JPS6235316B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal recording/reproducing apparatus such as a VTR, and particularly to a servo circuit for editing a tape.

Helical scan VTR with rotating head
Accordingly, when editing a tape, for example, when recording a video signal A recorded on a tape by connecting a video signal B input from an external source, the conventional method is as follows. First, after rewinding the tape for a few seconds from the point where you want to edit signal B,
Start the VTR in playback mode. At this time, drum servo is applied using the vertical synchronization signal of signal B as a reference, and capstan servo is applied using the control signal recorded together with signal A as a reference. This allows the reproduced signals A and B to be synchronized. When the tape runs to a desired editing point in this state, it switches to the recording mode and records signal B. As a result, the transition from signal A to signal B at the editing point can be performed smoothly without any disturbance.

The drum servo circuit of this type of VTR uses the vertical synchronization signal of the input video signal as a reference signal during normal recording, and compares the phase of this reference signal with the pulses obtained from the pulse generator provided on the drum. There is. That is, as shown in FIG. 1, a trapezoidal wave signal T is created using the vertical synchronizing signal V as a reference, and the hypotenuse portion of this trapezoidal wave signal T is sampled with a pulse PG' which is obtained by delaying the pulse PG by a predetermined time. , an error voltage e is obtained. By controlling the rotational phase of the drum motor in accordance with this error voltage e, the pulse PG and the vertical synchronizing signal V are made to have a predetermined phase relationship. In this case, the drum servo is adjusted to lock when the predetermined phase relationship is obtained.

When performing the above-described editing, the drum servo circuit is externally synchronized with the vertical synchronization signal of signal B as a reference when signal A is reproduced. In this case, if the vertical synchronization signal of signal B deviates by a large width from the vertical synchronization signal V determined as shown in FIG. 1, the sampling position will deviate from the predetermined position. Therefore, the error voltage e does not have a predetermined magnitude. As a result, it is no longer possible to synchronize the drums with the predetermined phase relationship set by signal A, and if signal B is recorded as is, the screen will be distorted at the joint between signals A and B when the tape is played back. Become. Such problems are
This problem often occurs particularly when signal B is reproduced from a tape and that tape is recorded in a standard different from that of signal A tape.

The present invention is intended to solve the above problems,
When recording a signal recorded on a tape by connecting an external signal applied from a tape of a different standard or from another signal source, the drum servo is always synchronized in the same predetermined relationship with the vertical synchronization signal of the external signal. , the position of the vertical synchronization signal recorded on the tape before and after the editing point is always at the same position.

Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, as shown in FIG.
This is a case where a video signal B supplied from the outside is edited and recorded in the insert mode from point a on the tape 1 on which .

FIG. 3 shows the drum servo circuit and capstan servo circuit of a VTR when performing the above editing.
First, connect tape 1 of the editing VCR to connection point a in Figure 2.
Rewind for a few seconds from to point b. Next, this VTR is started in playback mode, and at the same time, signal B is supplied to input terminal 2 in FIG. At this time, switch 3,
4, 5, and 6 are closed to the PB (regeneration) side contacts.
The head drum 7 is rotated by a drum motor 8, and the heads 9 and 10 attached to this drum 7 are rotated by a drum motor 8.
The signal A recorded on the tape 1 is reproduced. The reproduced signal A is alternately taken out one field at a time through switches 3 and 4 and a switch circuit 11, demodulated by an FM demodulator 12, and taken out from an output terminal 13. Note that the reproduced signal A and signal B are each monitored on a monitor screen. The rotational speed of the motor 8 is detected by a pulse generator 14 provided on the drum 7, and a pulse PG of approximately 30 Hz is applied from the pulse generator 14 to the phase comparator circuits 15 and 16.

On the other hand, the signal B applied to the input terminal 2 is applied to the vertical synchronization separation circuit 17, and the vertical synchronization signal Vb is extracted. This vertical synchronizing signal Vb is frequency-divided by a 1/2 frequency divider 18, becomes a reference signal R of approximately 30 Hz, is applied to a phase comparator circuit 15, and is compared in phase with the pulse PG. This phase comparator circuit 15 is constructed as shown in FIG. 4, and its detailed construction will be described later. The delay amount is stored in memory, and servo errors are corrected in the same way. In order to perform this correction, this phase comparator circuit 1
5, the vertical synchronizing signal Va extracted from the reproduced signal A obtained at the output terminal 13 by the vertical synchronizing separation circuit 19 and the vertical synchronizing signal Vb are added. The error voltage e ₁ obtained from the phase comparison circuit 15 is applied to the motor 8 through an adder 20 to control the rotational phase of the motor 8. still,
Since this motor 8 is a DC motor, a speed servo is applied to it. For this purpose, the rotational speed of the motor 8 is detected by the frequency generator 21,
This detection signal is applied to the speed control circuit 22 to obtain an error voltage _e2 , and the motor 8 is controlled by the voltage obtained by adding the error voltage _e2 and the error voltage _e1 . The error voltage e ₁ is determined by the above-mentioned correction.
When the vertical synchronization signal Vb and the pulse PG have a predetermined phase relationship, a predetermined magnitude is obtained. As a result, the drum 7 is rotated in external synchronization with the vertical synchronization signal Vb of the signal B.

