JPS6367084A - Automatic switching device for reproducing function - Google Patents

Abstract

PURPOSE:To attain rapid and accurate switching, by discriminating a frequency ratio between a reproduction control signal, and the rotating pulse of a capstan, and switching the rotating speed of a rotary cylinder and a capstan motor based on a discriminated result. CONSTITUTION:A tape speed/field frequency discrimination circuit 40 detects the frequency ratio between an FG pulse from a waveform arranging circuit 13, and a control signal from a waveform arranging circuit 11, at time of reproduction. And based on the above detection, it is decided that a mode is a standard mode of field frequency 600Hz, and tape speed 33.35(-)/s, if the frequency ratio is '24' and the frequency of a reference signal being generated from a reference signal generator 15, the targeted value of a speed detector 21, and the comparison timing of a phase comparator 12, are switched. Furthermore, the targeted value of a speed detector 14 is switched by a tape speed setting signal, and it is controlled so as to set the rotating speed of the rotary cylinder 1 at 20.97Hz, and the tape speed at 33.35(-)/s.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention has a function of recording and reproducing two types of video signals with different field frequencies, and also has a function of recording and reproducing two types of video signals with different field frequencies, and a plurality of recording speeds and reproduction speeds. The present invention relates to an automatic playback function switching device for a magnetic recording and playback device (VTR).

(Prior art) In the past, two types of video signals were used: one in which the field frequency was 60 Hz, and the other in which the field frequency was 501-(Z).
There are VTRs that can record and play back various types of video signals, but during playback, these VTRs change the rotational speed of the rotating video head according to each field frequency, and also record the rotational speed of the capstan motor. The speed is changed to the same speed as the current time or to a specified speed.

Conventionally, manual switching methods and automatic switching methods are known as methods for switching such playback functions.

FIG. 3 is a circuit diagram showing the conventional configuration of a switching device that automatically switches the playback function. A video head 2 is attached to a rotating cylinder 1, and the rotational phase and rotational speed of the rotating cylinder 1 are controlled magnetically. rotational pulses (PG pulses and F pulses) corresponding to the rotational phase and rotational speed.
A pulse generator (P
G)3 and (FG)4 are arranged close to each other.

Further, a pinch roller 7 that presses the magnetic tape 5 against the capstan is arranged close to the capstan 6 that runs the magnetic tape 5, and a rotating shaft of a capstan motor 8 that provides rotational force to the capstan 6 is arranged close to the capstan 6 that runs the magnetic tape 5. combined. Further, a magnetic disk 9 is attached to the rotating shaft of the capstan motor 8, and a magnetic disk 9 in which N poles and S poles are arranged alternately at predetermined intervals on the circumferential surface is attached to a part of the circumferential surface of the magnetic disk 9. A pulse generator (FG) 9 that generates rotational pulses (FG pulses) corresponding to the rotational speed of the capstan motor 8 by magnetic coupling between the N and S poles is arranged in close proximity.

On the other hand, a control head 10 for recording and reproducing control signals (CTL signals) is provided on the tape running path between the rotary cylinder 1 and the capstan 6.

Here, during reproduction, the control signal reproduced by the control head 10 is input to the phase comparator 12 via the waveform shaping circuit 11, and the phase difference with the reference signal generated from the reference signal generator 15 is compared. . Also,
The FG pulse output from the FG 9 is input to the speed detector 14 via the waveform shaping circuit 13. The speed detector 14 discriminates the frequency of the FG pulse and outputs an acceleration/deceleration signal according to the deviation from the target value commanded by the tape speed setting signal. Further, the phase comparator 12 compares the phase difference between the reference signal inputted from the reference signal generator 15 and the reproduction control signal, and outputs an acceleration/deceleration signal corresponding to the phase difference. The acceleration/deceleration signals outputted from the phase comparator 12 and speed detector 14 are added by an adder 16 and then input to the capstan motor 8 via a drive amplifier 17. Thereby, the capstan motor 8 is controlled to rotate at the rotational phase and rotational speed commanded by the tape speed setting signal.

