Down-conversion of TV signal to 1MHz videophone signal

Abstract

We want to develop a system that converts the regular television signal to 1 MHz video signal, which is known to be adequate for a face-to-face visual communication. The new video signal has 262.5 lines per picture frame, and its resolution is half of the original TV signal in both vertical and horizontal directions. The features of this system are firstly that only two analog shift registers carry out the conversion. Secondly, the conversion ratio is a simple integer. Hence, the adaptation between the TV system and the new scanning system is simple, and the interpolation coefficients are constant during a whole field period. The conversion system is implemented, and experimental results are discussed in detail.