JPS60131662A - Record mode discriminating method - Google Patents

Abstract

PURPOSE:To attain the automatic discrimination of a record mode for a tracking system using a 4-frequency pilot signal by detecting the phase of a tracking error signal on the basis of a head switching signal and therefore discriminating the difference in tape speed between record and reproduction modes. CONSTITUTION:When the reproduction is carried out at a different speed from that of a record mode, scanning is performed with the mode switching voltage set at a low level in a record mode together with the detection output obtained from a terminal 24 at a high level respectively. Under such conditions, a trigger pulse G is supplied to an analog switch 22. While the pulse G is supplied to the R side of an R-S flip-flop 23 via the switch 22 if the voltage of the terminal 24 is set at a high level. Then the detection output obtained from the terminal 24 of the flip-flop 23 is changed to a low level. Thus the record mode is changed to a normal reproduction mode. No pulse output is obtained from a trigger pulse generating circuit 21 in the normal reproduction mode, and this state is held as it is. In this case, the pulse is supplied to the S side of the flip-flop 23 via the switch 22 by the output of a delay circuit 25 after the record mode is switched to the normal reproduction mode, and this state is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus (hereinafter referred to as a VTR) that uses a rotating head to sequentially record and reproduce signals as inclined discontinuous recording trajectories on a magnetic tape. , relates to a detection method for automatically determining a recording mode.

The configuration of the conventional example and its problems R By changing the tape feeding speed during recording, m
There is a VTR that you can record yourself on. VTR like this
automatically determines the recording mode during playback,
During normal playback, it is desired to play back at the same speed as the recording speed.

゛Currently, as a method to achieve this, a method has been proposed in Japanese Patent Application No. 126942/1983 to determine the recording mode in a tracking method that uses four types of pilot signals instead of using conventional control signals. This will be explained using an example.

First, a tracking method using four types of pilot signals will be explained.

FIG. 1 shows a recorded magnetization trajectory by the four-frequency pilot signal tracking method, and FIG. 2 is a schematic diagram of a reproducing circuit for obtaining a tracking error signal.

In FIG. 1, A1. B1. A2. B2... is an A head and a B"7 having predetermined azimuth angles that are different from each other.
)111% + -7°J″1°Qft?c[4°@
) 571'.

Arrow 1 indicates the scanning direction of the gutter to rotation.

In each recording track, pilot signals indicated by f1 to f4 are sequentially and repeatedly recorded for each field together with the video signal.

The recording order of the pilot signals is the order shown in Figure 1,
Within one field period, the frequency of one type of pilot signal is Mi! For example, the values shown in Table 1 are set.

Table 1 In Table 1, fH indicates the frequency of the horizontal synchronization signal, and 6.5fH indicates a frequency that is 6.5 times the frequency of the horizontal synchronization signal.

The frequency difference of the pilot signal between each recording track is the first
As shown in the figure, the frequency is fH or 3fH. When the head Ai (i=1.2・river...) scans the track, the frequency difference between the pilot signal of the scanning track and the pilot signal recorded on the adjacent track on the right side on the paper is always fH , and the one on the left is always 3fH.

When the head scans the Bi track, the relationship is reversed to that described above, and the frequency difference between the pilot signals between the scanning trunk and the adjacent track on the right is always 3fH, and that on the left is always fH.

Since the pilot signal is a relatively low frequency signal of around 100 kHz, the pilot signal recorded on the adjacent trunk can be reproduced as a crosstalk signal without the head scanning over the adjacent track.

For example, the pilot signal obtained when the head scans the A2 track while on-track is f3° f2. f4
f3 is the highest level, followed by f2. f4 is reproduced at the same level.

When the head slightly deviates from track A2 toward track B2 and performs reproduction scanning, the level of the pilot signal obtained is f3. f2. It becomes smaller in the order of f4.

Therefore, by separating and extracting the difference frequency signals fH and 3fH between the pilot signal on the main scanning track and each pilot signal recorded on both adjacent tracks, and comparing the reproduction levels of both signals, , the amount and direction of head deviation from the main scanning track can be known.

FIG. 2 is a block diagram of a reproducing circuit for obtaining a tracking chiller signal.

