JPS62141664A - Method for discriminating recording mode - Google Patents

Abstract

PURPOSE:To discriminate the difference of tape speed at the time of recording and reproducing and to switch it automatically to the same mode as the time of recording at the time of reproducing by tuning any one of four kinds of pilot signals. CONSTITUTION:When a tape recorded in an LP mode is reproduced in an SP mode, pulse output (c) having time width T3 is obtained. When the pulse shaping output (c) and pulse output (b) that becomes low for a time TA set by a time width setting circuit 19 are gated by an NAND gate 21, and the output and pulse output (d) that becomes low for a time TB set by a time width setting circuit 20 are gated by an AND gate 22, only output (e) of the NAND gate 21 can obtain pulse output having pulse width of (TA-T3). The pulse output (e) is inputted to S (set) side of a flip-flop 23, and Hi voltage output is obtained from an output terminal 24. At the time of switching voltage of an LP mode at the time of recording is selected to Hi voltage, the state of reproducing is switched to the state of normal reproduction (LP recording mode is LP reproduced).

Description

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

BACKGROUND OF THE INVENTION With current VTRs, it is essential to switch the tape feed speed during recording in a single VTR. 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 this, 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.

Problems to be Solved by the Invention However, this is a new format VTR system in which all tracking is performed based on signals reproduced by the rotating video head itself, and the system does not use the conventional control trunk in the longitudinal direction of the tape. , it is no longer possible to use conventional automatic discrimination means.

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

Means for Solving the Problems The present invention provides a tracking method using four types of pilot signals, comprising: a circuit that tunes any one of the four types of pilot signals and pulses the tuned output signal; A first time width setting circuit that outputs a pulse signal with a time width of T1 from the rise or fall of the pulsed pulse signal, and a second time width setting circuit that outputs a pulse signal with a time width of T2 from the rise or fall of the pulsed pulse signal. a width setting circuit; a gate circuit that gates the outputs of the first and second time width setting circuits and the pulse signal obtained by pulsing the tuning output signal;
This gate output activates R (reset) -
It is provided with 8 (set) flip-flops to determine the recording mode.

Effect of the Invention With the above-described configuration, the present invention can determine the difference between the tape speed during recording and the tape speed during playback, and can automatically switch to the same mode during playback as during recording.

Embodiment Before explaining the present invention in detail, a four-frequency pilot tracking method using four types of pilot signals without using a general control signal will be described.

FIG. 4 shows a recorded magnetization trajectory by the four-frequency pilot signal tracking method, and FIG. 5 is a block diagram of a reproducing circuit for obtaining a tracking error signal.

In FIG. 4, M1. Ih, Mu2. B2...
. . . are recording tracks recorded on the magnetic tape by the A head and the B head having different predetermined azimuth angles.

Arrow 1 indicates the scanning direction of the rotary head.

In each recording track, each pilot signal indicated by f1 to r4 is sequentially recorded field by field together with the video signal. The recording order of pilot signals is the order shown in FIG. 4, and one type of pilot signal is continuously recorded within one field period. The frequency of the pilot signal is set, for example, to the values shown in the table below.

In the table, fH indicates the frequency of the horizontal synchronization signal, for example 6.5, and fIi indicates the frequency of the horizontal synchronization signal, which is 6.
．． Indicates that it is 5 times larger.

The frequency difference of the pilot signal between each recording track is the fourth
As shown in the figure, the frequency is <, fa or 3fI (.

When the head scans an artificial (knee 1.2...) 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 f , and the one on the left is always 3 f.

When the head scans the entire Bi trunk, the relationship is reversed to that described above, and the frequency difference between the pyro 7) signals between the scanning track and the adjacent trunk on the right is always 3rH, and that on the left is fH.

Since the pilot signal is a signal of relatively low frequency in the vicinity of 100 KH2, it is possible to reproduce the pilot signal sound recorded on the adjacent track as a crosstalk signal even if the head does not scan the adjacent track.

For example, the pilot signals obtained when the head on-tracks and scans the multitrack track are fs, f2. f4
It is a composite signal of
Next, f'2. fa 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 obtained reproduction pilot signal decreases in the order of f3+fa*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 fs, f2 and r4. 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 difference frequency signals fH and 3fH can be extracted from the main scanning track. The amount and direction of head displacement can be determined.

FIG. 5 is a block diagram of a reproducing circuit for obtaining a tracking error signal. In Fig. 5, from terminal 2,
A reproduced RF signal in which a video signal and a pilot signal are combined is input.

3 is a low-pass filter that 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 scanning track and the pilot signals recorded on both adjacent trunks. .

