JPH063657B2 - Magnetic recording / reproducing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for detecting a tape feeding speed during recording.

[Background of the Invention]

8 mm video is ATF (Automatic Track Finding) that performs tracking control using pilot signals of 4 frequencies.
The method is adopted. An example of this is JP-A-53-116120. With this method, unlike the VHS and β methods, it is not possible to detect the tape speed during recording by using the playback frequency of the CTL signal recorded on the dedicated track.

Also, in order to realize the recording tape speed discrimination in the 8 mm video multi-channel PCM system having a plurality of tracks in the width direction of the tape, a new recording tape speed discrimination means using a pilot signal is required. .

[Object of the Invention]

An object of the present invention is to provide a magnetic recording / reproducing apparatus suitable for detecting the recording tape feeding speed including the multi-channel PCM by using a pilot signal.

[Outline of Invention]

According to the present invention, in order to determine the tape speed at the time of recording, a pilot signal recorded on a track scanned by the head and 2
The tracking information is obtained by detecting the pilot signals recorded on the tracks separated by the track width. Further, in order to be able to discriminate even in the case of a plurality of tracks such as multi-channel PCM, a sample hold circuit is provided to hold tracking information during a period other than the tracks to be diluted.

Example of Invention

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a basic block diagram of a recording tape speed discriminating circuit which is an embodiment of the present invention. It will be described below with reference to the drawing. In FIG. 1, 1 is a magnetic tape, 2 is a magnetic head, 3 is a scanning track which the head is currently scanning, 4 is an adjacent track which is separated from the scanning track 3 by two track widths, and 5 is a pilot signal of the scanning track. First to detect
Band-pass filter 6, a second band-pass filter 6 for detecting the pilot signals of the tracks 4 adjacent to each other, 7 a first full-wave rectifier for detecting the amplitude level of the output of the band-pass filter 5, and 8 a band-pass filter. Second full-wave rectifier for detecting the amplitude level of the output of the converter 6, 9 is an adder for obtaining a difference signal between the output signal of the first full-wave rectifier and the output of the second full-wave rectifier, and 10 is a sample hold circuit , 11 is a low-pass filter, 12 is a reference voltage source, 13 is a comparator, 14 is a first frequency divider for dividing the pilot signal amplitude change repetition signal f _PH output from the comparator 13 by n, and 15 is a cap. CFG signal input terminal whose frequency is proportional to the rotation frequency of the stun motor, 16 is a second frequency divider that divides the CFG signal by m, 17 is an RS flip-flop, 18 is a D flip-flop, 19 is f _PLT and CFG Discrimination circuit that compares the frequencies of 20 and 20 outputs the discrimination result SP / LP A terminal for.

Here, the pilot signal frequency is f ₁ = 6.5f _H (f _H is the horizontal frequency f _H ≈1.5 KHz) f ₂ = 7.5f _H f ₃ = 10.5f _H f ₄ = 9.5f _H (in case of NHSC) The recording tape speed discrimination will be described with reference to FIG. In 8mm video, each track has f
The pilot signals _{1 to} f ₄ are recorded in a cyclic order.
This pilot signal is used for capstan control and corresponds to the conventional CTL signal. In the present invention, the pilot signals of the scanning track (f ₃ track in the figure) and the adjacent track (f ₁ track in the figure) are detected. That is, the first band-pass filter 5 (hereinafter referred to as BPF) and the second BPF 6 detect the pilot signals of the scanning track and the adjacent track, respectively, and the first full-wave rectifier 7 and the second full-wave rectifier 7 are detected. The wave rectifier 8 detects each amplitude component. The outputs of the full-wave rectifiers 7 and 8 become a difference signal in an adder 9 and are compared with a reference voltage source V _Ref in a comparator 13 via a sample hold circuit 10 and a low pass filter (hereinafter referred to as LPF) 11. The repetitive signal f _PLT of the pilot signal amplitude change is obtained by.

Here, the f _PLT frequencies are summarized in Table 1.

LP is a long-time mode (Long Play) with tape speed about 1/2 of SP (Standard Play).

As shown in Table 1, in the present system, f _PLT = OHz during SP recording / SP reproduction and LP recording / LP reproduction, and this detection is important.
Next, the detection of f _PLT = OHz will be described.

