQs are designed for the memoryless Gaussian, Laplacian, and Gauss-Markov sources at a rate of R=1 bit per sample with encouraging results; a SQNR of 5.92 dB has been achieved on the Gaussian source