Adaptive encoding system of moving picture frame

摘要

A frame of a picture is first divided into a plurality of blocks, each of which is subject to orthogonal transform to provide picture pels in the form of matrixes, which have a coefficient of DC component, and coefficients of AC components. AC components in said matrix are subject to a pre-quantization for each frame evaluate total code length (L') in the encoding. A number (N') of significant coefficients which are not zero in each block or each macro block is counted. A step size in quantization is determined according to said values L' and N' and coefficient position. The quantized block is subject to effective baseband selection for further reduction of information amount so that a zero coefficient after EOB in the block along the selected scanning line defined by the selected effective baseband is eliminated. If the information amount after the eliminating of zero coefficients still exceeds a preferable bit rate, a high order coefficient in the matrix is further eliminated, so that a picture frame is encoded into a predetermined fixed bit rate.