a digital signal coding / decoding circuit for coding / decoding digital scanning line signals by means of an mr coding / decoding algorithm has an mr coding / decoding circuit , a line buffer for temporarily storing information about a reference line which has been already coded or decoded , and a preparation circuit for producing compression codes from the reference line and for later expanding the compression codes into the reference line . the line buffer can be compact because it temporarily stores the compression codes rather than the reference line itself .