JPS5948453B2 - playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a helical scan type VTR (magnetic recording/reproducing device), generally, as shown in FIG.
The signal is supplied to two rotating magnetic heads, IA, IB, and the heads 1Λ, IB are rotated at the frame frequency in synchronization with the luminance signal, with an angular spacing of 1800.

The magnetic tape 2 is wound diagonally around the rotating peripheral surfaces of the heads IA and IB over an angular range of over 1800 degrees, and the tape 2 is run at a constant speed.
Therefore, the FM luminance signal is recorded on the tape 2 so that one field corresponds to one diagonal magnetic track.

During reproduction, the heads IA and IB scan the track in the same manner as during recording to reproduce the FM luminance signal, and the original luminance signal is demodulated from this reproduced signal.

In such a VTR, it is possible to switch the running speed of the tape 2 in three ways.

That is, in that case, as shown in FIG. 2, the inclinations, so-called azimuth angles, of the operating gaps Ga and Gb of the heads IA and IB are made different from each other, and the track width of the heads IA and IB is set to, for example, 30 capes.

Then, during recording, the running speed of the tape 2 is set to the first speed (for example, 4C7rL/sec), and at this time, as shown on the left side of FIG. For example, add a guard pad of 30 tt.
Form with a width of m.

Also, the tape speed is set to a second speed, for example, 1/2 of the first tape speed (i.e., 2 cwL/sec), and in this case, as shown in the center part of FIG. 3, the track 3 has a width of 30 Itm. The tracks 3 are formed so that they are in contact with each other.

Further, the tape speed is set to a third speed, for example, 1/3 of the first tape speed (i.e., 1.3 cm/sec), and at this time, as shown on the right side of FIG.
By overlapping recording on track 3 one field before, track 3 is recorded with a width of 20 ttm.
In addition, they are formed so as to be in contact with each other.

In addition, at the time of any recording. A pulse having a frame frequency obtained by dividing the vertical synchronizing pulse is recorded on the side edge of the tape 2 as a control pulse Pc during reproduction.

Although there is no guard band in the track patterns in the center and right portions of FIG. 3, crosstalk between tracks during playback can be ignored due to azimuth loss in heads IA and IB.

Therefore, for example, with tape 2 for one hour, it is possible to record and play for one hour, record and play for two hours, and record and play for three hours. A one-hour mode can be used for reproduction, and a three-hour mode can be used for long-time recording and reproduction.

Alternatively, other VTRs may have tape 2 compatibility even if they only have one-hour mode. However, when the tape speed can be switched in this way, it is of course necessary to use the same tape speed during playback as during recording.

Switching the tape speed during playback is as follows:
Preferably, this is done automatically. Particularly in cases where the tape speed can be switched in as many as three ways, automation would be inconvenient and could even lead to accidents. SUMMARY OF THE INVENTION In view of these points, the present invention provides a VTR that can automatically switch the tape speed during playback to the tape speed during recording.

Now, among tracks 3, every other track 3A is formed by head IA, and every other track 3B remaining is formed by head IB. do.

In addition, the recording and playback modes for the track patterns on the left, center, and right portions of FIG. 3 are set to "IH mode" and "2
These will be referred to as "H mode" and "3H mode." Then, when track 3 recorded in 3H mode is played back in -IH mode, tape 2 runs at three times the recording speed, so the scanning loci of heads IA and IB are
This results in trajectories 4A and 4B shown by broken lines in Figure A.

At this time, since the azimuth angles of head IA and track 3B are different, no reproduced signal can be obtained even if head IA scans track 3B. Therefore, the level of the reproduced signal Sa from the head IA is as shown in FIG. 4B (
IV is one field period) and changes every other field period. Similarly, the level of the reproduced signal Sb from the head IB changes every other field period with a one field period difference with respect to the signal Sa, as shown in FIG. 4C. Therefore, when the signals Sa and Sb are obtained alternately every one field period, the level of the field sequential signal Sc of the signals Sa and Sb changes over one field period as shown in FIG. 4C. Change as.

On the other hand, when track 3 recorded in 2H mode is played back in IH mode, the scanning trajectories of heads IA and IB become trajectories 4A and 4B shown by broken lines in FIG. 5A. The levels of the reproduced signals Sa and Sb of IB are as follows:
It changes as shown in Figures B and C.

