Hybrid coding process by transformation for the transmission of picture signals

Claim 1

Process for hybrid coding by transformation for reducing the data volume necessary for representing pictures, in which the pictures are defined by a sequence of frames, each frame containing a set of matrix-organized blocks, each block containing a set of matrix-organized digital data representing part of the picture, characterized in that the process involves transforming each digital data block into a block transformed coefficients representing said block in the frequency range, quantifying the transformed coefficients of each block to obtain quantified transformed coefficients, each having a value taken from a limited set of predetermined values, scanning each block of quantified transformed coefficients to produce a sequence of quantified transformed coefficients and evaluating the data volume necessary for coding said sequence by statistical coding, calculating a block of difference coefficients by a difference between a block of quantified transformed coefficients and the corresponding block of the preceding frame, scanning the block of difference coefficients for producing a sequence of difference coefficients and evaluating the data volume necessary for coding said sequence of difference coefficients by said statistical coding, comparing of the data volumes necessary for coding a block and deciding on the coding mode as a function of said data volumes and the maximum volume authorised by the rate on the transmission lines and statistical coding of the block, in accordance with the decided mode, by said statistical code.