Image coding using a classified DCT/VQ based on two-channel conjugate vector quantization

Abstract

An adaptive image coding technique-two-channel conjugate classified discrete cosine transform/vector quantization (TCCCDCT/VQ)-is proposed to efficiently exploit correlation in large image blocks by taking advantage of the discrete cosine transform and vector quantization. In the transform domain, a classified discrete cosine transform/vector quantization (CDCT/VQ) scheme is proposed and TCCCDCT/VQ is developed based on the CDCT/VQ scheme. These two techniques were applied to encode test images at about 0.51 b/pixel and 0.73 b/pixel. The performances of both techniques over a noisy channel have been also tested in the transform domain. The performances of both adaptive VQ techniques are perceptually very similar for the noise-free channel case. However, when channel error is injected for the same bit rate, the TCCCDCT/VQ results in less visible distortion than the CDCT/VQ, which is based on ordinary VQ. >