JPS5919260A - Recording mode discriminating system - Google Patents

Abstract

PURPOSE:To obtain a detecting signal, by discriminating accurately a recording mode with a comparatively simple constitution even by a tracking system using no conventional control signal, to obtain a detecting signal, and switching the automatic reproduction at the same tape speed as a recording mode, in a device discriminating the recording mode with different periods. CONSTITUTION:A magnetic tape recorded in LP and SP modes is reproduced continuously in the LP mode, and therefore a tracking error signal starts its level change in a 1/7.5Hz period. Then an f/V converter circuit 36 works to obtain the voltage EB corresponding to the set 1/7.5Hz period out of an output. An output terminal 42 is set at the Low voltage. Therefore this state is held if the switch voltage of the SP mode is set at a low level in a recording mode. Then a magnetic tape recorded in SP and LP modes is reproduced continuously in the SP mode. Then the tracking error signal starts its level change in a 1/15Hz period, and the circuit 36 operates. Thus the voltage EA corresponding to the set 1/15Hz period is obtained out of an output, and the terminal 42 is kept at the Hi voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting a recording mode of a magnetic recording/reproducing apparatus (hereinafter referred to as a VTR).

In the health-based scan VTR, a method is currently used in which the recording time is changed by switching the tape feed speed for recording. In such cases, it is desirable to automatically determine the recording mode during playback and playback at the same speed as the recording speed during normal playback.
As a method for realizing this, a method has been adopted in which it is determined whether the reproduction period of the control pulse recorded in the control signal deviates from the regular period. However, as a new format VTR,
For systems that perform tracking based on signals reproduced by the rotating video head itself, and do not use conventional control tracks in the longitudinal direction of the tape, conventional automatic discrimination means should be used. become unable to do so.

The present invention provides a method for automatically determining the recording mode even in the tracking method that does not use a control signal.

Before giving a detailed explanation of the present invention, the configuration of a tracking method that does not use a general control signal is shown in FIG. 1 and will be explained.

At the time of recording, a video signal to be recorded inputted from the terminal 1 is inputted to a luminance signal processing circuit 2 and a color signal processing circuit 3, where they are respectively processed and mixed.

The video signal to be recorded is further input to a horizontal synchronization separation circuit 5 via a switch 4, and only the horizontal synchronization signal of frequency fH is separated and output.

The frequency fH of this horizontal synchronizing signal is input to the PLL 6 and converted to fH multiplied by n. fH multiplied by n obtains output signals f1P, f2P, f3P, and f4P of frequencies.

These flP, f2P, f3P, and f4P are head switching pulses (H, 5W) (i
The signal is input to a 4-field switching circuit 12, and the output of the 4-field switching circuit 12 is input to a switch that alternately switches every field during the 4-field period.

f4P is flP -f2P-f4P"f3P -fl
It is obtained by performing a switching operation so that the order of P... is obtained.

The pilot signal obtained from the switch 13 is passed through the low-pass filter 14 to the signal processing circuits 2 and 3.
The signal is superimposed on the processed and mixed video signal to be recorded, and after being amplified by the recording amplifier 15, it is input to the video head 17 via the switch 16 and recorded on the recording medium.

During playback, the playback video signal played back from the video head 17 is input to the playback head amplifier 18 via the switch 16, where it is amplified and then input to the luminance signal processing circuit 19 and the color signal processing circuit 20, where it is processed respectively. , mixed and sent to the monitor as a playback video signal. This reproduced video signal is input to the switch 4, and the horizontal synchronizing signal separation circuit 6 obtains a reproduced horizontal synchronizing signal of frequency fH.

On the other hand, only the recorded pilot signal is extracted from the output of the head amplifier 18 through the low-pass filter 21, and the pilot signal obtained from the output of the low-pass filter 14 and the reproduced pilot signal, which is different for each field, are obtained for four field periods. The signal is input to the balanced modulator 22, and is input to the output of the balanced modulator 22 and bandpass filters 23 and 24.

The outputs of the bandpass filters 23 and 24 are sent to the detection circuit 2.
5.26 and low-pass filters 27 and 28, and are input to a comparison circuit 29, respectively.

The output of the comparison circuit 29 is inputted to one side of a switch 31 which is switched according to the H/SW multiplied signal inputted from the terminal 11 via an analog inversion circuit 30, and the output of the comparison circuit 29 is inputted to the other side. is input, and the output of the switch 31 is taken out alternately every field, and the output of the switch 31 is passed through the low-pass filter 32 to obtain a tracking error signal, which is supplied to the capstan servo system as a phase error signal. Controls the tape feed speed.

Next, the principle of operation will be specifically explained using FIG. 2 and the table below.

(Table) When recording, if the configuration described above is used, as shown in Figure 2, 1) flP - f2P - f4P for each rack.
Pilot signals are repeatedly stored on the tape in the following order: = f3P = fI P.

For example, the recorded pilot signal flP, f2P, f3P
.

The frequency of f4P, fl, is 6-5 x f H, f
2 is 7.5 X fH, f3 is 9-5 X, 7'
H, f4 is 10, and the output frequency of PLL6 and the frequency division ratio (n
1 to n4), the head can move between A1°A2. A3. A4...
When a track is being reproduced and scanned, the frequency difference with respect to the left direction on the paper is 3 x fH, and the frequency difference with the right direction is I x fH. Also, the head is B. , B1. B2
．． B4......When playing back and scanning a track,
The frequency difference in the left direction on the paper is 1 x fH, and in the right direction is 3 x fH.

As mentioned above, pilot signals (flP, f2P.

f3p+f4p) are recorded in order, and when the reproduced pilot signal obtained from the output of the low-pass filter 21 and the reference pilot signal obtained from the output of the low-pass filter 14 are balanced-modulated by the balanced modulator 22 during reproduction,
From the output of the balanced modulator 22, 1 x fH and 3 x
Only the fH crosstalk signal is detected.

Here, the heads are A, , A2. A3. A4・
...When a track is reproduced and scanned, if it deviates to the left from the on-track position (the center of the trunk) on the paper, the level of the crosstalk signal will be 1 x fH (
3X fH, and if it shifts to the right, IXfH') 3X
It becomes fH.

Also, the head is Bo, B1. B2. B3. B4...
When a track is reproduced and scanned, if it deviates to the left from the on-track position on the paper, it becomes 1X fH) 3fH, and if it deviates to the right, it becomes IX fH (3fH).

This crosstalk signal is I x fH and 3 x f
Bandpass filters 23 and 24 set to the frequency of H
and pass through the detection circuit 26, 260-pass filter 2, 2B, and the low-pass filter 27, 28.
These rainfall force signals are smoothed in a direct current manner by a comparator circuit 29.
A level comparison is performed at , and a signal corresponding to the power difference between the two rivers is obtained.

That is, a signal corresponding to the track deviation is obtained from the output of the comparison circuit 29.

Therefore, the tape feeding speed may be controlled so that the level of the rainfall signal obtained by the low-pass filter 2 over two days is equal.

Note that, as mentioned above, the head is A1. A2. A3
゜A4...When reproducing and scanning a track, the head is Bo, B1... B2. B3. B4...When a track is reproduced and scanned, the relationship between the direction of track deviation and the level difference of the crosstalk signal on the paper is opposite.

Therefore, it is necessary to reverse the polarity of the tracking error signals obtained from the A head and the B head.
One of the switches 31, which is switched according to the SW multiplier signal, inputs the output of the comparator circuit 29 via an inverting circuit 30 that inverts it in an analog manner, and the other inputs the output of the comparator circuit 29, and then switches It is obtained from the output of 31.

The above is an explanation of the operating principle based on the configuration of the tracking method that does not use a control signal as shown in FIG.

According to the above-mentioned operating principle, the reference pilot signals f1P, f2P, and f3P are obtained from the output of the low-pass filter 14 and input to the balanced modulator 22 during reproduction.

When f4P is fixed at one value, the level change of the output of the comparator circuit 29 is the crosstalk signal 1
When the levels of fH and 3×fH are equal, if the zero reference is used, the result will be as shown in FIG.

The present invention is a method for automatically detecting the recording mode during playback when recording is performed at at least two different speeds in a tracking system configuration as shown in FIG. 1, for example.

Here, there are two types (sp = 1 hour recording, for example.

An example having a recording mode of LP (for example, 2-hour recording) will be described.

First, a case where a tape recorded in SP mode is played back in LP mode will be described.

FIG. 4 shows the locus of the rotary head when a recording pattern recorded in the SP mode is reproduced in the LF' mode.

When scanning in this way, the period in which the pilot signal 11P is recorded is flP and f2P, the period in which the next f2P is recorded is f4P and f3P, and the period in which the next f4P is recorded is flP and 12P. Then, the period during which the next f3P is recorded is balanced modulated with the reference pilot signals of f4P and f3P, respectively, and the state of the tracking error signal output at this time is shown based on Fig. 3. 1-2-+ 3-14-15-+ as shown in Figure 5
6 →7 →8-41'-1-2' ,,,,. changes in the order of

Next, a case where a tape recorded in LP mode is played back in SP mode will be described.

FIG. 6 shows the locus of the rotary head when a recording pattern recorded in the LP mode is reproduced in the SP mode.

When such a scan is performed, a pilot signal f1P is generated.

The two-track period in which 12P is recorded is flP, the next period in which f4P and f3P are recorded is f2P, then the period in which f1P + f2P is recorded is f4P,
The recording periods of the next f4P and f3P are balanced-modulated in turn with the reference pilot signal of f3P, and the state of the tracking error output at this time is shown based on Fig. 3. 1-12→3 as shown in Figure 7
It changes in the order of →4→5→6→end→8→1'→2'...-.

In other words, the change in the tracking error signal when reproducing at a speed different from the recording mode is determined by the H and SW of the cycle.
As shown in FIG. 8, the tracking error signal when a tape recorded in SW mode is played back in LP mode is 7. The tracking error signal changes at a cycle of 5Hz, and when a tape recorded in LP mode is played back in SP mode, the tracking error signal is
It changes at a period of 5 Hz, which is a different period from the above.

The present invention discriminates the recording mode based on these different cycles, and an embodiment of a detection circuit for discriminating the recording mode according to the present invention is shown in FIG. 9 and will be described.

First, to explain the configuration, a tracking error signal is inputted via a terminal 33 to a waveform shaping circuit (7-unit circuit) 34 that obtains a rectangular wave output.
The rising or falling edge of the rectangular output is input to a trigger pulse generation circuit 35 that generates a relatively short pulse, and the output of the trigger pulse generation circuit 36 is input to an fV conversion circuit 36.
The output of the fV conversion circuit 36 is converted into a voltage as shown in FIG. 11 according to the output cycle of the trigger pulse generation circuit 35. The output Id of the f-V conversion circuit 36,
A dark value is set between the Low voltage (zero voltage) and the voltage EA obtained by f-■ conversion of a pulse with a period of 5 Hz (in this example, it is set as El), and if it is lower than the threshold value, the output becomes a Low voltage. If it becomes higher than the threshold, the output becomes H.
a detection circuit section that detects the voltage to be 16H2;
Voltage EA obtained by f-V conversion of 0 period pulse and 7.5H
A threshold is set between the voltage EB obtained by f-V conversion of a pulse with a period of z (in this example, it is E2), and if it is lower than the threshold (for example, in the case of a pulse with a period of 15H2)
If the output is low voltage, higher than the dark value (for example, 7.5
In the case of pulses with a period of Hz), the outputs are inputted to the detection circuit 38 so that the output becomes the Hl voltage.

The outputs of the detection circuit 37 and the detection circuit 38 are Low.
Trigger pulse generation circuit 39 which is triggered by the rise of the voltage to Hi voltage and obtains an appropriate pulse width output.
40 respectively. The trigger pulse generation circuit 3
The output of 9 is input to the set terminal (S) side of the R-3F, F circuit 41, and the output of the trigger/ga pulse generation circuit 40 is input to the R-3F, F circuit 41 set terminal (S) side.
It is input to the glue set terminal (R) side of the 8F and F circuits, and a detection signal for determining the recording mode is obtained from the output terminal 42 of this R-3F-F circuit.

Next, the operating principle based on the configuration shown in FIG. 10 will be explained.

When playing back a magnetic tape recorded in LP mode and SP mode, if you continue to play it in LP mode, the part recorded in SP mode will be played back in LP mode, and during normal playback (LP mode recording section When reproducing in LP mode), the tracking error signal 1l remains unchanged, or the tracking error signal 1l remains unchanged, as shown in Figure 8.
The level begins to change at a cycle of -i7.6H, . This tracking error signal is input to the waveform shaping circuit 34, and the rectangular output of the waveform shaping circuit is inputted to the trigger pulse generation circuit 35.
．． A pulse with a period of 5 Hz is obtained. This pulse output causes the f-V conversion circuit 36 to operate, and a voltage EB of 7.5 Hz corresponding to the set cycle is obtained from the output.

When the output of the f-V conversion circuit 36 rises from the Low voltage to the voltage EB according to the set period of 7.5/Hz,
It becomes higher than the threshold E1 and the output of the detection circuit 37 becomes Low.
The voltage becomes Hi voltage at T1, and a trigger is generated by this rise, and a pulse output is obtained from the output of the trigger pulse generation circuit 39. Name 1), R-8F-F
The circuit 41 is set to the output terminal], and one end becomes a Hi voltage. However, the EB becomes higher than the threshold E2, and the output of the detection circuit 3B also changes from Low voltage to High at 12 o'clock.
voltage, and by this rising -F, a pulse output is obtained from the output of the trigger pulse generation circuit 40, so R-3F
, F circuit 41il-11, after being set at T1, is reset at 12:00, which is later than T1, and the output terminal 42 becomes a low voltage. Therefore, S at the time of recording
If the P mode switching voltage is selected as Low voltage, this state will be maintained. Next, when playing back a magnetic tape recorded in SP mode and LP mode, if you continue playing in SP mode, the part recorded in SP mode will be played back in LP mode, and during normal playback (SP mode When the recording section is reproduced in the LP mode), the tracking error signal does not change, but the level of the tracking error signal begins to change at a cycle of 16 Hz as shown in FIG.

This tracking error signal is input to the waveform shaping circuit 34, and the rectangular output of the waveform shaping circuit is inputted to the trigger pulse generation circuit 35, and from the output, a relatively short width is generated.
A pulse with a period of 5 Hz is obtained.

This pulse output operates the f-■ conversion circuit 36,
A voltage EA corresponding to the set period of 1 and H2 is obtained from the output.

The output of the f-V conversion circuit 36 is low voltage (during normal playback)
When the voltage rises to the voltage EA corresponding to the period of 6H2, it becomes higher than the threshold value E1, and the output of the detection circuit 37 changes from a low potential to a high voltage, and is triggered by this rise, and a pulse output is obtained from the output of the trigger pulse generation circuit 39. That is, the R-S F, F circuit 41 is set at time T1, and the output terminal 42 becomes Hl voltage. At this time, the output voltage of the fV conversion circuit 36 is
Since the threshold value E2 set in is not reached, the output of the detection circuit 38 is 11 cm of Low voltage, and the output of the trigger pulse generation circuit 4 is
No pulse output is obtained from the output of o. Therefore, R-8F
The -F circuit 41 is not reset after being set at time T1, and the output terminal 42 is held at Hi voltage.

Therefore, if the switching voltage of the LP mode during recording is selected as Hi voltage, the OJ voltage maintained in this state will be as follows.
This is the operating principle of a detection circuit for determining the recording mode of the present invention.

According to the present invention, even in a conventional tracking method that does not use a control signal, the recording mode can be reliably determined with a relatively simple configuration, and by obtaining a detection signal, playback can be automatically performed at the same tape speed as when recording. It is possible to switch to

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional tracking method that does not use a control signal. FIG. 2 is a diagram schematically showing the tape pattern in the tracking method shown in FIG. 1, and FIG. 3 is an output waveform diagram of the comparator circuit when the reproduction reference pilot signal is set to a single frequency with respect to the recording pattern. Fig. 4 is a diagram showing the scanning locus of the rotary head when a tape pattern recorded in SP mode is played back in LP mode, Fig. 5 is a tracking error signal waveform diagram during the scanning shown in Fig. 4, and Fig. 6 7 is a diagram showing the scanning locus of the rotary head when a tape pattern recorded in LP mode is played back in SP mode, and FIG. 7 is a tracking error signal waveform diagram during scanning shown in FIG. 6.
FIG. 8 shows H during scanning shown in FIGS. 4 and 6;
A diagram showing the relationship between the SW multiplication signal and the tracking error signal,
FIG. 9 is a block diagram showing an embodiment of a detection circuit for discriminating between SP mode and LP mode of the present invention, and FIG. 10 shows the pulse period of the f-■ conversion circuit, the output of the f-V conversion circuit, and , is a correlation diagram with the threshold value of the detection circuit. 34...Waveform shaping circuit, 36...Trigger pulse creation circuit, 36...fV conversion circuit, 3
7, 38...detection circuit, 39.40...
・Trigger pulse generation circuit, 41...R-8FφF circuit. Name of agent Patent attorney Toshio Nakao and 1 other person + Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] When recording television video signals on a magnetic tape as a group of discontinuous inclined recording tracks using a rotating magnetic head, a pilot signal for trunking control during playback is superimposed on the television signal to be recorded during recording. During playback, a tracking error signal is used to match the recording track and playback using a tracking error signal that corresponds to the level difference between the cross-talk signals of the pilot signals reproduced from the recording tracks that are adjacent to the recording track before and after the recording track to be reproduced. The configuration is configured to control the relative position of the magnetic throat with respect to the playback scanning locus, and detect the presence or absence of periodic changes in the tracking error signal during playback to determine the tape speed during recording and the tape speed during playback. A recording mode discrimination method that determines the difference between