JPS60217546A - Recording mode discriminating system - Google Patents

Abstract

PURPOSE:To discriminate recording mode automatically and surely when reproducing at tape speed different from the time of recording by converting DC variation level of a crosstalk signal into pulse and discriminating the difference of tape speed between the time of recording and reproducing based on the period. CONSTITUTION:A crosstalk signal when a magnetic tape recorded in an SP mode is reproduced in an LP mode is inputted from a terminal 15 through a detector rectifier circuit, and becomes pulse output (a) in a waveform shaping circuit 16 and passes through a 1/4 frequency dividing circuit 17. A signal (b) is differentiated by a differentiation pulse generating circuit 18 and inputted to an S side of an R-SFF. At the same time, the output of the frequency divider 17 is inputted to a terminal of a NAND circuit 20, and at the samt time, inputted to another terminal of the circuit 20 through a delay pulse generating circuit 19, and the output of the circuit 20 is inputted to an R side of an FF21. A signal of Hi potential that discriminates recording mode is outputted from a terminal 22, and the state of reproduction is changed automatically to the state of SP reproduction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a detection method for automatically determining a recording mode in a magnetic recording/reproducing device (hereinafter referred to as a VTR) that sequentially records and reproduces signals as discontinuous recording trajectories inclined to the field of industrial application. .

Conventional configuration and its problems Healthal scan VTRs have VTRs that can record by changing the tape feed speed during recording with a single VTR.
There is TR. In such a VTR, it is desired that the recording mode be automatically determined during playback, and playback be performed at the same speed as the recording speed during normal playback.

Conventionally, as a method for realizing the hole, a method has been adopted in which it is determined whether the period of the control pulse recorded on the control track deviates from the regular period. However, as a new format VTR,
A system that performs tracking based on the signal reproduced by the rotating video head itself, and does not use a conventional control track in the tape length direction. Surplus 1911 jin's pressure 1
You won't be able to do eight things.

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

Structure of the Invention The present invention sequentially repeats pilot signals having four different frequencies for each field, superimposes them on a television signal and records them, and when reproducing them, the pilot signals are recorded on the front and rear adjacent to the recording track to be reproduced. The crosstalk signals of the pilot signals reproduced from the recording tracks are converted into direct current, and a tracking signal corresponding to the conversion level difference is used to control the position of the recording track and the reproduction scanning locus of the reproduction magnetic head separately. In a tracking method that performs
When reproducing at a tape speed different from that during recording, the conversion level, which changes at a constant period, is converted into a pulse, and a detection circuit is configured to determine the period of this pulse signal, and the tape speed during recording and the tape speed during playback are This method detects the difference between the two and automatically switches to the same mode as recording.

DESCRIPTION OF THE EMBODIMENTS Before describing the present invention in detail, a four-frequency pilot signal tracking method using four types of pilot signals without using a general control signal will be described.

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

In FIG. 1, A, r B1r 2. B2...
. is each recording track recorded on the magnetic tape by a human head and a B head having different predetermined azimuth angles.

Arrow 1 indicates the scanning direction of the rotary head.

In each recording track, pilot signals indicated by f, to f4 are sequentially and repeatedly recorded for each field along with the video signal. The recording order of pilot signals is the order shown in FIG. 1, and one type of pilot signal is continuously recorded within one field period. The frequency of the pilot signal is set to a value shown in Table 1, for example.

Table 1 f =...1025 (KHz) = e, ts f
Hf-=・118.9 (KHz) = -r, 5fH
f, -...16 B2 (K&) #10.6 f
Hf...-= 148.7 (KH2) = 9.
5 fH In Table 1, the symbol indicates the frequency of the horizontal synchronizing signal; for example, 6.54 indicates a frequency that is 6.6 times the frequency of the horizontal synchronizing signal.

The frequency difference between the pilot signals between each recording track is fH or 3fH, as shown in FIG.

When the head scans the track Ai (i=1.2...), the frequency of the pilot signal of the scanning track and the pilot signal recorded on the adjacent track on the right side on the paper The difference is always 4, and the one on the left is always 3fH.

When the head scans the Bi) rack, the above-mentioned reverse play F%l'l-Can Spring Tiger 1. Moreover, the frequency difference of the pilot signal with the adjacent track on the right side is always 3 fH, and that on the left side is fH.

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

For example, when the head scans the A2 rank on-trunk, the f3, f2,...
It is a composite signal of f4, and its level is the highest for f, followed by f2. f4 is played back at the same level.

When the head slightly deviates from track A2 toward track B2 and performs reproduction scanning, the levels of the reproduced pilot signals obtained are f3', f4. 0 decreases in the order of f2. Conversely, the level of the pilot signal obtained when the head shifts to the track B1 side and scans decreases in the order of f2.degree.f. Therefore, if the difference frequency signals 4 and 3fkI between the pilot signal on the main scanning track and each pilot signal recorded on both adjacent tracks are separated and extracted, and the reproduction levels of both signals are compared, The amount and direction of head deviation from the main eclipse track can be known.

FIG. 2 is a block diagram of a reproducing circuit for obtaining a tracking error signal. In Figure 2, from terminal 2,
A reproduced FtF signal in which a video signal and a pilot signal are combined is input.

3 is a low-pass filter, which separates and extracts only the pilot signal from the reproduced RF signal. The pilot signal obtained at this time is a composite signal of the main running distorted track and the pilot signals recorded on both adjacent tracks.

4 is a balanced modulation circuit, which outputs the above-mentioned composite signal and terminal 6.
A reference signal supplied from the reference signal is calculated. 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 FIG. 1, when the head scans the track 2 for reproduction, the input signal to the balanced modulation circuit 4 is f
2+Z5+f4 is the reference signal f3 supplied from the terminal 6. Therefore, the output signal of the balanced modulation circuit 4 is f2. f3. Frequency sum and difference signals between each signal of f4 and the 14 signals are output.

6 is a tuned amplifier circuit that tunes to the 3f signal, and 7 is a 3f
This is an H tuned amplifier circuit. 8 and 9 are detection rectifier circuits, and 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 then the level comparison circuit At step 10, a signal corresponding to the level difference is extracted. When the reproduction level of fH is higher than the reproduction level of 31H, a positive voltage corresponding to the level difference is extracted from the signal obtained by the level comparison circuit 10, and in the opposite case, a negative potential is extracted. Served. Note that the signal obtained by the level comparison circuit 1o can be used as a 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 head displacement direction and the crosstalk signal (or 3fH) obtained at that time is opposite to each other for the M track and the B track.

In FIG. 2, the circuit 11 is an analog inversion circuit;
The circuit 12 is an electronic switch that switches according to the period of the head switching signal supplied from the terminal 13. Therefore, for example, when the head reproduces and scans the A track, the output signal of the level comparison circuit 10 is outputted as is, and when the head reproduces and scans the B track, the output signal of the level comparison circuit 10 is output in analog form. is inverted and output. Therefore, the signal obtained at terminal 14 is A
, B) Regardless of the rack, a positive potential is always output 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.

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.

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, a device having two types of recording modes (3p→for example, 1 hour recording, LP→for example, 2 hour recording) will be described.

When a recording pattern recorded in SP mode is reproduced in LP mode, the locus of the rotating head is shown in Figure 3, and if this scanning is expressed in another way, it is as shown in Figure 4. , 1 → 2 → 3 → 4 → 6 for the recording pattern
→ 6 → 7 → 8 → 9 → 1o, etc.).

The level of the crosstalk signal obtained during normal playback from the tuned amplifier circuit 6 tuned to the signal of 1 is also the same as that of the main signals, that is, when a track recorded at f is scanned at the time of the playback reference signal of f2. When the track recorded at f4 is scanned at the time of the reproduction reference signal f, the signal level taken out from the tuning amplifier circuit 6 is sufficiently higher, so if the crosstalk signal level is ignored, ,
By performing the above scanning, as shown in FIG.
→10... When the output signal 0) is obtained from the output of the tuned amplifier circuit 6 at the time of scanning, the output signal (b) is obtained from the detection rectifier circuit 8.

