JPH0640402B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a magnetic recording / reproducing apparatus such as a video tape recorder (hereinafter referred to as VTR). And, in particular, it relates to a configuration for joint photography.

[Technical Background of the Invention] In a conventional VTR, when joint-shooting is performed, the joint between tracks is determined based on a control pulse recorded on a magnetic tape.

For example, in the method shown in FIG. 6, when the pause button is operated, first, the magnetic tape is rewound by, for example, 18 frames while counting the control pulses, and the VTR is set to the pause mode. After that, when the pause mode is released, the VTR is set to the reproduction mode, and tracking control for tracking the rotary head to the recording track is performed. In this state, the control pulse is counted, and when it advances by 15 frames, the VTR is set to the recording mode. As a result, the joint shooting is started so as to overwrite the remaining three frames.

FIG. 7 shows a recording pattern of the magnetic tape 11,
In the figure, 12 is a recording track formed by the helical scan of the rotary head, and 13 is a control track formed by the control head. x ₁ is the running direction of the magnetic tape 11, and x ₂ is the head scanning direction. Reference numeral 12a is a track formed when the pause button is operated, 12b is a track 18 frames before the track 12a, and 12c is a track 3 frames before the same.

The track joint is set to the track 12c. In this case, the VTR will wait 15 seconds after the pause mode is released.
Since the tracking position of the rotary head has converged to the regular convergence position at the stage of reproducing the frame, it is possible to realize joint shooting without image distortion at the joint.

8 and 9 are timing charts showing another example of joint shooting. In the illustrated example, when the pause button is pressed, an RF switching signal (a signal serving as a reference for generating a head switching signal or a control pulse (CTL)) (RF
The duty of the control pulse (CTL) generated from P) is changed. After that, the signal (PR) instructing the recording mode is set to the low level to release the recording mode, the magnetic tape is rewound for a predetermined period, and then the Pogue mode is set. When the pause mode is released from this state, as shown in FIG. 9, the drive signal (P
D) is set to the high level to start the tape running, and the signal (PR) for instructing the reproduction mode is set to the high level to set the VTR to the reproduction mode. At this time, the change position is detected while monitoring the duty of the control pulse (CTR). Then, the joint is judged from this detection output, and when the joint is reached, the VTR is set to the recording mode and joint photographing is started. The control pulse (CTLR) shown in FIG. 8 is a recording control pulse, and the control pulse (CTLL) shown in FIG.
P ₁ ) is the reproduction output of the control pulse (CTL), and (CTLP ₂ ) is its waveform shaping output.

[Problems of Background Art] However, since the conventional joint photographing method is a method of judging a joint based on a control pulse (CTL),
Control pulse (C
It cannot be used in a VTR that does not record TL).

Further, even in the system for recording the control pulse (CTL), the control head is apt to cause the clogging, so that it is not possible to secure a highly accurate joint unless the VTR is properly maintained.

[Object of the Invention]

The present invention has been made to cope with the above circumstances, and provides a magnetic recording / reproducing apparatus that enables joint photographing regardless of whether or not control pulses are recorded and that can set highly accurate joints. With the goal.

[Outline of Invention]

According to the present invention, when an operation for setting the pause mode is performed, the recording mode is canceled after the recording of the predetermined specific track is stopped, and the capstan is reversed to set the rewinding mode for a predetermined period. . Then, the number of pulses synchronized with the rotation of the capstan is counted from the time the tape rewinding is started to the time it is stopped. Next, when the pause mode is released and the reproduction mode is set, the pulses are counted. Then, the specific track is detected using the count value of the pulse in the reproduction mode and the count value of the pulse in the rewinding, and the mode is switched from the reproduction mode to the recording mode according to the detection output to perform the joint shooting. It is the one.

Example of Invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In the following description, a case where the present invention is applied to a 4-frequency pilot type VTR will be described as a representative.

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention.

