JPS5898859A - Automatic discriminating device for recording speed of magnetic tape - Google Patents

Abstract

PURPOSE:To discriminate automatically the recording speed with a simple constitution, by sampling and monitoring a tracking error signal, which is generated from a synchronizing signal superposed and recorded onto a video track, to change the reproducing speed. CONSTITUTION:A tracking error signal generated from a synchronizing signal superposed and recorded onto a video track is inputted to a microcomputer 5 through a buffer amplifier 1, a sampling holding circuit consisting of an analog switch 2 and a capacitor 3, and an A/D converter 4. Each time a tracking error signal is detected, the microcomputer 5 discriminates the release of servo lock and changes the reproducing speed successively; and when the tracking error signal is not detected, the reproducing speed is fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic magnetic tape recording speed determination device that automatically determines the speed recorded on a magnetic tape during recording in a magnetic recording and reproducing apparatus during playback, and performs playback at the same speed as during recording. .

In a rotary head helical scan type magnetic recording backing device such as a home VTR, all synchronization signals are recorded on the magnetic tape in the recording section, and the above-mentioned synchronization signals are played back and recorded on the capstan or The rotational phase of the rotary head cylinder is fully controlled, and tracking control is performed by a servo circuit so that the rotary head correctly traces the entire video signal recording track on the magnetic tape.

As the signal for the same music, a method is used in which a half-cycle pulse E-g of a vertical IG synchronization signal, which is usually called a control signal (hereinafter abbreviated as CTL signal), is injected into the tape medium.

In the system using this control signal, it is easy to automatically determine and switch the speed recorded on the magnetic tape during recording.

An example of conventionally used means for automatic discrimination is FG (Fry, Qu, Ency Genera) attached to the capstan shaft or capstan motor shaft.
There is a method of counting the number of pulses of ttr ) @ the period of the CTL signal 2 and then determining the recorded speed 11''k from the counted value.

Does the above method apply to the method using CTL signals? However, this method cannot be used with another servo system, which records a synchronization signal superimposed on the video track.

The object of the invention is to eliminate the drawbacks of the prior art described above, and to
To provide an automatic recording speed discrimination device for magnetic tape which does not require L signals and has a simple configuration.

In order to achieve this purpose, a tracking error signal created from a synchronization signal (hereinafter referred to as a pilot signal) superimposed on a video track is frequently sampled and monitored, and a tracking error signal is detected. Each time the tracking error signal is detected, it is determined that the servo lock has been lost, and the playback speed is sequentially changed, and the playback speed is fixed when the tracking error signal is no longer detected.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an automatic magnetic tape recording speed determination device according to an embodiment of the present invention.

In this case, 1 is the tracking error signal Err.
2 and 3 are analog switches and capacitors for forming sampling and holding circuits, 4 is an AD converter, and 5 is a microcomputer for automatic discrimination logic.

Next, the present invention will be explained in detail using the block diagram of FIG. 1, the pattern on the tape and the waveform diagram of each part of FIG. 2, and the flow chart of FIG. 3.

In the case of standard speed recording (hereinafter abbreviated as SP) and long-time recording (hereinafter abbreviated as LP), when the tape recording pattern changes from SP to LP, it will be automatically switched to LP playback. explain.

In FIG. 2, the diagram on the left 0Ii1 shows a state in which normal reproduction is performed with all the SP recording patterns 10, and the diagram on the right shows a state in which this state has changed to the Lp pattern. In both cases, the tape running speed is Spl<the speed at which normal toning can be achieved. Here, it will be briefly explained that the pilot error signal Error as shown in the left figure and the right figure can be obtained. There are various methods for obtaining tracking error signals for auto-tracking, but here we use four types of frequencies: f+, fx, fs, ft? The method will be explained based on a method in which a pilot signal is written for each field during recording.

Let f and a be the horizontal synchronization frequencies, and 6.7. B,
9 (11, 12, 13.14 in the case of the right figure) tracks respectively fl-be5fti, ft = 7, "fJ
+f4 = 10, "+fs, fs = 9.5fH (repeat in this order). If you record the pilot +5, you can set it to L or 3f depending on the direction of the tracking deviation at the time of birth.
7. The number of traveling waves is n, and its amplitude is proportional to the deviation. 1 is the video head switching signal 57p'3o
The direction of the shift can also be determined by the phase of (2 field period). Therefore, it is possible to obtain the tracking error signal Error using the above information. The means for obtaining this signal is well known and will not be described in detail.

First, as shown in the flowchart of the third [i:l (α)], the microcomputer 5 is started and the speed change command B and the regeneration command PB (/C are used for the system control and servo circuit of the magnetic needle tooth regeneration device). etc. are temporarily set to SP mode.

After a delay in the Delay routine when the servo circuit stabilizes at i, the servo lock state is determined. The servo lock determination process is performed as shown in the third step (h).

