In a still frame playback mode, a video disc player reproduces a carrier signal which is frequency modulated in accordance with a composite video signal representative of successive repetitions of two interlaced image fields constituting a single image frame and comprising a luminance signal component,...http://www.google.com.tw/patents/US4093959?utm_source=gb-gplus-share專利 US4093959 - Chrominance signal transcoding apparatus