FIG. 2 shows the relationship between the pilot signal reproduction level and the tracking shift amount. As shown in FIG. 2, during normal reproduction, that is, when the tracking deviation is 0, the pilot signal of the adjacent track is extremely smaller than the pilot signal of the scanning track. That is, the output of the adder 9 is 2
The difference signal between the two pilot signals has the maximum amplitude, and can be easily converted into f _PLT (= OHz) in the comparator 13. This is the greatest merit of detecting the pilot signals of the scanning track and the adjacent track. That is, if instead of the pilot signals of the scan track and the adjacent track,
When the pilot signals of both adjacent tracks are used, during SP recording / SP reproduction and LP recording / LP reproduction, that is, when the tracking deviation is 0, the pilot signal levels of both adjacent tracks are almost the same as shown in FIG. It becomes a level. Therefore, the output of the adder 9 has the minimum amplitude, and the comparator 13
Therefore, there is a problem that a malfunction is likely to occur due to a slight noise when compared with the reference voltage source V _R 12.

Next, the determination of the recording tape speed using the detected f _PLT will be described. Now, we are playing a tape recorded in SP speed at LP speed, for example f _CFG = 90Hz, n = 1, m
= 20. The output signals of the n-divider 14 and the m-divider 16 are, as shown in FIG. 3, f _PLT /n(n=1)=7.5 Hz (SP recording / LP reproduction) f _CFG /m=4.5 Hz (m = 20), the Q output of the RS flip-flop 17 and the Q output of the D flip-flop 18 are as shown in 3-c and 3-d. Also, when the tape recorded at the LP speed is reproduced at the SP speed, the Q output of the D flip-flop 18 becomes "High".
Conversely, f _{SPLT for} SP recording / SP playback and LP recording / LP playback
= OHz, the Q output of the D flip-flop 18 is "Lo
w ″. In other words, when reproducing at a tape speed different from that at the time of recording, the Q output of the D flip-flop 18 becomes ″
High ″.

Next, an embodiment of the discrimination circuit 19 will be described in more detail.

Table 2 shows an example of f _CFG , f _PLT and f _PLT / f _CFG . Therefore, f _PLT / f _CFG is used to determine the recording tape speed.
That is, when f _PLT / f _CFG is larger than the discrimination ratio, it is determined that the reproduction is performed at a speed different from that at the time of recording. An example circuit is shown in FIG. 4 and a timing diagram is shown in FIG.
_{Reference numeral} 31 is an input terminal of f _PLT , 32 is an edge detection circuit that detects a falling edge of f _PLT , 33 is an input terminal of a prohibition pulse that prohibits discrimination, 34 is an AND gate, and 35 is a hexadecimal counter. 5-a is f _PLT , 5-b is the output of the edge detection circuit 32, 5-c is f _CFG , 5-d is the Q output of the RS flip-flop 17, and 5-e is the Q output of the D flip-flop 18. .

As shown in FIGS. 4 and 5, f _PLT / f _CFG is the discrimination ratio 1 /
When it becomes larger than 24, the carry output of the 24-bit counter 35 is input to the reset terminal of the RS flip-flop 17 by the output of the edge detection circuit 32, and the 24-bit counter is output.
The RS flip-flop 17 is not reset because 35 is reset, and the Q output "High" of the D flip-flop 18 is output from the output terminal 20. By the way, the discrimination ratio is counter 35
It can be changed by switching the count number of.

Next, another embodiment for detecting the amplitude change repetition frequency f _PLT of the pilot signal will be described with reference to FIGS. 6 to 8. In the figure, 41 is an input terminal for the reproduction pilot signal, 42 is a variable gain amplifier for outputting the reproduction pilot signal at a constant level, and 43 is a conductive state during the "High" period of the gate signal input from the input terminal 44. A gate circuit that is in a cutoff state during a Low period, 44 is a gate signal input terminal, 45 is a frequency converter that performs frequency multiplication with the output signal of the gate circuit 43 and the local pilot signal input from the input terminal 62, and 62 is a local Pilot signal input terminal, 46 is BPF for extracting 3f _H component, 47 is BP for extracting f _H component
F and 48 are the first full-wave rectifier that rectifies the output signal of BPF46,
49 is a second full-wave rectifier that regulates the output signal of the BPF 47, 50
Is an output terminal of f _PLT , 51 is a first frequency converter for performing frequency multiplication of the output signal of the gate circuit 43 and the local pilot signal A input from the input terminal 53, and 52 is an output signal of the gate circuit 43 and an input A second frequency converter for performing frequency multiplication with the local pilot signal B input from the terminal 54, 53 is an input terminal for the local pilot signal A,
54 is the input terminal of the local pilot signal B, 55 is the first f _H BPF, 56 is the second f _H BPF, 57 is the first sample and hold circuit, 58 is the second sample and hold circuit, and 59 is the first of
LPF, 60 is a second LPF, and 61 is a comparator for comparing the output signals of the first LPF 59 and the second LPF and outputting f _PLT .