In FIG. 2, a reproduced RF signal in which a video signal and a pilot signal are combined is input from a terminal 2. The circuit 3 converts it into a low-pass filter, and separates and extracts only the pilot signal from the reproduced RF signal.

The pilot signal obtained at this time is a combination of the pilot signals recorded on the main scanning track and both adjacent tracks.

Circuit 4 is a balanced modulation circuit and multiplies the above-mentioned composite signal by the reference signal supplied from terminal 5. The reference signal supplied from the terminal 5 is a pilot signal having the same frequency as the pilot signal recorded on the main scanning track. For example, in Figure 1, the head is on track A.
2, the input signals to the balanced modulation circuit 4 are f2+13 and f4, and the reference signal supplied from the terminal 5 is f3. Therefore, the output signal of the balanced modulation circuit 4 is f2. f3. Each signal of f4 is output. 0
The circuit 6 is a tuned circuit tuned to a signal of fH, and the circuit 7 is a tuned amplifier circuit of sfH. Circuits 8 and 9 are detection rectifier circuits, and circuit 1o is a level comparison circuit.

Therefore, each pilot signal taken out as a crosstalk signal from both adjacent tracks is separated and taken out as a difference signal from the pilot signal recorded on the main scanning track and the rack, and then sent to the bell comparison circuit 10. A signal corresponding to the level difference is extracted. When the reproduction level of fH is higher than the reproduction level of 3fH, a positive voltage corresponding to the level difference is extracted from the signal obtained by the level comparison circuit 10. Note that this level comparison circuit 1
The signal obtained at 0 can be used as a ζ tracking error signal because it includes information on the amount and direction of the head's track deviation. However, a tracking error signal that is actually suitable for practical use requires further processing. This is because, as is clear from FIG. 1, the relationship between the direction of head deviation and the crosstalk signal (fH or 3fH) obtained at that time is opposite to that of the A track and the B track.

In FIG. 2, the circuit 11 is an analog inversion circuit, and the circuit 12 is an electronic switch that switches according to the cycle of a head switching signal (hereinafter referred to as H, SW signal) supplied from a terminal 13. Therefore, when the head reproduces and scans the A track, the output signal of the level comparison circuit 10 is output as is, and when the head reproduces and scans the B track, the output signal of the level comparison circuit 10 is output as is, to the terminal 14. When the head reproduces and scans the B track, the output signal of the level comparison circuit 10 is inverted in analog form and output.

Therefore, the signal obtained at the terminal 14 is always a positive potential when the head deviates to the right from the track to be scanned, and a negative potential is always output when the head deviates to the left, regardless of the rack.

Therefore, if the signal obtained at the terminal 14 is supplied as a tracking error signal and the tape feeding speed is controlled, the head will always scan on-track on the main scanning track.

The above is an overview of the method for obtaining a tracking error signal using four types of pilot signals.

When such a tracking method is used, when a tape recorded in SP mode (for example, 1 hour recording) is played back in LP mode (for example, 2 hour recording), detailed explanation is as follows.
Although excluded here, as shown in FIG. 3, the tracking error signal changes at the cycle of one blade. Furthermore, when a tape recorded in LP mode is played back in SP mode, the tracking error signal changes with a cycle of 1 as shown in Figure 3.
6 times, and the cycle will be different from the above.

Japanese Patent Application No. 57-126942 proposes a method of determining the recording mode by installing a detection circuit that determines the period based on the tracking error signals of these different periods, but this method is only suitable for normal playback (SP recording mode). When playing in SP mode or playing in LP recording mode,
An essential condition is that the tracking error signal does not change periodically.

However, there is no problem in the case of self-recording and playback (for example, recording on a VTR called A and playing back on a VTR called A), but there is no problem with compatible playback (for example, recording on a VTR called A and playing back on a VTR different from A).
In the case of TR reproduction), the trajectory of the rotating head changes slightly between recording and reproduction, so for example, the tracking error signal causes level fluctuations at a cycle of 60 degrees as shown in Figure 4a. . In addition, the frequency 6 of the 4-frequency pilot signal
．． 15fH to 1o, 5fH, or noise with a frequency close to the above-mentioned frequencies mixes into the regenerated pilot signal and unevenly affects the output level of the tuned amplifier circuit 8.9 that tunes to the above-mentioned fH and 3fH signals. As shown in Figure 4c, when the
- A tracking error signal with steps in the period will be obtained. In this way, even during normal playback, if the tracking error signal changes at the above-mentioned period, 7. '
511z' 151 makes this method of determining the recording mode extremely difficult to determine.