Therefore, at this time, if the signals Sa and Sb are obtained alternately every one field period, the level of the field sequential signal Sc changes every two field periods as shown in FIG. 5D. Further, when track 3 recorded in the IH mode is reproduced in the 1H mode, since this is a normal reproduction mode, the level of the field sequential signal Sc is always constant.

This invention focuses on the above points and is designed to automatically set the tape speed during playback to the same tape speed as during recording.

Let's explain one example below.

In FIG. 6, reference numeral 10 indicates a servo circuit for adjusting the tape speed to the first to third tape speeds.

That is, 11 is a pinch roller, 12 is a capstan, this capstan 12 is provided with a frequency generator 13, and an alternating signal from this is supplied to a frequency discrimination circuit 15 through a shaping amplifier 14 to correspond to the rotational speed of the capstan 12. This voltage is supplied to the voltage comparison circuit 16, and at the same time, the reference voltage Er is supplied to the comparison circuit 16 from the reference voltage source IT. The comparison output of the comparison circuit 16 is then supplied to the motor 19 that drives the capstan 12 through the amplifier 18. In this way, the tape 2 is run at the first to third speeds based on the voltage Er of the voltage source IT. Further, 20 indicates a drum servo circuit. That is, a control pulse Pc is reproduced from the tape 2 by the magnetic head 21, and this pulse Pc is supplied to the phase comparator circuit 23 through the reproduction amplifier 22. is installed, and from this head 1A,
One pulse is taken out for each rotation of 1B, and this pulse is supplied to the comparator circuit 23 through the shaping amplifier 26. The comparison output of the comparison circuit 23 is supplied through an amplifier 27 to a motor 28 that drives the heads 1A and 1B. In this way, the servo control of the heads 1A and 1B is performed, so that the heads 1A and 1B scan the track 3 in the same relationship as during recording. Then, the heads 1A and 1B alternately reproduce the FM brightness signals Sa and Sb from the tape 2 every field period, and these signals Sa and Sb
is connected to the switch circuit 32 through the playback amplifiers 31A and 31B.
supplied to

Further, another pulse generating means 41 is provided on the rotating shaft 24,
From now on, one pulse is extracted for each rotation of the heads 1A and 1B and delayed by one field period with respect to the pulse from the pulse generating means 25, and this pulse is supplied to the RS flip-flop circuit 43 through the shaping amplifier 42. At the same time, the pulse from the amplifier 26 is supplied to the flip-flop circuit 43, which forms a rectangular wave signal that is inverted every field period in synchronization with the rotation of the heads 1A and 1B. Supplied as a signal. In this way, the signals Sa and Sb are alternately taken out from the switch circuit 32 every one field period, that is, they are taken out continuously as the FM luminance signal Sc.

This signal Sc is then supplied to the FM demodulation circuit 34 through the limiter 33 to demodulate the original luminance signal, and this signal is taken out to the output terminal 36 through the de-emphasis circuit 35.

Furthermore, 50 indicates a circuit that determines the tape speed during recording and switches to that tape speed. That is, 51 is a play button, 53 is an initial reset circuit, 54 is a counter, 55 is a decoder, 56 is a hold circuit, and the count value of the counter 54 is sent to the hold circuit 56 through the decoder 55.
At the same time, the hold circuit 56 holds the initially supplied count value until it is reset next time. The hold output of this hold circuit 56 is supplied to the voltage source 17, and its reference voltage Er is set to a value E1 corresponding to the first tape speed when the hold value of the hold circuit 56 is ``O''''.゛1
When "", the value E3 corresponds to the third tape speed, and when "2", the value E corresponds to the second tape speed.

Then, when the playback button 51 is operated, the switch 52 linked to this is turned on, whereby a reset pulse is formed in the initial reset circuit 53, and this reset pulse is supplied to the counter 54 and the hold circuit 56. and hold circuit 56 (Mat'o''
” is set.

Since the hold value of the hold circuit 56 is 0'', the reference voltage Er of the voltage source 17 becomes the value E1 corresponding to this 0'', and therefore the tape 2 begins to run at the first tape speed. At this time, it is assumed that track 3 is recorded on tape 2 in 3H mode.

