Efficient classification and codebook design for CVQ

An efficient block classification and a new codebook design algorithms for classified vector quantisation (CVQ) are presented. The classification method is particularly simple and suited for hardware or software implementation. For each nonshade block, a local threshold is computed and used to binarise the block. The binary block is then compared with a predefined set of binary edge templates to decide its nature. On the other hand, the codebook design algorithm generates the codevectors in a short time, while providing considerable computational savings. It only uses the AC energy of the training set vectors to produce the codebook and the AC energy of an input block for its encoding. Subsequently, the actual codebook does not have to be present at the transmitter end. Good quality images, as measured by subjective and objective measures, are produced at bit rates in the range 0.64-0.87 bits per pixel (bpp)