Dynamic address-vector quantisation of RGB colour images

Address-vector quantisation (A-VQ) is a new class of vector quantisation (VQ) technique that exploits the statistical redundancy between the neighbouring blocks, to reduce the bit rate to a much smaller value than a standard vector quantiser can achieve. The underlying idea of A-VQ is that the interblock correlation is exploited by encoding a group of neighbouring VQ addresses together. The VQ addresses are obtained by vector quantisation of each individual block. An address codebook, which consists of a set of address codevectors, is then used to encode the neighbouring VQ addresses together; this process introduces no extra coding error since it is a vector dimensionality reduction process. The A-VQ coding technique is extended to encode RGB colour images by utilising the interblock as well as the intercolour correlation. Also, a modified A-VQ technique named dynamic address-vector quantisation (dynamic A-VQ) is introduced for the encoding of colour images. In the dynamic A-VQ, the encoder dynamically tracks the local characteristics of the input image. Experimental results show reconstructed images at bit rates of 0.5-0.6 bits per pixel. The resulting bit rate is less than a standard VQ coding technique by a factor of at least two, with the same quality of reconstructed images.<>