On the other hand, a control signal CTL of approximately 30 Hz recorded on the control chart of the tape 1 is detected by the CTL head 23, and is applied to a phase comparator circuit 16 where the phase is compared with the pulse PG. This error voltage e ₃ controls the capstan motor 25 through the adder 24. Since this motor 25 is a DC motor, speed servo is applied by a frequency generator 26 and a speed control circuit 27. Error voltage e ₄ and error voltage of this speed servo
The motor 25 is controlled by the voltage obtained by adding _e3 . This allows capstan 28
Tracking servo is achieved by controlling the rotation of the . As a result of the above, the reproduced signal A obtained at the output terminal 13 is synchronized with the vertical synchronization signal Vb.

Next, when tape 1 runs to point a in Figure 2 in this state, when you press the edit button on the VTR, this VTR switches to recording mode, and switches 3, 4, 5, 6 are pressed.
is switched to the REC (recording) side contact. As a result, the phase servo is separated from the capstan 28, leaving only the speed servo. Also, pulse PG
The signal is recorded on the tape 1 as a CTL signal via the CTL head 23. Then, the signal B applied to the input terminal 2 is FM modulated by the FM modulator 29, and then
By the heads 9 and 10 via the switches 3 and 4,
One field at a time is recorded on tape 1 alternately.
In this case, since the drum 7 is rotating in synchronization with the vertical synchronization signal Vb, the signal A on the tape 1 is
The video track of signal B and the control signal CTL are recorded at a predetermined pitch.

Next, the configuration and operation of the phase comparison circuit 15 will be explained with reference to FIGS. 4 and 5.

In the above-described operation, when the tape 1 is being played back, the vertical synchronizing signal Va shown in FIG. 5A is applied to the input terminal 30 of the phase comparison circuit 15 shown in FIG. A vertical synchronizing signal Vb shown in FIG. 5B is added. Further, a reference signal R shown in FIG. 5C is applied to the input terminal 32, and a pulse PG shown in FIG. 5E is applied to the input terminal 33. A D-type flip-flop circuit 34 is used to prevent malfunctions from when the tape 1 is started from point b and the drum motor 8 is driven until it enters a stable state.
will be provided. This D-type flip-flop circuit 3
4 is provided to the AND gate 25 as Q1 output " ₁ " (high level) when the pulse PG and the vertical synchronizing signal Vb have a phase relationship within a predetermined range. The other terminals 36 and 37 of this AND gate 35 are connected to a signal I which becomes "1" in the reproduction mode and becomes "0" when the reproduction mode is switched to the recording mode.
A clock CK ₁ of several Hz is added to each. Therefore, at this time, this AND gate 35 is clock CK ₁
This clock _CK1 is counted by the up-down counter 38. This counter 38
is from terminal 39 when power is applied to the VTR.
A preset signal is applied to the PE (preset enable) terminal, thereby presetting a predetermined count start value N. Also, at this time, the vertical synchronizing signals Va and Vb are added with a certain phase difference. When the vertical synchronizing signal Vb triggers the monomulti 40, a pulse of a predetermined width is outputted from the monomulti 40 and applied to the D-type flip-flop 41. Since this flip-flop 41 is triggered by the vertical synchronizing signal Va,
When Vb has a phase difference larger than the pulse width, this flip-flop 41
_Q2 output is "0". The counter 38 counts down or counts up the clock CK1 from the preset value N, depending on whether the _Q2 output is "0" or " ₁ ".

On the other hand, the trapezoidal wave generating circuit 42 generates a trapezoidal wave signal T shown in FIG. 5D based on the reference signal R. This trapezoidal wave signal T is transmitted to the sampling hold circuit 43.
In addition to this, the signal is sampled with a sampling pulse S applied from the monomulti 44. This sampled voltage is taken out from the output terminal 45 as an error voltage e ₁ and is then taken out from the adder 20 in FIG.
added to. Pulse PG also triggers D-type flip-flop 46. Since this flip-flop 46 has a voltage +B applied to its D terminal, its _three outputs fall from "1" to "0" every time it is triggered by a pulse PG. As a result, counter 47 is preset to the count value of counter 38. This counter 47 is a 1/M (M>N) frequency division counter and counts the 1-2 MHz clock _CK2 applied to the terminal 48. The counter 38 receives vertical synchronization signals Va and Vb from the flip-flop 41.
The counting direction is set based on the determination result of the phase state. Thus, the counter 38 is clocked.
After counting down or counting up CK ₁ n times from the preset value N, when the counter 47 is preset by the pulse PG, this counter 4
7 counts the clock _CK2 with N+n or N-n as the preset value. Therefore, this counter 4
7 is clock CK ₂ M-(N+n) or M-(N
+n) outputs the signal P.
Therefore, this signal P is a delayed version of the pulse PG, and the amount of delay has a magnitude corresponding to the frequency and phase shift of the vertical synchronizing signals Va and Vb. This signal P is further converted into a sampling pulse S shown in FIG. This sampling pulse S is equivalent to the pulse PG' in FIG.
The sampling position is a predetermined position when the pulse PG and the vertical synchronization signal Vb have a predetermined phase relationship. Note that signal P resets flip-flop 46 and also triggers flip-flop 34. Furthermore, since the output of the monomulti 40 is applied to the D terminal of the flip-flop 34, when the motor is driven and reaches a predetermined speed, its _Q1 output becomes "1".

