| 摘要 |
PURPOSE:To prevent, at switching, the generation of noise such as clicking, etc. and harm, such as AM, etc. by switching respective audio signals different in an amount of delay at the time they are at non-sound level respectively. CONSTITUTION:The video-delay difference (f) between an asynchronous video input signal (a) and a reference video input signal (b) is detected, and an audio signal (d) is A/D-converted 12, and stored in an RAM14. An control circuit 15-1 generates an offset address to obtain a necessary audio delay corresponding to the variation of the delay difference (f). Based on this address, the data is read out from the RAM14, and is latched by holders 17 and 17'. Detectors 18-1 and 18'-1 respectively detects that the absolute values of the held data are approximately of non-sound level, and generates a non-sound flag, respectively. When the respective non-sound periods coincide with each other, a trigger pulse 20 is generated to control a switching unit 21, and consequently,an output signal is supplied to a D/A converter 22.
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