Conditional entropy-constrained vector quantization of displaced frame difference subband signals

We study the performance of conditional entropy-constrained vector quantizers when used to quantize subbands of the displaced frame differences derived from video sequences. Chou and Lookabaugh (1990) originally suggested a locally optimal design of this new kind of vector quantizer which can be accomplished through a generalization of the well known entropy-constrained vector quantizer (ECVQ) algorithm. This generalization of the ECVQ algorithm to a conditional entropy-constrained is called CECVQ, i.e., conditional ECVQ. The non-memoryless quantization performed by the conditional entropy-constrained VQ is based on the current vector to be encoded and the previous encoded vector. A new algorithm for conditional entropy-constrained vector quantizer design is derived and it is based on the pairwise nearest neighbour technique presented by Equitz (1989).