NTSC compatible wide-screen TV system with PCM sound using QAM

摘要

A CATV (cable television) transmission experiment proved the complete compatibility of a wide-screen QAM (quadrature amplitude modulation) based TV system with CATV. Even under the worst CATV conditions (50 dB CTB, 38 dB C/N, slight annoying reflections), no specific impairment or degradation was perceived in the wide-screen TV or the NTSC. As a result of a subjective estimation of interference to conventional NTSC TV sets, it is shown that there is no need for a guard band between NTSC- and QAM-based TV channels. The system is capable of transmitting PCM (pulse-code-modulated) stereo sound. 320-kHz, 16 bit/sample data are efficiently band-compressed into about 250 kb/s using subband coding, and transmitted during some parts of the vertical blanking and vertical overscanning periods through the QAM channel.