JPS5935085B2 - Recording and playback method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording and reproducing method for video and audio signals in a rotating head type magnetic recording and reproducing apparatus (hereinafter referred to as a VTR).

In general, simple VTRs employ the so-called helical scan method, in which video signals are recorded as an inclined recording trajectory on a magnetic tape run by a rotating magnetic head, and audio signals are provided at the widthwise ends of the magnetic tape. The recorded audio track is recorded or reproduced by a fixed head using the running speed of the magnetic tape as a relative speed.

On the other hand, in order to reduce the amount of magnetic tape consumed by increasing the recording density of video signals, and to reduce the size and weight of tape cassettes and devices, the width of the recording trajectory and the running speed of the magnetic tape have been reduced. It will be done. However, there is a natural limit to reducing the traveling speed extremely and obtaining sufficient frequency characteristics of the reproduced audio signal.

Therefore, for example, it is conceivable to record the video signal and the audio signal separately on magnetic tapes running at different speeds and play them back synchronously. However, this method has the disadvantages that it tends to cause sound distortion due to differences in sound quality, and also tends to increase the size of the device itself. Also,
It is also possible to record a composite signal of a video signal and an audio signal using the same rotating magnetic head, but in this case, for example, after-recording only the audio signal would be extremely difficult, and it would be difficult to play back adjacent recording trajectories at the same time. In this case, the field and frame correlation in the video signal cannot be expected in the audio signal, resulting in a problem of direct crosstalk. The present invention solves these drawbacks of the conventional system, and the recording and reproducing system of the present invention will be described below with reference to drawings of embodiments.

FIG. 1 shows an example of the configuration of a magnetic recording/reproducing apparatus implementing the method of the present invention. In the figure, 1 is a first magnetic head, and 2 is a head at a predetermined angle θ and a step d with respect to the first magnetic head 1. A second magnetic head is arranged with a relative position.

The first and second magnetic heads 1 and 2 are housed in an upper rotating cylinder 4 that rotates in the direction of arrow 3. A magnetic tape 7 running in the direction of arrow 6 is attached to the tape guide cylinder consisting of the upper rotary cylinder 4 and the fixed lower cylinder 5.
is wound at an angle of (360+α) degrees (α: overlap angle). The magnetic tape 7 runs while its running position is guided by a tape guide post 8 near its winding start and end positions. The above-mentioned upper rotating cylinder 4 rotates at a field period, and a frequency-modulated video signal is applied to the first magnetic head 1.
The second magnetic head 2 is supplied with an audio signal (eg, 1.2 MHz±50K1Iz) corresponding to the video signal obtained by frequency modulating a specific carrier wave different from the video signal. In such a tape running system, as shown in FIG. 2, a video signal recording locus 9 and an audio signal recording locus 10 are sequentially recorded on the magnetic tape 7 so as to be adjacent to each other.

Note that the running speed Vt of the magnetic tape 7 is sufficiently small, and the widths of the residual recording trajectories 9 and 10 that are approximately equal to each other are the same as those of the magnetic head 1.
, 2 is set to be approximately equal to the width of the gaps 1G and 2G.

In FIG. 2, Fv indicates the field frequency. Also, the first
The recording locus 9 of the video signal adjacent to the recording locus 10 of the audio signal on a straight line perpendicular to the still locus 11 of the second magnetic head 1 (or the still locus 12 of the second magnetic head 2)
The recording positions of the horizontal synchronization signals H within are mutually (m+0.5)
They are set to be arranged at intervals of 1H (1H is a length corresponding to one horizontal synchronizing signal period on the recording trajectory 9, m=0, 1, 2, . . . ). Further, in detail regarding the relative positions of the first and second magnetic heads 1 and 2,
The contact length with the magnetic tape 7 corresponding to the angle θ in FIG. 1 is NlH (n-0, 1, 2, 3...)
The step d is set equal to the sum of half the widths of the gaps 1G and 2G of the first and second magnetic heads 1 and 2, respectively. In this way, the video and audio signals are recorded on the magnetic tape 7 at trajectories 9 and 10, respectively.
After recording as follows, the running speed V of the magnetic tape 7 at the time of recording is
When playing at the same speed as t, the first and second
The magnetic heads 1 and 2 scan and reproduce video and audio recording trajectories 9 and 10, respectively, to obtain reproduced video and audio signals, respectively.

Note that the tracking may be changed so that the first and second magnetic heads reproduce audio and video signals, respectively. To further explain using the schematic system diagram of recording and reproduction shown in FIG. is supplied to the magnetic head 1.

Also, the audio signal 17 corresponding to the video signal 13 is passed through a pre-emphasis circuit 18 and then sent to a frequency modulator 19 (for example, the carrier frequency is selected to be 1.2 MHz, and the modulation depth is 1.
．． The signal is frequency-modulated (set at 2 MHz±50 MHz) and further supplied to the second magnetic head 2 via a recording amplifier 16. Then, recording loci are formed on the magnetic tape 7, respectively. In addition, when performing after-recording of audio or video signals, an erase head (not shown) scans in advance of the second magnetic head 2 or the first magnetic head 1 and erases only the recording trajectory of the audio or video signal. ), a new audio or video signal is scanned and recorded on an already recorded recording trajectory while erasing or by overwriting without providing an erase head. When playing, it is played as follows. That is, the reproduction output of the video signal from the first magnetic head 1 is amplified by the reproduction amplifier 21, passes through the switch circuit 22 turned to the N side, further passes through the limiter 23, and then passes through the filter 1 (for example, BEF) 24.
The audio signal component due to mistracking or the like is removed, the signal is demodulated into a video signal by a frequency demodulator 25, and the video signal is amplified by a video amplifier 27 via a de-emphasis circuit 26 to obtain a reproduced video signal 28. On the other hand, the reproduction output of the audio signal from the second magnetic head 2 is amplified by the reproduction amplifier 29, passes through the switch circuit 22 turned to the N side, further passes through the limiter 30, and then is sent to the filter 1 (for example, BPE) 31. A video signal component due to mistracking or the like is removed, and a reproduced audio signal is obtained similarly through a frequency demodulator 32, a de-emphasis circuit 33, and an audio amplifier 34. In addition, when the tracking is changed and the first and second magnetic heads reproduce audio and video signals respectively, the switch circuit 22 is turned to the S side, and the reproduced audio and video are respectively traced through the previously described reproduction paths. Signals 35 and 28 are obtained. Next, a case will be described with reference to FIGS. 3 and 4, in which the traveling speed of the magnetic tape 7 during reproduction is made lower than that during recording to perform so-called slow motion reproduction. FIG. 3 is a detailed schematic diagram of the end of the magnetic tape 7, and shows the first and second magnetic heads 1, 2, video and audio when the running speed of the magnetic tape 7 is lowered to, for example, 1/6. It shows relative scanning positions (tracking positions) 37 to 45 with respect to the recording trajectories 9 and 10. That is, the first
The magnetic head 1 records the video signal recording trajectory 9 at 37, 38,
The relative scanning position 39 is scanned a total of three times to obtain the reproduced signal, and when the relative scanning position 40 is to be scanned, the recording locus 10 of the audio signal is mainly scanned. But the first
When the scanning position of the magnetic head 1 is at a relative position of 40, the step difference d of the second magnetic head 2 with respect to the first magnetic head 1 is a value corresponding to approximately half the sum of the air gaps 1G and 2G, as described above. Since the second magnetic head 2 is at the relative scanning position of 37, the video signal is reproduced at the second position.
The magnetic head 2 is switched to the same recording trajectory 9 again at 37.
, 38 and 39 are scanned a total of three times, and a reproduced video signal is obtained from the reproduced output from the second magnetic head 2. That is, the recording locus 9 of the same video signal is scanned and reproduced six times in total by the first and second magnetic heads 1 and 2, resulting in 1/6 slow motion reproduction. Note that when the second magnetic head 3 continues to scan the relative scanning position of 40, the first magnetic head 1 moves to the relative scanning position of 40.
3, and the recording trajectory 9 of the adjacent video signal is 43,4.
The reproduction of the video signal is switched from the second magnetic head 2 to the first magnetic head 1 for scanning and reproduction at relative scanning positions 4 and 45, and thereafter, the recording locus 9 of adjacent video signals is sequentially scanned and reproduced in the same manner. It is something we will continue to do. As described above, the first magnetic head 1, to which a video signal is supplied during recording, and the second magnetic head 2, to which an audio signal is supplied, both reproduce video signals during slow motion playback, and mutually transmit the video signals. Since the switching is made to compensate for mistracking with respect to the recording trajectory 9, a good slow-motion reproduced image can be obtained. Switching between the first and second magnetic heads 1 and 2 during slow motion reproduction is performed using, for example, a pulse generator that generates pulses as the upper rotating cylinder 4 (FIG. 1) rotates, as shown in FIG. This is accomplished by switching the switch circuit 22 to the N side or the S side using a periodic switching signal 36 obtained by well-known means such as a counter (both not shown). Note that it is also effective to change the running position of the magnetic tape 7 during slow motion to achieve complete tracking.
Furthermore, it is clear that the reproduction of audio signals during slow motion can be simultaneously achieved by connecting the switch circuit 22 shown in FIG. Furthermore, the continuity of the horizontal synchronizing signal when switching the first and second magnetic heads 1 and 2 is such that the relative position is NlH (n=0, 1, 2...) as described above. This is compensated for by selecting the correct value, and no disturbance of the reproduced image occurs.

