Variable speed playback controller for a video tape recorder

Abstract

A magnetic tape transport controller for a magnetic recording and reproducing apparatus in which a pilot signal for tracking control having four different frequencies is recorded on a magnetic tape by a rotary magnetic head and the magnetic tape is transported in a playback mode at a different tape speed than that in a recording mode. The tape transport controller has means for detecting an amplitude change of a specific one of signals derived by frequency-converting a reproduced pilot signal and controlling the tape speed such that the frequency of the amplitude change is maintained at a predetermined frequency. It also has a phase control loop to control the tape speed such that a phase of the specific signal coincides with a phase of a reference signal. In the playback mode in which the tape is transported at the different speed than that in the recording mode, frequencies of a local pilot signal used to frequency-convert the reproduced pilot signal are switched in the opposite order to that of the switching of the frequencies in the recording mode. A detection circuit which detects a difference between two frequency converted signals of different frequencies and amplifies the difference inverts a polarity of an output signal for each track switching in a standard speed playback mode and does not invert the polarity in a variable speed playback mode.