JPS63113841A - Automatic discriminator for recording speed of magnetic tape - Google Patents

Abstract

PURPOSE:To simplify the system constitution by generating a clock signal of a frequency being proportional to a reproducing speed, and discriminating a recording speed from a ratio to a frequency of a reproducing control signal. CONSTITUTION:In accordance with a reproducing mode different in speed, a switch 33 is switched and by an oscillator 20, a 1/3 frequency divider 21 and a 1/2 frequency divider 22, a clock signal of a frequency being proportional to a reproducing speed is generated. This clock signal is counted for one period of a reproducing control signal CTL by a counter 23 which is reset through a delaying circuit 29. In accordance with counting of a frequency ratio of both these signals, T-type FFs 25, 26 are controlled by an L signal outputted by the counter 23, and an H signal different in timing, and in accordance with outputs of D-type FFs 27, 28, an output of one of gates 30-32 corresponding to each recording speed is inverted to H, and the recording speed is discriminated automatically. In such a way, the constitution of a magnetic recording and reproducing device system is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a magnetic tape system that automatically determines the recording tape speed of a video tape recorder or the like during playback and automatically switches to a predetermined mode. This invention relates to an automatic recording speed discrimination device.

Background of the Invention In a helical scan type magnetic recording/reproducing device using a rotating head, such as a video tape recorder, some kind of synchronizing signal is recorded on the magnetic tape during recording, and the synchronizing signal is reproduced during playback to the capstan. Alternatively, the rotational phase of the rotary head cylinder is controlled, and a servo circuit performs tracking control so that the rotary head correctly traces the recording track of a video signal or the like on a magnetic tape.

In conventional home video tape recorders (CTI
J type) is used. In the servo tracking control method using this control signal, the gap between the control signals recorded on the tape varies depending on the recording tape speed. For example, reduce the recording tape speed by 1/1 for long-term recording.
If it is set to 2, the gap between control signals will also be 1/2.

(C) Prior Art Conventionally, in magnetic recording and reproducing apparatuses such as video tape recorders, the recording tape speed is automatically determined during reproduction, and automatic switching to a predetermined mode is performed. As a method of automatically determining the recorded tape speed during playback, the frequency of the control signal during playback and the signal obtained from a frequency generator attached to the capstan shaft or capstan motor shaft representing the playback tape speed are determined. Discrimination is made based on the ratio of

That is, there is a specific relationship between the recording tape speed and the reproduction frequency of the control signal and the frequency of the signal obtained from the frequency generator. Figure 4 is a diagram showing these relationships. In the diagram, the recording speed mode is SP (Standard Play).

It represents three modes: LP (long play) and BP (economy play). The CTL signal represents a control signal, and in normal playback conditions in any mode, the frame frequency of the TV signal is 30H.
A signal of z is obtained.

The CFG signal represents a signal obtained from a frequency generator attached to the capstan mode shaft, and a frequency signal corresponding to each tape speed mode is obtained. The ratio between the CTL signal and the CFG signal has a unique value depending on each recording mode of tape speed.

The value of this ratio remains constant regardless of the tape speed that can be applied during playback. Conventionally, using this relationship, the tape recording speed is determined based on the ratio between the reproduction frequency of the control signal and the frequency of the signal obtained from the frequency generator.

Specifically, the recording speed is determined by counting the number of repetitions of the CFG signal included in one cycle of the CTL signal.(d) Problems to be solved by the invention Automatic determination of the recording speed of the conventional magnetic tape described above In the device, the system configuration is complicated because the discrimination is based on two pieces of information: the frequency of the control signal and the signal obtained from the frequency generator attached to the capstan shaft or the capstan motor shaft.

The present invention provides an automatic recording speed determination device for a magnetic tape that can simplify the system configuration by determining the recording speed of a magnetic tape using only a control signal and with a small circuit configuration. It is an object.

