JPS58111492A - Video signal reproducer - Google Patents

Abstract

PURPOSE:To obtain an excellent still video, by stopping recording media when a delayed vertical synchronizing signal and dropout are coincident with each other. CONSTITUTION:A reproduced video signal (a) without dropout from a terminal 1 is inputted to Synchless circuit 3. Then, a horizontal synchronizing signal is picked up and since no horizontal synchronizing signal exists in the dropout part, the dropout part is detected. Further, this signal (a) is inputted to a vertical synchronizing separation circuit 5 and a vertical synchronizing signal (c) is picked up. The output of a delay circuit 6 is inverted after a prescribed time when the signal (c) is inputted. When the output (d) of the circuit 6 is inverted, a capstant stop signal is generated from a capstan stop signal generator 4 with the output (b) of the circuit 3. The inversion of the output of the circuit 6 where the said prescribed time is determined suitably is given to the next vertical blanking period. Thus, after the generation of the capstan stop signal, dropout is given to the vertical blanking period, and excellent still reproduction is obtained.

Description

[Detailed Description of the Invention] The present invention is a video signal reproducing device Kll that can reproduce still images.
do.

For example, in a helical scan type magnetic recording and reproducing device (hereinafter referred to as a VTR), a still image can be reproduced by stopping a magnetic tape on which a video signal is recorded. However, when the tape is stopped, the scanning trajectory of the one-turn magnetic heald scans is different from the rounded image trajectory. Therefore, there is a period when no playback signal is obtained.

In other words, a double act occurs.Therefore, Kusunoki's method of preventing damage to still images by positioning this period in the vertical return period has been proposed. There is a method in which the KH1 tape is stopped so that the detection signal and the rotation of the rotating magnetic head have a predetermined phase relationship.However, with this method, the round playback video that detects the phase of the rotating magnetic head is This increases the number of wiring between 1g1w1 that processes signals and control circuits such as motors, which is undesirable for implementation.
This is also unfavorable in terms of noise countermeasures.

Another method is to detect the jump during one horizontal synchronization period that occurs at the transition when the magnetic head is scanned across the iI contact frame, and to determine whether the jump occurs within the vertical return period Nj. 41 to put it! There is also a way to stop the tape.

However, the jumping is 1 in the dropout period fM1.
He had the disadvantage that it was difficult to detect rounding.

Furthermore, in order to eliminate disturbances in the vertical synchronization on the monitor, a method has been proposed in which a pseudo-normal phase signal generated from the rotational phase of the magnetic head is demodulated and mixed into the reproduced video signal. In order to prevent this, it was necessary to create pseudo vertical synchronization signals for different times (generally 1.5 horizontal synchronization minutes) in different fields, which required a complex path and high mechanical accuracy.

The present invention aims to provide a video signal reproducing device that eliminates the above-mentioned drawbacks. That is, focusing on the fact that the dropout of the reproduced video signal occurs once every two fields, the recording medium is stopped at 9 o'clock when the good signal and the dropout coincide with the vertical synchronization signal.

As a result, a good still image can be obtained with a simple circuit configuration, and a 4 [similar to direct synchronization @I signal generation circuit] can be easily constructed.

FIG. 1 is a plotter diagram showing one embodiment of the present invention. 1
is the input terminal of the playback video IJllIgr, 2 is the mixing 6.6
Ha Ei 11! Syncless detection circuit that detects the part where there is no horizontal synchronization signal in the signal, 4 is a capstan stop signal generator that stops the capstan motor, 5 is vertical synchronization No. 18 separation circuit, 6 is a delay circuit, 7# is a pseudo a pulse generator that generates a vertical synchronization signal; 8 is an output terminal for a reproduced video signal;
9 is the output terminal of capstan stop No. 1g.