4 is a balanced modulation circuit, which outputs the above-mentioned composite signal and terminal 5.
Multiply by the reference signal supplied from 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. 4, when the head reproduces and scans the track, the input signal to the balanced modulation circuit 4 is f
2. fs.

f4, and the reference signal supplied from terminal 5 is rs. Therefore, the output signal of the balanced modulation circuit 4 is r2. rs
, fa and the signal f4, the frequency sum and difference signals are output.

6 is a tuned amplifier circuit tuned to the rH signal, and 7 is a tuned amplifier circuit tuned to the rH signal;
f) I tuned amplifier circuit. 8 and 9 are detection rectifier circuits, and 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 3fI, a positive voltage corresponding to the level difference is extracted from the signal obtained at 0, and in the opposite case, a negative potential is extracted. The signal obtained by the level comparison circuit can be used as a tracking error signal because it includes information on the amount and direction of track deviation of the head.However, a tracking error signal suitable for practical use requires further processing.

This is because, as is clear from FIG. 4, the relationship between the A track and the B track with the crosstalk signal (ro or 3 rH) obtained when the head is misaligned is opposite to each other. .

In FIG. 6, 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 1o is output as is, and when the head reproduces and scans the B track, the output signal of the level comparison circuit 10 is outputted as an analog signal. is inverted and output. Therefore, the signal obtained at terminal 14 is A
, B Regardless of the track to be scanned, 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 trunk.

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 reproduction when recording is performed at at least two or more different speeds in a tracking system configuration as shown in FIG. 5, for example.

Here, two types (s p-+, for example, 1 hour recording, LP
→For example, a recording mode having a recording mode of 2 hours recording will be explained.

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

FIG. 6 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. 6 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 among the four types of recording pilot signals, the f1 recording track will be scanned for two field periods (rl here).

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

FIG. 8 shows the locus of the rotation throat when the recorded pattern recorded in the LP mode is reproduced in the iLP mode.

If the scanning shown in FIG. 8 is expressed in another way, it becomes as shown in FIG. 9, and the scanning shown in FIG.
It will be scanned in the order of →6 →6 →7 →8・river・→.

Now, if we focus on fl among the four types of recorded pilots,
As shown in FIG. 9, the f1 recording track is scanned during the ring field period.

Also, normal playback (SP mode playback with SP mode recording, LP mode playback with LP mode recording @r
), it goes without saying that the r1 recording track is scanned during one field period.

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. 1 and will be described.

First, to explain the configuration, a regenerated pilot signal is inputted via a terminal 15 to a tuning circuit 16 that obtains an output signal by tuning to only one type of frequency out of four types of pilot signals, and the output of the tuning circuit is After being input to the detection rectifier circuit 17 and processed, the signal is converted into pulses by the pulse shaping circuit 18.

The output obtained from the pulse shaping circuit 18 is input to the first time width setting circuit 19 and the second time width setting circuit 2o, and is also input to one terminal of the NAND gate 21 and the AND gate 22.

Note that the first time width setting circuit 19 has an A field time (key 8.3 m5) shorter than one field time (16.6 m5) from the rise of the pulse output of the pulse shaping circuit 18.
The second time width setting circuit 20 is set to obtain an output that is Low only for a longer time than the pulse shaping circuit 18 (key 33.m5). 3m5) and longer than one field time (16.6m5).

The output of the first time width setting circuit 19 is input to the other terminal of the NARD gate 21, and the output of the first time width setting circuit 2o
The output of is input to the other terminal of the AND gate 22.

The output of the HmuD gate 21 is input to the S (set) side of the R-S flip-flop 23, and the output of the AND gate 22 is input to the R (reset) side of the R-S flip-flop 23.
A detection signal for determining the recording mode is obtained from the output terminal 24 of the R-S flip-flop 23.

Next is the operating principle based on Figure 1? explain.

When a tape recorded in the LP mode is reproduced in the SP mode, as described above, for example, the track eV field period in which fl is recorded is scanned.

Therefore, since the tuning circuit 16 is configured to tune only fl, the tuning circuit output (A) is output as shown in FIG.
7 and the obtained detection rectifier output (b) is inputted to the Hals shaping circuit 18, a pulse output (c) having a time width of T3 can be obtained from the output. T
3 is Habo A field time (8.3m5).

This pulse shaping output (c) is converted into a pulse output (
(b) is gated by the NAND gate 21, and the pulse output which becomes Low for the TB time set in advance by the time width setting circuit 2o is gated by the 1AND gate 22, the NAND gate 21 as shown in FIG. A pulse output having a pulse width of only the output (to) of No. 21 (Tmu-T5) can be obtained.

