Because the bit rate can be adjusted depending on the network traffic situation, the variable bit rate is more suitable than a fixed rate for transmitting images on the network. IN this paper, a new variable rate hierarchical classified vector quantization (VHCVQ) scheme is proposed. This technique is suitable for progressive trans- mission. In our two-stage VHCVQ scheme, we use the differences between the first-stage input vectors and the first-stage quantized vectors, called residual vectors, to code the image in the second stage. Usually the values between thee differences are small and each is close to one another. Using the difference to code the image may reduce the codebook size and the bit rate as well. In our simu- lation, using these differences reduced the bit rate by abut 0.075 bpp.
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