JPS60131661A - Record mode discriminating method - Google Patents

Abstract

PURPOSE:To attain the automatic discrimination of a record mode even with a tracking system using no control signal by discriminating the difference of tape speed between th record and reproduction modes by a detection circuit which detects the cycle change of a pulse signal. CONSTITUTION:The pulse output obtained through a pulse shaping circuit 18 is supplied to an f/V converter 19, and the output of the converter 19 is converted into voltage in response to the pulse output cycle of the circuit 18. Then the output of the converter 19 is supplied to a Schmitt circuit 20 which is set at the lower threshold voltage EA between voltages E1 and E2 obtained by giving f/ V conversion to the pulses of 1/30Hz and 1/15Hz cycles and at the higher threshold voltage EB between voltages E2 and E3 obtained by giving f/V conversion to the pulses of 1/15Hz and 1/7.5Hz cycles. The output is set equal to voltage Hi when the circuit 20 is set at <=EA. When the level of the circuit 20 is set at a level between EA and EB, the output state of the circuit 20 is maintained. While the output is set at voltage Low in case the circuit 20 is set at >=EB. Then a detection signal is delivered from an output terminal 21 to decide the record mode.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a magnetic recording/reproducing device (hereinafter referred to as VTR) that uses a rotating head to sequentially record and reproduce signals as an inclined discontinuous recording trajectory on a magnetic tape. The present invention relates to a detection method for automatically determining a recording mode.

Conventional Structure and Problems The Hercal Scan VT'H includes a VTR in which recording can be performed by changing the recording time by changing the tape feed speed during recording with a single VTR. In such a VTR, it is desirable to automatically determine the recording mode during playback and playback at the same speed as the recording speed during normal playback. Conventionally, the method to achieve this was to record on the control track. A method was used to determine whether the period of the control pulse being used deviated from the normal period. However, in a new format VTR system that performs tracking based on the signal played by the rotating video head itself and does not use the conventional control track in the longitudinal direction of the tape, the conventional automatic discrimination is not possible. You will not be able to use any means.

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

Structure of the Invention The present invention combines pilot signals with four different frequencies into one
This is repeated for each field in sequence and recorded superimposed on the television signal, and during playback, the signal is recorded according to the level difference in the level of the cross-talk signal of the pilot signal reproduced from the recording track adjacent to the recording track before and after the recording track to be reproduced. ,
In a tracking method that uses a tracking error signal to control the relative position between a recording track and a reproduction scanning locus of a reproduction magnetic head, the reproduced pilot signal is set to one of four different pilot signal frequencies.
After passing through a tuning circuit that tunes the signal to This method determines the difference in the nasal disc and automatically switches to recording mode.

DESCRIPTION OF EMBODIMENTS Before describing the present invention in detail, a four-frequency pilot signal tracking method using four types of pyro-node 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, A1. B1. A2. B2.・・・・・・
. is each recording track recorded on the magnetic tape by head A and head B having different predetermined azimuth angles.

Arrow 1 indicates the scanning direction of the rotary head.

In each recording track, pilot signals indicated as f1 to f4 are sequentially and repeatedly recorded for each field together 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 In Table 1, fH indicates the frequency of the horizontal synchronization signal, and 6,5 fH indicates a frequency that is 6.6 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 scans track A, (i=1.2°...), 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 B1 track, the relationship is opposite to that described above, and the frequency difference between the pilot signals between the scanning track and the adjacent track on the right is always 3 f H
, and the one on the left is always fH.

The pilot signal is 1. Since the signal has a relatively low frequency near OOkH1, the pilot signal recorded on the adjacent track can be reproduced as a crosstalk signal even if the head does not scan the adjacent track.

For example, the pilot signal obtained when the head on-trunk scans the A2 track is f3° f2. f4
f3 is the highest level, followed by 12. f4 is squared by the same level.

When the head slightly deviates from track A2 toward track B2 and performs reproduction scanning, the level of the reproduction pilot signal obtained is f3. f4. It becomes smaller in the order of f2. Conversely, when the head shifts to the trunk B1 side and scans, the level of the pilot signal obtained is f3° f2. It becomes smaller in the order of f4. Therefore, if we separate and extract 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 calculate the raw level 'rrJ 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 error 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. Circuit 3 is a low-pass filter, and the reproduction R
Separate and extract only the pilot signal from the F signal. The pilot signal obtained at this time is a composite signal of the main scanning track and the pilot signals recorded on 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 FIG. 1, the head is on track A.
2, the input signal to the balanced modulation circuit 4 is f2° f3 . f4 and the base signal f3 supplied from terminal 5. Therefore, the output signal of the balanced modulation circuit 4 is a frequency sum and difference signal between each signal of f 2 + f 3 + f 4 and the signal of f4.