This pulse output (to) is input to the S (set) side of the R-8 flip-flop 23, and an H1 voltage output is obtained from the output terminal 24.

Therefore, if the switching voltage for the LP mode during recording is selected as the H1 voltage, the playback state will be switched to the normal playback state (LP recording mode is played back). The track on which <fl is recorded is scanned for one field period.

Therefore, from the output of the pulse shaping circuit 18, a pulse shaped output (c) having approximately one field time width (1 cs, ems) T22 is obtained.

Even if this pulse shaping output (c) is gated with the pulse output of the time width setting circuit 19) using the 1NAND gate 21, and the pulse output (e) of the time width setting circuit 20 is gated with the AND gate 22, As shown in FIG.
ND Gate 21. The outputs (f) and (t) of the AND gate 22 are both Low, and the R-S flip-flop 2
The voltage at the output terminal 24 of No. 3 is not reversed, and the Hi voltage state is maintained as it is, entering a stable state and continuing normal reproduction.

Next, when playing back a magnetic tape recorded in SP mode, L
When reproducing in P mode, the f+gold recording track is scanned for one frame period as described above.

Therefore, as shown in FIG. 2, from the output of the pulse shaping circuit 18, approximately one frame time width (33.3 m5) Tlf
This pulse-shaped output (c) is gated with the pulse output of the time width setting circuit 19 by the 1NAND gate 21, and the pulse shaped output (c) is gated with the time width setting circuit (e). If gated by the 1AND gate 22, a pulse output having a pulse width equal to only the output (T) of the AND gate 22 (T1-Ta) can be obtained as shown in FIG.

This pulse output (T) is input to the R (IJ upper set side) of the R-S flip-flop 23, and is output from the output terminal 24 to the L
ow voltage output is obtained.

Therefore, if the H1 voltage is selected as the switching voltage for the SP mode during recording, the playback state is switched to the normal playback (sp recording mode Isp playback) state.

Now, when switching to normal reproduction in the same way as above, the output of the pulse shaping circuit 18 is approximately 1 field time width (1 s).
, ems) A pulse-shaped output (c) with T2 f is obtained, and the NAND gate 21 and
The outputs (to) and (g) of 2 are both Low, and R-
The voltage at the output terminal 24 of the S flip-flop 23 is not reversed, and if it is in the Low power state, it is maintained as it is, enters a stable state, and continues 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 that does not use control signals, the recording mode can be reliably determined with a relatively simple configuration, and by obtaining the detection signal, the tape can be automatically recorded on the same tape as when recording. It is possible to switch so that playback can be performed at a high speed, and it is also possible to determine the mode relatively quickly.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a detection circuit for mode discrimination in one embodiment of the present invention, Figs. 2 and 3 are operational waveform diagrams of this embodiment, and Fig. 4 shows a detection circuit using four types of pilot signals. Tape pattern diagram for tracking method, Figure 6 is 4
Figure 6 is a block diagram of a reproduction processing circuit using a tracking method using different types of pilot signals. Figure 6 is a scanning locus diagram of the rotary head when a tape pattern recorded in SP mode is reproduced in iLP mode. Figure 7 is its timing diagram. Figure 8 iLP
FIG. 9 is a timing diagram showing the scanning locus of the rotary head when a tape pattern recorded in the SP mode is reproduced in the SP mode. 16... Tuning circuit, 17... Detection circuit, 18... Pulse shaping circuit, 19.20...
...Time width setting circuit, 21...RkND gate, 22...AND gate), 23...
R-S flip-flop. Name of agent: Patent attorney Toshio Nakao and one other name
1 Figure t Figure 2 Figure 3s 4111 Figure 5 Figure 61! ! Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] A magnetic recording and reproducing device that records television video signals as a group of discontinuous inclined recording tracks on a magnetic tape using a rotating magnetic head, and records four types of pilot signals with different frequencies for each field during recording. are repeated in sequence, superimposed on the television signal, and recorded.
During playback, a tracking error signal corresponding to the level difference between the crosstalk signals of pilot signals read from recording tracks adjacent to the front and rear of the recording track to be played back is used to determine the playback scanning trajectory of the recording track and the playback magnetic head. and means for tuning any one of the four types of pilot signals having different frequencies during playback, and means for pulsing the tuned output signal, A recording mode determination method that determines the difference between the tape speed during recording and the tape speed during playback by managing the pulse time width of this pulsed signal or the period of the pulse signal.