JPH0574138B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a servo circuit for dubbing a VTR.

(b) Prior Art A VTR that enables dubbing by integrating two VTRs has already been proposed in Japanese Patent Laid-Open No. 150106/1983.

In this conventional example, two VTRs of different systems are integrated to enable mutual dubbing, and the head servo system compares the phase of the head rotation detection output of the playback side VTR and the playback control signal. The resulting head motor control output is commonly input to the recording and reproducing head motors.

However, in the above-described configuration, it is difficult to control the rotation of the recording head motor even if the control output of the reproducing head motor is supplied to the recording head motor.

Furthermore, in dubbing, two VTRs are usually connected and the reproduced video signal played from one VTR is recorded on the other VTR.

Therefore, the recording VTR uses the vertical synchronization signal in the reproduced video signal as a reference signal. but,
This vertical synchronization signal is accompanied by time axis fluctuations associated with playback, and the recording VTR is controlled to follow this fluctuation, but in reality, the fluctuation speed is faster than the response of the recording VTR, so the recording VTR Unable to follow the fluctuations, the servo was unnecessarily disturbed and the dubbing characteristics deteriorated.

In addition, the vertical synchronization signal in the reproduced video signal is recorded at the scanning start edge of the recording track, and correct synchronization separation may not be possible due to SN deterioration, resulting in loss of the reference signal of the recording VTR or phase shift. Things were also hot.

(C) Problems to be Solved by the Invention As described above, the present invention aims to eliminate the deterioration of dubbing characteristics caused by fluctuations in the reference signal of the recording VTR during dubbing.

(d) Means for solving the problems In order to solve the above-mentioned problems, the present invention includes the following steps:
The present invention is characterized in that the fixed reference signal of the reproducing VTR is used as the reference signal of the recording VTR.

(E) Function In the present invention, the recording VTR is controlled by a stable fixed reference signal of the reproducing VTR, thereby achieving stable recording.

(F) Embodiment The present invention will be described below with reference to an illustrative embodiment. The figure shows a servo circuit block diagram of a dubbing VTR that integrates two VTRs of different types. In this embodiment, the servo circuit of the left VTR is in the playback mode, and the servo circuit of the right VTR is in the record mode.The components of the VTR on the playback side are marked with an A, and the components of the VTR on the recording side are in the recording mode. The components of the VTR are identified by the reference numeral B. Note that the carrier oscillation circuit 1 and the first frequency dividing circuit 2, which constitute the fixed reference signal generating means in the figure, are common components to both VTRs.

First, I will explain the operation of the playback VTR.
The playback VTR performs the same servo operation as before. The reproduction side VTR has a 60Hz fixed reference signal obtained by dividing the output of the 3.58MHz subcarrier oscillation circuit 1 in the first frequency dividing circuit 2 as a reference input.
The fixed reference signal inputted through the a side contact of the first changeover switch SA is frequency-divided by 1/2 by the 1/2 frequency divider circuit 4A, and the frequency-divided output is divided into 1/2 by the 1/2 frequency divider circuit 4A.
It is input to 11A.

The PG pulse that detects the rotation of the video head as the head motor 10A is driven is amplified by the PG amplifier 9A, and then delayed by the delay circuit 8A.
The signal is input to the first sampling pulse generation circuit 7A. The first sample and hold circuit 6A samples and holds the first reference wave using the first sampling pulse, and the rotational phase of the head motor 10A, that is, the video head is controlled by this sample and hold output.

On the other hand, the output of the control amplifier 14A that amplifies the playback control signal is the tracking circuit 1.
After being delayed at 5A, the second changeover switch TA
The signal is input to the second sampling pulse generation circuit 13A through the C-side contact of the pulse generator. The second sample and hold circuit 12A samples and holds the second reference wave using a second sampling pulse, and the rotational phase of the capstan motor 18A is controlled by this sample and hold output.

It is obvious that on the playback VTR, the vertical synchronization separation circuit 3A, the FG amplifier 17A, and the second
The frequency dividing circuit 16A does not directly contribute to the reproduction operation.

The operation of the recording VTR will be explained below.
A feature of this embodiment is that the first changeover switch SB is switched to the a-side contact even during dubbing. That is, in this embodiment, the recording side
VTRs also use a fixed reference signal as their reference input.

Therefore, the output of the 1/2 frequency divider circuit 4B, which inputs the fixed reference signal, is input to the first reference wave generation circuit 5B and the second reference wave generation circuit 11B. The PG pulse for detecting the rotational phase of the video head rotating as the head motor 10B is driven is amplified by the PG amplifier 9B and then delayed by the delay circuit 8B.
The signal is input to the sampling pulse generation circuit 7B.
The first sample and hold circuit 6B samples and holds the first reference wave using the first sampling pulse, and this sample and hold output is output to the head motor 1.
Controls the rotation phase of 0B.

On the other hand, the FG pulse that detects the rotation of the capstan motor 18B is amplified by the FG amplifier 17B and then input to the second frequency dividing circuit 16B. This second
The frequency dividing circuit 16B divides the frequency of the FG pulse to derive a frequency divided output of 30Hz, and this frequency divided output is input to the second sampling pulse generation circuit 13B via the C side contact of the second changeover switch TB. be done. Therefore, the second sample and hold circuit 12B samples and holds the second reference wave using the second sampling pulse, and the rotational phase of the capstan motor 18B is controlled by this sample and hold output.

As described above, according to this embodiment, two VTRs
Because it is integrated, the reference signal generation means is shared,
The derived fixed reference signal is used as the reference input for both VTRs, but when dubbing is performed using two independent VTRs, both VTRs are provided with external input/output terminals for the fixed reference signal and recorded from the playback VTR. It is sufficient to supply a fixed reference signal to the side VTR.

Furthermore, in this embodiment, the left VTR is set to playback mode and the right VTR is set to record mode, but it is also possible to set the left VTR to record mode and the right VTR to playback mode. It is only necessary to invert only the data, and dubbing between different methods is also possible.

(g) Effects Therefore, according to the present invention, dubbing is performed using a stable reference signal, and the effects are great.

[Brief explanation of the drawing]

The figure shows a servo circuit block diagram according to an embodiment of the present invention. 1... Subcarrier oscillation circuit, 2... First frequency dividing circuit, 10A, 10B... Head motor, 18
A, 18B...Capstan motor.

Claims (1)

[Claims] 1. In a dubbing system in which a reproduced video signal obtained from one VTR is recorded on another VTR, the rotational phase of the head motor and capstan motor of the reproduction side VTR is controlled by a unique fixed oscillation circuit and A dubbing device comprising: a servo circuit for controlling a servo circuit; and a servo circuit for controlling rotational phases of a head motor and a capstan motor of a recording side VTR, and supplying the output of the oscillation circuit as a phase reference signal for both the servo circuits. Servo circuit for.