Circuit 6 is a tuned amplifier circuit tuned to an fH signal, and circuit 7 is a 3 fH tuned amplifier circuit. Circuits 8 and 9 are detection rectifier circuits, and circuit 10 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. A signal corresponding to the difference is extracted. Level comparison circuit 1
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 at o, and in the opposite case, a negative potential is extracted. Note that the signal obtained by the level comparison circuit 10 includes information on the amount and direction of the head's track deviation, and therefore can be used as a tracking error signal. However, a tracking error signal that is actually suitable for practical use requires further processing.

This is because, as is clear from Figure 1, the relationship between the direction of head deviation and the crosstalk signal (fH or 3fH) obtained at that time is opposite between the A track and the B trunk. be.

In FIG. 2, circuit 11 is an analog inversion circuit, and circuit 12 is an electronic switch that switches according to the cycle of a head switching signal supplied from terminal 13. Therefore, for example, when the head reproduces and scans the A track, the output signal of the level comparison circuit 1o is outputted as is, and when the head reproduces and scans the B track, the output signal of the level comparison circuit 1o is outputted as an analog signal. 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 tetratracking 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 or more different speeds in a tracking system configuration as shown in FIG. 1, for example.

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

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

If the scanning shown in FIG. 3 is expressed in another way, it becomes as shown in FIG.
Scanning is performed in the order of 5→6→7→8→9→10...→.

Now, if we focus on one pilot signal out of the four types of recording pilot signals (in this case, it is assumed to be fl), as shown in FIG. It will be scanned in th.

That is, scanning is performed every 8 fields (4 frames).

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 LP mode.

If the scanning shown in Fig. 5 is expressed in another way, it becomes as shown in Fig. 6, where the recording pattern is 1→2→3→4→
Scanning is performed in the order of 6→6→7→8...→.

Now, focusing on fl among the four types of recording pilot signals, as shown in FIG. 6, the f1 recording track is scanned by the first and then the third scan. That is, scanning is often performed every two fields (one frame).

Also, normal playback (when SP mode recording is performed and LP mode playback is performed when LP mode recording is performed)
Needless to say, the f1 recording track is scanned every four fields (two frames).

The present invention determines the recording mode based on the different relationships described above, and an embodiment of a detection circuit for determining the recording mode according to the present invention is shown in FIG. 7 and will be described.

First, to explain the configuration, the Mon'o Noiro Nodo signal is inputted via the terminal 15 to a tuning circuit 16 that obtains an output signal by tuning to only one frequency among the four types of N640 Node signals, A detection rectifier circuit 17 detects the output of the tuned circuit.
After inputting and processing 1. sll Pulse is generated by the pulse shaping circuit 18. The pulse output obtained by the /Nll pulse shaping circuit 18 is input to the f-V conversion circuit 19, and the f-V conversion circuit 1
The output of 9 is converted into a voltage as shown in FIG.

The output of the f-V conversion circuit 19 is also a threshold value between the voltages E1 and E2 obtained by converting the pulse of one period to f-V in the f-V conversion circuit 19. Voltage EA (
lower threshold voltage) and 16 cycles of ``- and two and one periods.
1 created between the voltage E2 and E3 obtained by f-V conversion of 7.6 yen Rus
It is input to the Schmitt circuit 20 set to the threshold voltage EB (higher threshold voltage), and when the Schmitt circuit 2O becomes equal to or less than one inverse value voltage EA, the output becomes H.

If the voltage is between the threshold voltage EA and the threshold voltage EB, the state of the Schmitt circuit output is maintained, and if the voltage is higher than the threshold voltage EB, the output becomes Low. A detection signal for determining the recording mode is obtained from the terminal 21.

Next, the operating principle based on the configuration shown in FIG. 7 will be explained.

When a magnetic tape recorded in SP mode is played back in LP mode, as mentioned above, for example, the track on which f is scanned requires 8 fields (4 frames).
It becomes every.

