Semicompatible High Definition Television Using Field Differential Signals

Abstract

In a previous paper we proposed transmitting high definition television (HDTV) by means of semicompatible HDTV (SC-HDTV) signals which utilized differences between scan lines. The line-differential SC-HDTV waveform had the virtue of being easily convertible to an NTSC compatible color picture. The line-differential SC-HDTV signal required three present-day CATV channels for local distribution. With the advent of inexpensive electronics and memory, the possibility arises of incorporating field memories into HDTV receivers. Thus, in this paper we propose a field-differential SC-HDTV signal, which, like its predecessor, is easily converted to NTSC. However, the field-differential SC-HDTV waveform may be transmitted using only two present-day CATV channels. In order to produce an HDTV picture from the field-differential SCHDTV signal, the receiver requires comb filters, 2:1 time compressors and a field memory of about 245 kilopixels. These are implementable using today's technology.