Time-base correction of audio signals in video tape recorders

Abstract

The time-base corrector of this invention corrects the time-base of audio signals reproduced from video tapes without correcting the time-base of video signals which are associated with the audio signals. Reference signals such as the horizontal synchronizing pulses which accompany video information are used for correcting the time-base of audio signals if such reference signals have been subjected to substantially the same time compression or expansion as the audio signals. In the preferred embodiment, the reproduced audio signals are sampled and written into a sampled data delay and read out of it by means of a control circuit. The control circuit receives as input the undistorted reference signal and the reproduced reference signal which has undergone time compression or expansion. The control circuit derives a write clock signal with a frequency equal to k times the frequency of the distorted reference signal. The reproduced (and therefore time compressed or expanded) audio signal is sampled and read into the sampled data delay by the write clock signal. The audio signal stored in the sampled data delay is then read by the control circuit at a frequency of a read clock signal with a frequency equal to k times the frequency of the undistorted reference signal. The audio signal read in the above manner will be time-base corrected.