OBJECTS OF THE INVENTION The present invention provides a method different from the above-described method for automatically determining a recording mode in a tracking method using a four-frequency pilot signal.

Structure of the Invention The present invention records a tracking control pilot signal during reproduction by superimposing it on a television signal to be recorded, and during reproduction, reproduces from recording tracks adjacent to the recording track before and after the recording track to be reproduced. The tracking error signal corresponding to the level difference of the crosstalk signal of the pilot signal is used to control the relative position between the recording track and the reproduction scanning locus of the reproduction magnetic head, and the tracking error signal is passed through a low-pass filter (LPF).
After the head switching (H, SW) signal is frequency-divided by 1, a trigger pulse is created at the rising edge of the 1-frequency dividing circuit output, and this trigger pulse is used to control the LPF output signal. Sample and hold (
S&H).

The S&H output is input to the trigger pulse generation circuit,
A DC change in the S&H output is detected and a trigger pulse is generated. Input this trigger pulse to an analog switch, input the two outputs of the analog switch to the set S side and reset) R side of the R and S flip-flop circuits, and output automatic discrimination from the output of the R-S flip-flop. It is configured to obtain Further, the output of the R, S flip-flop is connected to a delay circuit so that the output of the delay circuit is used to switch to one of the two outputs of the analog switch to obtain a trigger pulse.

When playing back at a speed different from the recording mode, 1. As mentioned above, 7.5. +1. The tracking error signal changes with a period of 〒1[. Since phase control is not yet applied at this time, the tracking error signal is not synchronized in phase with the H-SW multiplied signal and shifts in phase.

The present invention has the above-mentioned configuration.
This is a recording mode discrimination method that detects the presence or absence of a phase shift in a signal and obtains a detection signal that automatically discriminates the recording mode.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention is shown in FIG. 6, and will be explained using the operational waveform diagram in FIG.

A tracking error signal is input to terminal 15, and 1
LPFl set to a frequency slightly higher than 5 Hz
6 is input.

By passing this LPF, relatively high frequency components superimposed on the tracking error signal can be removed.
Obtain the fid output from the LPF1e output.

From the terminal 18, the H-SW signal is inputted to a one-frequency divider circuit 19, and the frequency-divided signal is inputted to a trigger pulse generation circuit 20 which is triggered at a rising edge or a falling edge to obtain a pulse output e. This trigger pulse e has a period of □, and the output d of the 61L LPFI 6 is sampled and held in the S&H circuit 17 using this pulse.

During normal playback, the tracking error signal changes as shown in Figure 4 a, b, and c.
Since the SW signal and the tracking error signal are synchronized in phase, 151-1.
Even if sample-and-hold is performed using a trigger pulse e having a period of , the output of the S&)(circuit 17) is a DC-like voltage that hardly changes.

However, when playing back at a speed different from the recording mode, for example, if a tape recorded in SP mode is played back in LP mode, the period of 77 seconds will change, and if a tape recorded in LP mode is played back in SP mode, the □ The tracking error signal 16 changes periodically, and the phase of the tracking error signal shifts out of synchronization with the H-SW signal.

At this time, as shown in Fig. 6d and e, a trigger pulse e synchronized with the H and SW times signals, for example, a tracking error signal) va-+vb-+vo-+vd→v8...
From the output of the S&H circuit 17, which is used to sample and hold voltages different from →, output signals f having different voltages can be obtained in a cycle of 115×−.

The output signal f of this S&H circuit 17 is sent to a trigger pulse generation circuit 2 that detects a DC change position (for example, va→V b , V b -+V,) and generates a trigger pulse G.
1, and the pulse output G of the trigger pulse generation circuit 21 is input to the analog switch 22.

The analog switch 22 is an R-3 flip-flop 2.
When the output of the delay circuit 26 inputted from the output terminal 24 of 3 is at a LOW voltage, it is switched to be input to the S side of the R-S flip-flop 23, and the output of the delay circuit 25 is input to the S side of the R-S flip-flop 23.・Set the signal to be switched so that it is input to the R side of the S flip-flop 23.

