JPH0463453B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mode determining device for a magnetic recording/reproducing device, and more particularly to a mode determining device during reproduction in a magnetic recording/reproducing device capable of recording and reproducing at a plurality of tape speeds.

Conventionally, in magnetic recording and reproducing apparatuses, there have been two types of tape running control systems: one using a control signal and the other using a pilot signal.

In the system using control signals, a control track separate from the video signal track is provided on the magnetic tape, and tape running is controlled by recording and reproducing control signals using the control track.

In the method using a pilot signal, a pilot signal for tape control generated in synchronization with the rotation of a rotating magnetic head is superimposed with the video signal on the video signal track of the magnetic tape and recorded, and during playback, the pilot signal is recorded from the playback signal. A pilot signal was detected and the tape running was controlled based on the pilot signal.

By the way, some magnetic recording and reproducing devices that use control signals are capable of recording and reproducing at multiple tape speeds, and these devices are equipped with a mode discrimination device to automatically determine the tape running mode during playback. It was prepared. This mode discrimination device discriminates the tape running mode during playback by utilizing the above-mentioned control signal.

On the other hand, with respect to magnetic recording and reproducing apparatuses that use pilot signals, only devices that record and reproduce data at a single tape speed are currently available on the market. Naturally, therefore, such devices are not provided with a mode discrimination device for determining tape speed.

This invention was made based on this background. An object of the present invention is to provide a magnetic recording and reproducing apparatus that uses pilot signals, when a device is configured that can record and reproduce data at a plurality of tape speeds. An object of the present invention is to provide a mode discriminating device capable of automatically discriminating a tape speed at a time.

Simply put, during playback, this invention uses the output of a circuit that detects a pilot signal from the playback signal as one input, obtains the output pulse output from the speed generator of the capstan motor from the other input, and detects the pilot signal. A mode discriminating device for a magnetic recording/reproducing device comprising a comparison discriminating means that counts the number of output pulses of a speed generator at a signal detection interval and compares the counted value with a predetermined reference value to determine the tape speed. It is.

The above-mentioned objects and features of the present invention will become clearer from the following description of embodiments with reference to the drawings.

FIGS. 1A and 1B are diagrams showing the relationship between a video track (video signal track) pattern formed on a magnetic tape and a pilot signal recorded superimposed on the video track. FIG. 1A shows the pattern of the video track 2a when a video signal is recorded at a relatively high tape speed _v1 . The track pitch along the longitudinal direction of the magnetic tape 1a at this time is defined as _p1 . 1st B
The figure shows the pattern of the video track 2b when a video signal is recorded at a relatively low tape speed v ₂ (v ₁ >v ₂ ). The track pitch along the length of the magnetic tape 1b at this time is assumed to be _p2 .

In each of the video tracks 2a and 2b shown in FIGS. 1A and 1B, a pilot signal is recorded superimposed on the video signal as described above. The frequency of the pilot signal is set to be considerably lower than that of the video signal. Now, as pilot signals, different frequencies f ₁ , f ₂ , f ₃ , f ₄ (frequency is f ₁ < f ₂
< f ₄ < f ₃ ) is used. Then, on video tracks 2a and 2b,
As shown in the figure, pilot signals of different frequencies f ₁ , f ₂ , f ₃ , and f ₄ are sequentially superimposed and recorded. Therefore, in FIGS. 1A and 1B, a pilot signal of frequency f ₁ is recorded every fourth video track, in other words at pitch intervals of 4×p ₁ (or 4×p ₂ ).

Next, FIG. 2 is a block diagram of an embodiment of the present invention. In FIG. 2, an output pulse signal (hereinafter referred to as "CP-FG") of a speed generator of a capstan motor is applied to a terminal 3. CP−
Before being applied to terminal 3, FG is amplified and waveform shaped as necessary.

Terminal 4 is supplied with a video signal and a pilot signal reproduced from video tracks 2a, 2b (FIGS. 1A and 1B) by a rotating head.
Of the video signal and pilot signal applied to the terminal 4, the pilot signal of frequency _f1 is detected by the pilot signal _f1 detector 5. That is, the pilot signal f ₁ detector 5 separates only the pilot signal of frequency f ₁ from the output signal of the rotating video head, and outputs it to the next comparison rotation 6.
Furthermore, the pilot signal f ₁ detector 5 determines from the signal level of the detected pilot signal f ₁ whether or not the rotary head is accurately tracking the video track on which the pilot signal f ₁ is recorded. The discrimination output is given to the control circuit. Since the pilot signal f ₁ detection circuit 5 can be easily constructed using a known technique using a filter, a comparator, etc., a detailed explanation of its construction will be omitted here.

CP-FG applied from the terminal 3 and the detection output output from the pilot signal _f1 detector 5 are applied to a comparator 6, respectively. Comparator 6 includes at least a counter and a comparator. The counter of comparator 6 counts the number of CP-FG pulses applied from terminal 3. Further, the counter is reset each time there is a pilot signal f ₁ detection output given from the pilot signal f ₁ detector 5. Therefore, the counter of the comparator 6 is set to CP-FG in the interval from when a signal indicating that a certain pilot signal f ₁ has been detected until when a signal indicating that the next pilot signal f ₁ has been detected is input. The number of pulses will be counted. In other words, the counter counts the number of CP-FG pulses during the detection interval of the pilot signal _f1 . and,
The count output of this counter is compared, for example, by a comparator to see whether it is larger or smaller than a predetermined reference value (set value). Then, the tape speed during magnetic tape recording is automatically determined based on the comparison result, and is outputted from the terminal 7 as a determination output.

This determination output is then given to a mode switching circuit (not shown), etc., and the playback mode is switched to the determined mode.

The above description will be explained in more detail with reference to FIGS. 1A and 1B. As shown in FIG. 1A, when the tape speed is v ₁ and the track pitch of the video track 2a is p ₁ , let N ₁ be the count number of CP-FG counted by the counter (not shown) of the comparator 6. . Similarly, the count number of CP-FG in the case shown in FIG. 1B is assumed to be _N2 . Then, the relationship between the track pitches P ₁ , P ₂ and the counts N ₁ , N ₂ of CP-FG is N ₁ /N ₂ =p ₁ /p ₂ . Therefore, for example, by setting the predetermined reference value to (N ₁ + N ₂ )/2, CP-
If the FG count is larger than this reference value, it can be determined that the pitch of the video track is _p1 and the running speed of the magnetic tape during recording is _V1 . Conversely, if the count number of CP-FG is smaller than this reference value, it can be determined that the running speed of the magnetic tape during recording is _v2 .

Furthermore, as already explained, the pilot signal f ₁
Since its frequency is set to a considerably lower frequency (several 100 KHz or less) compared to the video signal, the influence of the azimuth effect of the head is small during playback, and playback is possible even with a head with a different azimuth from that during recording.

FIG. 3 is a block diagram of another embodiment of the present invention. A feature of the embodiment shown in FIG. 2 is that the driving mode is determined using two pilot signals f ₁ and f ₃ (see FIGS. 1A and 1B). That is, in FIG. 3, the pilot signal
The f ₃ detector 8 performs the same function for the pilot signal f ₃ as the f ₁ detector 5 performs for the pilot signal f ₁ .
This is a circuit for Therefore, the pilot signal f ₁ detector 5 outputs a detection output of the pilot signal f ₁ , and the pilot signal f ₃ detector 8 outputs a detection output of the pilot signal f ₃ .
Each of these outputs is applied to a comparator 6 via an OR gate 9. In the comparator 6, the counter in the comparator 6 is reset every time there is an output from the OR gate 9, as in the first embodiment described above.

Therefore, in the embodiment shown in FIG. 3, magnetic tapes 1a and 1b (FIGS. 1A and 1B)
The mode discrimination can be performed with half the moving distance of the embodiment shown in FIG.

In this case, the predetermined reference value to be compared with the output of the counter provided in the comparator 6 may be, for example, (N ₁ +N ₂ )/4.

In the two embodiments described above, four pilot signals of different frequencies f ₁ , f ₂ , f ₃ , f ₄ are used.
The case where only the pilot signal f ₁ is used from among f ₁ , f ₂ , f ₃ , and f ₄ and the case where the pilot signals f ₁ and f ₃ are used have been explained. However, the present invention is not limited to this, and the other pilot signals f ₂ and f ₄ may be used alone, or the pilot signals may be used in an appropriate combination.

The reason why four signals having different frequencies are used as pilot signals in each of the above embodiments is to match the format of an existing magnetic recording/reproducing apparatus that uses pilot signals. Therefore, even if the number of pilot signals is different from the above four signals, the present invention can be similarly applied to perform mode discrimination.

As described above, the present invention calculates the tape speed by counting the number of output pulses output from the speed generator of the capstan motor at the detection interval of the pilot signal and comparing the counted value with a predetermined reference value. Since the mode discriminating device is capable of discriminating the running mode of the magnetic tape, a pilot signal for controlling the tape speed generated in synchronization with the rotation of the rotating magnetic head is recorded on the video signal track of the magnetic tape by superimposing it with the video signal. In a reproducing type magnetic recording/reproducing apparatus, when recording/reproducing at a plurality of tape speeds, the mode of the tape speed at the time of recording can be automatically determined. Furthermore, since this mode discrimination device is constructed by utilizing existing circuits as much as possible, it can be constructed at low cost.

[Brief explanation of the drawing]

FIGS. 1A and 1B are explanatory diagrams showing the relationship between a video track on a magnetic tape and a pilot signal recorded on the track in a superimposed manner with a video signal. FIG. 2 is a block diagram of an embodiment of the present invention. FIG. 3 is a block diagram of another embodiment of the present invention. In the figure, 1a and 1b are magnetic tapes, 2a,
2b is the video track, p ₁ and p ₂ are the pitch of the video track, v ₁ and v ₂ are the tape speed, 3 is the output pulse signal input terminal of the speed generator of the capstan motor, and 4 is the output signal of the rotating head. input terminal,
5 is a pilot signal f ₁ detector, 6 is a comparator, 7 is a mode discrimination output terminal, and 8 is a pilot signal f ₃ detector. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1 Recording and playback are possible at multiple tape speeds, and a pilot signal generated in synchronization with the rotation of a rotating magnetic head is superimposed on the video signal to be recorded to generate the video signal on the magnetic tape. A magnetic recording/reproducing device for recording on a track, which includes a circuit for detecting the pilot signal recorded in a superimposed manner from a reproduced signal during reproduction, and a speed generator provided in a capstan motor for driving the magnetic tape. a device, counting the number of output pulses output from the speed generator during the detection interval of the pilot signal detected by the detection circuit, comparing the counted value with a predetermined reference value, and detecting the magnetic tape. A mode discriminating device for a magnetic recording/reproducing device, including a comparison discriminating means for discriminating tape speed.