| 摘要 |
In recording, a carrier is FM-modulated with a video signal to produce a FM carrier. The phase of the FM carrier corresponding to a tip portion of a horizontal synchronizing pulse in the video signal (sync-tip carrier), is reset so that the phase is fixed at a reference phase at a leading edge of the horizontal synchronizing pulse during every period of the horizontal synchronizing pulse width. The sync-tip carrier with its phase fixed is recorded in a magnetic recording medium. In reproducing, the FM carrier picked up by the magnetic recording medium, with its frequency doubled by a doubler, is demodulated by a pulse count-type FM demodulator with a doubler function. Then, a part of the FM carrier spectrum leaks into the FM demodulated video signal band, but the FM carrier is always in phase with the horizontal synchronizing pulse in the video signal, so that beat stripes or moiré do not appear on the reproduced picture, and the interference due to the leakage appears as reproduced picture distortion in correlation with the video signal. Since the reproduced picture distortion is not likely to be detected by a human being as compared to asynchronously drifting beat stripes, the output of the doubler does not have to be passed through a high-pass filter to cut off a part of the lower sideband of the FM carrier. The reference burst signal necessary to a time base corrector is extracted from the reproduced sync-tip carrier.
|