Therefore, since the tuning circuit 16 is configured to tune only to fl, the tuning circuit output (a) is output as shown in FIG. By inputting the obtained detection rectification circuit output (b) to the pulse shaping circuit 18, a pulsed noklua with a period of □, 5 city output (c) can be obtained from the output. . When the pulse output (c) with a period of 7.514 is input to the f-V conversion circuit 19,
As explained using FIG. 8, the output voltage of the f-■ conversion circuit is E3, which is higher than the threshold voltage EB of the Schmitt circuit 20, and the output voltage of the Schmitt circuit becomes a Low voltage.

Therefore, if the SP mode switching voltage during recording is selected as Low voltage, the playback state will be normal playback (SP mode).
Switch the recording mode to SP replay) state.

Now, when switching to normal playback, the track in which fl is recorded is scanned every four fields (two frames) as described above.

Therefore, as shown in FIG. 9, a pulse output (c) with a period of i is obtained from the pulse shaping circuit 18.

If the pulse output (c) with period i is input to the f-V conversion circuit 19, the f-V conversion circuit output voltage becomes E2, but at this time, the Schmitt circuit output is not inverted and is in the LoW voltage state. is maintained as is, enters a stable state, and continues normal playback.

Next, when playing back a magnetic tape recorded in LP mode,
When playing back in SP mode, the trunk in which fl is recorded is scanned every two fields (one frame) as described above.

Therefore, as shown in FIG. 9, from the output of the pulse shaping circuit 17, a pulsed 730 yen pulse output (c) with a cycle of "-" can be obtained.

Knee period pulse output (-U to fV conversion circuit 193
0, as explained using FIG. 8, the f-■ conversion circuit output voltage becomes El, which is lower than the threshold voltage EA of the Schmitt circuit 20, and the Schmitt circuit output voltage becomes a Hi voltage. .

Therefore, if the switching voltage of the LP mode during recording is selected as Hi voltage, the above-mentioned playback state 75; normal playback (L
Switch the P recording mode to the LP playback state 0 Now, when switching to normal playback as described above, the Nockles shaping circuit 18 outputs a Nockle pulse e with a cycle of 15Hz.
get something.

The pulse output (c) of the above period is converted to f-V conversion circuit 1915.
If input to the mountain, the f-V conversion circuit output voltage becomes E2,
At this time, the Schmitt circuit output is not inverted, and the Low voltage state is maintained as it is, entering a stable state and continuing normal reproduction.

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 the conventional tracking method using control signals, the recording mode can be reliably determined with a relatively simple configuration, and by obtaining the detection signal, the recording mode can be automatically determined in the same way as when recording. It is possible to switch to play at tape speed.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a tape pattern in a tracking method using four types of pilot signals. Figure 2 is a block diagram showing a tracking method using four types of pilot signals. Figure 3 is a block diagram showing a tracking method using four types of pilot signals.
The figure which shows the scanning locus of the rotary head when reproducing in mode. FIG. 4 is a diagram showing the scanning shown in FIG. 3 in another way. Figure 5 shows the tape pattern recorded in LP mode.
The figure which shows the scanning locus of the rotary head when reproducing in mode. , - FIG. 6 is a diagram showing the scanning shown in FIG. 5 in another way. FIG. 7 is a block diagram showing an embodiment of a detection circuit for discriminating between SP mode and LP mode according to the present invention. FIG.
The correlation diagram between the conversion circuit output and the threshold value of the Schmitt circuit. FIG. 9 is an operational waveform diagram of the same embodiment. 16... Tuning circuit, 17... Detection rectifier circuit, 18... Pulse shaping circuit, 19...
...f-V conversion circuit, 2O...Schmitt circuit. Name of agent Compiled by patent attorney Toshio Nakao and one other person
l Figure *22, . 9 Figure 4 Figure 6 Figure 7 Figure 8 → Synchronization Figure 9

Claims (1)

[Claims] Television video signals are recorded on a magnetic tape as a group of inclined, discontinuous recording tracks using a rotating magnetic head.During recording, pilot signals with four different frequencies are sequentially repeated for each field and superimposed on the television signal. At the time of playback, the recording track and playback are performed using a tracking error signal according to the level difference of the crosstalk signal of the pilot signal reproduced from the recording track adjacent to the recording track before and after the recording track to be reproduced. When controlling the relative position of the tm air head with respect to the reproduction scanning locus, during reproduction, one of the pilot signals of the four types of different frequencies is tuned, and the cycle at which a tuned output signal is obtained is detected. A recording mode determination method for determining the difference between the tape speed during recording and the tape speed during playback.