Now, assuming that the VTR is in the recording mode, information signals such as video signals and pilot signals are recorded by the rotary heads 23 and 24 on the magnetic tape 22 driven and driven by the capstan 21. The information signal is generated by the information signal generation circuit 25, and the pilot signal is generated by the pilot signal generation circuit 26.
It is frequency-multiplexed at 7 and given to the rotary heads 23 and 24.

The cylinder 28 having the rotary heads 23 and 24 is rotationally driven by a motor (M) 29. In this case, the signal generated from the rotation detector 30 is passed through the amplification circuit 31 and the waveform shaping circuit 32 to generate a switching pulse (SWP). Then, the switching pulse (SWP) is applied to the servo circuit 33, and the servo circuit 33 compares the phase of the switching pulse (SWP) with the reference signal applied from the system control circuit 34 to obtain the switching pulse (SWP). The rotation of the cylinder 28 is controlled so that is a 30 Hz rectangular wave. As a result, the cylinder 28 is controlled to rotate at a constant speed and a constant phase.

The switching pulse (SWP) is further applied to the recording / reproducing amplifier circuit 27 and the pilot signal generating circuit 26. The recording / reproducing amplifier circuit 27 switches the input of the mixed signal of the information signal and the pilot signal to the rotary heads 23 and 24 according to the switching pulse (SWP). The pilot signal generation circuit 26 divides the switching pulse (SWP) into two to generate a pulse (P ₀ ) having a frequency of 15 Hz, and according to this pulse (P ₀ ) and the switching pulse (SWP), the division ratio of the reference clock (CP). , And four pilot signals with different frequencies are sequentially and repeatedly output. When the frequencies of the four pilot signals are respectively ( ₁ to ₄ ), the recording state of the pilot signals on the magnetic tape 22 is as shown in FIG.

On the other hand, in the tape running control, the output signal of the frequency generator 36 that detects the rotation of the capstan motor 35 is shaped into a pulse (P ₁ ) through the amplification circuit 37 and the waveform shaping circuit 38, and the pulse (P ₁ ) is applied to the servo circuit 39. Then, the servo circuit 39 compares the phase (P ₁ ) of the pulse of the frequency generator 36 with the reference pulse, and the comparison result is given to the motor control circuit 40 to control the rotation of the capstan motor 35, thereby running the tape. Is controlled to be constant.

When the pause button (not shown) is operated while the VTR is in the recording mode, the signal (S ₁ ) instructing the pause mode is input to the system control circuit 34. When this signal (S ₁ ) is given, the system control circuit 34 releases the recording mode as shown in FIG. 3 at the timing when the recording of the predetermined specific track is completed, and the motor control circuit 34 40
A reverse rotation signal (CRVS) is applied to the VTR to set the VTR to the rewind mode.

As the predetermined specific track, for example, a track on which a pilot signal of frequency ( ₄ ) is recorded is selected. Frequency ₍₄₎ pulse (SWP) to record the pilot signal, when viewed in relation to _{(P 0),} they are made when both the low level. Therefore, the system control circuit 34 uses the pulse (SWP),
The VTR is set to the rewind mode at the timing when both (P ₀ ) rise. System control circuit 34
Is a stop signal (COF) for stopping the capstan motor 35 after a predetermined time has elapsed since the reverse rotation signal (CRVS) was generated.
F) is generated and the VTR is set to the pause mode.

Reverse rotation signal (CRV
S) is generated, the counting circuit 41 causes the frequency generator 36
The number of output pulses of is counted. This counting operation is continued until a stop signal (COFF) is output from the system control circuit 34, whereby the rotation of the capstan motor 35 is completely stopped. The count value of the counting circuit 41 is held in the system controller 34.

