JPS6127828B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for editing images.

FIG. 1 shows an example of a magnetic tape pattern diagram when a new signal is re-recorded from the middle of a tape that has already been recorded on a conventional home VTR. 1 is an audio track, 2 is a control track, 3 is a video signal track of channel 1, and 4 is a video signal track of channel 2. Home VTRs generally employ a two-head helical scan system, in which video signals are recorded alternately in two heads (channel 1 and channel 2) as shown in FIG. Furthermore, since these two heads record with different head gap directions (azimuth recording), it is almost impossible to reproduce signals recorded by other channel heads. For this reason, as shown in Figure 1, if the alignment of both video signal tracks is recorded out of order during splice recording, the head will not be able to accurately trace the desired track during playback, and because of azimuth recording, this portion The disadvantage was that the image S/N ratio deteriorated, white noise was generated, and the image became unsightly.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to eliminate unsightly white noise in spliced recorded portions and S/N deterioration of images during playback.

In order to achieve the above object, the present invention provides that when re-recording is performed using a tape that has already been recorded, the tape is run in a playback state before the re-recording starts, and the video is recorded on the tape in accordance with the video track phase. Detects the playback synchronization signal. Next, synchronize this with the newly recorded synchronization signal (CTL) by generating reverse torque in the capstan motor for a time corresponding to the phase difference between the two, and at the same time, the capstan motor is activated only during this time. By decreasing the voltage applied to the tape over time, the tape speed is delayed (that is, the playback synchronization signal is delayed), and the phases of the two are matched accurately and in a short time, and then recording is started. As described above, recording can be performed without disturbing the arrangement of the new and old video signal tracks.

The present invention will be explained in detail below with reference to Examples.

The entire structure of the present invention is shown in FIG. 2, a time chart for explaining its operation is shown in FIG. 3, a main part of an embodiment of the invention is shown in FIG. 4, and its effects are shown in FIG. 5.

In FIG. 2, 5 is a pinch roller, 6 is a capstan shaft, 7 is a capstan motor, 8 is a magnetic tape, and 9 is a CTL head. 10 is a switch for switching the connection to the CTL head during recording and playback, 11 is a recording CTL signal input terminal, and 12 is a recording CTL amplifier. 13 is a reproduction CTL amplifier, 14 is a phase difference detector for detecting the phase difference between the reproduction CTL and the recording CTL, and 41 is an initial offset adding circuit. 15 is a capstan motor control circuit, and 16 is a motor drive circuit.

The operation of this configuration will be explained using the time chart shown in FIG. a is the recording switch signal 17;
b is the playback described in the present invention from the recording switch signal.
The recording start signal 18 is shown delayed by the time necessary for phase alignment between the CTL and the recording CTL. c is the recording CTL signal 19 extracted from the video signal to be recorded;
d is a reproduced CTL signal 2 detected by tape running from a CTL signal already recorded on the tape.
0 and e are phase difference pulses 21 obtained by detecting the phase difference between the reproduction CTL signal 20 and the recording CTL signal 19 using a flip-flop or the like. f is the phase difference pulse 2
The control pulse 22, g, which is obtained by adding an appropriate offset pulse time to the control pulse 22, is a motor applied voltage waveform 23 whose voltage is decreased over time by the period of the control pulse 22.

Here, when the recording switch is turned on (T ₁ ), the recording operation is stopped for a certain period of time (T ₂ - T ₁ ) and the tape is run, during which time the CTL signal 20 already recorded by the CTL head 9 is read. It is detected and amplified via a switch 10 and a reproducing CTL amplifier 13. Also, records extracted from newly recorded video signals
The CTL signal 19 is detected and amplified via a recording CTL amplifier 12, and a phase difference 21 between the two is obtained by a phase difference detector 14 using a flip-flop or the like. An appropriate initial offset pulse width is added to the phase difference pulse 21 obtained here by an initial offset adding circuit 41 to generate a control pulse 22. This control pulse 22 is applied to the motor drive circuit 16 of the capstan motor 7, which is controlled at a constant speed by the motor control circuit 15, to generate maximum torque in the reverse direction, and to change the motor applied voltage over time for this period. (waveform 23). This rapidly slows down the rotational speed of the capstan motor, changes the tape running speed, and changes the phase of the reproduced CTL signal. As a result of the above, the phase difference between the two is instantly improved, and when recording starts ( _T2 ), the phases of the two match, and recording can be performed without disturbing the already recorded head channel phase and the newly recorded head channel phase. I can do it.

