JPH0650581B2 - Automatic recording speed discriminating device for magnetic tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Use The present invention relates to a magnetic tape that automatically determines the recording tape speed of a video tape recorder or the like during reproduction and automatically switches to a predetermined mode. The present invention relates to an automatic recording speed determination device.

(b) Background of the Invention In a helical scan type magnetic recording / reproducing apparatus using a rotary head such as a video tape recorder, some synchronization signal is recorded on the magnetic tape at the time of recording, and the synchronization signal is reproduced at the time of reproduction. The rotation phase of the stun or rotary head cylinder is controlled, and tracking control is performed by a servo circuit so that the rotary head correctly traces a recording track such as a video signal of a magnetic tape.

In a conventional home video tape recorder, a method (a CTL method) of writing a pulse signal having a frequency of ½ of a vertical synchronizing signal, which is usually called a control signal, to a tape end is used. In the servo tracking control method using this control signal, the gap between the control signals recorded on the tape differs depending on the recording tape speed.
For example, if the recording tape speed is halved for long-time recording, the gap between control signals is also halved.

(c) Conventional Technology Conventionally, in a magnetic recording / reproducing apparatus such as a video tape recorder, the recording tape speed is automatically discriminated at the time of reproduction and automatically switched to a predetermined mode. As a method of automatically determining the recording tape speed during playback, the frequency of the control signal during playback and the frequency of the signal obtained from the frequency generator attached to the capstan shaft or capstan motor shaft that represents the playback tape speed. It is determined from the ratio of.

That is, there is a specific relationship between the recording tape speed, the reproduction frequency of the control signal and the frequency of the signal obtained from the frequency generator. FIG. 4 is a diagram showing these relationships, in which the recording speed modes are SP (standard play), LP (long play), and EP.
It shows the three modes of (economy play). C
The TL signal represents a control signal, and a signal of 30 Hz which is a frame frequency of a television signal can be obtained in a normal reproduction state in any mode. 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 according to each recording mode of the tape speed. The value of this ratio is constant regardless of the tape speed that can be played. Utilizing this relationship, the tape recording speed is conventionally 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 CFG included in one cycle of the CTL signal
The recording speed is determined by counting the number of signal repetitions.

(d) Problems to be Solved by the Invention In the above-mentioned conventional recording speed automatic discriminating device for magnetic tape, the frequency of the control signal and the signal obtained from the frequency generator attached to the capstan shaft or the capstan motor shaft are The system configuration was complicated because the discrimination was performed based on the two pieces of information.

The present invention provides a magnetic tape recording speed automatic discriminating apparatus capable of simplifying the system constitution by discriminating the recording speed of a magnetic tape by using only a control signal and using a small circuit constitution. It is an object.

(e) Means for Solving the Problems The magnetic tape recording speed automatic discriminating apparatus of the present invention includes a clock signal generating means for generating a clock signal having a frequency proportional to the reproducing speed in accordance with the reproducing speed, and a reproduced signal. A counter that counts the number of pulses of the clock signal over one cycle of the control signal, and determines the recording speed of the magnetic tape from the count value of the counter.

(f) Operation With the above configuration, 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 becomes a value according to the recording speed mode regardless of the reproduction speed. FIG. 3 is a diagram showing these relationships.

The example shown in FIG. 3 uses a clock signal of 900 Hz when the reproduction speed mode is the SP mode, 450 Hz when it is the LP mode, and 300 Hz when it is the EP mode. For example, when the magnetic tape recorded in the SP mode is reproduced in the SP mode, since the reproduction frequency of the control signal is 30 Hz, the count number is 900/30 = 30 counts. When the magnetic tape recorded in the SP mode is reproduced in the LP mode, the reproduction frequency of the control signal is 15 Hz, but the clock frequency used at this time is 450 Hz, so the count number 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,
Since the clock frequency used at this time is 300 Hz, the number of counts is 300/10 = 300 counts. In addition, the magnetic tape recorded in the LP mode is S
When reproduced in P mode, the reproduction frequency of the control signal is 60 Hz, and the count number at that time is 900.
/ 60 = 15 counts. When the same magnetic tape is reproduced in the LP mode, 15 counts are similarly obtained.
Thus, the count number corresponding to the recording speed mode can be obtained regardless of the reproduction speed mode.