In this case, the rotational phase reference signal generated by the reference signal generator 15 is switched by the field frequency setting signal (or cylinder rotation speed setting signal) so that it becomes 25H7 when the field frequency is a video signal of 50H2.

On the other hand, the output signal of FG3 representing the rotational phase of rotary cylinder 1 is input to phase comparator 19 via waveform shaping circuit 18. The phase comparator 19 receives a reference signal having a phase commanded by the field frequency setting signal from the reference signal generator 1.
5, the phase comparator 19 compares the phase difference between the reference signal and the PG pulse input from the FG3, and outputs an acceleration/deceleration signal for the rotating cylinder 1 according to the phase difference. Furthermore, the FG pulse output from the FG 4 is input to the speed detector 21 via the waveform shaping circuit 20.

The speed detector 21 discriminates the frequency of the FG pulse and outputs an acceleration/deceleration signal according to the deviation from the target value commanded by the tape speed setting signal. The acceleration/deceleration signals output from the phase comparator 19 and the speed detector 21 are added by an adder 22, and then sent to the cylinder motor 24 via a drive amplifier 23.
is input. Thereby, the rotating cylinder 1 is controlled to rotate at the rotational phase and rotational speed commanded by the field frequency setting signal.

In this case, similarly to the capstan control system, the rotational phase reference signal is switched to 25H2 when the field frequency is a video signal of 50H2, and the rotational speed of the rotary cylinder 1 is controlled to be 25H2. .

With such capstan servo and cylinder servo, the trace of the video head 2 on the magnetic tape 5 becomes the same as that during recording, and an appropriate playback output is taken out from the preamplifier 26° demodulation circuit 27 of the video signal processing circuit 25.

On the other hand, during recording, the color subcarrier component of the video signal is converted into a low frequency by the modulation circuit 28 of the video signal processing circuit 25, and then input to the video head 2 via the recording amplifier 29.

The video signal is also input to the sync separation circuit 30.

The synchronization separation circuit 30 separates and extracts the vertical synchronization signal from the input video signal, and divides the vertical synchronization signal into 1/2 by the frequency division circuit 31.
After dividing the frequency by two, the signal is input to the control head 10 via the recording amplifier 321.

Roughly speaking, the synchronization separation circuit 30 inputs the separated and extracted vertical synchronization signal to the field frequency discrimination circuit 32, which discriminates whether the field frequency is 50H7 or 60H2.

Based on the field frequency determination result, a target value for the velocity detector 21 of the cylinder servo system is set, and the reference signal frequency of the rotational phase generated from the reference signal generator 15 is controlled. Furthermore, the signal resulting from the determination of the field frequency is inputted to the tape speed determination circuit 33 as a field frequency setting signal.

The tape speed determination circuit 33 determines the necessary tape running speed based on the field frequency setting signal and the recording speed setting signal input from an operation panel (not shown), and outputs the determination result signal to the capstan as a tape speed setting signal. It is input to the speed detector 14 of the servo system and a target value is set. Further, the tape speed determination circuit 33 inputs a signal resulting from the determination as a signal for controlling the frequency division ratio of the frequency divider 34.

The frequency divider 34 divides the frequency of the FG pulse inputted from the waveform shaping circuit 13 to the frequency of the reference signal of the rotational phase corresponding to the field frequency, and its output is inputted to the phase comparator 12, where it is A phase difference between the rotational phase and a reference signal is compared.

Then, the rotational phase of the capstan motor 8 is controlled according to the phase difference. In this case, capstan motor 8
The rotation speed is controlled by the output of the speed detector 14 to a speed corresponding to the combination of the field frequency and the recording speed setting signal.

On the other hand, in the cylinder servo system, 1 of the vertical synchronization signal
The phase difference between the /2 frequency divided output and the PG pulse is determined by the phase comparator 19.
The rotational phase of the cylinder motor 24 is controlled according to the phase difference. Further, the target value of the speed detector 21 is set by the field frequency setting signal,
The rotational speed of the cylinder motor 24 is controlled to a speed corresponding to the field frequency.

