METHOD FOR IMAGE COMPRESSION CODING IN AN IMAGE TRANSMISSION SYSTEM

An image compression coding method of a digital image transmission system utilizes a known vector quantization process. In the method, at the transmitting end the block (13) to be coded is divided into quadrants (14); each quadrant is subjected to vector quantization in a sub-coder (19), utilizing a classified codebook (20), the class thereof being defined on the basis of the vector index (1) of the original block and the quadrant label (A', B', C', D') of the sub-block; the vector index (j) of the sub-block with respect to this classified codebook (20) is transmitted to the receiving end; at the receiving end, there is utilized a classified codebook which is chosen on the basis of the transmitted vector index (i) of the original block and the quadrant label (A', B', C', D') of the sub-block; at the receiving end, the chosen classified codebook, which is identical with the classified codebook at the transmitting end, the code vector index of the transmitted sub-block, so that a reconstruction is obtained for the sub-block. When designing each classified codebook, the utilized image set which receives a class index corresponding to the particular class of the codebook, when the above-described method is applied to the training image set itself.