When an operation for canceling the pause mode is performed in the pause mode, the system control circuit 34 sets the stop signal (COFF) to the low level to drive the magnetic tape 22 as shown in FIG. Further, the system control circuit 34 sets the VTR to the reproduction mode. In this reproducing mode, the pilot signal reproduced from the magnetic tape 22 is given from the recording / reproducing amplifier circuit 27 to the automatic tracking control circuit (ATF) 42.
The automatic tracking control circuit 42 detects the deviation of the tracking positions of the rotary heads 23 and 24 from the reproduction output of the pilot signal and the pilot signal supplied from the pilot signal generation circuit 26, and supplies it to the servo circuit 39. As a result, servo is applied so that the pilot signal reproduced from the magnetic tape 22 matches the pilot signal output from the pilot signal generation circuit 26. In this way
After the tracking pull-in is completed, the system control circuit 34 detects the last recorded track in the recording mode and sets the recording mode for the joint shooting.

The detection of the final track is performed according to the count value of the counter circuit 41 in the rewind mode and the count value of the counter circuit 41 in the reproduction mode. That is, when the stop signal (COFF) becomes low level and the start of the motor 35 is started, the counting circuit 41 counts the output pulse (P ₁ ) of the frequency generator 36 as in the rewinding mode.

The detection of the last track will now be described in more detail.
Now, the frequency of the switching pulse (SWP) is set to 29.9.
7 Hz, the switching frequency of the rotary heads 23 and 24 is 59.
It is set to 94 Hz. It is also assumed that the output pulse (P ₁ ) has a frequency of 359.64 Hz at the set tape speed. Therefore, when the tape 22 is running at the set speed, six pulses (P ₁ ) are generated during the selection period of each head 23, 24 as shown in FIG. On the other hand, the number of pulses (P ₁ ) generated is less than 6 during the transition period of the tape stop → constant speed and constant speed → stop.

The rewinding of the tape 22 in the rewinding mode is
Assuming that the number of pulses (P ₁ ) generated on the assumption that the tape is run at a constant tape speed over the entire section is N and the number of decrease of pulses in the transition period is ΔN, the pulse (P ₁ ) in the rewind mode is Number of occurrences (N
₁ ) becomes N ₁ = N−2ΔN (1). Similarly, the pulse (P ₁ ) in the above reproduction mode
The number (N ₂ ) of occurrences of N ₂ is N ₂ = N−ΔN (2) In addition, here, it is assumed that the number of reductions during the transition period of stop → constant speed and constant speed → stop is equal.

In the reproducing mode, the number of pulses (P ₁ ) generated when the rotary heads 23 and 24 scan the last four tracks (Tn- ₃ ) to (Tn) is 24. If this is in the rewind mode, a transition period from stop to constant speed is entered, so 24-Δ
N. Here, considering the number (N ₃ ) obtained by subtracting the value of 24-ΔN from the equation (1), the count value of the counting circuit 41 becomes this N ₃ (= N-ΔN-24) in the reproduction mode. Is the time when the scanning of the track immediately preceding the last four tracks has ended. Therefore, the timing at which all of the pulses (SWP) and (P ₀ ) become low level first from the timing when the count value of the counting circuit 41 becomes N ₃ corresponds to the scanning timing of the final track (Tn). . The system control circuit 34 detects the last track (Tn) as described above, and detects the last track (Tn).
The VTR is set to the recording mode with the scanning end timing of n) as the joint timing. In this case, the final track can be accurately detected even if there is an error in the counting of the counting circuit 41. Incidentally, if taking into account the reduction in the transient period of the pulse, simply using the N-24 in place of N _3.