By the way, the field frequency setting signal during playback is obtained by inputting the playback video signal demodulated by the video signal @ processing circuit 25 to the synchronization separation circuit 35 and separating and extracting the horizontal synchronization signal, and then changing the frequency of the horizontal synchronization signal to the horizontal Synchronous frequency discrimination circuit 3
It is extracted by making a distinction in step 6,
The determined horizontal synchronization signal frequency is 13 as shown in Figure 4.
．． If it is 125KllZ, the horizontal synchronizing signal frequency is 15.734 when the field frequency is 601-IZ.
KH2 The rotational speed of the rotating cylinder 10 is output from the discrimination circuit 36 (field frequency setting signal).
29.971-12. Similarly,
When the horizontal synchronizing signal frequency is 18.731KH2, the rotational speed of the rotating cylinder 1 is switched to 25H2 so as to match the horizontal synchronizing signal frequency of 15.625KH2 when the field frequency is 50H2.

(Problem to be solved by the invention) However, as mentioned above, when the rotating cylinder 1
If the rotational speed and tape running speed are changed based on the determination result of the horizontal synchronizing signal frequency, ■ When the head trace position is misaligned with respect to the recording track, ■ When the magnetic tape 5 is scratched, ■ When the playback output When the level is extremely low, the horizontal synchronization signal may be lost or disturbed by noise, etc., and the field frequency may be misjudged. There was a problem that it became impossible to play. Further, since it is not possible to decide whether to set the control signal to 30H2 or 25H2 until the determination of the field frequency is completed, there is a problem in that the determination of the tape speed is delayed and the switching of the tape speed is delayed.

The purpose of the present invention is to solve the above-mentioned problems, and to provide an automatic playback function switching device that can quickly switch a recorded video signal to a playback state that matches its field frequency and tape speed and reliably play it back. The purpose is to provide.

[Structure of the Invention] (Means for Solving the Problems) The present invention is based on the field frequency of the video signal recorded on the magnetic tape based on the frequency ratio of the control signal reproduced from the control track and the rotation pulse signal of the capstan. The present invention is characterized in that it includes a discrimination circuit for discriminating the magnetic tape speed and the speed of the rotating video head and the capstan motor based on the discrimination output thereof.

That is, when considering the combination of field frequency and tape speed of the VH8 system, for example, the following table 1 (A>, (
There are combinations as shown in B), but the frequency ratios between the FG pulse and the control signal in each combination are all different.

The present invention switches between the rotational speed of the rotary cylinder and the tape running speed by determining the difference in this frequency ratio.

(The following is a margin) Table 1 (A) (The following is a margin) Table 1 (B) (Operation) As shown in Table 1, the discrimination circuit discriminates the difference in the frequency ratio of the hFG pulse and the control signal. Depending on the result, the rotation speed of the rotating cylinder and capstan motor is switched. Therefore, a two-step discrimination operation of determining the tape speed after determining the field frequency is not necessary, and the field frequency and tape speed can be quickly switched.

Furthermore, even if the horizontal synchronizing signal is disturbed, it will not be affected at all, so the field frequency and tape speed can be switched reliably to match the recording format of the recorded video signal.

(Embodiment) FIG. 1 is a circuit diagram showing an embodiment of the present invention, which differs from the conventional configuration in that a tape speed/field frequency discrimination circuit 40 is provided in place of the tape speed discrimination circuit 33, and a reference signal generator is provided. The frequency of the reference signal generated from the speed detector 15, the target value of the speed detector 21, the comparison timing of the phase comparator 12, the target value of the speed detector 14, and the frequency division ratio of the frequency divider 34 are switched by the discrimination output of the discrimination circuit 400. This is what I did.

