JPH0235374B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic recording and reproducing method suitable for avoiding occurrence of disturbances at recording joints on a magnetic tape when a helical scan VTR temporarily stops recording and then resumes recording. Regarding the method.

As is well known, the helical scan VTR has 1
Because the fields are recorded diagonally,
If the magnetic tape is temporarily stopped during recording, and then the magnetic tape is run and recorded, the recording phase of the diagonal tracks at the joint may be different.
Since the inclination angle of the track changes before and after the temporary stop, the reproduced image of that part becomes distorted.

A so-called electronic editing method is used to remove the disturbances at the joints of images on the magnetic tape described above, but in this case, the magnetic tape is played back once, and editing and recording is performed by predicting the recording editing point or by adding some kind of mark. . This method is very tedious, but
Disturbances at the joints of images are eliminated.

The present invention provides a magnetic recording and reproducing method that allows an electronic editing system to be completed in a short time and eliminates operational complexity.

In order to solve the above-mentioned problems, the present invention, when temporarily stopping the magnetic tape during recording, stops the recording from the moment of the temporary stop, and a times the steady recording speed υ for a certain period of time _T1 ( The capstan motor is rotated in reverse at a speed of 1 < any positive number of a), the magnetic tape is reversely fed, the pinch roller is separated, the capstan motor is returned to normal rotation, and then the temporary stop is performed. When releasing the pause, immediately press the pinch roller to the capstan, run the magnetic tape at a steady speed υ, and wait for a certain period of time from the moment the pause is released.
After T ₂ has passed, recording is restarted, and at this time the above a.
The relationship between T ₁ and T ₂ is set to 1≦aT ₁ /T ₂ <1.5, so that the joints of recorded image signals on the magnetic tape are continuous.

An embodiment of the present invention will be described below based on the drawings. FIG. 1 shows a plan view of a running system for a magnetic tape 1 and a rotating magnetic head device 2 used in this embodiment, and FIG. 2 shows a front view and a circuit block diagram of the device 2. In FIGS. 1 and 2, the magnetic tape 1 is transferred by a capstan 3 and a pinch roller 4 in the direction of arrow A.
The pinch roller 4 is attached and detached by a pinch roller attachment/detachment device 5 composed of a solenoid or the like. In the embodiment of the present invention, a so-called DD capstan type is shown in which the shaft of the capstan motor 6 is the capstan 3. On the other hand, there is a rotating magnetic head device 2 on the way of the magnetic tape running. Video signals are recorded on the magnetic tape 1 by the video heads 8A, 8B on the rotary disk 7 of this device 2 as diagonal video tracks 41 as shown in FIG. Therefore, the magnetic tape 1 is attached to the guide pole 9.
A and 9B are wound around the drum 10 by more than 180 degrees, and are moved diagonally along the lead 11 on the drum 10. Also the fourth
It is necessary to control the rotational phase of the drum motor 13, which is directly connected to the rotary disk 7 by the shaft 12, so that a video signal can be recorded in each field of the video track 41 shown in the figure.

The control method is as follows. That is, the shaft 12 directly connected to the drum motor 13
A magnet 15 is placed on a rotating disk 14 fixed to
If a fixed magnetic head 16 is provided near the rotating circumference of the magnet 15, the rotational phase of the video head 8A or 8B on the rotary disk 7 can be obtained as the output of the fixed magnetic head 16. Therefore, by controlling the drum motor 13 using the error signal obtained by comparing the phases of this rotational phase signal and the vertical synchronization signal of the video signal to be recorded, recording can be performed as shown in FIG. 4.