Next, a specific example of the motor drive circuit 16 that applies the control pulse 22 is shown in FIG.

In the figure, 24 is a motor coil, 25 is a rotating body that rotates the capstan shaft, and 26 is a motor coil 2.
4 shows a group of switches that change the direction of the current flowing. 27 is a transistor for applying a speed control signal; 28 is a transistor for controlling the maximum voltage applied to the motor; 29 is an amplifying and inverting transistor; 30, 31, 32, and 33 are resistors; 34 is a diode; 35 is a static transistor; capacitance, 36 is control pulse 22
shows the input terminal of Here, when the control pulse 22 is input to the input terminal 36, the switch group 26 is first switched to reverse the direction of the current flowing through the motor coil 24, and at the same time, the motor control circuit 15, resistor 30,
A speed control loop controlled by a closed loop of transistor 27, switch group 26, and capstan motor 7 is controlled by applying a control pulse to the base of transistor 27 via a diode to maximize the speed control voltage. At the same time, this control pulse 22 is integrated by a resistor 31 and a capacitor 35, and the transistor 2
9, transistor 29, resistor 3
The signal amplified and inverted by transistors 2 and 33 is transferred to transistor 2.
Receive at the base of 8, transistor 2 from the emitter
7 to the capstan motor. At this time, the emitter of the transistor 28 becomes as shown in waveform (g) 23.

Next, waveform (g) 2 reduces the voltage applied to the motor over time for the period of this control pulse 22.
The effect of No. 3 is shown in FIG.

In the figure, the vertical axis is the tape delay amount due to control pulses,
The horizontal axis shows the control pulse width. 38 indicates desired characteristics, and 39 and 40 indicate actual characteristics. Here, the characteristic curve 39 is obtained when a circuit for reducing the voltage applied to the motor over time during this control pulse period is not provided. This is because the equation of motion of a rotating body is generally expressed as Jdω/dt+Bω+Q _L =T (where J is the moment of inertia of the rotating body, B is the drag coefficient, and T
is the motor generated torque, _QL is the load torque, and ω is the rotational speed).The tape delay amount is not proportional to the control pulse width, and is approximately a square curve. Therefore, characteristic 39 is improved to characteristic 40 by lowering the voltage applied to the motor in proportion to the control pulse width, and an initial offset ΔT is added to the phase difference pulse to obtain the effect of approaching desired characteristic 38.

Further, when a recording is paused, for example, by operating the rewinding function of the magnetic tape and rewinding it by a certain amount, the same effect as described above can be obtained when the pause is canceled.

As described above, according to the present invention, during continuous shooting, the head switching phase of the already recorded signal and the head switching phase of the newly recorded signal are precisely aligned in a short time, so that the continuous shooting portion can be recorded. It is possible to eliminate poor S/N ratio and white noise in the reproduced image, allowing beautiful continuous shooting.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an example of a magnetic pattern in a conventional splicing portion, Fig. 2 is a block diagram showing the entire configuration of the present invention, and Figs. 3 a to g are time charts for explaining the operation of Fig. 2. , FIG. 4 is a specific circuit diagram showing a main part of an embodiment of the present invention, and FIG. 5 is a characteristic diagram showing the effects of the present invention. 7; Capstan motor, 9; CTL head,
10; switch, 12; amplifier, 13; amplifier,
14; Phase difference detector; 16; Motor drive circuit; 28; Transistor; 26; Switch group.

Claims (1)

[Claims] 1. In a device that re-records a new signal from the middle of an already recorded magnetic tape and edits an image, a new signal is recorded with a synchronized signal on the already recorded magnetic tape at the time of re-recording. The apparatus includes means for generating a reverse torque in the capstan motor for a time corresponding to a phase difference between the synchronizing signals, and at the same time reducing the voltage applied to the capstan motor over time for a time corresponding to the phase difference. , a magnetic recording/reproducing apparatus characterized in that re-recording is started after the phase difference between the two is sufficiently reduced. 2. The magnetic recording and reproducing apparatus according to claim 1, characterized in that the magnetic recording and reproducing apparatus is equipped with means for rewinding the magnetic tape by a predetermined amount when the recording is paused.