That is, during reproduction, the discrimination circuit 40 distinguishes between the FG pulse whose waveform has been shaped by the waveform shaping circuit 13 and the waveform shaping circuit 1.
For example, in the frequency ratio combination of the VH3 system shown in Table 1, if the frequency ratio is "24", the field frequency is -60H2, the tape speed is 33. It is determined that the standard mode (SP mode) is 35 mm/s, and the frequency of the reference signal generated from the reference signal generator 15 is determined by the speed detector 2.
1 and the comparison timing of the phase comparator 12 are switched by the field frequency setting signal, which is one of the discrimination result signals, and the target value of the speed detector 14 is switched by the tape speed setting signal, which is one of the discrimination result signals. The switching is controlled so that the rotation speed of the rotary cylinder 1 is 29.97H2 and the tape speed is -33.35 mm/s.

Similarly, the frequency ratio of the FG pulse and the control signal is ■12. ■8. ■20.18, ■10.09, then ■field frequency -60H2, tape speed = 16.
68 mm/s double (LP) mode, ■Field frequency = 60H2, tape speed = 11.12 mm/s triple (EP) mode, ■Field frequency 50H2.

SP mode with tape speed = 23.39 mm/s, ■field frequency = 50H2, tape speed -11,70m
It is determined that the LP mode is m/S, and the rotational speeds of the rotary cylinder 1 and capstan motor 8 are switched according to the respective field frequencies and tape speeds.

FIG. 2 shows the frequency ratio discrimination area in the discrimination circuit 40, where (I> is EP with field frequency = 60Hz).
mode, (n) is LP mode with field frequency = 50H2, (I [I) is field frequency - 60H2 (7)
LP mode, (■v) Haffield frequency 1 = 501 - (
Z 17) SP mode, (VH, t field frequency =
60H2 SP mode determination areas are shown. Here, the magnetic tape 5 is sandwiched between the pinch roller 7 and the capstan 6 immediately after the start of running, runs without slipping, and does not stay near the control head 10, so that during high-speed and low-speed playback, the magnetic tape 5 runs without slipping. Also, the ratio between the FG pulse and the control signal is constant as shown in Table 1.

Therefore, by providing the discrimination area shown in FIG. 2 and discriminating the frequency ratio between the FG pulse and the control signal,
It is possible to precisely match the field frequency and tape speed during reproduction to the recording format of the recorded video signal.

In addition, since the running of the magnetic tape 5 is stopped in the still image mode, the determination result before switching to the still image mode is retained, and the rotational speed of the rotary cylinder 1 and the capstan motor 8 is controlled by this retention signal. good.

Note that in FIG. 1, the video signal processing circuit is not shown because it is not related to the gist of the present invention.

[Effects of the Invention] As explained above, according to the present invention, the frequency ratio between the reproduction control signal and the capstan rotation pulse is determined, and the rotation speeds of the rotary cylinder and the capstan motor are switched based on the determination result. Therefore, the effect is that the switching can be performed quickly and accurately.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing the discrimination range of the frequency ratio of the FG pulse and control 1 to roll signals in the embodiment, and Fig. 3 is the configuration of a conventional switching device. FIG. 4 is a diagram showing the relationship between the rotational speed of the rotating cylinder and the frequency of the reproduced horizontal synchronizing signal. 1...Rotating cylinder 2...Video head 5
...Magnetic tape 6...Capstan 8.
... Capstan motor 9 ... Rotating pulse generator 1
0...Control head 12, '19...Phase comparator 14.21...Speed detector, 15...Reference signal generator'16.22...Adder 40...Field frequency/ Tape speed determination circuit. Agent Patent Attorney Nori Chika Yudo Hiroshi Uji

Claims (1)

[Claims] In a magnetic recording and reproducing device that has the function of recording and reproducing two types of video signals with different field frequencies and has multiple recording speeds and reproducing speeds, the control signal reproduced from the control track and the rotation pulse for the capstan servo are used. Equipped with a discrimination circuit that discriminates between the field frequency of the video signal recorded on the magnetic tape and the magnetic tape speed at the time of recording based on the frequency ratio of the signal, and the speed of the rotating video head and capstan motor is switched based on the discrimination output. A reproduction function automatic switching device characterized by: