JP2889060B2 - Magnetic recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus such as a VTR (video tape recorder).

[0002]

2. Description of the Related Art In a conventional VTR, a head used for recording and reproducing a video signal has a rotating cylinder of 18 heads.
Since it is arranged at 0 °, when recording is performed at a tape feed speed that is 1/6 of the standard mode (hereinafter referred to as a 6 × mode), 0.25H (H
(One horizontal scanning period), each line is printed in a shifted state. Therefore, during reproduction, crosstalk occurs from an adjacent track, and the image quality is reduced.

Therefore, a head used for recording / reproduction in the 6 × mode is mounted on a rotating cylinder at 180 ° + α (α is 0.
The angle of rotation of the rotary cylinder is set at 25H), and a video signal of a frame composed of 4m + 3 and 4m + 4 (m is 0 and a natural number) fields is n ×
By delaying by 0.5H (n is a positive odd number), it is conceivable to realize H arrangement of recording patterns.

In this case, 4m + 1 and 4m +
Frame consisting of two fields, 4m + 3 and 4
If the period of the vertical synchronizing signal is not continuous with the frame including the field of m + 4, vertical jitter will occur on the monitor.

[0005] For this reason, it is conceivable that a pilot signal is superimposed on a video signal for each frame and recorded, and the pilot signal is reproduced to ensure the continuity of the period of the frame during reproduction.

[0006]

However, in the above-mentioned conceivable configuration, since the pilot signal is frequency-multiplexed with the video signal and recorded, there is a problem that the frequency band of the video signal becomes narrow and the image quality deteriorates. doing. Also,
Since the circuit scale for recording / reproducing the pilot signal becomes large, there is also a problem that the VTR becomes expensive.

[0007]

According to the present invention, there is provided a magnetic recording / reproducing apparatus including at least a pair of video heads on a rotating cylinder, and a video tape feeding speed in a standard mode. In a magnetic recording / reproducing apparatus for recording / reproducing a video at 1/6 of the feed speed, the pair of video heads is (180+
α) degrees, α is set to an angle at which the rotating cylinder rotates during a quarter of one horizontal scanning period,
Delay means for delaying the video signal by a period that is a half integral multiple of one horizontal scanning period; first switching means for switching between a signal delayed by the delay means and a signal not delayed for each frame; A second switching means for switching every frame in the reverse order to the first switching means, and a second switching means for switching a pulse interval of a vertical synchronization signal separated from a reproduced video signal from a predetermined time interval. And control means for controlling the switching timing of the video signal for each frame by the switching means to shift by one frame. The video signal switched by the first switching means is output to the video head and recorded. And the video signal reproduced by the video head is switched by the second switching means and output as a reproduction signal.

[0008]

According to the above arrangement, an image can be recorded on a video tape six times as long as in the standard mode. In addition, since the positions of the horizontal synchronizing signals are arranged on the video tape, so-called H arrangement, correlation can be made between adjacent tracks. This makes it difficult for beat-like interference on the screen to occur during playback. Further, when the pulse interval of the vertical synchronizing signal included in the reproduction signal is shifted from a predetermined time interval, control means for controlling the switching timing of the video signal for each frame by the second switching means so as to be shifted by one frame. , So even if there is a frame shift,
The time axis of the reproduction signal can be made continuous.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

The VTR of this embodiment is, as shown in FIG.
Video heads 2R and 2L for recording and reproducing in a 6-times mode (a mode in which the tape feed speed is 1/6 of the standard mode) are provided. α = 0.25H, H is arranged in one horizontal scanning period).

The VTR has video heads 2R and 2L.
A switching circuit 3 for switching between recording and reproduction, a switching circuit 4 for switching between recording and reproduction, and a video signal to be recorded for each frame.
Video signal delay circuit 6 for delaying by 0.5H (delay means)
And a switch circuit 5 (first switching means) for switching between a delay signal delayed by the video signal delay circuit 6 and a through signal not passing through the video signal delay circuit 6.

The switch circuit 3 is controlled by a head switching pulse from a cylinder servo circuit 7. The switch circuit 4 is controlled by a control signal instructing recording / reproduction. The above switch circuit 5
The head switching pulse is controlled by a control signal obtained by dividing the frequency of the head switching pulse by two in the divide-by-2 circuit 8.

Further, the VTR has a video head 2R.2
A video signal reproducing circuit 10 for reproducing a video signal from a signal from L, a video signal delay circuit 12 (delay means) for delaying the reproduced video signal by 0.5H for each frame, and a video signal delay circuit 12 for delaying the reproduced video signal. And a switching circuit 11 (second switching means) for switching between the delayed signal and a through signal which does not pass through the video signal delay circuit 12.

The switch circuit 11 is switched by a video signal delay control signal. The video signal delay control signal is an output signal from the divide-by-2 circuit 8 or a signal obtained by inverting the output signal from the divide-by-2 circuit 8 by the inverting circuit 9, and these are switched by the switch circuit 13. The switch circuit 13 is controlled by the inversion selection signal.

The inversion selection signal includes a vertical synchronizing separation circuit 14 for separating the vertical synchronizing signal from the output video signal output via the switch circuit 11, a pulse cycle measuring circuit 15 for measuring the period of the vertical synchronizing signal, Period measurement circuit 15
Is a signal obtained by a 60 Hz comparator 16 (control means) for detecting whether the pulse cycle obtained in step 1 is shifted from 1/60 second, and the pulse cycle of the vertical synchronization signal is shifted from 1/60 second. Is output from the 60 Hz comparator 16.

In the above configuration, when recording a video signal, the switch circuit 4 is switched to the switch circuit 5 by a control signal instructing recording / reproduction. The switch circuit 5 is switched every frame by a control signal from the divide-by-2 circuit 8. Therefore, a through signal that does not pass through the video signal delay circuit 6 and a 0.5H delay signal that passes through the video signal delay circuit 6 are alternately output from the switch circuit 5 for each frame. The video signal from the switch circuit 5 passes through the switch circuit 4 and is input to the switch circuit 3. The switch circuit 3 is switched for each field by a head switching pulse from the cylinder servo circuit 7. Therefore, video signals are alternately recorded for each field by the video heads 2R and 2L.

As a result, on the video tape 17, as shown in FIG. 2, the positions of all the horizontal synchronizing signals are arranged on a straight line. That is, H arrangement can be realized in the 6-times mode.
In the figure, 1 to 525 indicate line numbers, and the prime indicates that the latter half of the line. Also, (1)
（(6) indicate field numbers, and A, B, and C indicate reference frame numbers. In the figure, reference frame numbers A and C are through signals and reference frame numbers B
Is a 0.5H delayed signal.

When reproducing a video, the switch circuit 4 is switched to the video signal reproduction circuit 10 by a control signal instructing recording / reproduction. The switch circuit 3 is switched for each field by a head switching pulse from the cylinder servo circuit 7. That is, when the field numbers are (1), (3), (5),.
As shown in (a), when the head switching pulse goes high, the video head 2R is selected, and when the field numbers are (2), (4), (6)..., The head switching pulse goes low. , Video head 2L
Is selected. Thus, the video heads 2R and 2L are alternately switched for each field.

The signal read from the video tape 17 is sent to the video signal reproducing circuit 10, where the video signal is reproduced. The switch circuit 11 is switched for each frame by a video signal delay control signal as shown in FIG. That is, when a through signal is recorded in a frame (reference frame numbers A and C in FIG. 2), the video signal delay control signal goes high, and the video signal from the video signal reproduction circuit 10 is output from the video signal delay circuit 12. In the case of the frame in which the delay signal is recorded and the delay signal is recorded (reference frame number B in FIG. 2), the video signal delay control signal becomes low level, and the video signal from the video signal reproduction circuit 10 is not delayed. . Thus, the signal passed through the video signal delay circuit 12
A 0.5H delay signal and a through signal which does not pass through the video signal delay circuit 12 are alternately switched every frame.
1 is output.

As a result, as shown in FIG. 3C, the pulse interval of the vertical synchronizing signal becomes constant, and the continuity of the video signal is ensured. In other words, the time axis of all frames is continuous.

Incidentally, it cannot be distinguished whether a frame being reproduced is a frame in which a through signal is recorded or a frame in which a delay signal is recorded. For this reason, if the video signal delay control signal is inverted as shown in FIG. 3D, the pulse interval of the vertical synchronizing signal becomes
As shown in (e), it deviates from 1/60 second. In the drawing, ○ indicates that the pulse interval is 1/60 second, and x indicates that the pulse interval is shifted from 1/60 second.

Therefore, in this embodiment, the 60 Hz comparator 1
6 determines that the pulse interval of the vertical synchronizing signal is shifted from 1/60 second, the switching circuit 13 is switched to the divide-by-2 circuit 8 by outputting the inversion selection signal. In this way, by inverting the level of the video signal delay control signal, the switching timing of the video signal for each frame by the switch circuit 11 is shifted by one frame, and control is performed so that the time axis of all frames is continuous. ing.

If a sudden disturbance is applied to the rotation of the rotary cylinder 1 and the capstan (not shown) due to a scratch or the like on the video tape 17, the period of the vertical synchronizing signal may be discontinuous instantaneously. is there. At this time, it is preferable that the switch circuit 13 is not switched. For this purpose, for example, the configuration may be such that the inversion selection signal is output only when the 60 Hz comparator 16 continuously detects a shift in the pulse interval of the vertical synchronization signal.

Immediately after the video signal delay control signal is inverted, the cycle of the vertical synchronizing signal may be discontinuous. At this time, it is preferable that the switching circuit 13 is not switched.

The above-mentioned pulse period measuring circuit 15, 60 Hz
The comparison circuit 17 is a microcomputer (not shown) hardware for the cylinder servo circuit 7,
Alternatively, it can be easily realized by software for controlling this microcomputer without adding a new circuit separately.

In the above embodiment, the video signal delay circuit 6
Although the delay time of No. 12 is set to 0.5H, a similar result can be obtained even if n × 0.5H (n is an odd number). Also, if the video signal delay circuits 6 and 12 are not provided separately but are shared, the VTR
Costs can be reduced. Also, the 60 Hz comparator 16 that outputs the inversion selection signal when the pulse interval of the vertical synchronization signal deviates from 1/60 second is provided. However, the present invention is not limited to this. The present invention can be applied to various video systems if it is configured to output an inversion selection signal.

The VTR according to the first aspect of the present invention has at least one pair of video heads 2R.
A video recording / reproducing system which has a 2L video feed rate of 1/6 of the feed rate of the standard mode in the video tape 17
In the TR, the pair of video heads 2R and 2L are disposed on the rotary cylinder 1 at (180 + α) degrees, and α is set to an angle at which the rotary cylinder 1 rotates during a quarter of one horizontal scanning period. The video signal delay circuits 6 and 12 delay the video signal by a half integral multiple of one horizontal scanning period, and switch between a signal delayed by the video signal delay circuit 6 and a signal not delayed for each frame. A switch circuit 5, a switch circuit 11 for switching a video signal for each frame in the reverse order to the switch circuit 5, and a pulse interval of a vertical synchronization signal separated from a reproduced video signal being shifted from a predetermined time interval. When the switch circuit 1
60-Hz comparator 1 that controls the switching timing of the video signal for each frame by 1 by one frame
The video signal switched by the switch circuit 5 is output to the video heads 2R and 2L for recording, and the video signal reproduced by the video heads 2R and 2L is switched by the switch circuit 11. This is a configuration for outputting as a reproduction signal.

According to the above configuration, a video can be recorded on the video tape 17 for six times as long as the standard mode. Moreover, since the positions of the horizontal synchronizing signals are arranged on the video tape 17 in a so-called H arrangement, correlation can be made between adjacent tracks. This makes it difficult for beat-like interference on the screen to occur during playback. Furthermore, even if there is a frame shift, the time axis of the reproduced signal can be made continuous.
TR can be realized with a simple configuration.

[0029]

As described above, according to the magnetic recording / reproducing apparatus of the present invention, a pair of video heads are mounted on a rotating cylinder (18).
0 + α) degrees, and α is a quarter of one horizontal scanning period.
And a delay means for delaying the video signal by a period of a half integral multiple of one horizontal scanning period, and a signal delayed by the delay means and a signal not delayed. First switching means for switching every frame, second switching means for switching the video signal every one frame in the reverse order of the first switching means, and switching of the vertical synchronizing signal separated from the reproduced video signal. When the pulse interval deviates from the predetermined time interval, the second
And control means for controlling the switching timing of the video signal for each frame by the switching means to shift by one frame. The video signal switched by the first switching means is output to the video head and recorded. And the video signal reproduced by the video head is switched by the second switching means and output as a reproduction signal, so that the video can be recorded on the video tape for six times the time in the standard mode. In addition, since the positions of the horizontal synchronizing signals are arranged on the video tape, so-called H arrangement, correlation can be made between adjacent tracks. This makes it difficult for beat-like interference on the screen to occur during playback. Further, there is an effect that a magnetic recording / reproducing apparatus capable of making the time axis of a reproduction signal continuous even if there is a frame shift can be realized with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a VTR in a 6 × mode of the present invention.

FIG. 2 is an explanatory diagram showing a recording pattern when a video is recorded on a video tape by the VTR of FIG. 1;

FIG. 3 is a timing chart showing an operation of the VTR of FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 rotating cylinder 2R video head 2L video head 5 switch circuit (first switching means) 6 video signal delay circuit (delay means) 11 switch circuit (second switching means) 12 video signal delay circuit (delay means) 14 vertical synchronization Separation circuit 15 Pulse period measurement circuit 16 60 Hz comparison circuit (control means) 17 Video tape

Claims (1)

(57) [Claims] 1. A magnetic recording / reproducing apparatus comprising: at least one pair of video heads on a rotating cylinder, wherein a video tape is fed at a feed rate of 1/6 of a feed rate in a standard mode for recording and reproducing video. A pair of video heads are mounted on a rotating cylinder (180
+ Α) degrees, where α is set to the angle at which the rotating cylinder rotates during a quarter of one horizontal scanning period, and delays the video signal by a half integral multiple of one horizontal scanning period. Means, first switching means for switching the signal delayed by the delay means and non-delayed signal for each frame, and second switching means for switching the video signal for each frame in the reverse order of the first switching means. Switching means, and when the pulse interval of the vertical synchronizing signal separated from the reproduced video signal is shifted from a predetermined time interval,
And control means for controlling the switching timing of the video signal for each frame by one switching means by one frame. The video signal switched by the first switching means is output to the video head and recorded. And a video signal reproduced by a video head is switched by a second switching means and output as a reproduction signal.