As described above, when the vertical synchronizing signals Va and Vb are synchronized and the reproduced signal A is completely synchronized with the signal B, the VTR is switched to the recording mode and the signal B is recorded. At this time, and gate 35
Since the terminal 36 changes from "1" to "0", the counter 38 stops counting. Therefore, the preset value of the counter 47 is fixed, and from now on, the counter 47 is set to 1/M-(N+n) or 1/M-(N-n).
Operates as a frequency division counter. As a result, the sampling pulse S becomes the pulse PG delayed according to the frequency and phase of the vertical synchronizing signal Vb, and this drum servo circuit operates using the vertical synchronizing signal Vb as a reference signal.

The second video signal A is recorded on the tape 1 on which the first video signal A is recorded.
The recording and reproducing apparatus is configured to edit and record the video signal B of the tape from the editing point a of the tape. a first phase comparator 4 that compares the phase of the video signal with the vertical synchronization signal Vb and generates an error signal _e1 ;
2, 43, 44, 46, 47, etc., a servo circuit that controls the rotation of the head drum based on the error signal, and a detection means 36 that detects whether the recording/reproducing device is in the reproduction mode or the recording mode.
I, etc., second phase comparators 40 and 41 that compare the phases of the vertical synchronization signal Va of the first video signal and the vertical synchronization signal Vb of the second video signal when in the playback mode; Phase control means 35 and 38 for controlling the phase relationship between the pulse given to the first phase comparator and the vertical synchronization signal of the second video signal in accordance with the output of the second phase comparator. , when the detection means detects that the recording/reproducing apparatus has been switched from the reproduction mode to the recording mode at the editing point, the control operation of the phase control means is stopped and the pulse and the second The present invention relates to a recording and reproducing apparatus in which the phase relationship between a video signal and a vertical synchronizing signal is fixed to the phase relationship immediately before the switching.

Therefore, according to the present invention, when editing a tape, the playback signal of the tape can be synchronized with an external signal, and when recording an external signal, the drum servo is applied based on the vertical synchronization signal of the external signal. be able to. Especially when editing two tapes with different standards, the phases of the reproduced vertical synchronization signals often differ from each other, and if this is recorded as is, the position of the vertical synchronization signal on the video track will shift. During playback, the screen will be significantly distorted at the editing point. Since the present invention performs control by comparing the phases of the vertical synchronization signals Va and Vb of the two signals A and B, the deviation between the two vertical synchronization signals can be corrected and recorded at the same position on each video track. I can do it. Therefore, no matter which tape's signal is recorded on the other tape, the recording can be performed according to the standard of this other tape. Further, after the editing point is passed, the operation of the phase control means is prohibited, so that the phase relationship is maintained and stable control can be performed without malfunction.

[Brief explanation of the drawing]

Figure 1 is a waveform diagram to explain the principle of obtaining error voltage during recording in the drum servo circuit, Figure 2 is a schematic diagram of a tape edited in insert mode, and Figure 3 is the drum servo circuit of a VTR according to the present invention. 4 is a circuit system diagram showing an embodiment of the capstan servo circuit, FIG. 4 is a circuit system diagram showing an embodiment of the phase comparator circuit, and FIG. 5 is an output waveform diagram of each part of FIG. 4. In addition, in the symbols used in the drawings, 1...
... tape, 7 ... head drum, 8 ... drum motor, 14 ... pulse generator, 15 ... phase comparison circuit, 17 ... vertical synchronization separation circuit, 38 ...
...up-down counter, 41...D-type flip-flop, 42...trapezoidal wave generation circuit, 43...sampling hold circuit, 44...mono multi,
47...Counter.

Claims (1)

[Claims] 1. In a recording and reproducing apparatus configured to edit and record a second video signal on a tape on which a first video signal has been recorded, from an editing point of the tape, according to the rotational phase of the head drum. a pulse generating means for generating a pulse; a first phase comparator for generating an error signal by comparing the phases of the pulse and a vertical synchronizing signal of the second video signal; a servo circuit for controlling; a detecting means for detecting whether the recording and reproducing device is in a reproduction mode or a recording mode; and a vertical synchronization signal of the first video signal and the second video signal when in the reproduction mode. a second phase comparator that compares the phase of the signal with the vertical synchronization signal;
The above pulse given to the phase comparator of
and a phase control means for controlling the phase relationship between the video signal and the vertical synchronization signal, and the detecting means detects that the recording and reproducing apparatus has been switched from the reproduction mode to the recording mode at the editing point. the recording/reproducing apparatus, wherein the control operation of the phase control means is stopped to fix the phase relationship between the pulse and the vertical synchronization signal of the second video signal to the one immediately before the switching.