Example of FIG. 6 is a pilot signal of the pilot signal and the next adjacent track of the scan track and frequency conversion by the frequency converter 45, which was configured to be detected by the respective 3f _H BPF 46 and f _H BPF47, local Table 3 for pilot signals
Select as shown in.

In the embodiment shown in FIG. 7, two frequency converters are provided, and the pilot signals of the scanning track and the adjacent track are firstly provided respectively.
Both of the f _H BPF55 and the second f _H BPF56 are configured so that they can be detected by f _H BPF.
Are selected as shown in Table 4.

The embodiment of FIG. 8 has a configuration in which the adder 9 and the reference voltage source 12 are omitted, and two systems of a sample hold circuit and LPF are provided.

Next, the multi-channel PCM which is the second feature of the present invention
The recording tape speed determination at the time will be described. First, the multi-channel PCM will be described with reference to FIGS. 9 and 10. FIG. 9 is a multi-channel PCM tape pattern, and FIG. 10 is a state diagram in which the tape is wound around the cylinder. In the 8 mm video, the tape is wrapped around the cylinder about 216 °. So in multi-channel PCM, divide this 216 ° into 6 channels,
It is configured so that PCM audio can be recorded independently on each channel. In this multi-channel PCM system, SP recording and LP recording can be arbitrarily selected for each channel, so it is necessary to determine the recording tape speed for each channel. Eighth mechanism for discriminating recording tape speed during multi-channel PCM
This will be described with reference to the drawings and FIG. 11-a is a head switching pulse of 30 Hz, 11-b is a reproduction envelope waveform, 11-c is f _H BPF
55 output, 11-d output of full wave rectifier 48, 11-e output of sample hold circuit 57, 11-f output of f _H BPF56, 11-g output of full wave rectifier 49, 11-h Is the output of the sample and hold circuit 58, 11-i is the input of the comparator 61, and 11-j is the output terminal 50.
_FPLT that is output to. Thus, the full-wave rectifier 48,
By providing a sample and hold circuit in the subsequent stage of 49 and holding during a period other than when the desired track is being reproduced, it is possible to easily detect f _PLT even in multi-channel PCM.

If a pilot signal can only be obtained intermittently with a cycle of 1/60 Hz, as in multi-channel PCM, the sampling theorem shows that half of the sampling frequency (60 Hz in this case) is used.
The above f _PLT is difficult to detect. However, in this method, as shown in Table 1, f _PLT is 15 Hz or less, and therefore f _PLT can be detected even in multi-channel PCM.

Next, an embodiment in which the tape speed is actually switched will be described with reference to FIG. 12 by using the determination result. In FIG. 12, 81 is the f _PLT detection circuit 82 described in FIGS.
Discrimination circuit corresponding to FIG. 19 or FIG. 4, this discrimination circuit
The output signal SP / LP of 82 is a signal which becomes "High" when the recording tape speed and the reproducing tape speed are different. 83 is a discrimination circuit
Output SP / LP of 82 and playback tape speed "SP""High" LP "
EXOR for exclusive SOR signal and exclusive OR
A circuit, 84 is an n-ary counter (n is usually 2 to 10) that counts the number of coincidences of the discrimination results, 85 is an AND circuit that gates the carry output of the n-ary counter 84 by the output INH signal of the monomulti 88, and 86 is a D circuit. The flip-flop 87 is a first edge detection circuit for detecting the edge of the output of the EXOR 83, 88 is an INH signal of a constant pulse width, and the monomulti 89 is a control input from a system control circuit (abbreviated as syscon) 90. A second edge detection circuit for detecting a change point of the tape feeding speed by a signal, 90 is a syscon, and 91 is a servo circuit for controlling a capstan motor.

Next, the circuit operation will be described. If the determination circuit 82 determines that the recording tape speed and the reproduction tape speed are different,
The output SP / LP of the discrimination circuit 82 becomes "High", and the EXOR 83 inverts the SLP signal to switch the playback tape speed. However, a protection circuit is necessary to prevent malfunction due to noise. The protection circuit is roughly classified into the following two types.

First, the tape speed is not switched until the discriminated results repeatedly coincide with each other, and protection by the number of coincidences is made up of an n-ary counter 84 and an edge detection circuit 87. This is the result of discrimination, EXOR83
When the output of is switched, the edge detection circuit 87 resets the n-ary counter 84. Then, n times (normally n =
2 to 10 is appropriate) If all the discriminated results match, n
The carrier output of the advance counter 84 is input as the clock of the D flip-flop 86, and the SLP signal is switched.