(1) Means for Solving 41 Problems The magnetic tape recording speed automatic determination device of the present invention has a clock signal generating means that generates a clock signal with a frequency proportional to the playback speed according to the playback speed, and a playback speed. and a counter that counts the number of pulses of the clock signal over one cycle of the control signal, and the recording speed of the magnetic tape is determined from the count value of the counter.

(f) Effect With the above structure, the clock signal generating means generates a clock signal proportional to the reproduction speed of the magnetic tape, and the counter counts the number of pulses of the clock signal over one cycle of the control signal. Therefore, the count value of this counter is a value corresponding to the recording speed mode regardless of the playback speed. FIG. 3 is a diagram showing these relationships.

The example shown in FIG. 3 uses clock signals of 900 Hz when the reproduction speed mode is SP mode, 450 Hz when it is LP mode, and 300 Hz when it is EP mode. For example, when a magnetic tape recorded in SP mode is played back in SP mode, the playback frequency of the control signal is 30 Hz, so the number of counts is 900/30=30 counts. When a magnetic tape recorded in SP mode is played back in LP mode, the playback frequency of the control signal is 15Hz, but since the clock frequency used at this time is 450Hz, the number of counts is 450/15 = 30 counts. Become. Similarly, when the same magnetic tape is reproduced in EP mode, the reproduction frequency of the control signal is 10 Hz, but since the clock frequency used at this time is 300 Hz, the number of counts is 300/10=30 counts. Furthermore, when a magnetic tape recorded in LP mode is played back in SP mode, the playback frequency of the control signal is 60Hz, and the count number at that time is 900/6.
0=15 counts. If the same magnetic tape is played back in LP mode, the count will be 15 in the same way. In this way, the count number corresponding to the recording speed mode can be obtained regardless of the playback speed mode.

In this way, the recording speed of the magnetic tape is determined from the count value of the force counter.

(+1 Embodiment FIG. 1 shows a block diagram of a tape speed control unit of a video tape recorder using an automatic magnetic tape recording speed determination device according to an embodiment of the present invention. A control track is provided in which a control signal is recorded.The capstan motor 2 is a motor for conveying the magnetic tape 1 at a constant speed, and the capstan motor 2 is a motor for conveying the magnetic tape 1 at a predetermined speed according to the playback speed mode. The magnetic tape is conveyed. Reference numeral 8 represents a control head, which reproduces the signal on the control track of the magnetic tape 1.The reproduced control signal is amplified by the amplifier circuit 9, and reproduced as a rectangular wave by the waveform shaping circuit 10, and the mode It is given to the discriminator 1). The capstan motor 2 is provided with a frequency generator 3, whose frequency signal is amplified by an amplifier circuit 4 and waveform-shaped by a waveform shaping circuit 5. The FV conversion circuit 6 is a circuit that converts a frequency signal into a voltage signal, and supplies the voltage signal to the motor drive amplifier 7. Increased vertical width circuit 4. A servo circuit is constituted by the waveform circuit 5 and the FV conversion circuit 6, and the capstan motor 2 is driven at constant speed rotation.

The mode discriminator 1) determines whether the magnetic tape 1 is
A signal indicating the reproduction speed mode is output to the FV conversion circuit 6 in order to determine the recording speed of the recording speed and drive the capstan motor according to the determined speed.

