JPS59148165A - Tape speed discriminating device for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent the misdiscrimination of a tape speed by controlling the inhibition for discrimination of tape speed in response to the state of a tape driving means. CONSTITUTION:A system controller 21 supplies the information on the fast reproduction, pause, etc. to a speed controller 20. A feedback control is applied to a capstan 23, and the tape speed varies in response to modes. The information is fed from the controller 21 is also supplied to a trigger circuit 6, and a time constant circuit 7 is controlled via the circuit 6 and in response to the mode to inhibit the output of a control pulse cycle measuring circuit 4 which supplies a reproduced control signal corresponding to the mode to a mode discriminating circuit 5. Thus the discrimination of mode is inhibited for an optimum period in response to the selected mode when the mode is switched. Thus no discrimination of mode is carried out during a transient period when the tape traveling is unstable in a mode switching. This prevents the misdiscrimination of tape speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic recording/reproducing apparatus, which is a magnetic tape recorder recorded at a plurality of speeds, and a device that automatically determines the tape recording speed during reproduction, and particularly relates to an apparatus for automatically determining the tape recording speed during reproduction. The present invention relates to a system capable of shortening the prohibition time when a change occurs.

[Prior art]

2. Description of the Related Art Conventionally, magnetic recording and reproducing devices (hereinafter abbreviated as VTl't) have performed recording and reproducing at a plurality of tape speeds.

Each of these recording and playback modes is set to 5P (8tanda).
rd play), L P (Long play)
, BP (Extralong play) mode, etc.

Conventional example of a circuit that automatically determines these modes during playback
Y, shown in 1'1 figure. In addition, the main waveforms of the same figure are shown in Figure 2.

In the diagram, 1 is the control head, 2 is the amplifier,
3 is a waveform shaping circuit, 4 is a control pulse (hereinafter referred to as CT
(abbreviated as LP) period measurement circuit, 5 is S from the period measurement value of 4
7 is a mode discrimination circuit that discriminates between P, LP, and EP; 7 is a discrimination prohibition circuit that prohibits mode discrimination for a certain period of time; and 8 is a CT LP frequency division circuit for quick playback.

Next, to explain the operation, during normal playback, c'rr, p on the control track of the magnetic tape (not shown).
It is reproduced by the ioyr control head 1.

This CT L Plo passes through an amplifier 2 and a waveform shaping circuit 3, becomes a signal 11, and enters a switch 9 (hereinafter referred to as 5W9).

During normal playback, SW9 is connected to the a side, and CT L Pl
l is directly input to the period measuring circuit 4.

The period measuring circuit 4 measures the CTLP period and sends the information to the mode determining circuit 5 for each measurement, and the mode is determined as SP, LP, or BP. The determination signals are set so that, for example, when an SP recording tape is reproduced, the SP signal 17 is 1"HI", the LP signal 18 is LO", and the EP signal 19 is LO".

The CTLP signal 10, which is reproduced regardless of the SP, LP and EP states, is IHz in the case of the TV transmission/reception system NTSC.Hereinafter, the case of the N'rSC system will be explained.

, 3.

Assume that the recording mode has now changed from the EP mode to the SP mode. The CTLP period played from the tape is S
Since it is played back at the speed of CTLPiEP mode recorded at P speed, the period is 10) 12, which is three times the normal period (To).
VC measurement is possible. Therefore, the information of the period measuring circuit 4 changes and the mode output of the discriminating circuit 5 changes accordingly. That is, the SP signal 17 changes from IILoI+ to ``Hi'' and the BP signal 19 changes from ``Hi'' to LO, and SP is displayed.

If you play part 82 during SP playback or L when playing BP
Since the CTLP cycle also changes when the P portion is reproduced, each mode is discriminated by the mode discrimination circuit 5 based on the CTLP cycle.

Next, the case of quick playback will be explained. At this time, 8W9 is b
The output of the divider 8 is input to the period measuring circuit 4. This frequency divider 8 is set to divide the C'r L P11'Y frequency by a number equal to the double speed number of the quick playback and output it.
The signal is input to the TLP cycle measuring circuit 4, and the tape recording/recording mode is determined in the same manner as during playback.

In the case of quick playback, the speed is generally selected to be an odd multiple that reduces noise.

Here, when performing a quick look at 3x speed in SP mode, the CTLP period is measured at 5x speed during LP and 9x speed during EP. Therefore, it is necessary to change the frequency division ratio of the divider 8 according to each mode switching.

Now, the discrimination output is from BP to 1. Suppose that it becomes P.

On the other hand, the speed control system changes so that the tape speed changes from EP to I to P (however, since the capstan motor cannot make steep speed changes, the playback C'f'LP cycle gradually returns to normal. It changes periodically.

On the other hand, when frequency divider 8 changes from EP to I to P, the frequency division ratio becomes 9.
The signal 11 changes instantaneously from 5 to 5, and the signal 11 is measured in a short period, resulting in erroneous discrimination.

Also, the case where the playback operation changes, such as normal playback, fast playback, reverse playback, etc., will be explained with reference to Fig. 6.

Discrimination prohibited time setting using conventional single trigger mode ・4
- In a single circuit, if you switch from quick playback to normal playback at time a, which is slightly shorter than the time constant T2, as shown in Figure A of Fang 5, the motor will take some time to switch to normal playback, but it will not respond instantly. . In this case, the discrimination prohibition circuit does not receive a trigger, so it makes a time discrimination of T3 from point b. Since the reproduced CTLP at this time is a regular one, it has the drawback of causing erroneous determination.

In addition, in the case of quick playback from forward rotation to double speed to reverse rotation to double speed as shown in Figure 3B, the prohibition section T4 must set the time during which the rotation speed of the capstan motor stabilizes from forward rotation to reverse rotation. However, in other operation modes such as stop and normal playback, there is a drawback that the determination time is delayed.