The second protection circuit prohibits discrimination until the tape speed reaches a constant state, and is composed of a second edge detection circuit 89, a monomulti 88, and an AND 85.

This requires some time for the tape speed to settle to a certain value, for example, when moving from the stationary state to the playing state or from the playing state to the high-speed search state, or when switching from SP playing to LP playing, Discrimination when the tape speed is not constant is apt to cause a malfunction.

Therefore, the change in tape speed is detected by the edge detection circuit 89 by the control signal input from the syscon, and the
88 Depending on the tape speed change point,
2sec is appropriate) INH signal is output and AND85 cuts off the clock of D flip-flop 86. The INH signal is normally "High" and is "Low" during the period in which the discrimination is prohibited from the change point of the tape speed.

By providing such a protection circuit, it is possible to automatically switch the reproduction tape speed by using the determination result of the recording tape speed without malfunction.

〔The invention's effect〕

According to the present invention, since the pilot signals of the scanning track and the adjacent track are detected next to each other, it is possible to reliably detect the repeated amplitude change signal of the pilot signal during reproduction. Also, by providing a sample hold circuit, it is possible to easily discriminate the recording tape speed with multi-channel PCM.

[Brief description of drawings]

FIG. 1 is a block diagram of a recording tape speed discriminating circuit according to the present invention, FIG. 2 is a diagram showing a relationship between a pilot reproduction level and a tracking deviation amount, and FIG. 3 is a timing diagram for explaining the operation of the discriminating circuit. Is a block diagram of another embodiment of the discrimination circuit, FIG. 5 is a timing diagram for explaining the block diagram of FIG. 4, and FIGS. 6, 7, and 8 are blocks showing an embodiment of the f _PLT detection circuit. Fig. 9 is a tape pattern diagram of multi-channel PCM, Fig. 10 is a cylinder diagram of multi-channel PCM, Fig. 11 is a timing diagram for explaining multi-channel PCM, and Fig. 12 is a block diagram of a tape speed discriminating circuit. is there. 3 ... Scanning track 4 ... Adjacent tracks 5,6 ... Bandpass filter 7,8 ... Full wave rectifier 10 ... Sample hold circuit 12 ... Reference voltage source 13 Comparator 19 ... Discrimination circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-59-19260 (JP, A) JP-A-59-35152 (JP, A) JP-A-60-223052 (JP, A)

Claims (5)

[Claims] 1. At least two kinds of tape feeding speeds can be switched at the time of recording / reproducing, and position control of a head at the time of reproducing is performed by using four kinds of pilot signals having different frequencies recorded on tracks on a magnetic tape. In a magnetic recording / reproducing apparatus for performing, a pilot signal recorded on a track controlled to be scanned by a head and 2 from the track.
A pair of bandpass filters and amplitude detection circuits for detecting pilot signals recorded on tracks separated by track widths;
A means for detecting a difference signal between the output signals of the pair of amplitude detection circuits, and a frequency detection circuit for detecting a repetition frequency of the amplitude change of the output signal of the means for detecting the difference signal,
A magnetic recording / reproducing apparatus characterized in that a tape feeding speed at the time of recording is discriminated based on a repetition frequency of an amplitude change of an output signal of a means for detecting the difference signal. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein the magnetic recording / reproducing apparatus has a plurality of tracks in the width direction of the tape, frequency-multiplexes a signal obtained by digitally converting an audio signal signal and the pilot signal, Helical scan recording is performed independently for each track, and a sample hold circuit is provided for holding the output signal of the means for detecting the difference signal before the period other than when the head scans the desired track. Magnetic recording / reproducing device. 3. A magnetic recording / reproducing apparatus according to claim 1 or 2, wherein during normal reproduction, if the repetition frequency of the amplitude change is higher than a predetermined frequency, different tape feeding is performed. A magnetic recording / reproducing apparatus characterized by being configured to switch to speed. 4. The magnetic recording / reproducing apparatus according to claim 1 or 2, wherein during normal reproduction, the repetition frequency of the amplitude change is greater than a predetermined multiple of the rotational speed of the capstan motor. The magnetic recording / reproducing apparatus is characterized in that it is configured to switch to a different tape feeding speed when it is high. 5. A magnetic recording / reproducing apparatus according to claim 1, 2 or 3 or 4, wherein the change in amplitude is maintained for a predetermined period from the time when the tape feeding speed is changed. A magnetic recording / reproducing apparatus characterized in that it is configured to prohibit switching of the tape feed speed depending on the repetition frequency.