Circuit for discriminating the tape speed in speed-change playback mode

摘要

A circuit discriminates the tape speed in a speed-change playback mode in a video processing system based upon the drop out signal derived from the video signal read off the tape. The circuit discerns differences between the pulse widths of the drop out signals of standard play (SP) and long play (LP) recorded video signals. The circuit has a low pass filter (51) connected in series with a comparator (53). The low pass filter (51) takes the drop out pulse signal from a pre-amplifier (10) or from a luminance/chroma processor and filters the drop out pulse signal to determine its DC level. The comparator compares the filtered DC level of the drop out pulse signal to a reference voltage, and based upon the comparison makes a determination whether the video signal on the tape is recorded at standard play speed or long play speed.