Quantificacao vectorial aplicada a video digital de baixa cadencia.

Abstract

This work describes a video coder based on a hybrid DPCM-Vector Quantization algorithm which is suited for bitrates ranging from 8 to 16 kbit/s. The proposed approach involves segmenting difference images into variable sized and variable shaped blocks and performing segmentation and motion compensation simultaneously. The purpose of obtaining motion vectors for variable sized and variable shaped blocks is to improve the quality of motion estimation, particularly in those areas where the edges of moving objects are situated. For the larger blocks, decimation takes place in order to simplify vector quantization. For very active blocks, which are always of small dimension, a specific vector quantizer has been developed, the Fuzzy Classified Vector Quantizer (FCVQ). FCVQ is based on a fuzzy classifier and reduces the complexity of code book search while improving the subjective quality of the coded blocks. The coding algorithm described displays a good performance in the compression of test sequences at the rates of 8 and 16 kbit/s; the signal to noise ratios obtained are excellent in both cases. The complexity of the coder implementation is comparable to that of conventional hybrid coders, while the decoder is much simpler in this proposal.Available from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1249-074 Lisboa, Portugal / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga