HIGHLY EFFICIENT RUN-LENGTH CODING SCHEME FOR FACSIMILE TRANSMISSION.

Run-length coding is widely used in digital facsimile transmission as an efficient means of bandwidth compression. This paper examines a variable-length block-coding scheme which is efficient and easy to implement and, as a result, proposes a new coding scheme of higher efficiency. The proposed coding scheme is based upon the conventional variable-length block-coding method, but the efficiency is raised by utilizing all possible states, using the Golomb coding method with the multimode technique, and choosing the block length that matches the run-length distribution. Applying this method to an actual facsimile signal, an approximate improvement of 20% in compression rate is obtained over present coding methods and, with simultaneous application of two-dimensional prediction, a 40% improvement can be achieved. The construction of the encoder is also examined and it is concluded that the only change required will be to put the conventional encoders into serial connection and that a complex system is not necessary.