JPS628355A - Electronic editing servo method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electronic editing servo system in a magnetic recording/reproducing apparatus (hereinafter referred to as a VTR) equipped with a capstan servo system.

BACKGROUND OF THE INVENTION Conventional VTRs use a capstan servo system to improve tracking during playback.

In a VTR equipped with this capstan servo system, during recording, the rotation detection signal of the capstan or capstan motor is compared in phase with a reference signal to control the speed of the magnetic tape at a constant level, and the reference signal is used as a control signal to record the magnetic tape. During 0 playback recorded on the control track, the playback control signal from the control track is compared in phase with the reference signal, and the magnetic tape is controlled so that the phase difference between the two signals becomes a predetermined value, and tracking servo is performed. There is.

Assembled editing (recording of spliced shots) on the relevant VTR
When performing this, first the magnetic tape is rewound from the unrecorded area to the recorded area by a predetermined amount. After a short period of standby mode, the mode is switched to recording mode. This standby mode period is within the range of the rewinding amount of the magnetic tape, and the synchronization signal in the video signal to be recorded is used as the reference signal. , tracking servo is performed in phase with the playback control (CTL) signal, and preparations are made so that the recording pattern at the seam is not disturbed. When switching to recording mode, the playback CTL signal cannot be obtained, so switch to the rotation detection signal of the capstan or capstan motor.
At this time, if the playback CTL signal and the rotation detection signal are not phase matched, the phase lock will be lost.Then, in order to become phase locked again, the phase will be pulled in, and a transient response will occur on the tape. Therefore, when a tape recorded in this way is played back, tracking cannot be taken at the seams, causing disturbances in the playback image.As a countermeasure for this, playback CT
An example of mitigating synchronization disturbance in the capstan servo system by performing phase matching between the L signal and the rotation detection signal is the
It is disclosed in Japanese Patent No. 18805. A conventional example will be explained below with reference to the drawings.

FIG. 6 is a block diagram of the configuration of a phase matching method in conventional assemble focusing, and FIG. 7 is an operational waveform diagram thereof.

In FIG. 6, 1 is a capstan or capstan motor, 2 is a frequency generator (FG), s is a speed comparison circuit, 4 is a drive circuit, 5 is a frequency dividing circuit, 6 is a first switch, 7
is a phase comparison circuit, and 8 is a second switch.ONormally, the capstan motor 1 is provided with a speed control loop consisting of an FG 2, a speed comparison circuit 3, and a drive circuit 4, and the rotation speed of the capstan motor 1 is controlled by the speed. Constant speed rotation control is performed to match the reference speed in the comparator circuit 3. Furthermore, the above-mentioned phase control loop is provided by the frequency dividing circuit 6, the first switch 6, and the phase comparator circuit 7, and one reference signal 57 is used during recording.
By comparing the phase with the output S4 obtained by dividing the frequency of the FG signal S2 by the frequency dividing circuit 6, the reference signal S7 and the reproduced CTL signal S3 are determined during reproduction.
The speed comparison circuit 3 is controlled by the output S8 obtained by phase comparison with the speed comparison circuit 3 to enable phase control.

Next, the operation when switching from standby mode to recording mode during assemble editing will be explained using FIG. 7. In the standby mode where the mode switching signal S1 is @L'', the first switch 6 and the second switch 8 are connected to the playback CTL signal S.
Outputs 3. Therefore, the frequency divider circuit 5 that divides the frequency of the FG signal S2 is reset by the reproduced CTL signal S3, and the frequency divider circuit 6 counts the FG signal S2 after the reset,
1 pulse immediately after reset as rotation detection signal (divided output) S
I got it as 4. This is a phase matching state between the reproduced CTL signal and the rotation detection signal. On the other hand, the phase comparison circuit 7 forms a phase comparison trapezoidal wave S6 by inputting the reference signal (vertical synchronization signal in the video signal to be recorded) S7, and uses the reproduced CTL signal S6 output from the first switch 6 as a comparison signal. The structure is such that the phases are compared and the center position of the slope is sampled in a phase-locked state. At this time, the phase comparison output S8 obtained is a value near the center value, and is set to be in this state at least immediately before switching to the recording mode.

When the mode switching signal S1 enters the recording mode of "H#", the reproduction CTL signal S3 disappears, so the first switch 6 outputs the divided output S4 of the frequency dividing circuit 6, and the second switch 8 stops outputting. Here, the division output S4 is a signal that is phase-matched to the reproduced CTL signal S3 in standby mode, and when the reset operation by the output of the second switch 8 is released, the frequency division circuit 5 is a signal that is phase-matched to the reproduced CTL signal S3. Since it returns to the frequency state, there is no disturbance in the frequency division operation.Therefore, even after switching to the recording mode, the division output S4 can be obtained at almost the same timing as the reproduced CTL signal S3.

Problems to be Solved by the Invention However, it is impossible to make the phase shift ΔT zero, and a phase shift of one period of the FG signal S2 is involved.

Therefore, immediately after switching, the phase comparison output S8 changes from the center value to a low level, and it is impossible to prevent some synchronization disturbance due to this.

The present invention solves the above conventional problems, and includes:
The object of the present invention is to provide an electronic editing servo method and formula that can eliminate synchronization disturbances during assembly editing with an extremely simple configuration.

Means for Solving the Problems The present invention provides a magnetic recording and reproducing apparatus equipped with a capstan servo system, in which in standby mode reproduction is performed based on a phase comparison output between a vertical synchronization signal of a video signal to be recorded and a reproduction control signal. The present invention provides an electronic editing servo method in which the recording operation is performed based on an output that maintains the phase comparison output immediately before switching after switching to the recording mode, and after switching to the recording mode, the phase comparison output is maintained. This is an electronic editing servo method in which a recording operation is performed based on a constant output corresponding to a center value of operation for comparison.

By configuring the present invention as described above, it is possible to perform stable and reliable assemble editing without causing synchronization disturbance at the time of mode switching. The structure and operation of the invention will be explained.

FIG. 1 is an electrical block diagram showing an embodiment of the present invention, and FIG. 2 is an operating waveform diagram thereof. 1
The other configurations are the same except that switch e is omitted and the output S9 of the second switch is used as the comparison input of the phase comparator circuit 7. With this configuration, as shown in FIG. 2, when switching to the recording mode, the reproduced CTL signal S3 disappears and its output is also stopped by the second switch 8, so the output S9 as a comparison signal is eliminated. can do. Thereby, the phase comparison circuit 7 can maintain the phase comparison output S8 immediately before switching, and the phase comparison output S8 will not fluctuate. Therefore, no synchronization disturbance occurs at the seams. That is, in the present invention, in standby mode, tracking servo is enabled by phase comparison between reference signal S7 and reproduced CTL signal S3, and in recording mode, phase comparison output S8 is held at the value immediately before switching, and tracking servo is enabled only in the speed control loop. The configuration can be extremely simple. It is well known that an integral compensation filter is used in the normal speed control loop, and even when the phase control loop is released, the absolute speed of the magnetic tape can be sufficiently controlled, and there are no practical problems. do not have.

FIG. 3 is an electrical block diagram showing a second embodiment of the present invention. FIG. 3 shows that the frequency dividing circuit 6 and second switch 8 are removed from the conventional example (FIG. 6), and the recording CTL signal S1° is input to the first switch 6 instead of the output S of the frequency dividing circuit 6. ◎Normally, in standby mode, the recording CTL signal S1° is in the same phase as the reproduction CTL signal S3, and when switching to the recording mode, the CTL signal is configured to be recorded with continuity maintained. Therefore, in the recording mode, if the recording CTL signal S1° is used as the output S5 of the first switch 6 and as the comparison input of the phase comparison circuit 7, the phase comparison output S8 can be obtained as a constant value at the center of the operation. This allows stable and reliable editing as in the first embodiment (FIG. 1) of the present invention.