This will be specifically explained with reference to the block diagram in FIG. 2 and the signal waveform diagram of each block in FIG. A video signal to be recorded, shown in FIG. 3a, is applied to terminal 21. This video signal is transmitted to the vertical synchronization signal separation circuit 22.
and modulator 23 (usually a frequency modulator). As shown in FIG. 3b, only the vertical synchronizing signal part of FIG.
2 is applied to the frequency divider 24, resulting in the square wave signal shown in FIG. 3c. Further, the rectangular wave signal is applied to a phase comparator 25. Since the phase comparator 25 also receives the signal shown in FIG. 3d, which is the output of the fixed magnetic head 16 and indicates the rotational phase of the video head 8A, a phase error signal of both signals is obtained. By adding the phase error signal to the drum motor 13 whose rotational speed can be controlled, a phase control loop is formed, and the video heads 8A and 8B are connected to the vertical synchronization signal of the video signal to be recorded and the phase difference α [third
Figure d]. Accordingly, a video track is sequentially formed on the magnetic tape 1 in contact with the drum 10, one field at a time. At this time, the capstan motor 6 is also controlled to have a constant rotational speed, and the magnetic tape 1 is transferred at a constant speed by the capstan 3 and the pinch roller 4. Note that the output of the modulator 23 is amplified by the recording amplifier 26, and is further amplified by the brushes 17A, 17B and the slip ring 18.
The video heads 8A and 8B are connected to the video heads 8A and 8B via A and 18B.
has been added to.

The above is a general explanation of the recording method in a VTR, but as mentioned above, the present invention is capable of temporarily stopping or so-called splicing in order to cut out parts that do not need to be recorded during such recording. This is intended to eliminate disturbances at the joints of images when recording, and in principle, the recording phase of the video track 41 shown in FIG. 4 is aligned, and the recording phase of the control signal 42 is also aligned. This is what we are trying to do. For example, if a temporary stop is made during recording, the recording track will no longer be the same as when the magnetic tape 1 was running (the dotted line 43 in FIG. 4 indicates the scanning locus at the time of a temporary stop). Even if you restart recording next time,
Since it is difficult to change the rotation of the capstan motor 6 in steps, the video track 41,
It is clear that the recording phase of the control signal 42 is disturbed.

In the present invention, when a temporary stop is performed, the magnetic tape 1 is immediately reversed, and when recording is restarted, the magnetic tape 1 is moved in the forward direction to a certain portion of the reversely traveled portion, and the video track 41 and the control signal 4
In this method, recording is restarted when the two phases are aligned. At this time, the magnetic tape running speed υ (rotational speed of the capstan motor 6) during reverse movement of the magnetic tape 1, the time T ₁ during reverse movement, and the time T ₂ until the start of recording during forward movement. This is a method of controlling the relationship between the two and achieving good connections.

When the VTR user pauses the video, if he presses the pause button 27, the pause mode is memorized in the memory circuit 28, and when he presses the pause button again, the pause is canceled (memory is released). It is assumed that the output of the memory circuit 28 is at H level during a temporary stop, as shown in FIG. 3e. Memory circuit 28
The output of is applied to timing circuit 29 and timing circuit 30. The timing circuit 29 obtains a pulse signal for time _T1 from the moment the pause mode is entered, and its output is as shown in FIG. 3f. Further, the timing circuit 30 obtains a pulse signal for time T2 as shown in FIG. _3g from the time when the pause is released. The signal of FIG. 3f of timing circuit 29 is applied to capstan drive circuit 31. This drive circuit 31 also includes a motor control circuit for switching the rotation direction of the capstan motor 6 and at the same time increasing the rotation speed to a times the normal rotation speed (1<a). When added to the drive circuit 31, the capstan motor 6
is reversed for T ₁ hour from a pause and rotates at a times the normal speed. Then, the length l of the tape that is fed backwards becomes l=aυT ₁ (1), where υ is the steady feed speed described above.

At the end of this time _T1 , it is necessary to remove the pinch roller 4, in which case the signal shown in FIG. 3i is applied to the pinch roller detacher 5. Assuming that the pinch roller 4 is separated from the capstan 3 when the signal is at H level, the signals in FIG. 3i are as shown in FIG.
The signal of f is connected to an exclusive logic OR circuit 32 (Exclusive
OR).

Now, the capstan motor 6 rotates in reverse at a speed a times the normal speed for the time _T1 , but before it is temporarily stopped, it is in a normal recording state, and the capstan is controlled as follows at that time. Assuming that the capstan motor 6 also includes a rotational frequency generator (hereinafter referred to as FG) and that several hundred pulses are generated for one revolution of the capstan motor 6, this signal is frequency-divided. By doing so, one pulse per rotation, that is, a rotational phase signal of the capstan motor 6 can be obtained. The output of the FG is applied to a resettable frequency divider 33. At the output of this frequency divider 33, a signal shown in FIG. 3I is obtained. This signal passes through a switch circuit 34 and is applied to a phase comparator 35. This phase comparator 35 includes the 1/2 frequency divider 2.
The third frequency is divided by 1/2 of the vertical synchronization signal obtained in step 4.
The signal in Figure c is added, and the phase error signal of both signals is obtained here. This phase error signal is applied to the capstan motor drive circuit 31, where a phase control loop is formed, and the capstan motor 6 rotates a fixed number of times in synchronization with the vertical synchronization signal of the video signal to be recorded. do. This control is performed during the period before the pause and after _T2 hours after the pause is released [after the recording is restarted]. That is, the switch circuit 34 is supplied with the signal shown in FIG.
is added to the phase comparator 35. Note that since the signals shown in FIG. 3e and g are applied to the OR circuit 36, the signal shown in FIG. 3h is obtained as an output.

Now, during T ₁ hour when the temporary stop is performed, the capstan motor 6 is operated at a steady speed as described above.
As already mentioned, the capstan motor 6 rotates in the normal direction after T ₁ hour has elapsed and until the temporary stop is released. Since the pinch roller 4 and the capstan 3 are separated from each other, the capstan motor 6 is rotating, but the tape does not advance.
Further, the capstan motor 6 may be rotated at a substantially constant rotation speed in preparation for the next operation.

Next, we will explain the control for T ₂ hours until the pause is canceled and recording is restarted. As mentioned above, since the magnetic tape 1 is being fed backwards for T ₁ hours (the length of the magnetic tape is indicated by l in equation (1)), if recording is resumed immediately after the pause is released, then Double recording will occur, and the track recording phase and control recording phase will be disturbed. Therefore, the present invention employs a method in which recording is resumed after the reversely fed magnetic tape 1 is moved in the forward direction for T ₂ hours. i.e.
The purpose is to match the recording phase of the track and the phase of the control signal during _T2 hours. First, when the temporary stop is released, the pinch roller 4 is pressed against the capstan 3 by the pinch roller attachment/detachment device 5, and the magnetic tape 1 runs. Since the switch circuit 34 receives the signal shown in FIG. 3h from the OR circuit 36, the signal from the control magnetic head 19 is transmitted to the phase comparator 35 at the same time as the magnetic tape 1 runs. That is, a control signal as shown in FIG. 3j is transmitted to the phase comparator 35. Note that the switch circuit 34 is configured to transmit the output of the control magnetic head 19 to the phase comparator 35 from the moment the temporary stop is effected. Therefore, no control signal is generated.

When the control signal is applied to the phase comparator 35 as described above, the phase comparator 35 receives the signal shown in FIG.
Since the 1/2 frequency divided signal of the vertical synchronization signal of the video signal to be recorded as shown in FIG. A phase control loop is formed here, and although a synchronization relationship is not obtained immediately after the pause is released, the phases of the vertical synchronization signal and the control signal match during time _T2 . In other words, even if recording of the video signal and control signal is started after time _T2 has elapsed, the phase of the previously recorded video track 41 matches the phase of the newly recorded video track. The phase of the control signal 42 also matches. By the way, the capstan motor 6 is controlled from the time when recording is resumed.
A phase control loop is formed by the signal obtained by dividing the FG output by the frequency divider 33 and the output of the 1/2 frequency divider 24 shown in FIG. Since the incoming signal changes from the control signal (Fig. 3 i) to the output signal of the frequency divider 33 (Fig. 3 l), in order to match the phase of both signals at the time of switching, the frequency divider 33 is changed to the control signal 42. and reset it. The gate circuit 37
This is for applying the control signal to the frequency divider 33 only during the _T2 period.

