Low-Resolution TV: An Experimental Digital System for Evaluating Bandwidth Reduction Techniques

It is well known that redundancy is inherent in television signals. This fact, invites the use of many coding techniques for the removal of redundancy in order to achieve bandwidth compression for increased efficiency of transmission. In the search for these techniques the human receiver must not be ignored since man is a constituent part of visual communication systems. For this reason, it is imperative that promising methods of coding be demonstrated in real time before final conclusions are drawn. This permits careful judgment to be made of picture impairment introduced by the coding scheme or transmission errors. Subjective testing may also be performed to determine and evaluate 167 168 T H E B E L L SYSTEM T E C H N I C A L J O U R N A L , J A N U A R Y 1967 the factors affecting the acceptability of various bandwidth compression techniques. In the process of subjective testing, new knowledge of the perceptual properties of the human receiver may be gained which will be of value in the design of a communication system matched to the human channel. Many effective techniques of removing the redundancy inherent in television signals require digitalization and storage of the picture signal. To explore this approach, an experimental low-resolution television system, which employs both digital and storage techniques, has been constructed to demonstrate various bandwidth compression techniques in real time. The description of this facility is presented in its use to show frame repetition and uniform density picture replenishment systems.