The above has been explained using an example in which the tape is wound by (360+α) degrees, but as shown in FIG.
It is obvious that the present invention can be realized even if the magnetic head is wound by 0+β) degrees (β is the overlap angle) and scanned by two first and second magnetic heads 1 and 2, respectively. As described above, according to the present invention, it is possible to obtain a reproduction signal having good reproduction frequency characteristics even when the running speed of the magnetic tape is extremely low, and at the same time, it is possible to realize a high recording density of video signals. Since the recording trajectories of the video and audio signals are adjacent to each other, the recording trajectories of the video signal serve as a guard band against crosstalk of the audio signal where field and frame correlation cannot be expected, and furthermore, it is possible to prevent after-recording of only the audio signal or the video signal. is also possible.

Further, during slow motion reproduction, it has excellent advantages such as a good slow motion reproduced image can be obtained by switching with the magnetic head used for recording the audio signal.

[Brief explanation of the drawing]

FIG. 1 shows an example of the configuration of a recording/reproducing device implementing the method of the present invention, in which a is a schematic plan view, b is a side view, and FIG. 2 is a diagram showing a recording trajectory recorded on a magnetic tape of the device. A pattern explanatory diagram, FIG. 3 is an explanatory diagram showing the relative scanning position of the magnetic head and the recording trajectory during slow motion reproduction, FIG. 4 is a schematic recording/reproducing system diagram, and FIG. 5 is another embodiment of the present invention. FIG. 1, 2... Magnetic head, 4... Cylinder, 7... Magnetic tape, 8... Guide pin, 9, 10... Recording trajectory.

Claims (1)

[Claims] 1. A video signal is supplied to a first magnetic head that rotates and scans at a predetermined angle with respect to the running direction of the magnetic tape;
supplies an audio signal corresponding to the video signal to a second magnetic head that rotates integrally with the magnetic head and is arranged at a predetermined relative position, and records the video signal produced by the first magnetic head on the magnetic tape. A recording method characterized in that recording is performed so that a recording trajectory and a recording trajectory of the audio signal by the second magnetic head are adjacent to each other. 2. A video signal is supplied to a first magnetic head that rotates and scans at a predetermined angle with respect to the running direction of the magnetic tape, and a first magnetic head that rotates integrally with the first magnetic head and is disposed at a predetermined relative position. An audio signal corresponding to the video signal is supplied to a second magnetic head, and the recording trajectory of the video signal by the first magnetic head and the recording trajectory of the audio signal by the second magnetic head are mutually recorded on the magnetic tape. Record adjacently,
During reproduction, the running speed of the magnetic tape is lowered and the first and second magnetic heads sequentially scan the recording locus of the video signal by the first magnetic head a plurality of times, thereby performing slow motion reproduction. A recording and playback method that uses