Furthermore, when a recording pattern recorded in LP mode is reproduced in sp mode, the locus of the rotating head is shown in Figure 6, and if this scanning is expressed in another way, it is as shown in Figure 7. Then, for the recording pattern, 1→2→3→
The scanning is performed in the order of 4→5→6→7→8→9→10...

When such a scan is performed, if the crosstalk signal is ignored as described above, the external signal is rfflWtM+
The output signal is taken out from the tuned amplifier circuit 6 at f
One is when the track recorded at f3 is scanned when the reproduction reference signal is f1, and the other is when the track recorded at f3 is scanned when the reproduction reference signal is f4.

That is, as shown in FIG. 8, 1→4→5→8...
...At the time of the th scan, the output signal (a) of the tuned amplifier circuit 6 is obtained, and the output signal (A) from the detection rectifier circuit 8 is obtained.
b) An output signal can be obtained.

Therefore, an output signal of a different period from the output of the detection rectifier circuit 8 can be obtained when the recording pattern recorded in the SP mode is reproduced in the LP mode.

The present invention determines the recording mode based on the different relationships described above61.An embodiment of a detection circuit for determining the recording mode according to the present invention is shown in FIG. 9 and will be described.

First, the configuration will be explained. The output signal of the detection rectifier circuit 8 shown in FIG. 2 is connected to the terminal 16. The signal is inputted to the waveform shaping circuit 16 via the waveform shaping circuit 16, and is converted into a pulse.

The pulse output obtained by the waveform shaping circuit 16 is input to a frequency dividing circuit 17 and frequency-divided. Here, the frequency division ratio is set to ^. The output of this frequency dividing circuit 17 is connected to a differential pulse generating circuit 18 that generates a differential pulse at the rising or falling edge of the output of the frequency dividing circuit 17. ems) time delay width (for example, delay time T' (H6 field)) and one input of the NARD circuit 20. Also, the HAND circuit 20
The output of the delayed pulse generating circuit 19 is input to the other input of the delay pulse generating circuit 19.

The output of the differential pulse generation circuit 18 is input to the S (set) side of the R-8 flip-flop 21, and the output of the NAND circuit 2o is input to the R (I) side of the R-S flip flop 21.
A detection signal for determining the recording mode is obtained from the output terminal 22 of the R-S flip-flop 21.

Next, the operating principle based on the configuration shown in FIG. 9 will be explained.

First, when playing back a magnetic tape recorded in sp mode,
The reproduction in P mode will be explained using the operation waveform diagram in FIG. 10. As mentioned above, when an LP is reproduced by sp recording, the signal output shown in FIG. 5(b) is obtained from the output of the detection rectifier circuit 8.

By inputting this signal to the waveform shaping circuit 16,
From the output of the waveform shaping circuit 16, a pulse output a is obtained.

The pulse output a is frequency-divided by a frequency dividing circuit 17 to obtain a pulse output having a periodicity of 16 fields.

By inputting the output of the frequency dividing circuit 17 to the differential pulse generation circuit 18, a differential pulse output C is obtained from the output of the differential pulse generation circuit 18 at the time of rising of the output. By inputting to the S side of the flip-flop 21, the output terminal 22 of the R-57 flip-flop 21 is
The detection signal obtained from is in a Hi potential state. At this time, when the output of the frequency dividing circuit 17 input to the NAND circuit 2o and the output d of the delay pulse generation circuit 19 are both in the Low state, there is no period in which the output is in the Low state.
1-1, Low state, H-'S7') Since the tube flop 21 is not reset, the detection signal obtained from the output terminal 22 is maintained in the Hi potential state.

Now, if the switching voltage of the s'p mode during recording is selected to Hi potential, the reproduction state is normal reproduction (the sp recording mode is switched to the sp re-reproduction state).

When switching to normal reproduction, the output signal (b) of the detection rectifier circuit 8 is mostly DC and does not change, so the waveform shaping circuit 16 no longer provides a pulse output.

Therefore, the normal reproduction state continues without setting or resetting the R-S flip-flop 21.

Next, a case in which a magnetic tape recorded in the LP mode is reproduced in the SP mode will be explained using the operational waveform diagram of FIG. 11.

As mentioned above, when an LP is reproduced by sp recording, the signal output as shown in FIG. 8(b) is obtained from the output of the detection rectifier circuit 8.

By inputting this signal to the waveform shaping circuit 16,
A pulse output a is obtained from the output of the waveform shaping circuit 16.

The frequency of the pulse output a is divided by a frequency dividing circuit 17 to obtain a pulse output having a periodicity of 8 fields.

By inputting the output of the frequency dividing circuit 1γ to the differential pulse generation circuit 18, a differential pulse output C is obtained from the output of the differential pulse generation circuit 18 at the time of output rise, and this output C is R By inputting to the S side of the -8 knob flop 21, the output terminal 22 of the R-S flip 70 knob 21
The detection signal obtained from the first end is in a Hi potential state.

However, from this state, when the output of the frequency dividing circuit 17 input to the NAND circuit 20 and the output d of the delayed pulse generation circuit 19 are both in the Low state, a pulse output e is obtained from the output of the NAND circuit 20, and this pulse By the output e, R-S
The flip 70 knob 21 is reset, and the detection signal obtained from the output terminal 22 becomes a Low potential state.

If the switching voltage of the LP mode at the time of recording is selected to Hi potential, the reproduction state is switched to the normal reproduction state (LP recording mode is changed to LP reproduction).

When switching to normal reproduction, as described above, the R-S flip-flop 21 is not set or reset, so this state is maintained and the normal reproduction state continues.

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

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram schematically showing the pattern in the tracking method using four types of pilot signals, Fig. 2 is a block diagram showing the L-racking method using four types of pilot signals, and Fig. 3 is the SP An explanatory diagram showing the scanning locus of the rotating spatula (pa) when played back in the cheats pattern 'iL'P mode, Figure 4 is an explanatory diagram showing the scanning shown in Figure 3 in a different way, Figure 5 is a diagram of the output waveforms of the tuned amplifier circuit 6 and the detection rectifier circuit 8 during the scanning shown in Figure 3, and Figure 6 is the scanning of the rotary head when a tape pattern recorded in the LP mode is reproduced in the SP mode. An explanatory diagram showing the locus, FIG. 7 is an explanatory diagram showing the scanning shown in FIG. 6 in a different way, and FIG. 8 shows the tuned amplifier circuit 6 and the detection rectifier circuit during the scanning shown in FIG. 8 is an output waveform diagram, FIG. 9 is a block diagram showing an embodiment of the detection circuit for discriminating between SP mode and LP mode of the present invention, and FIG. 10 is a diagram showing the output waveform when a tape recorded in SP mode is played back in LP mode. FIG. 11 is a waveform diagram showing the operation of the main part of the detection circuit according to the present invention when a tape recorded in Lp mode is played back in SP mode. 3... ρ-pass filter (LPF), 4...
・Balanced modulator (B-M), 6.7... Tuned amplifier circuit 1.8.9-... Detection rectifier circuit, 10...
Comparison circuit, 11...Inversion circuit, 12...
Analog switch, 16...Waveform shaping circuit, 17
...1 Frequency division circuit, 4 18... Differential pulse generation circuit, 19 Old... Delayed pulse generation circuit, 2o... NAND circuit, 2
1...R-S flip-flop. Name of agent: Patent attorney Toshio Nakao, 1st person, 2nd person
Figure @ Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 9 Figure I8 q Figure 10 (er L Figure 11

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 playback, a cross signal is detected from the adjacent recording track before and after the recording track to be reproduced. The talk signal is taken out and each of the crosstalk signals is detected and rectified, and the tracking signal corresponding to the conversion level difference is used to control the relative position between the recording track and the reproduction scanning locus of the reproduction magnetic head, and the crosstalk signal is detected and rectified. A recording mode discrimination method is characterized in that the difference between the tape speed during recording and the tape speed during playback is determined by detecting periodic changes in a signal that is detected and rectified.