Then, as explained in FIG. 4, the levels of the reproduction signals Sa and Sb of the heads 1A and 1B change as shown in FIG. 4B and C, and the level of the signal Sc from the switch circuit 32 changes as shown in FIG. It changes as shown in Figure 4D. Therefore, this signal Sc is supplied to the detection circuit 62 through the amplifier 61, and as shown in FIG. As shown in FIG. 4E, the square wave signal Se of the field frequency is generated.
is supplied to the flip-flop circuit 64, and as shown in FIG. 4F, is divided into a rectangular wave signal Sf with a frame frequency that is inverted every time the signal Se rises. Also amp 2
The frame frequency pulses from 6 and 42 are sent to the OR circuit 65.
This pulse Pg is supplied to the AND circuit 66, and the signal Sf from the flip-flop circuit 64 is supplied to the AND circuit 66.

Therefore, from the AND circuit 66, as shown in FIG. 4H,
One pulse Pi is obtained per frame period. This pulse Pi is supplied to the counter 54 as its counting input, and the signal Sf is supplied as a set input to the counter 54 through the differentiating circuit 6T, and the counter 54 is reset every time the signal Sf rises.

Therefore, the counter 54 counts the number of pulses Pi in one cycle period of the signal Sf, so as shown in FIG. 4I, the count value of the counter 54 becomes 1''. , the hold circuit 5 through the decoder 55
Since the hold value is "1", the voltage Er of the voltage source IT becomes the value E, and the tape speed is switched to the third speed.

In this case, the pulse Pi
(the number per cycle period of the signal Sf) changes, but in the hold circuit 56 the initial count value ゛1
” is held until the next reset, so the tape speed becomes the third speed.

Therefore, the tape 2 recorded in the 3H mode is played back in the 3H mode, that is, played back in the correct playback mode. On the other hand, by operating the playback button 51, the tape 2 is
When you start traveling at a speed of , tape 2 has track 3.
Suppose that is recorded in the 2H mode, then the signal Se-Pi becomes as shown in FIG. Therefore, the count value of the counter 54 is 2"
becomes.

Therefore, the hold value of the hold circuit 56 is also "2", so the voltage Er becomes the value E, and the tape speed becomes the second speed. Therefore, the tape 2 recorded in the 2H mode becomes the 2H mode.
mode, that is, played in the correct play mode. Furthermore, it is assumed that when the tape 2 starts running at the first speed, the track 3 is recorded on the tape 2 in the IH mode.

At this time, the level of the signal Sc becomes constant and the flip-flop circuit 64 is reset by the reset pulse from the initial reset circuit 53, so the pulse Pi is not supplied to the counter 54 and its count value is o''. Therefore, since the hold value of the hold circuit 56 is also "o", the tape speed remains at the first speed, and therefore the tape 2 recorded in IH mode is
mode plays correctly. Thus, according to the present invention, no matter what tape speed recording is being performed, playback is automatically performed at the same tape speed as at the time of recording.

Furthermore, in this case, the cycle of the signal Sc is determined and the tape speed is switched based on the output of this determination, so that a code signal indicating the tape speed during recording is not required at all. In the above description, when the playback button 51 is operated, the counter 54 and the hold circuit 56 change to "o" and the tape speed becomes the first speed, and thereafter the tape speed is switched to the correct tape speed. The hold circuit 56 may be set to "3" and the tape speed becomes the third speed, and thereafter the tape speed may be switched to the correct tape speed.

Further, the signal Sa or Sb may be used instead of the signal Sc.

[Brief explanation of the drawing]

1 to 5 are diagrams for explaining this invention, and FIG. 6 is a system diagram of an example of this invention. 10 and 20 are servo circuits, and 50 is a discrimination switching circuit.

Claims (1)

[Claims] 1. A recording medium in which the feeding speed during recording is at least a predetermined first or second speed, and in which an information signal is frequency-modulated and recorded by a rotating head as a recording track diagonal to the feeding direction. , the apparatus for reproducing the information signal detects the envelope of the modulated information signal reproduced from the rotary head, determines the period of change in level of the detected envelope, and outputs the determined output. A playback device that automatically switches the feed speed during playback of the recording medium to be equal to the feed speed during recording based on the above.