A rule in which the absolute value of the error error is sampled at several points in one field using the sampling pulse Sα shown in FIGS. 1 and 2 using the sampling hold circuit and the AD converter 4 and stored in advance in the microcomputer 5 Compare with 1st shift. In addition, if the tracking error signal is input with a certain offset instead of positive or negative, is it converted to an absolute value? This is done within the microcomputer 5. If the absolute value is within the specified value (indicated by the arrow 15), it is determined that the lock is in the locked state, and if it is equal to or greater than the current value, it is determined that the lock is complete. The timing of Sα is 5
7r'30'i or may be created based on the clock in the microcomputer. Here, it was created based on ff'3[17.

In FIG. 3, the lock is -J'f1. If not,
(Status shown in the left diagram of Figure 2) Return to the Delay routine and continue monitoring the lock status. If the lock is lost (the state shown in the right diagram of Figure 2), it is considered that the mode is LP recording mode, so change the speed change command B to the LP mode and perform the same lock determination process.1. /'1 Continue monitoring.

The above processing enables automatic discrimination between SP and Lp, and automatic switching. The recording speed is set by inputting the recording speed change command A shown in FIG.

Next, FIG. 4 will be spread out for another embodiment of the present invention. In the method described above, malfunctions may occur if the SN ratio of the tracking error signal is poor. The hardware configuration of the implementation described below is the same as that shown in FIG. 1, and only the LUCK determination routine shown in FIG.

In the same figure (C), the absolute value of the error level is sampled, one sample is temporarily stored in the buffer memory, and after a delay is performed to adjust the sampling intercostal space, it is compared with the fixed value. The number of times the value exceeds a specified value is counted, and when it exceeds, for example, four times, it is determined that the servo lock has been lost, and the LOCK flag is all lowered and the process returns to the main routine shown in FIG. 3 (α).

ic, unlike the above method, for example, 4 fields can be
It is also possible to use a method of sampling the absolute value t of the tracking error signal of 10 U points as one unit, storing it in memory, and making a determination.

By carrying out the above processing, it is possible to put the invention into practical use even when considering the S/N ratio.

Although the embodiment has been described with reference to two speeds, it is clear that automatic discrimination of three or more speeds is similarly possible.

Fl used in microcomputer for automatic discrimination logic
It goes without saying that a similar function could be realized using individual circuits.

As explained above, since the present invention does not require a CTL signal, it can be used for any auto-tracking servo system as long as it can obtain a tracking error signal. This is possible, and the configuration is also simple if the automatic discrimination logic is also used as a microcomputer for controlling the entire system.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a device for automatically determining the recording speed of a magnetic tape, which was implemented in an embodiment of the present invention, and Fig. 2 shows a pattern on a tape and waveforms of various parts to demonstrate an embodiment of the present invention. figure,
FIG. 3 is a flowchart for explaining the non-inventive process, and FIG. 4 is a flowchart for explaining another embodiment of the invention. 1...Buffer amplifier 2...Analog switch 3...Capacitor 4...AD converter 5...Microcomputer representative patent attorney Hiroshi 1) Toshiyuki, 11 Kyushu 1 Figure

Claims (1)

[Claims] Magnetic tape recorded at one or more recording speeds? In a rotating head helical scan type magnetic recording recording device with a rolling head, there is provided a means for changing a playback speed, a means for detecting the presence of a tracking error signal of a predetermined value or more, and a detection means detecting the presence of a tracking error signal of a predetermined value or more. The recording speed of the magnetic tape is characterized by having means for sequentially changing the playback speed each time the tracking error signal is detected, and means for completely stopping the change of the playback speed when the presence of the tracking error signal exceeding a predetermined value is no longer detected. I regret thinking about myself. 2 means for frequently detecting the level of the tracking error signal and converting it into an absolute level of tracking error; means for comparing the age vs. value with a preset regulation 1 [1; The magnetic tape recording speed automatic discrimination device described in Patent No. dL Claims No. 1 is characterized in that it has means for determining that the presence of a tracking error signal exceeding a predetermined value has been detected in the above case. 3. Claims 1 to 2 are characterized in that an appropriate delay means is provided during the process of starting to determine whether or not the tracking error signal exists above a predetermined level after the reproduction speed is completely changed. Self-manufactured and discriminating device for recording speed of magnetic tape as described in Section 1. means for sampling and detecting the level of the tracking error signal at a plurality of points within a period of 41 fields or several fields, converting it into an absolute value of the tracking error and storing it; and a means for determining that the presence of a tracking error signal of a predetermined value or more is detected when the number of times the absolute value is equal to or more than a predetermined value within the period is 11-1 or several times or more. A magnetic tape recording speed self-discriminating device as set forth in any one of claims 1 to 3, characterized in that the apparatus comprises: 5. The magnetic tape according to Claims 1 to 4, characterized in that the tracking engineer signal is a signal created by processing all the pilot symbols superimposed on the video track in advance. Recording speed automatic discrimination device