JPS6332756A - Method for discriminating recording mode - Google Patents

Abstract

PURPOSE:To surely discriminate a recording mode and to automatically reproduce at the same tape speed with the time of recording by detecting the phase deviation of tracking error signals and signals synchronizing with a rotational phase. CONSTITUTION:Tracking error signals are inputted to a trigger pulse generating circuit 17 through a waveform shaping circuit 16. On the other hand, FG signals obtained in proportion to the rotation speed of a rotary cylinder are sent to a sample holding circuit 19, and sample-held by trigger pulses from a circuit 17. Output of the circuit 19 is inputted to an analog switch 20, and the output is sent to the S-side and R-side of R-SFF 21. The Q output of the FF 21 becomes a detection output for mode changing. The detection output changes over the switch 20 through a delay circuit 23.

Description

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

Conventional helical scan type VTRs include a VTR that can perform recording by switching the tape feed speed during recording with a single VTR. In such a VTR, it is essential to automatically determine the recording mode during playback and to play back at the same speed as the recording speed for normal playback.

Currently, as a method for realizing this, a method for determining the recording mode in a tracking method using four types of pilot signals without using the conventional control signal has been proposed in Japanese Patent Application Laid-Open No. 1980-19280. This will be explained using an example.

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

FIG. 6 shows a recorded magnetization trajectory by the four-frequency pilot signal tracking method, and FIG. 7 is a block diagram of a reproducing circuit for obtaining a tracking error signal.

In FIG. 6, A1. B,,A2. B2...
A head and B head have different predetermined azimuth angles.
Each recording track is recorded on the head magnetic tape.

Arrow 1 indicates the scanning direction of the rotary head.

In each recording track, each pilot signal indicated by f1 to f4 is sequentially recorded field by field together with the video signal.

The recording order of the pilot signals is as shown in Fig. 6.
Within the field period, the frequency of one type of 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 6.5fH 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 trunk is the 6th
As shown in the figure, the frequency is fH or 3fH. When the head scans A i (i=1 + 2...) tracks, 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. , that on the left is always 3fH.

When the head scans rack B,), the relationship is reversed to that described above, and the frequency difference between the pilot signals between the scanning track and the adjacent track on the right side is always 3fH, and that on the left side is always 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, the pilot signal obtained when the head scans the A2 track 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 A2 toward track B2 and performs reproduction scanning, the level of the pilot signal obtained is f3.
f4. It becomes smaller in the order of f2.

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 head from the main scanning track can be detected. The amount and direction of deviation can be known.

FIG. 7 is a block diagram of a reproducing circuit for obtaining a tracking error signal.

In FIG. 7, a reproduced RF signal in which a video signal and a pilot signal are combined is input from terminal 2. Circuit 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 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 6. The reference signal supplied from the terminal 6 is a pilot having the same frequency as the pilot signal recorded on the main scanning track. For example, in FIG. 6, when the head reproduces and scans the track A2, the input signal to the balanced modulation circuit 4 is f
2 , f 3 rf4, and the reference signal supplied from terminal 6 is f3. Therefore, the output signal of the balanced modulation circuit 4 is f2. f3. Each signal of f4 is output. Circuit 6 is a tuned circuit tuned to an fH signal, and circuit 7 is a 3fH 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, and then sent to the level 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. The signal obtained by the level comparison circuit 10 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. 3, the relationship between the head displacement direction and the crosstalk signal (fH or 3fH) obtained at that time is opposite to each other for the A track and the B track.

In FIG. 7, a circuit 11 is an analog inversion circuit, and a circuit 12 is an electronic switch that switches according to the period of a head switching signal (hereinafter referred to as H, SW signal) supplied from a terminal 13. Therefore, the terminal 14 has, for example, A
When the head reproduces and scans the 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 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 A or B track.

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. This is an overview of how to obtain a tracking error signal using , a detailed explanation will not be given here, but as shown in Figure 8, the tracking error signal is 7.5
It changes with a period of Hz. Furthermore, when a tape recorded in the LP mode is played back in the SP mode, the tracking error signal changes at a cycle of 15H2 as shown in FIG. 8, which is a different cycle from the above.

In addition, the tracking error signal that changes at a frequency of 7.5 Hz with the above-mentioned period changes over time, as shown in FIG. Therefore, the H-3W signal has a synchronous relationship with the H-3W signal. This is a method for determining whether the
When playing back in LP recording mode and playing back in LP recording mode, it is an essential condition that the tracking error signal does not change periodically.

However, although there is no problem in the case of self-recording and playback, in the case of compatible playback, the trajectory drawn by the rotating head differs slightly between recording and playback, so the tracking error signal is e.g. o Causes level fluctuations at a frequency of Hz. In addition, the frequency of the 4-frequency pilot signal is 6.5 f
H ~ 10.5 f Hl or noise with a frequency close to the above frequency is mixed into the regenerated pilot signal,
When the output levels of the tuned amplifier circuits 8 and 9 tuned to the fH and 3fH signals mentioned above are affected unevenly, as shown in FIG.

As shown in C, a tracking error signal with steps at 60 Hz and i periods is obtained.

Problems to be Solved by the Invention As described above, when the tracking error signal changes at the above-mentioned period even during normal playback, this method of determining the recording morph, 5H21esHz, from the different periods of □ and □, makes it difficult to distinguish. becomes extremely difficult.

The present invention aims to solve these problems by providing a method different from the above-described method for automatically determining a recording mode.

Means for Solving the Problems The present invention provides waveform shaping of the tracking error signal when controlling the relative position between the recording trunk and the reproducing scanning locus of the reproducing magnetic head using four types of pilot signals. This is a recording mode discrimination method that discriminates by detecting a phase shift between this waveform-shaped signal and a signal synchronized with the rotational phase of the rotary cylinder.

The working tracking error signal maintains a synchronous relationship with a signal synchronized with the rotational phase only during normal playback, but when the tape is played back at a tape speed different from the recording mode, the synchronous relationship is no longer maintained.

Therefore, the recording mode can be determined by detecting the phase shift between the tracking error signal and the signal synchronized with the rotational phase.

Embodiment An embodiment of the present invention is shown in FIG. 1, and will be explained using operational waveform diagrams in FIGS. 2 and 3.

The tracking error signal A is inputted from the terminal 15 and applied to the waveform shaping circuit 16, and a rectangular wave output port is obtained as an output.

This output port is triggered by a rising edge or a falling edge, and is input to a trigger pulse generation circuit 17 that obtains a pulse output cover.

An FG signal 2 obtained in proportion to the rotational speed of the rotary cylinder is inputted from the terminal 18, sent to a sample and hold circuit 19, sampled and held by the 1-IJ pulse output cover.

The output of the sample-and-hold circuit 19 is input to an analog switch 20, one output of this analog switch 20 is sent to the S side of an R-S flip-flop 21, and the other output is sent to the R side. A detection output for switching the mode is taken out from the output terminal 22 of the R-S flip-flop 21. Further, this detection output is input to the delay circuit 23, and the analog switch 2Q is switched based on this output.

The above is the configuration of this embodiment. Next, we will discuss the operation.

Now, when playing back at a speed different from the recording mode, as mentioned above, for example, if a tape recorded in SP mode is played back in LP mode, the cycle will be 7.5 Hz, and if a tape recorded in LP mode is played back in SP mode, the cycle will be 15H2. A tracking error signal is obtained with a period of . This signal is input to the waveform shaping circuit 16, and a pulse output port is obtained from the output. This output signal port is input to the trigger pulse generation circuit 17, and a trigger pulse is obtained from the output. This trigger pulse is not synchronized with the FG multiplied signal obtained in proportion to the cylinder rotation speed, and changes over time, for example, TlP-T2 P-T3P.
The phase shifts as shown by .... Therefore, at this time, as shown in the third diagram, the rainy period of the Hi and Low states of the FG signal 2 is sampled and held in the S&H circuit 19 by the trigger pulse No. 2, so the pulse output of the S&H1 circuit 19 is input to the analog switch 2o. be done.

This analog switch 20 switches the output of the delay circuit 23 so that when the output of the R-S flip-flop 21 is inputted to the S side of the R-3 flip-flop 21 when the output is at a low voltage, the output of the delay circuit 23 is inputted. It is set so that when the voltage is Hi, the signal is switched so that it is input to the R side of the R-S flip-flop 21.

That is, the delay circuit 23 switches the analog switch 20 with an appropriate time delay when the output of the R-S flip-flop 22 suddenly changes from Low voltage to Hi lightning voltage or from Hi lightning voltage to Low voltage. .

In addition, when a pulse signal is input to the S side of the R-S flip-flop 21 described above, the output terminal 22 of the R-S flip-flop 21 is set to a high state.When a pulse signal is input to the Hi lightning voltage R side, the R-S flip-flop 21 is The output terminal 22 of the flip-flop 21 is set to a low voltage.

Now, if you play back at a speed different from the mode during recording, for example, if the mode switching voltage during recording is Low voltage,
When the detected pressure output obtained from the terminal 22 during reproduction is high and scanning, a pulse signal is input from the output of the S&H circuit 19 to the analog switch 2o as described above. Also, the voltage at the terminal 22 is Hi
If there is lightning voltage, the pulse signal is input to the R side of the R-S flip-flop 21 via the analog switch 20, and the detection output obtained from the output terminal 22 of the R-S flip-flop 21 is switched to a low voltage. and switches to normal playback mode. When the normal reproduction mode is entered, as described above, no pulse signal is obtained from the output of the S&H circuit 19, and this state is maintained. At this time, the output of the delay circuit 23 switches to the normal playback mode and is then switched to be input to the S side of the R-8 flip-flop 21 via the analog switch 20 and held.

In addition, when the mode switching voltage during recording is H1 voltage and the detection output obtained from the terminal 22 during reproduction is a Low voltage and scanning is performed, the pulse signal from the S&H circuit 19 is Via analog switch 20, R-
It is input to the S side of the S flip-flop 21, and this R-3
The detection output obtained from the output terminal 22 of the flip 70 and the knob 21 is switched to the Hi main voltage, and the mode is switched to the normal reproduction mode. As described above, when the normal reproduction mode is entered, no pulse signal is obtained from the S&H circuit 19, so this state is maintained. Also, at this time, from the output of the delay circuit 23,
After switching to the normal reproduction mode, the signal is switched and held so as to be input to the R side of the R-S flip-flop 21 via the analog switch 20.

The first embodiment of the present invention has been described above, and the second embodiment, which is further improved, will be described with reference to FIGS. 4 and 5.

During normal playback, the tracking error signal may change as shown in Figure 9 a, l) and c.
H-5W signal and FG double signal tracking error signal (
The phase is synchronized with a). However, there is no problem if the signal swings at the rising and falling timings of the H-3W signal as shown in Fig. 9(a).
If a change like this occurs, please refer to A1. The tracking error signal waveform at B1 may differ depending on the difference in the reproduction output of the A head and the B head and the difference in the recording pilot signal.

When such a signal is waveform-shaped, the timing of the rise or fall of the waveform-shaped output (b) differs from the rise or fall timing of the SW times signal for each field.

In such a case, even if the phase is synchronized with the FG multiplied signal tracking error signal (A), the rising or falling timing of the waveform shaping output ←) becomes the Hi potential of the FG multiplied signal →. or the potential may become low, making it difficult to achieve the object of the present invention.

Therefore, in the present invention, in order to eliminate these disadvantages, the waveform shaping circuit output (o) is frequency-divided by four.

By dividing the frequency by L, the rising or falling timing of the frequency-divided output ((e)) is always at the point where the same pilot signal is written.

In general, the tracking error signal waveforms of fields written and illuminated by the same pilot signal are extremely equal, so the above-mentioned disadvantages are eliminated.

Therefore, with the trigger pulse output e, the FCi signal)
Even if sampled and held, the output of the S&H circuit 19 is only a DC-like voltage that does not change.

Hereinafter, the operation of obtaining a detection output from the terminal 22 when reproducing at a speed different from the recording mode operates in the same manner as described in the embodiment of the cylinder 1 of the present invention.

Effects of the Invention According to the present invention, in a tracking method using four types of pilot signals, even if the tracking error signal fluctuates periodically during normal playback, the recording mode can be reliably determined without any malfunction, and the recording mode can be automatically determined. It is possible to switch to playback at the same tape speed as when recording.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing an embodiment of a detection circuit for determining the recording mode of the present invention, FIGS. 2 and 3 are operational waveform diagrams of the detection circuit of FIG. 1, and FIG. A circuit block diagram of the second embodiment, FIG. 6 is an operation waveform diagram of the same embodiment, FIG. 6 is a pattern diagram showing a recording pattern on a tape in a tracking method using a four-frequency pilot signal, and FIG. 7 8 is a block diagram showing the configuration of a playback processing circuit for a tracking method using a 4-frequency pilot signal. FIG. FIG. 9 is a waveform diagram showing the relationship between the tracking error signal and the H-3W signal when reproducing the data. FIG. 9 is a waveform diagram showing the change in the tracking error signal during normal reproduction. 16...Waveform shaping circuit, 24...Rump frequency dividing circuit, 17...Trigger pulse generation circuit, 19...
...S&H circuit, 20...analog switch, 21...R-S flip-flop, 23.
...Delay circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person
1121 Figure 2 23 Figure 4 Figure 6 Figure 8 Figure 9

Claims (1)

[Claims] A pilot signal for tracking control is superimposed on the video signal to be recorded and recorded sequentially on the recording medium as adjacent recording tracks, and during reproduction, it is reproduced as crosstalk from the recording tracks adjacent to the recording track before and after the recording track to be reproduced. When controlling the relative position between the recording track and the reproduction scanning locus of the reproduction magnetic head using the tracking error signal corresponding to the level difference of the pilot signal, the tracking error signal during reproduction is waveform-shaped;
A recording mode determination method that determines the tape speed during recording and the tape speed during playback by detecting a phase shift between this waveform-shaped signal and a signal synchronized with the rotational phase of a rotating cylinder.