FIG. 2 is a waveform diagram in which the waveforms at various parts (al to rut) in FIG. 1 are omitted. The operation will be explained below. When commanded to play a still image, the capstan transports the magnetic tape at a slow speed until it stops. At this time, a reproduced video signal with dropouts as shown in FIG. 2(a) is input to terminal 1. This dropout appears as a noise bar on the monitor. The video signal (IL) is input to the syncless circuit 6. Then, Q shown in Figure 6R)
U<Horizontal synchronization Ig is removed, and then since there is no horizontal synchronization signal in the dropout part, a rainbow dropout part shown in FIG. 3(B) is detected. -Variable Hoso signal (1) i'i--It is input to the serial synchronization separation circuit 5 and the vertical synchronization signal (0) is scattered. The output of the delay circuit 6Fi is inverted after a predetermined time τ1 after the input of the vertical period signal (el).Then, when the output of the delay circuit 6 (,i) is inverted, if there is an output of the syncless circuit 3, the capstan is stopped. Signal generation! From 4, a capstan stop signal is generated as shown in No. 211 (6) K. The predetermined time τ1 is set as appropriate and the reversal of the output of the circuit 6 is converted to the following direct recursion. Enter the period 0 As a result, after the middle Yapstan stop signal is generated, the dropout enters the direct line period and good still playback can be obtained.
4 is a line diagram showing an example of a specific circuit of pulse generation Ii7. R, am R, is a resistor, 01 to C4 are capacitors, MuNDi, MuND2 are Ando), Try
.

Try is a transistor, FIiFiD type 7 rig 7
0g, INV is inverter, D is diode, BU
Fl, BU121j y:y 7 amplifier, 10.
11 is a terminal to which a constant voltage Vac is applied. Maku 11
(0) to (f) Fi shown in Figure 4 (C) shown in Figure 2
~(f) and -1 part. According to the configuration shown in Fig. 4, τ1 is composed of resistor R1, capacitor G1, and buffer amplifier B.
It is determined by the threshold voltage of UF1 (indicated by Vtht in Figure @5).

Next, we will write a 0-dot writhing act to explain the operation of forming a pseudo vertical synchronization signal from the vertical synchronization signal (e). No vertical sync signal is 1
Obtained every other field. The vertical synchronization signals for every other field separated by the vertical synchronization separation circuit 5 are delayed by a predetermined time τ2 in the pulse generator Z. Then, a pulse signal (f) having a pulse width of τ for a predetermined time is generated.

This pulse signal (f) is pseudo! II [As a synchronization signal,
In place of the vertical synchronizing signal that has disappeared at the dropout portion, it is mixed into the reproduced video signal (-) by the mixer 2. In addition, in the pulse generator 7 having the configuration shown in Fig. 14, τ2 is the resistance R1, the capacitor C2, and the buffer increaser IIIAtIB.
At the threshold voltage of UF2, Mayu τ1 is KRs,
They are determined by the threshold voltages of the capacitor c1 and the impermeator NV, respectively.

According to the above configuration, when the dropout coincides with the delayed vertical synchronization fd signal without dropout once every two fields, the magnetic f-driving is stopped.
As a result, the stop of the recording medium can be accurately controlled with a small number of circuits during the vertical retrace period, and a high-quality still image can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a waveform diagram of each part of the 11th part, Fig. 6 is a waveform diagram showing the function of the sinkless path, and Fig. 4 is a waveform diagram of the main parts of the present invention. FIG. 5 is a circuit diagram showing one embodiment, and FIG. 5 is a waveform diagram of each part of FIG. 4. 1 is an input terminal for a reproduced video signal, 8 is an output terminal for a still video signal, and 9 is an output terminal for a cabstan stop 1i-@. Applicant Canon Co., Ltd. FM Gi Marushima -, N2

Claims (1)

[Claims] 1) In a video signal reproducing device that reproduces a still video by stopping a recording medium in which a video signal is reproduced, a first detection means for detecting a vertical synchronization signal in the reproduced video signal; The dropout detection means detects the dropout of the 31! A video signal reproducing device comprising: delay means for delaying; and means for stopping the recording body according to the output of the delay means and the output of the dog act detection means.