As described above, the conventional technology has the drawback that misjudgment occurs due to the balance between the time constant and the transient in the transient state from quick playback to normal playback. Furthermore, since the single trigger is used, the time constant has to be set at a time when the motor rotation becomes stable during quick playback from forward rotation to reverse rotation, so it has to be set long. This has the drawback that the determination is delayed due to the rise of the signal during normal playback, and that the permissible cycle is long, such as every 5 seconds, on tapes recorded in multiple recording modes such as EP, SP, and EP.

[Purpose of the invention]

The object of the present invention is to maintain the discrimination mode until the tape speed reaches the desired speed, and to provide a trigger switching circuit to enable discrimination in a shorter time based on information regarding changes in motor speed, so as to quickly and without malfunction. The object of the present invention is to provide a device for making the determination.

[Summary of the invention]

The inventive feature is that the trigger method of the discrimination prohibition means is switched between t-trigger and trigger according to the state of the drive means, and by selecting the trigger method that best suits the system, the optimum discrimination prohibition time is selected and prompt discrimination without malfunction is possible. It is to do.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be explained with reference to FIG. In Fig. 4, parts having the same functions as Fig. 1 have the same numbers. In the figure, 23 is a capstan;
22 is a motor drive circuit, 25 is an amplifier, 20 is a speed control device, and 21 is a system controller (hereinafter abbreviated as system controller). 6 is a trigger circuit. Next, the operation will be explained. Pulse generating means (not shown) attached to capstan 2 and Hihalus detector 2
4, a signal that is an integral multiple of the rotational speed of the capstan 23 is obtained, and this signal passes through an amplifier 25 and becomes a capstan signal 26. The capstan signal 26 is input to a speed control circuit 20 which is a frequency-to-voltage converter, and its output is input to a capstan motor drive circuit 22 at the next stage. Are these normal speed control loops? The motor is now controlled so that the frequency of the Yapstan signal 26 becomes a predetermined frequency. As a result, the capstan 23 is kept at a constant rotational speed, allowing stable tape running.

- Also, the system controller 21 sends information such as quick playback and pause to the speed control device, and based on this information, the capstan motor is rotated at a desired speed to perform special playback. At the same time, the system controller 21 sends playback mode change information to the trigger circuit 6.

The trigger circuit 6 triggers the time constant circuit 7 based on the input reproduction mode information, inhibits discrimination and holds the output for a time set by the time constant circuit 7.

The trigger circuit 6 switches the trigger mode between normal playback and special playback based on the information from the system controller 21, and makes a normal judgment by prohibiting judgment during a transient response until a stable state is reached depending on the state of the capstan motor. Do only.

On the other hand, the tape speeds are in an integer ratio between SP, LP, and BP, and are 1/! of the EP recording tape speed i8P! 1. LP S
If it is 1/2 of P, it is necessary to send the tape at each tape speed during playback, and if the capstan signal frequency is 6 for SP, the frequency is 3 for LP and 2 for BP.

The determination during normal playback is the same as the conventional one.

Next, trigger modes associated with changes in operation, such as from stop to normal play, from normal play to pause, from pause to normal play, and from normal play to forward and reverse quick play, will be explained with reference to FIG.

An operation related to stopping the capstan motor is triggered from the trigger circuit 6 to the time constant circuit 7 only when the capstan motor rotates from a stopped state.

The trigger circuit 6 also triggers the time constant circuit 7 for operations from normal playback to forward/reverse quick playback, and vice versa, to prevent misjudgment during transient response of the capstan motor. By setting the trigger to be triggered by a change in other operating conditions, mode Y, which could not be prohibited in the past, can be prohibited and malfunctions can be prevented.

By switching the trigger mode to set the discrimination prohibition time, the motor start-up time χ from normal rotation N times to reverse rotation is no longer required, and the rise time from stop to normal rotation is reduced to about half of the conventional speed. Quick determination can be made even during normal playback or the like.

〔Effect of the invention〕

According to the present invention, it is possible to eliminate erroneous determinations during transient responses of the Yabustan motor, such as quick playback or pauses, due to changes in operation, and to accurately determine the tape mode. Moreover, it can be realized by adding a small amount of circuitry without making any major changes to the conventional method, and is suitable as an IC circuit.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional tape speed determination circuit, Figure 2 is a block diagram of a conventional tape speed determination circuit.
Figure 1 is a waveform diagram of the main part of Figure 1, Figure 173 is a waveform diagram associated with the operation, Figure 4 is a block diagram of the tape speed discrimination circuit of the present invention, and Figure 5 is a waveform diagram associated with the operation of the present invention. It is. 1... Control head 4... Control pulse period measurement circuit 5... Mode discrimination circuit 6... Trigger circuit 7... Time constant circuit 8... Branch unit 23... Cab stun 20...・Speed control circuit Fig. 2 (S) +++/ri Fig. 3 (A,) (B)

Claims (1)

[Claims] 1.? A magnetic recording and reproducing apparatus having a recording tape speed of J number and automatically distinguishing between the recording speeds during reproduction includes a control means for controlling a tape drive means, a discrimination circuit for discriminating the recording tape speed, and a discrimination circuit for discriminating the recording tape speed. The invention is characterized in that it has a discrimination prohibition circuit that prohibits the function of the discrimination prohibition circuit and a trigger circuit that triggers the discrimination prohibition circuit and has a plurality of trigger methods, and switches the trigger method according to the state of the driving means. Tape speed determination device for magnetic recording and reproducing devices. 2. A tape speed determination device for a magnetic recording/reproducing g position as set forth in claim 1, characterized in that the single trigger method is switched by switching the system operation.