The delay circuit 25 described above is configured so that the output of the R, -S flip-flop circuit 23 changes from the LOW voltage to the i voltage (or
This is a circuit in which the output changes suddenly from the H1 voltage to the LOW voltage, and after an appropriate time delay, the output changes from the LOW voltage to the Hi lightning voltage or from the H1 voltage to the LOW voltage.

Further, in the R-S flip-flop 23 described above, when the trigger pulse G is input to the S side, the output terminal 24 of the R-S flip-flop circuit 23 is at the H1 voltage, and when the trigger pulse G is input to the R side, , R, S flip-flop circuit 23 is set to have a LOW voltage.

If you play back at a speed different from the recording mode,
For example, when the mode switching voltage during recording is a LOW voltage and the detection output obtained from the terminal 24 during playback is a Hi lightning voltage and scanning is performed, the analog switch 22 has a trigger pulse G as described above. is input. If the voltage at the terminal 24 is Hi lightning voltage, the trigger pulse G is input to the R side of the R-3 flip-flop 23 via the analog switch 22, and the detection signal obtained from the output terminal 24 of the R-S flip-flop 23 is input. The output is switched to LOW voltage and the mode is switched to normal playback mode. When the normal reproduction mode is entered, the trigger pulse generation circuit 21 no longer generates a pulse output, and this state is maintained. At this time, the signal is switched to the normal reproduction mode by the output of the delay circuit 25, and is then switched to be input to the S side of the R, S flip-flop 23 via the analog switch 22 and held.

Further, when the mode switching voltage during recording is Hi lightning voltage and the detection output obtained from the terminal 24 during reproduction is LOW voltage and scanning is performed, the analog switch 22 has a trigger pulse G as described above. is input to the S side of the R-S flip-flop 23 via the analog switch 22,
The detection output obtained from the output terminal 24 of the R-S flip-flop 23 switches to Hi lightning voltage and switches to the normal playback mode.As described above, when the normal playback mode is entered, a pulse output is obtained from the trigger pulse generation circuit 21. Keep this state. Also at this time, delay circuit 2
The output of R-8 flip-flop 2 switches to normal playback mode by the output of R-8 flip-flop 2 via analog switch 22.
It is switched and held so that it is input to the R side of No. 3.

The above is the operating principle of the detection circuit for determining the recording mode of the present invention.

Effects of the Invention According to the present invention, in a conventional tracking method that does not use a control signal, even if the tracking error signal changes synchronously even during normal playback, the recording mode can be reliably determined with a relatively simple configuration, and the detection signal can be detected. By obtaining the tape speed, it is possible to automatically switch to playback at the same tape speed as at the time of recording.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a recording pattern on a tape in a tracking method using four-frequency pilot signals. FIG. 2 is a block diagram showing the configuration of a reproduction processing circuit for a tracking method using a four-frequency pilot signal. FIG. 3 is a diagram showing the relationship between tracking error signals and H and SW multiplication signals when a tape recorded in SP mode is played back in LP mode and when a tape recorded in LP mode is played back in SP mode. FIG. 4 is a diagram showing changes in the tracking error signal during normal playback. FIG. 5 is a block diagram showing an embodiment of a detection circuit for determining the recording mode according to the present invention. FIG. 6 is an operation waveform diagram of FIG. 5. 16...Low pass filter (LPF), 17...
...S&H circuit, 19...-frequency divider circuit, 20゜2
1...Trigger pulse generation circuit, 22...
Analog switch, 23...R, S flip-flop circuit, 25...delay circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 3 Figure 4

Claims (1)

[Claims] A pilot signal for tracking control is superimposed on a video signal to be recorded and sequentially recorded on a magnetic recording medium as an adjacent recording track, and during reproduction, crosstalk y from recording tracks adjacent to the recording track before and after the recording track to be reproduced is generated.
Using a tracking error signal corresponding to the level difference between the pilot signals to be reproduced, the relative position between the recording track and the reproduction scanning locus of the reproduction magnetic head is controlled, and the tracking error signal is adjusted based on the head switching signal. A recording mode discrimination method that determines the difference between the tape speed during recording and the tape speed during playback by detecting the phase of the error signal.