An experimental study of the possible bandwidth compression of visual image signals

It is a fact that the eyes are used far less often than the ears in telecommunication systems. The obvious reason for this is that an adequate signal can usually be obtained in aural communication channels with relatively little data, but in contrast the eyes are considered to require a very great deal of data in order to receive an adequate signal. There may be very many industrial applications of a visual communication system if only the data could be greatly reduced for such channels, so that adequate pictures of various kinds might be transmitted and received in relatively narrow bandwidths. Again, the criteria by which we judge these two kinds of channel are very different; we regularly make use of aural channels which are highly distorted and noisy, whereas we frequently judge vision channels, facsimile, etc., at very high levels of quality, presumably because we are conditioned by the needs of domestic television. This paper, together with an accompanying paper by Kubba, describes experiments upon the possibilities of automatic data reduction or bandwidth compression of visual channels, for both black and white diagrams and for half-tone pictures, using electronic equipment and accepting realistic noise levels.