JPH0690870B2 - Control signal reproduction device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control signal reproducing device which can be used in a rotary two-head type helical scan type video tape recorder.

2. Description of the Related Art FIG. 3 is a block diagram of a control signal reproducing apparatus according to the prior art, and FIG. 4 is a waveform diagram of each signal in FIG. In FIG. 3, a magnetic head (not shown)
The control signal reproduced by is amplified by the amplifier circuit 2 from the input terminal 1, shaped into a pulse waveform by the waveform shaping circuit 3, and then output from the output terminal 4. The waveforms of the output signal A of the amplifier circuit 2 and the output signal B of the waveform shaping circuit 3 are shown as A and B in FIG. The control signal has a positive pulse and a negative pulse as shown in FIG. 4A, but generally only the positive pulse is handled as the control signal.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the rotary 2-head type helical scan type video tape recorder, a video signal for one field is output in a finite length of 1 when a rotary drum (not shown) makes 1/2 rotation. Recording is performed on a recording track (also referred to as a video track, not shown) of a book, and one control pulse (a positive pulse in FIG. 4A) is recorded during one rotation of the rotary drum. That is, one control pulse corresponds to two video tracks.

Therefore, when an image track is searched by the control pulse, there is a problem that one image track cannot be designated by one control pulse.

An object of the present invention is to solve such a problem and to provide a control signal reproducing apparatus capable of designating one video track by one control pulse.

Means for Solving the Problems A control signal reproducing device of the present invention is a reproduction control signal extracted by a magnetic head, amplified and waveform-shaped by a reproduction circuit, and rotation of a rotating body which rotates the reproduction control signal as the magnetic tape runs. The number of pulses of the control signal is doubled by obtaining the logical sum with the delayed control signal delayed based on the pulse signal indicating the angle.

With the above-described structure, the video track can be reliably searched, which is extremely advantageous particularly when variable speed reproduction is performed using the movable head.

EXAMPLES Examples of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a control signal detected by a magnetic head (not shown) is input from an input terminal 1, amplified by an amplifier circuit 2, and then subjected to waveform shaping processing by a waveform shaping circuit 3. A pulsed reproduction control signal A is obtained. The waveform of the reproduction control signal is shown by A in FIG. Note that FIG. 2 shows each signal waveform in FIG. 1, and the signals D, E, F described later also correspond to the signals D, E, F in FIG. The reproduction control signal A is input to the integrating circuit 5 and the OR circuit 7 in FIG.

On the other hand, the FG signal generating circuit 4 in FIG. 1 is, for example, a disc with a slit and a fixed disc that rotates together with a capstan shaft (not shown) provided for controlling the running of the magnetic tape in the video tape recorder. Means a circuit for processing a signal obtained from a well-known rotary encoder (not shown) composed of a photo interrupter or the like so as to be adapted to the apparatus of this embodiment, and a tape traveling direction detection signal indicating a traveling direction of a magnetic tape. B and a pulsed FG signal C corresponding to tape running are generated. In the apparatus of this embodiment, the FG signal C is the reproduction control signal A
There are 144 pulses in the period from one pulse to the next.

Next, the integrating circuit 5 in FIG. 1 is composed of an up / down counter and several logic gates, and receives the FG signal C,
The tape running direction detection signal B and the playback control signal A are input, and the preset value is "143".
Is given. The tape traveling direction detection signal B indicates "H" level when the magnetic tape (not shown) is traveling in the forward direction (the same direction as when recording), and "L" level when traveling in the reverse direction. . Therefore, when the magnetic tape (not shown) is running in the forward direction, as can be seen from the gate configuration shown in FIG. 1, the up / down counter of the integrating circuit 5 counts up with the FG signal C, Each time a pulse of the reproduction control signal A is input, the counter value (integrated data D) is reset to "0". Similarly, when the magnetic tape (not shown) is running in the reverse direction, the up / down counter of the integrating circuit 5 counts down by the FG signal C, and the counter value is input every time the pulse of the reproduction control signal A is input. (Integrated data D) is preset to "143".

In FIG. 1, the integrated data D which is the output of the integrating circuit 5
Is input to the comparator 6. "71" is given to the comparator 6 as a reference value, and the comparator 6 outputs a pulse signal only when the value of the integrated data D is "71". This pulse signal is referred to as a delay control signal E, and is also input to the logical sum circuit 7 in FIG. 1 to obtain a logical sum with the reproduction control signal A. It is output through the output terminal 8. FIG. 2 shows these matters as a timing chart. FIG. 2 shows the waveforms of the reproduction control signal A, the integration data D, the delay control signal E, and the doubler control signal F when the magnetic tape (not shown) is running in the forward direction. The data D is represented in analog for easy viewing. As shown in FIG. 2, the delay control signal E is generated as if it were recorded on the magnetic tape (not shown) at the pulse of the reproduction control signal A and at an intermediate position between the pulses. It is understood that the number of pulses of the control signal is doubled by the logical sum operation of the control signal E.

As described above, according to the present invention, the number of pulses of the control signal is set to 2
It doubles. Therefore, one control pulse corresponds to one video track, and the video track can be reliably searched based on the control pulse. This is extremely advantageous when variable speed reproduction is performed using the movable head.
It should be noted that of the configurations of the present invention, the integrating circuit, the comparator, the logical sum circuit, and the like can be realized by using a microcomputer.

[Brief description of drawings]

FIG. 1 is a block diagram showing the essential parts of an embodiment of a control signal reproducing apparatus according to the present invention, FIG. 2 is a signal waveform diagram in FIG. 1, FIG. 3 is a block diagram showing a conventional example, and FIG.
The figure is a signal waveform diagram in FIG. 1 ... input terminal, 2 ... amplifier circuit, 3 ... waveform shaping circuit, 4 ... FG signal generation circuit, 5 ... integration circuit, 6 ... comparator, 7 ... OR circuit, A ... reproduction control Signal, B ... tape running direction detection signal, C ... FG signal, D ... integrated data, E ... delay control signal,
F: Doubler control signal.

Claims (1)

[Claims] 1. A device for reproducing a control signal recorded on a magnetic tape, comprising a magnetic head, a reproducing circuit,
A pulse signal generating circuit for generating a pulse indicating a rotation angle of a rotating body that rotates as the magnetic tape runs, a delay circuit, and an OR circuit are provided, and an output signal of the magnetic head is input to the reproducing circuit. The output signal of the reproduction circuit,
Input to a delay circuit controlled by the output pulse signal of the pulse signal generation circuit, input the output signal of the reproduction circuit and the output signal of the delay circuit to the logical sum circuit, from the output terminal of the logical sum circuit 2 of the output signals of the reproduction circuit
A control signal reproducing device characterized in that it is configured to obtain a control signal having twice the number of pulses.