JPH029749B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a rotation system control device for a video tape recorder, and is particularly designed to be applicable to cases where different television signal formats are handled.

Technical Background of the Invention FIG. 1 is a block diagram showing a capstan motor servo system of a video tape recorder (hereinafter referred to as VTR). 11 is a capstan motor, and 12 is a capstan rotation system. The capstan rotation frequency is determined by the rotation detector 13.
This rotation detection signal is detected by the automatic frequency control (hereinafter referred to as AFC) circuit 1.
4 and one input terminal R of the recording/playback switch 15. Record/playback switch 1
A control pulse (CTL) is applied to the other input terminal P of VTR 5 during playback of the VTR. The output of the recording/reproducing switch 15 is input to an automatic phase control (hereinafter referred to as APC) circuit 16. The APC circuit 16 is supplied with a vertical synchronizing signal passed through a 1/2 frequency divider 18 during recording, and a reference signal from a reference signal generator 19 during reproduction, via a recording/reproduction switch 17. is input. The APC circuit 16 includes a switch 15,
The phase error from the AFC circuit 17 is detected, and its output is combined with the output from the AFC circuit 14 in a combiner 20. And the combined output is motor 1
1 control input.

During the recording operation of the VTR, a rotation control output is obtained by the AFC circuit 14 so that the rotation detection signal is constant, and the rotation detection signal and the 1/2 frequency of the vertical synchronization signal have a constant phase relationship. like
A phase control output is obtained from the APC circuit 16. Further, during playback operation of the VTR, a rotation control output is obtained by the AFC circuit 14 so that the rotation detection signal is constant, and a phase control output is obtained so that the playback control pulse and the reference signal have a constant phase relationship. is obtained.

Now, the frequency of the control pulse (CTL)...
…… Frequency of _CTL detection signal…… _d Frequency of reference signal (1/2 of vertical synchronization signal)… _S
Then, in order to perform playback APC and recording APC, it is necessary to satisfy the following conditions: _CTL = _S (1) _d = n _S (2) (n: integer).

In general, when recording magnetically on tape using the different methods NTSC and CCIR (PAL, SECAM), the standard requires recording at different tape speeds. In addition, between both methods, the control pulse frequency _CTL , that is, the reference signal frequency _S
are different.

Hereinafter, _S in the CCIR system will be expressed as _SC , and _S in the NTSC system will be expressed as _SN .

Therefore, for example, in a VTR dedicated to the CCIR method _{, d}
=n _SC ......(3).

Now, if you are trying to perform recording APC according to the NTSC system on a VTR dedicated to the CCIR system, and if the rotation detection signal frequency at the tape speed of the NTSC system is _d , then ′ _d = v _N /v _{C d} ... ...(4) v _N ...NTSC tape speed v _C ...CCIR tape speed. From the recording APC conditional expression (2), it is necessary to satisfy ' _d = n _SN , that is, from the expressions (3) and (4), _SN = v _N /v _{C SC} (5). In other words, if you record an NTSC signal on a CCIR-dedicated VTR and try to perform recording APC, the ratio of the frequency _SC of the reference signal in the CCIR method to the frequency _SN of the reference signal in the NTSC method will be different from that of the CCIR method. It must be equal to the ratio of the tape speed v _C and the tape speed v _N of the NTSC system.

Problems with the Background Art However, since _SN / _SC ≠v _N /v _C (according to the standard), the above formula (5) cannot be satisfied.

For example, _SN / _SC = 30 / 50 = 1.20 v _N /v _C = 20 / 18.75 = 1.0678, and formula (5) cannot be satisfied.

For this reason, in VTRs that have only one set of capstan and rotation detector, CCIR method,
Recording APC is not possible by simply changing the tape speed etc. for both NTSC formats.
It was necessary to prepare capstans with different shaft diameters.

Purpose of the Invention The present invention was made in view of the above circumstances, and it is possible to improve the system by providing a highly reliable electrical processing circuit without changing the conventional VTR capstan and its rotation detector. It is an object of the present invention to provide a rotation system control device for a video tape recorder that can stably perform capstan control in recording and reproducing processing of television signals with different tape speeds.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention does not add a mechanical capstan shaft and a rotation detector that are likely to cause accuracy errors, but uses a set of capstan and rotation detector, and uses an electrical signal. AFC circuits 24, 25 and reference signal generator 3 that perform processing
By providing 3, 35, and 36 and switching between them according to the CCIR method and NTSC method,
Both types of recording APC are designed to provide stable control operations.

