Abstract: Hybrid coding process by transformation for the transmission of images or pictures. The pictures are defined by a sequence of frames, each frame containing a set of matrix-organized blocks, each block containing a set of digital data organized in matrix form and representing part of the picture. The process successively comprises the stages of transforming each block in the frequency range, quantifying the transformed coefficients of each block, evaluating the data volume necessary for coding said transformed block by an intraframe mode statistical coding, evaluation of the data volume necessary for coding said transformed block by an interframe mode statistical coding, comparison of said data volumes and decision concerning the coding mode as a function of said date volumes and the maximum volume authorized by the flow rate on the transmission line and statistical coding of said block by a variable length code.