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

(g) Embodiment FIG. 1 is a block diagram of a tape speed control unit of a video tape recorder using an automatic recording speed discriminating apparatus for a magnetic tape according to an embodiment of the present invention. The magnetic tape 1 is provided with a control track at its end, and a control signal is recorded therein. The capstan motor 2 is a motor for conveying the magnetic tape 1 at a constant speed, and conveys the magnetic tape at a speed predetermined according to the reproduction speed mode. Reference numeral 8 denotes a control head, which reproduces a signal on the control track of the magnetic tape 1. The reproduced control signal is amplified by the amplifier circuit 9, reproduced by the waveform shaping circuit 10 as a rectangular wave, and given to the mode discriminating unit 11. The capstan motor 2 is provided with a frequency generator 3, the frequency signal of which is amplified by the amplifier circuit 4 and shaped by the 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. The amplifier circuit 4, the waveform shaping circuit 5, and the FV conversion circuit 6 constitute a servo circuit, and the capstan motor 2 is driven at a constant speed.

The mode discriminator 11 uses the control signal (CTL) output from the waveform shaping circuit 10 to determine the magnetic tape 1
The recording speed is discriminated and the signal representing the reproduction speed mode is output to the FV conversion circuit 6 in order to drive the capstan motor according to the recording speed.

FIG. 2 shows a circuit diagram of the mode discriminating unit 11 shown in FIG. In the figure, 20 is an oscillator circuit for generating a reference clock signal, which generates a 900 Hz clock signal. Reference numeral 21 represents a frequency dividing circuit that divides the input signal into ⅓, and 22 represents a frequency dividing circuit that divides into ½. 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. Reference numeral 33 represents a switch circuit that can be switched according to the reproduction speed mode. The symbol shown on each terminal represents the position according to the reproduction speed mode. Therefore, for example, when the reproduction speed mode is SP, the clock signal of 900 Hz is selected. The counter 23 is a counter that counts clock signals input to the CK terminal. The OR gate 24 outputs "H" level when the count value of the counter 23 becomes "12" or "22". 25,
Reference numerals 26 denote T-type flip-flops, which form a 2-bit binary counter. 27 and 28 are D
Type latch circuit, in which the Q output of the T-type flip-flop is connected to the input terminal D and the timing input terminal T is connected to C
The 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 output Q of 28 is connected to the 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
Counter 2 with a fixed time delay from the rising edge of the TL signal
The 3 and T-type flip-flops 25 and 26 are respectively reset, and then the reset is released.

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

The count value of the counter 23 is 10 in one cycle of the CTL signal.
Considering the case of counting, the output of the OR gate 24 remains "L". Therefore, the D-type latch circuit 27,
All of the outputs of 28 become "L" level. Therefore, the output of the gate circuit 32 becomes "H" level. At this time, the outputs of the 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 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 T
The type flip-flop 25 is set, and the D type latch circuit 27 latches the state at the next rising timing of the CTL signal. Therefore, at this time, the output of the latch circuit 27 becomes "H" level, the output of the latch circuit 28 becomes "L" level, and the output of the gate circuit 31 becomes "H" level.

Next, considering the case where the count value of the counter 23 reaches 30 counts in one cycle of the CTL signal, the count value is 1
T-type flip-flop 25 when changing from 1 to 12
Is set. When the count value thereafter reaches 21 to 22, the T-type flip-flop 25 is reset and 26 is set. In this state, the D-type latch circuits 27 and 28 are provided at the next rising timing of the CTL signal.
Latched on. Therefore, the output of the latch circuit 27 is "L".
The output of the level 28 becomes "H" level, and the output of the gate circuit 30 becomes "H" level.

As described above, when the counter 23 counts the clock signal in one cycle of the CTL signal, it is determined whether the count value is less than 12, less than 22, or more than 22 by the magnetic field. Determine the tape recording speed mode.

(h) Effect of the Invention As described above, according to the present invention, by counting the number of pulses of the clock signal according to the reproduction speed mode over one cycle of the control signal recorded on the magnetic tape, only the count value is obtained. Thus, the recording speed of the magnetic tape can be determined, and the system configuration can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram of a tape speed control unit of a video tape recorder using an automatic recording speed discriminating apparatus for a magnetic tape according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of the mode discriminating unit shown in FIG. FIG. 3 is a diagram showing a correspondence relationship between a recording speed mode, a reproduction frequency of a control signal, a count number, etc., with respect to a reproduction speed mode of a magnetic tape.
The figure shows 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, and the like.

Claims (1)

[Claims] 1. A magnetic tape when a control signal for tracking of a rotary head is partially recorded and a magnetic tape recorded in any one of several predetermined tape speed modes is reproduced. An automatic recording speed discriminating apparatus for a magnetic tape which discriminates the recording speed of a clock signal generating means for generating a clock signal having a frequency proportional to the reproducing speed according to the reproducing speed, and a cycle of the reproduced control signal. A magnetic tape recording speed automatic discriminating apparatus comprising: a counter for counting the number of pulses of the clock signal, and discriminating the recording speed of the magnetic tape from the count value of the counter.