Structure and coding characteristics of adaptive gain/shape vector quantizer for low bit‐rate motion picture coding

One of the highly efficient coding methods for motion pictures is to combine the motion‐compensation interframe prediction and the vector quantization. Among such methods, the normalized vector quantization is to represent the motion‐compensated interframe difference signal, to separate the average value and to normalize the amplitude. It has a merit in that the general codebook can be utilized. This paper shows that the approximation error does not always decrease in those conventional method, even if the vector quantization procedure is iterated. As a solution to this problem, it is shown to be sufficient to employ the vector quantizer with a gain/shape structure. An elaboration is made to the codebook size to handle the input vector amplitude. Then the motion picture coding algorithm is constructed using the proposed adaptive gain/shape vector quantizer. By optimizing the coding parameters aiming at the low bit‐rate coded transmission, practical temporal and spatial resolutions are obtained for TV confeferences and TV phones.