FIG. 4 is an electrical block diagram showing a third embodiment of the present invention. Figure 4 shows the second switch 8 from the conventional example (Figure 6).
is deleted, and the mode switching signal S1 is made a new input to the phase comparator circuit 7. As a result, the phase comparison output S8 in the recording mode is obtained as a constant value centered on the operation.◇In other words, the mode switching signal S8 in the recording mode
1, the trapezoidal wave S6 of the phase comparison circuit 7 is fixed at a constant value at the center of operation, and a constant output is obtained regardless of the timing of the comparison signal S6. In this embodiment as well, the first. Stable and reliable editing similar to the second embodiment is possible.

FIG. 5 is an electrical block diagram showing a fourth embodiment of the present invention. FIG. 5 shows a fixed value generation source 9 and a third switch 1o added to the third embodiment (FIG. 4), so that the phase comparison output S8 is output in standby mode, and the fixed value generation source 9 is output in recording mode.
The configuration is such that the output S11 of is led to the speed comparator circuit 3 as a switch output S12, and the mode switching signal S1 to the phase comparator circuit 7 is omitted. This embodiment is another embodiment of the third embodiment, and is equivalent to the third embodiment.

Here, the third. In the fourth embodiment, the comparison signal of the phase comparator circuit 7 in the recording mode is the output S4 of the frequency dividing circuit 6.
It is not limited to.

Effects of the Invention As is clear from the above explanation, in the standby mode of assemble editing, the present invention performs playback operation using a phase comparison output that uses the vertical synchronization signal in the video signal to be recorded as a reference signal and the playback CTL signal as a comparison signal. In the recording mode, the recording operation is performed only in the speed control loop using an output that maintains the phase comparison output immediately before switching or a constant output centered on the operation, and there is no synchronization disturbance due to switching, and it is stable. Reliable editing is possible, the configuration is simple, and the practical effects are extremely large◇

[Brief explanation of the drawing]

FIG. 1 is an electrical block diagram showing a first embodiment of the electronic editing servo method of the present invention, FIG. 2 is an operation waveform diagram thereof, and FIG.
4 and 5 are electrical block diagrams showing the fourth embodiment of the electronic editing servo method of the present invention, and FIG. 6 is an electrical block diagram showing a conventional example of the electronic editing servo method. Figure 7 shows its operating waveform diagram. 1... Capstan or capstan motor, 2... Frequency generator, 3... Speed comparison circuit, 4 ... Drive circuit, 5 ... Frequency divider circuit, 7 ... Phase comparison circuit, 9 ... Fixed value generation source, 6.8, 10 ... ... 1st, 2nd and 3rd switch 〇 Name of agent Patent attorney Toshio Nakao and 1 other person 1st
View (-7 snow-22 mbae-ni Σ''
Note: H9 Figure 3 Figure 4 Figure 5 Exit T-T-34, ?

Claims (5)

[Claims] (1) In standby mode, the playback operation is performed based on the phase comparison output between the vertical synchronization signal of the video signal to be recorded and the playback control signal, and after switching to recording mode, the output maintains the phase comparison output immediately before switching. An electronic editing servo method characterized by performing a recording operation based on. (2) In standby mode, playback operation is performed based on the phase comparison output between the vertical synchronization signal of the video signal to be recorded and the playback control signal, and after switching to recording mode, a constant output corresponding to the operation center value of the phase comparison is performed. An electronic editing servo method characterized by performing a recording operation based on. (3) The electronic editing servo method according to claim 2, wherein the constant output is obtained by phase comparison between the vertical synchronization signal and the recording control signal in a recording mode. (4) The electronic editing servo method according to claim 2, wherein the constant output is an output obtained by setting the phase comparison means at the center of operation using an arbitrary signal and sample-holding the output. (5) The electronic editing servo method according to claim 2, wherein the constant output is obtained from a fixed value generation source.