Further, if the number of reductions (ΔN) in the transition period can be strictly measured, a value obtained by adding ΔN to the count value N ₁ in the rewind mode period is calculated, and in the reproduction mode, the counting circuit 41 determines that the count value is N ₁
When + ΔN, the recording mode may be set. However, since it is difficult to predict and measure ΔN accurately and it is necessary to consider the counting error of the counting circuit 41, the simplest method is from N ₁ to, for example, one track or two tracks. The number of generated pulses (P ₁ ) of 6 or 12 is subtracted, and in the reproduction mode, the counting circuit 41
When the count value of becomes _N 1 -6 and _N 1 -12, pulse (SWP), by monitoring the state of the _{(P 2),} a method of detecting the last track and the like. That is, the system control circuit 34 causes the pulse (SWP), (P ₀ )
Of the last four tracks (Tn- ₃ ) to (Tn) at the timing of starting monitoring of the state of
(Tn- ₃ ), (Tn- ₂ ), (Tn except for n)
_-1 ) is set when scanning. By doing this, the frequency ( ₄ ) is the same as the last track (Tn).
System control circuit 3 at the time of scanning the track (Tn- ₄ ) four tracks before the pilot signal of is recorded.
It is possible to prevent the track No. _{4 from} judging this track (Tn- ₄ ) as the final track.

The pulse (SWP), _{(P 0)} tracks _(Tn-4) a timing to start the monitoring of the even set during the scanning of the previous track, the pulse (SWP), _{(P 0)} timing becomes low level both By counting
The final track (Tn) can be detected.

Further, in the above description, the case where the rewinding period is set by outputting the stop signal (COFF) after a fixed time has elapsed after outputting the reverse rotation signal (CRVS), but the count value of the counting circuit 41 is constant. Reverse signal when the value is reached
(CRVS) may be output. Even in this case, the count value of the counting circuit 41 at the timing when the magnetic tape 22 is completely stopped is set to the system control circuit 3
Needless to say, it is held at 4.

Further, the present invention is applicable not only to the 4-frequency pilot type VTR but also to a VTR using a control pulse. In this case, in the case of a VTR that uses, for example, two heads as the rotary head, the track recorded by either one of the two heads may be set as the specific track.

〔The invention's effect〕

As described above, according to the present invention, since the joint is detected based on the count value of the pulse synchronized with the rotation of the capstan,
It is possible to perform continuous shooting with or without recording control pulses. Further, it is possible to provide a magnetic recording / reproducing apparatus capable of setting a highly accurate joint.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the structure of an embodiment of the present invention, and FIG.
FIG. 4 is a diagram showing a tape recording pattern of a 4-frequency pilot system, FIGS. 3 to 5 are timing charts for explaining the operation of FIG. 1, and FIGS. 6 and 7 are examples of a conventional joint photographing method. FIG. 8, FIG. 8 and FIG. 9 are diagrams for explaining another example. 21 ... Capstan, 22 ... Magnetic tape, 23, 2
4 ... rotary head, 25 ... information signal generating circuit, 26 ...
... Pilot signal generating circuit, 27 ... Recording / reproducing amplifier circuit, 28 ... Cylinder, 29 ... Cylinder motor, 30
... Rotation detector, 31,37 ... Amplification circuit, 32,38 ...
… Waveform shaping circuit, 33, 39 …… Servo circuit, 34 ……
System control circuit, 35 ... Capstan motor, 36 ... Frequency generator, 40 ... Motor control circuit, 41 ... Counting circuit, 42 ... Automatic tracking control circuit.

Claims (1)

[Claims] 1. In a magnetic recording / reproducing apparatus for recording / reproducing by scanning a magnetic tape with a plurality of rotary heads, when an operation for setting a pause mode is performed in a recording mode, a predetermined identification is performed. The first mode switching means for canceling the recording mode and setting the rewind mode when the track recording is completed, and for canceling the rewind mode after a lapse of a predetermined period from the setting of the rewind mode, the pause mode And a third mode switching means for setting the playback mode, and a third mode switching means for releasing the pause mode and setting the playback mode when an operation for canceling the pause mode is performed at the time of setting the pause mode. Pulse counting means for counting the pulses synchronized with the rotation of the capstan, and at least the rewinding time in the pulse counting means. By using the count value and the count value in the reproduction mode, one or more tracks before the final track formed in the recording mode in the reproduction mode are detected, and thereafter, the pulse related to the track switching is used. A magnetic recording / reproducing apparatus comprising: fourth mode switching means for detecting a final track and switching the mode from a reproducing mode to a recording mode in accordance with the detected output.