Embodiments of the Invention Examples of the invention will be described below with reference to the drawings. In FIG. 2, 21 is a capstan motor, and 22 is a capstan. The rotation frequency of the capstan 22 is detected by the rotation detector 23, and the rotation detection signal is transmitted from the first and second
The signal is input to AFC circuits 24 and 25. 1st AFC
The circuit 24 is for the CCIR method, and the second AFC circuit 25 is for the CCIR method.
It is for NTSC system. First and second AFC circuits 2
The outputs of 4 and 25 are applied to first and second input terminals 26X and 26Y of a CCIR/NTSC changeover switch 26, respectively. This changeover switch 26 is a CCIR method,
The first or second input terminal 26X or 26Y is selected depending on when the NTSC system is handled, and its output is input to the synthesizer 37. 27 is a record/playback switch, the first input terminal R receives the rotation detection signal, and the second input terminal P receives the rotation detection signal.
Playback control pulse (CTL) during VTR playback
is input. This recording/playback switch 27
The output is input to one input terminal of the APC circuit 28. The selection output (reference signal) from the recording/reproduction switch 29 is input to the other input terminal of the APC circuit 28 . The first and second input terminals R and P of the recording/playback switch 29 are connected to the CCIR/NTSC switch 31, respectively.
The selection output from 34 is added.

One CCIR/NTSC changeover switch 31 sends the vertical synchronization signal to the first input terminal 31X to the 1/2 frequency divider 3.
A frequency-divided output obtained by dividing the frequency by 2 is added, and an output of the reference signal generator 33 is added to the second input terminal 32Y. The reference signal generator 33 outputs an NTSC vertical synchronization 1/2 frequency signal. The other CCIR
The NTSC changeover switch 34 is connected to the first input terminal 34X.
_{The SC} reference signal from the reference signal generator 35 is added to the reference signal generator 3 to the second input terminal 34Y.
_{The SN} reference signal from 6 is added. The output of the APC circuit 28 is input to the synthesizer 37 and becomes a phase control signal for the motor 21.

When a VTR recording operation is performed using CCIR system signals, the CCIR/NTSC changeover switch 26,
31 and 34 are first input terminals 26X and 3, respectively.
The 1X and 34X sides are selected, and the recording/reproduction changeover switches 27 and 29 select input terminals R and R. In this case, this control system has a form similar to that of a CCIR type VTR. Therefore, the tape speed is set to v _C , and the frequency _d of the rotation detection signal is adjusted so that _d = n _SC (n: integer) is satisfied.
The reference signal frequency _SC is set.

Next, when recording an NTSC signal, the switch 31 is switched to the reference signal generator 33 side.
In this case, since the tape speed becomes _vN , the rotation detection signal frequency becomes ′ _d . Therefore, ′ _d = v _N /v _{N d} , and _{the SC} based on the vertical synchronization signal is recorded.
The APC conditions will no longer be satisfied. For this reason, record
The frequency ' _SN is used from the reference signal generator 33 as the APC reference signal. This frequency ′ _SN is
NTSC recording APC becomes possible by setting ` _SN = n·v _N /v _C · _d so as to satisfy conditional expression (2) for recording APC. Further, the AFC circuit 25 can be used to set the rotation frequency according to the NTSC system.

On the other hand, when playing back a VTR, when dealing with CCIR system signals, the AFC circuit 24 is used and _{the SC} from the reference signal generator 35 is used.
In addition, when handling NTSC signals, an AFC circuit 25 is used, and _{the SN} from the reference signal generator 36 is used.
A reference signal is used.

Effects of the Invention According to the present device described above, there is no need to prepare or change multiple VTR capstan shaft diameter or rotation detection devices, that is, there is no need for mechanical development or design changes that are likely to cause errors. Through highly accurate electrical processing, recording APC can be made stable for both CCIR and NTSC systems.

[Brief explanation of drawings]

FIG. 1 is a structural explanatory diagram showing a conventional VTR rotation system control device, and FIG. 2 is a structural explanatory diagram showing an embodiment of the present invention. 23... Rotation detector, 24, 25... AFC circuit, 26, 31, 34... CCIR/NTSC selection switch, 27, 29... Record/playback selection switch, 28... APC circuit, 32... 1/ 2 divider, 3
3, 35, 36...Reference signal generator, 37...Synthesizer.

Claims (1)

[Claims] 1 a rotation detector that detects the rotation of a capstan rotated by a capstan motor and derives a rotation detection signal; and a rotation detector that receives the rotation detection signal and determines the rotation frequency of the capstan motor;
a first outputting a rotation control signal for controlling the rotation period according to the first and second television systems;
A second AFC circuit and one of the outputs of the first and second AFC circuits is selected in accordance with the handling status of the first and second television systems, and the rotation control signal and the synthesizer are a first switch for inputting to the
a second switch which selects either the rotation detection signal or the reproduction control pulse according to the recording mode or the reproduction mode and applies it to one input terminal of the APC circuit; is handled, the vertical sync signal is 1/2
a third reference signal generator which applies the divided frequency to the other input of the APC circuit and, if a second television signal is handled, the output of the first reference signal generator to the other input of the APC circuit; a switch, and when in playback mode and the first television signal is handled, the output of the second reference signal generator is switched to the second reference signal generator.
in addition to the other input of the APC circuit, a fourth switch applies the output of the third reference signal generator to the other input of the APC circuit when a second television signal is handled; The ratio of the output frequency ' _SN of the first reference signal generator to the output frequency _SC of the second reference signal generator is determined by the tape speed v _N when handling the first television signal and the second television signal. 1. A rotation system control device for a video tape recorder, characterized in that _{the SN} is set to be one integer fraction of a tape speed v _C when handling a digital signal.