In an electronic still camera, one field of a video signal is recorded on a floppy disk as one circular magnetic track in the form of a frequency modulated (FM) video signal. In this case, "field recording" and "frame recording" are known as the recording modes of the video signal. In the field recording, one field of a video signal is recorded on one magnetic track per recording, while in the frame recording, one frame of the video signal is recorded on two adjacent magnetic tracks by one field each per recording. One video floppy disk has a sum total track number of 50.
In such electronic still camera, an audio signal can be timebase-compressed and then recorded on a track different from the track of the video signal in the form of an FM audio signal.
In this case, as the recording mode of the audio signal, there is known a 5-second mode in which an audio signal of 5 seconds is compressed to one track (1 field=1/60 second) and then recorded, a 10-second mode in which an audio signal of 10 seconds is compressed to one track and then recorded, and a 20-second mode in which an audio signal of 20 seconds is compressed to one track and then recorded (see our U.S. Pat. No. 4,816,928).
Though not shown, a so-called PG yoke is provided at the center hub of the video floppy disk as a reference for a rotary phase.
When the aforementioned video signal and timebase-compressed audio signal are recorded, then the recording format of the video floppy disk is determined in such a fashion that a VD (vertical synchronizing signal) of a video signal is located in a range of 7H.+-.2H from the PG position as shown in FIG. 1 and that a start flag signal Fst of a timebase-compressed audio signal shown in FIG. 2 is located at the position of 2H from the PG position.
When the content of the video floppy disk in which the video signal and the timebase-compressed audio signal are recorded is copied onto other video floppy disk, i.e., in order to perform the stable dubbing of a short period of time, the assignee of the present application has previously proposed a technique in which an FM video signal and a FM timebase-compressed audio signal reproduced on the master disk side are demodulated and then FM-modulated again on the slave disk side, thereby being recorded (see Japanese Laid-Open Patent Publication No. 1-107369).
When the content of the video floppy disk is copied or dubbed, rotary phases of the master floppy disk and the slave floppy disk must be matched with each other. Generally, the PG signal of the master video floppy disk is employed as a reference signal of the phase servo carried out by a recording apparatus on the slave floppy disk side.
However, when the content of the video floppy disk is copied on the basis of the PG signal of the master video floppy disk, a signal is recorded on the same position as that of the slave video floppy disk.
Accordingly, if the recorded position of the video signal on the master video floppy disk is not conforming to the standard (see FIG. 1) of the aforementioned recording format, then the recording position of the video signal on the slave video floppy disk also is not conforming to the standard.
In order to solve the above-mentioned problem, the assignee of the present application has previously proposed a magnetic disk recorder (see Japanese Patent Application No. 2-203062). According to this previously-proposed apparatus, when a video signal on a first magnetic disk is reproduced by a reproducing means, a vertical synchronizing signal obtained from a reproduced video signal is used as a reference signal for the phase servo of a recording means, while when an audio signal is reproduced by the reproducing means, a panel signal obtained in response to a rotation of the first magnetic disk is used as a reference signal for the phase servo of the second magnetic disk in the recording means. Thus, when the recording timing of the video signal on the first magnetic disk is out of the standard range, the signal can be recorded again (dubbed) on the second magnetic disk with a proper recording timing.
The previously-proposed magnetic disk recorder will be described with reference to FIG. 3.
Referring to FIG. 3, a master disk reproducing apparatus 10 is provided with a motor 11 for rotating a master disk Dm, a PG coil 12 for obtaining a PG signal from the master disk Dm and a phase servo circuit 13 for controlling the rotation of the motor 11 on the basis of the PG signal. The phase servo circuit 13 is supplied with an external vertical synchronizing signal VDex as a reference signal.
A video signal and a timebase-compressed audio signal recorded on the master disk Dm are reproduced by a magnetic head 14 and supplied through an amplifier 15 to an FM demodulator 16.
A slave disk recording apparatus 20 is provided with a motor 21 for rotating a slave disk Ds, a PG coil 22 for obtaining a PG signal from the slave disk Ds and a phase servo circuit 23 for servo-controlling the rotation of the motor 21 on the basis of the PG signal, similarly to the master disk reproducing apparatus 10.
An output of an FM modulator 26 is supplied through an amplifier 25 to a recording head 24 of the slave disk recording apparatus 20, and the FM modulator 26 is supplied with the output of the FM demodulator 16 of the master disk reproducing apparatus 10, i.e., a video signal Y and a timebase-compressed audio signal Atc.
A reference signal control circuit 30 includes a synchronizing separating circuit 31 and a horizontal synchronizing signal detecting circuit 32. The output of the FM demodulator 16 in the master disk reproducing apparatus 10 is supplied to the synchronizing separating circuit 31 which detects a horizontal synchronizing signal from the output of the FM demodulator 16, thereby determining on the basis of the detected result of the horizontal synchronizing signal whether a reproduced signal is the video signal or the timebase-compressed audio signal.
When the reproduced signal is the video signal, a change-over switch S1 is connected in the opposite side (V to A in FIG. 3), whereby a vertical synchronizing signal VD separated by the synchronizing separating circuit 31 is supplied through a semifixed delay circuit 33 to the phase servo circuit 23 of the slave disk recording apparatus 20. A central value of the delay time of the delay circuit 33 is selected to be 7H (H is the horizontal period).
Therefore, the rotary phase of the slave disk Ds is servo-controlled so that a detection timing point of the vertical synchronizing signal VD from the master disk Dm is delayed from a detection timing point of the PG signal from the slave disk Ds by substantially 7H. Thus, even when the recording position (timing) of the video signal on the master disk Dm is displaced from the aforementioned standard range (7H.+-.2H), the signal can be recorded again (i.e., dubbed) on the slave disk Ds at a proper recording timing.
When the reproduced signal is the timebase-compressed audio signal, the change-over switch S1 is connected in the illustrated state (A), whereby the PG signal of the master disk reproducing apparatus 10 is supplied through a 7H delay circuit 34 and a shaping circuit 35 to the phase servo circuit 23 of the slave disk recording apparatus 20 as the pseudo vertical synchronizing signal.
Therefore, the rotary phase of the slave disk Ds is servo-controlled such that the detection timing point of the PG signal from the master disk Dm is delayed from the detection timing point of the PG signal from the slave disk Ds by the delay time of 7H, whereby jitter components of the master disk reproducing apparatus 10 and the slave disk recording apparatus 20 are removed and the timebase-compressed audio signal is dubbed (i.e., recorded again) on the slave disk Ds on the basis of the external vertical synchronizing signal VDex provided as the timing reference signal.
In accordance with the above-mentioned previously-proposed magnetic disk recorder, however, when the recording timing of the timebase-compressed audio signal on the master disk Dm is displaced from the standard range, such displacement of timing cannot be corrected into the standard range.