FIG. 2 shows a circuit diagram of the mode discriminator 1) shown in FIG. In the figure, 20 is an oscillation circuit that generates a reference clock signal, and generates a 900 Hz clock signal. Reference numeral 21 represents a frequency dividing circuit that divides the frequency of the input signal into one-third, and numeral 22 represents a frequency dividing circuit that divides the frequency of the input signal into one-half. Therefore, the frequency dividing circuit 21 outputs a clock signal of 300 Hz, and the frequency dividing circuit 22 outputs a clock signal of 450 Hz. 33 represents a switch circuit that can be switched according to the playback speed mode. The symbol shown on each terminal represents the position according to the playback speed mode. Therefore, for example, when the reproduction speed mode is SP, a 900 Hz clock signal is selected. The counter 23 is a counter that counts clock signals input to the CK terminal. The OR gate 24 outputs the "H" level when the count value of the counter 23 becomes "12" or "22". 25.
26 each represents a T-type flip-flop and constitutes a 2-bit binary counter. 27.28 is D
The Q output of the T-type flip-flop is connected to the input terminal, and the C output is connected to the timing input terminal T.
A TL signal line is connected. Therefore, the states of the T-type flip-flops 25 and 26 are latched at the rising timing of the CTL signal. D-type latch circuit 27.
The outputs Q of 28 are connected to gate circuits 30, 31, and 32, respectively. These gate circuits are circuits that determine the recording speed mode of the magnetic tape according to the output states of the D-type latch circuits 27 and 28. 29 represents a delay circuit, C
After a certain time delay from the rise of the TL signal, counter 2
3 and T-type flip-flops 25 and 26, respectively, and then release the reset.

Next, the operation of this circuit will be explained. First, the counter 23 is reset by a reset signal output from the delay circuit 29, and then counts clock signals.

The count value of the counter 23 is 10 in one cycle of the CTL signal.
Considering the case where the count is reached, the output of the OR gate 24 remains at "L". Therefore, the D-type latch circuit 27.
All outputs of 28 are at "L" level. Therefore, the output of the gate circuit 32 becomes "H" level. At this time, the outputs of gate circuits 30 and 31 are both at "L" level.

The count value of the counter 23 is 15 in one cycle of the CTL signal.
When the count value of the counter 23 reaches 12, the output of the OR gate 24 becomes "H" level. After that, the output of the OR gate 24 becomes "L" level again during the period when the count value is 13 to 15. Therefore, the T-type flip-flop 25 is set, and the D-type latch circuit 27 latches its state at the timing of the next rise of the CTL signal. Therefore, at this time, the output of the latch circuit 27 becomes "H" level, the output of the launch circuit 28 becomes "L" level, and the output of gate circuit 31 becomes "H" level.

Next, consider the case where the count value of the counter 23 reaches 30 counts in one cycle of the CTL signal.
) to 12, the T-type flip-flop 25
is cent. Thereafter, when the count value reaches 22 from 21, the T-type flip-flop 25 is reset and 26 is set. This state occurs at the timing of the next rising edge of the CTL signal.
latched to. Therefore, the output of the launch circuit 27 is "L"
When the counter 23 counts the clock signal in one cycle of the CTL signal as described above, the count value becomes 12. The recording speed mode of the magnetic tape is determined by determining whether the speed is less than 22, or 22 or more.

(h) Effects of the Invention As described above, according to the present invention, by calculating the number of pulses of the clock signal corresponding to the playback speed mode over -J13tll of the control signal recorded on the magnetic tape, only the calculated value can be calculated. The recording speed of the magnetic tape can be determined from the above, and the system configuration can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a tape speed control section of a video tape recorder using an automatic magnetic tape recording speed discrimination device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a mode discrimination section shown in FIG. 1. , Fig. 3 is a diagram showing the correspondence relationship between the recording speed mode, the playback frequency of the control signal, the count number, etc., with respect to the playback speed mode of the magnetic tape.
The figure is a diagram showing the relationship between the recording speed mode, the reproduction frequency of the control signal, the frequency of the signal obtained from the frequency generator provided in the capstan motor, etc.

Claims (1)

[Claims] (1) When playing back a magnetic tape on which a control signal for tracking of the rotating head is recorded in a part and recorded in one of several predetermined tape speed modes, the recording of the magnetic tape is performed. An automatic magnetic tape recording speed discrimination device for discriminating speed, comprising a clock signal generating means for generating a clock signal with a frequency proportional to the playback speed according to the playback speed, and a clock signal generating means for generating a clock signal with a frequency proportional to the playback speed, and a clock signal generating means for generating a clock signal with a frequency proportional to the playback speed, 1. A magnetic tape recording speed automatic determination device, comprising: a counter for counting the number of signal pulses, and determining the recording speed of the magnetic tape from the count value of the counter.