The control signal amplifier 38 applies the signal shown in FIG. 3c to the control magnetic head ₁₉ , and the OR circuit 36 shown in FIG. gate signal), control signal (indicated by the third
It is designed to prevent the recording of figure c). Similarly, the signal shown in FIG. 3h, which is the output of the OR circuit 36, is applied to the recording amplifier 26 so that recording is not performed during the above-mentioned period.

Now, here is the issue of setting T ₂ hours.
The length l _p of the magnetic tape that advances in time T ₂ is as follows, since the tape running speed during this period is approximately the steady speed υ during recording as described above, l _p =υT _{2 .} . . (2). First, if we set the relationship with the length l of the magnetic tape to be fed backwards so that l≧l _p , recording will start before the entire piece of backward feeding has been returned, so double recording will be performed on one copy. A part arises. The track with horizontal lines shown in FIG. 4 indicates a double recorded portion, and the area from point 44 to point 45 is the double recorded portion. It is better to keep this period as short as possible, but if the start-up of the capstan motor 6 and the phase alignment time are affected by temperature and humidity, the length of the magnetic tape sent during _T2 hours will _vary . It is desirable to provide such an overlap portion. It is clear from the above point that when l< _lp , some portions are not recorded, and such a setting must be avoided.

To explain with an example, a is set to 2 and υ
= 3.3 cm/sec, T ₁ = 0.5 sec, T ₂ = 0.7 sec, the length on the tape is 1 cm, and the number of tracks is approximately 20 for double recording. If the double recording part is too long, the signal/noise ratio, that is, S/N of the reproduced image in the double recording part will decrease somewhat, so from the relationship l/l _p = aT ₂ /T ₁ , 1≦aT ₂ / Duplicate recording with T ₁ <1.5 is desirable.

According to the present invention, helical scan VTR
When connecting images,
It is possible to eliminate image disturbances at the seams, and it automatically prepares for editing recording during the pause operation during recording, and there is a slight time delay (T ₂ period) when recording resumes. , it is possible to record good continuous images, and its industrial value is extremely large.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a plan view of a magnetic recording/reproducing apparatus used in the present invention, FIG. 2 is a front view and a circuit block diagram, and FIG. 3 is a diagram of each part of the circuit block in FIG. The waveform diagram in FIG. 4 is a recording track pattern diagram of the magnetic tape. DESCRIPTION OF SYMBOLS 1... Magnetic tape, 2... Rotating magnetic head drum device, 3... Capstan, 4... Pinch roller, 5... Pinch roller attachment/detachment device, 6... Capstan motor, 27... Temporary stop switch, 28...
...memory circuit, 29,30...timing circuit,
31... Capstan motor drive circuit, 32...
Exclusive logic OR circuit, 33... Frequency divider, 34... Switch circuit, 35... Phase comparator, 36... OR circuit, 37... Gate circuit, 38... Control signal amplifier.

Claims (1)

[Scope of Claims] 1. When temporarily stopping the magnetic tape during recording, the recording is stopped from the moment of the temporary stop, and the recording steady _- state feed speed v is multiplied by a (1<a
The capstan motor is rotated in reverse at a speed of (an arbitrary positive number), the magnetic tape is fed backwards, the pinch roller is separated, the capstan motor is returned to normal rotation, and the pause is then released. At this time, the pinch roller is immediately pressed against the capstan, the magnetic tape is run at a steady speed v, and recording is resumed after a certain period of time T ₂ has elapsed from the point at which the _pause is released _. A magnetic recording and reproducing method in which the relationship of 1≦aT ₁ /T ₂ <1.5 is set so that the joints of recorded image signals on a magnetic tape are continuous. 2. When the magnetic tape runs after the pause is released, the control signal recorded on the magnetic tape is played back for a certain period of time _T2 , and the phase of this signal is compared with the vertical synchronization signal of the video signal to be recorded. 2. The magnetic recording and reproducing method according to claim 1, wherein recording is restarted after phase adjustment is performed by applying the phase error signal obtained by the capstan motor to the capstan motor.