JPS6116057A - Information signal reproducer - Google Patents

Abstract

PURPOSE:To detect that the driving speeds of a recording medium at recording and reproduction are different each to each by detecting the distance driven in the lengthwise direction of the recording medium in a variance period of an ATF (tracking error) signal. CONSTITUTION:The mode detection is possible by counting the number of power generation frequencies FG produced in a variance period of an ATF signal. A comparator 103 compares the ATF signal with the Vth in case the ATF signal has variance centering on the Vth. Then the number of frequencies FG are counted in a period during which the ATF signal is kept at a level lower than the Vth. If the FG is set at 720Hz in a standard time mode, 24 pulses are produced in a frame period (1/30sec). Thus it is possible to detect that the driving speeds of a recording medium at recording and reproduction are different each to each when a counter 104 counts 24 in a period during which the output of the comparator 103 is kept at L.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field> The present invention relates to an information signal reproducing device, and more particularly, the present invention relates to an information signal reproducing device that reproduces video signals, audio signals, etc. from diagonal tracks formed by running a tape-shaped recording medium in its longitudinal direction at at least two different speeds. The present invention relates to a device for reproducing an information signal. Various types of playback devices can be considered as such playback devices, such as magnetic recording and playback devices and optical playback devices. This will be explained using VTI as an example.

<Description of Prior Art> In recent years, high-density recording has become possible, and VT (VT) has made long-term recording and playback possible by slowing down the running speed of the magnetic tape and narrowing the track pitch of diagonal tracks. has been developed and produced.

These VTRs generally have time modes with different recording and playback times, such as a standard time mode and a long time mode, in a single VTR so as to be compatible with conventional formats. When playing back a magnetic tape recorded on a VTR that can switch the time mode, unless the playback is performed in the same time mode as when recording, the center trajectory of the track on the tape and the trace trajectory of the head may differ. As a result, the reproduced image becomes distorted. On the other hand, it would be very difficult for the user to manually switch the playback time mode while looking at the playback image.

Conventionally, control signals (hereinafter referred to as CTL signals) are recorded at the edge of the tape at one-frame intervals during recording, and the output of a frequency generator detects the rotational speed of the capstan motor, which is proportional to the traveling distance of the magnetic tape during playback. (PG) is CTI
By counting the number of pulses output at each signal generation interval, it was detected whether or not the time mode was different between recording and playback, and the time mode for playback was automatically switched.

Here, such a conventional example will be explained based on the drawings. 1st
The figure shows a conventional CT], from the signal to the F of the capstan motor.
It is a diagram showing a method of counting G, in which 1
is a magnetic tape, which is run in the direction of the arrow by a capstan 2 and a pinch roller 3.

A video signal recorded obliquely with respect to the longitudinal direction of the magnetic tape 1 is reproduced from the magnetic tape 1 by a rotating magnetic head (not shown) attached to a known rotating drum. The capstan 2 is rotationally driven by a capstan motor 4 via a belt 5 at a predetermined speed. 6 is a frequency generator that detects the number of revolutions of the capstan motor 4, and the number of output pulses and the running speed of the magnetic tape 1 are in a proportional relationship, and this signal is sent to the counter 8 via the amplifier 7.
One side is input to the clock input terminal CK of the control head, which reproduces the CTL signal recorded frame by frame on the tape 1, and outputs the amplifier 10 and waveform shaper 11.
The signal is input to the reset terminal R of the counter 8 via the counter 8. With the above input, the number of revolutions of the capstan motor is counted in the CTL interval from the CTI signal to the next CTL signal, and the outputs Qi to Q4 are outputted to the magnitude comparator 16.

On the other hand, the comparator 13 compares the output of the set standard setter 12, and outputs a high level to the output Q5 when the output is greater or less than the reference set value. In other words, if the number of pulses input to the CTI section in the standard mode is 44 pulses, then in the long mode where the recording time is doubled, the tape feed speed is halved, so the CTL I
'! , 'l interval is 1/2 of the target rate mode. Therefore, when a magnetic tape recorded in the long time mode is reproduced in the standard mode, the number of pulses between the CTLs is not the original 44 pulses, but only half that number, 22 pulses. Therefore, set the standard setting value of 12 between these 22 and 44 pulses, and when playing in standard mode, if the count is less than the set value, the recording mode is set to long time mode, and when the count is more than the set value, the recording mode is set to long time mode. The recording mode is the standard mode. However, inconveniences occur when the CTL signal is missing, or when Format 5, in which no control signal is recorded from the beginning, is adopted during recording.

In other words, it has not been possible to perform automatic mode switching as described above in devices that perform tracking using the 4f pilot system, which will be described later, as has been proposed in recent years.

<Object of the Invention> In view of the above-mentioned points, it is an object of the present invention to provide a reproducing device that can detect a difference in the running speed of a recording medium at the time of recording even when a CTL signal is not recorded.

<Description of the embodiment> Figures 2 and 6 are principle diagrams for explaining this embodiment. Figure 2 (a) is a diagram showing the recording trajectory on the magnetic tape.
i * a2s... is a record of positive azimuth -\
Tracks recorded in RAD, bl, b2,...-0
is a recording track of minus ° azimuth, and in long-time mode al-bl-a2-b2-a3-b3 ・”0・
It is recorded that

Here track a1. a3, as..., the pilot signal of frequency f1 is sent to tracks b1, as...
In b3, b5, etc., fs is recorded superimposed on the video signal.

Frequencies f1, f2, fs, fi are fl <
If f2 < fs < fi, then f2- fi-
fi-fs-fs, fi-f2-fs-fl-f6, f
There is a relationship: s-IFf4, and f1. f2,
When playing back a trunk in which pilot signals of fs and fi are recorded, the pilot signals recorded in adjacent tracks are played back as a crosstalk component, and the playback output is a signal of the same frequency as the pilot signal being applied to the track. Signals F1, F2.

By multiplying F3 and F4, signals of frequencies f5 and F6 are obtained as crosstalk components. By comparing the levels of these signals, a tracking error signal (hereinafter referred to as ATF signal) is obtained.

Although the above is an example of obtaining an ATF signal, there are many possible combinations of frequencies to be superimposed on a video signal.

By the way, when recording the trunk recorded in 5th (
Long time mode) Replay at faster running speed (Standard mode)
Think about the case where you do.

The broken line in Figure 2 (a) shows the head trajectory when playing in standard mode, arrow α shows tape running, and arrow β shows head scanning direction. It is assumed that the width of the head used in the standard mode is 1/2 that of the standard mode, and the width of the head used in the standard mode for reproduction is twice that of the head used in the long time mode. In this state, when tracing is performed at the tape speed in standard mode, the slope of the track pattern on the tape and the trajectory of the playback head do not match, and furthermore, the pilot signals (f1 to f4) recorded on the track to be played back are There is no correspondence between the playback output and the frequency signals (F1 to F4) that are mixed during playback. Therefore, as shown in the same figure (b), A with a period of 2 frames
TF signal changes. In the same figure, if the playback head scans the B2 field, the frequency signal to be multiplied is F6 while scanning the B2 field, so the pilot signal F6 having the same frequency as F5 on the tape
The ATF signal output controls the phase of the capstan so that trunk b4, which is closest to B2, is played back among the tracks in which . During the B2 field, a good tracking condition is achieved only at the midpoint of the B2 field. At the scanning start point, the adjacent track a
4 pilot signal f4, at the scanning end point, instead of F4, the fl of the adjacent track a5 on the opposite side is played back greatly, so the ATF output is at a high level at the start point to speed up the tape advance, and at the end point, the tape advance is reversed. Low level to slow down.

Here, if the normal ATF output voltage is Vcc/2 and a good tracking condition, the ATF output will be Vcc/2.
A vibration waveform with a period of 2 frames centered at c/2 is shown.

FIG. 6 is a diagram showing a mistracking state when a recording recorded in the standard li-mode is reproduced in the long-time mode. The difference from FIG. 2 is that the same mistrunk condition is repeated at exactly 4 frame intervals. Therefore, the ATF output signal fluctuates at a cycle of 4 frames as shown in the figure (q).As shown above, when playing back at a tape feed speed different from that during recording,
It can be seen that the ATF output signal causes periodic fluctuations. In other words, if the ATF output signal fluctuates at a cycle of 2 frames in the standard time playback mode, or if the ATF output signal fluctuates at a cycle of 4 frames during the tri long playback mode. If it fluctuates in the time period, it can be determined that the playback mode is different. Also, even if the playback time mode is different at this time, the A
The length of the tape running during each oscillation period of the TF output signal is equal. Focusing on this, the capstan FG is counted during one cycle in which the ATF output signal fluctuates, and the count amount is a predetermined number (FG pulses generated while recording one frame of video signal in standard time mode). If the playback time mode is changed when the number matches)
It is possible to automatically match the tape running speed during recording with that during playback.

FIG. 4 is a block diagram showing the main structure of a reproducing apparatus as an embodiment of the present invention constructed based on the above concept. In FIG. 4, numeral 101 is an ATF circuit for obtaining an ATF signal, and its details are well known and will therefore be omitted. Low pass filter (LPF) for removing high frequency components such as noise from 102 ATF signals, 1o
3] is a comparator that compares the output signal of the PF with a predetermined voltage (Vth), and outputs the output signal from the 104H comparator 106.
1 is a counter that counts the capstan FG inputted through 1, 105 is a decoder for determining the counted value of the counter 104, and 106 is a device that outputs 1 pulse in synchronization with the rising edge of the output signal of the comparator 103. Multi, 107 is the output of decoder 105 and mono multi 106
108 is a counter that counts the output of the AND gate 107 , 109 is an AND gate that takes the AND of the output of the inverter 113 and the output of the monomulti 106 , 110 is the counter 10
A flip-flop that inverts on the rising edge of the output of 8,
Reference numeral 112 is a terminal for outputting a signal for instructing a system control circuit (not shown) to reproduce in standard time mode or long time mode.

The operation will be explained below. Mode detection is possible by counting the number of FGs that occur during one fluctuation period of the ATF signal that fluctuates periodically as described above. In this example, assuming that the ATF signal fluctuates around vth,
A comparator 106 compares the ATF signal with vth, and counts the number of FGOs during a period in which the ATF signal is at a lower level than vth. Assuming that the frequency of F'G in all standard time modes is 720Hz, 2
4 pulses are generated. Therefore, when the counter 104 counts 24 during the period when the output of the comparator 106 is L, it can be seen that the medium running speed during recording is different from that during reproduction.

However, as mentioned above, the recording level of the ATF signal is generally extremely low, so if the period during which the output of the comparator 106 is L is accurate to 1/30 seconds in the playback standard time mode and 1/15 seconds in the playback long time mode. is not limited. We will then set a certain tolerance range, and if it is within that range, it will be assumed that the tape is being played back at a different speed than when it was recorded.

Therefore, the decoder 105 determines that the count value N of the counter 104 is 2.
4-α<N<24+α, the output is at high level σ, N<
24 - α or 24 + α × N (α is a number indicating the set tolerance range. In this way, within the period when the ATF signal is a value lower than vth, If the number of generated F'G is within the range of (24-α) to (24+α), the output of the decoder 105 is H; otherwise, the output of the inverter 116 is H.

When the output of the comparator 106 changes to H, the Q output of the monomulti 106 generates one pulse, and one of the AND gates 107-1 and 109 generates one pulse, and the counter 108 It will be set as soon as the count goes up.

That is, when the tape is being played back at a different speed from the tape running speed than when it was recorded, the counter 108 is incremented. In principle, it is possible to switch the key with one detection, but even if playback is performed normally, the ATF signal may accidentally be lower than vth for one or two fields. Since it is conceivable that the level may become low, meaningless mode switching in such a case is prevented. In other words, in this embodiment, only when the mode error detection pulse, which is the output of the AND gate 107, occurs m times in succession, the Q output of the counter 108 changes to 1;
The Q output of the flip-flop 110 is inverted to switch the playback time mode.

With a VTR configured as described above, even when the so-called CTL signal is not recorded, the tape during recording can be automatically adjusted by detecting the traveling distance of the tape during the fluctuation period of the ATF signal. It is now possible to switch to playback at the same tape running speed as the tape running speed.

In the above embodiment, there are two types of tape running speeds during recording, but even if there are six or more types, the decoder 105
Mode errors can be similarly detected by changing the count value detected by the decoder 105.In addition, the conditions of the decoder 105 can be adjusted appropriately not only during normal playback but also during so-called search playback and slow playback in VT mode. This can be detected by switching.

Also, using this detection output, only switching the tape speed is described in line 5, or V
Of course, in the case of a TRK, this output is also used to switch the reproduction head.

Further, the circuit configuration is not limited to this embodiment, and it is of course possible to configure the circuit using well-known analog circuits.

<Description of Effects> As described above using the embodiments, according to the present invention, the CTL signal etc. can be recorded by detecting the traveling distance in the longitudinal direction of the recording medium during the fluctuation period of the tracking error signal. The present invention aims to provide an information signal reproducing device capable of detecting a difference between the traveling speed of a recording medium during recording and the traveling speed during reproducing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a circuit for detecting tape running errors in a conventional device. FIGS. 2 and 6 are principle diagrams for explaining the present invention in detail. FIG. 4 is an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of main parts of an information signal reproducing device as an information signal reproducing device. 101 is an ATF circuit that obtains a tracking error signal;
03 is a comparator, 104 is a counter, and 111 is a terminal to which a capstan FG signal is supplied. Adore? figure

Claims (1)

[Claims] An apparatus for reproducing an information signal recorded on a diagonal track formed by running a tape-shaped recording medium in its longitudinal direction at at least two different speeds together with a plurality of types of pilot signals for tracking control, wherein the pilot signal a means for obtaining a tracking error signal by reproducing the
An information signal reproducing apparatus comprising: means for detecting that a medium traveling speed during reproduction is different from that during recording by detecting a traveling distance in the longitudinal direction of the medium during a period of variation of the tracking error signal.