JPS5843684A - Drop-out compensating device - Google Patents

Abstract

PURPOSE:To exactly execute drop-out compensation, by delaying a reproducing picture signal containing a detecting signal component, and after that, detecting a drop-out signal component, and generating a correction command signal. CONSTITUTION:A reproducing RF signal is supplied to an FM demodulator 1 and a drop-out detecting circuit 2. When an omission of the reproducing RF signal has occurred, the drop-out detecting circuit 2 generates a drop-out detecting signal. Also, a signal synthesizing circuit 3 synthesizes a reproducing picture signal and a drop-out detecting signal, sends a signal of a prescribed level or above to a CCD circuit 5 in a prescribed period, and delays it. A drop-out detecting signal component contained in a signal delayed by this circuit 5 is drop- out-corrected 4, and in a period in which the drop-out detecting signal component exists, the reproducing picture signal is selectively outputted, and in a period in which no drop-out detecting signal exists, an output of the circuit 5 is selectively outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dropout compensation device, and more particularly to a dropout compensation device used in a video information reproducing device.

In information recording/reproducing devices, etc., it is inevitable that many information signals will be lost due to scratches or dust on the recording medium, resulting in so-called dropouts. To compensate for this, a dropout compensation device is provided. It is being As such a dropout compensator, there is already known a device which performs dopeout compensation using a reproduced video signal outputted from a delay element having a signal delay function of approximately IH (one horizontal opening period). ing. Such a conventional dropout compensator detects the amplitude of an RF signal and generates a dropout detection signal when the level drops significantly, and converts this detection signal into a monostable multiplayer. A correction command signal obtained by IH delay by a vibrator is output, and the transmission line of the reproduced video signal delayed by the variable delay element is turned off for the existence period of this correction command signal, and the transmission line of the reproduced video signal delayed by the variable delay element is turned off. The playback video signal is inserted between them to output the playback video.In the dropout compensator with this structure, when there are multiple dropouts in the IH, the first dropout causes the monostable multivibrator to be activated. It has the disadvantage that only the first dropout is compensated for, since the triggered and subsequent dropouts are ignored.Also, when the correction command signal is generated, it is output instead of the output of the variable delay element. If there is any disturbance in the playback video signal before being delayed, the playback video output which is the output of the dropout compensator will be disturbed, so the playback video output after dropout compensation is sent to the synchronization separation circuit 1.
The inconvenience arises that Jl*'1/4 is 1 □ 9 □ construction 8 construction + 1.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to be able to reliably compensate for dropouts of a reproduced video signal delayed by a predetermined time even when a plurality of dropouts exist within a predetermined time, and to compensate for dropouts in a reproduced video signal delayed by a predetermined time. It is an object of the present invention to provide a drone and pull-out compensation device that outputs a reproduced video signal without the risk of generating a synchronization signal.

The dropout compensation device according to the present invention supplies a signal obtained by combining a dropout detection signal and a reproduced video signal to a delay means, and at least during the existence period of the dropout detection signal included in the output of the delay means. The transmission line for the output of the delay means is turned off, and a reproduced video signal before being delayed by the delay means is inserted in its place, thereby producing a video output.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, for example, a reproduced RF signal obtained from a video disc is transmitted to an FM demodulator l and a dropout detection circuit 2.
is supplied to. The time axis error in the reproduced RF signal is corrected to the extent that slight color unevenness occurs in the resulting image, although synchronization is performed by APO (automatic phase control) in the video reproducing apparatus. The reproduced RF signal is converted into a reproduced video signal α by an FM demodulator l, and is supplied to an addition circuit 3 and a correction means 4 as signal synthesis means.

In the adder circuit 3, the reproduced video signal a is added to the dropout detection signal supplied from the dropout detection circuit 2. The adder circuit 3 is configured so that when the dropout detection signal S is supplied, the output voltage saturates to the positive side and outputs a voltage that is sufficiently higher than the white peak level of the reproduced video signal α. The dropout detection/circuit 2 also includes a retrigger pull mono multivibrator with a predetermined time constant (for example, zo7na) using one of positive or negative pulses obtained in synchronization with the zero cross of the reproduced RF signal as a trigger. The configuration is such that the ζ output of the retriggerable mono-multivibrator is outputted as a dropout detection signal.

The time constant approximately corresponds to the maximum period of the reproduced RF signal, and when the RF multiplied signal is lost, the retriggerable monomultipipulator is inverted and a dropout detection signal consisting of a positive pulse is output.

The output C of the adder circuit 3 is a COD (charge coupled device) 5 which is a variable delay element as a first delay means.
and is supplied to the synchronous separation circuit 6. A clock pulse for controlling the amount of delay is supplied to C0D5 from vCO (voltage controlled oscillator) 7. This VOO7 controls the oscillation frequency using a time axis error signal having a level corresponding to the phase difference between the color burst signal included in the reproduced video signal and the subcarrier and rear signals generated by the reference oscillator. Output as . And the first
CC which is a predetermined time! The signal delay time at D5 is l
It is variably controlled around a value near II.

The output d of the CCD 5 is supplied to the correction means 4. In the correction means 4, the output d is transmitted through the LPF (
The signal is delayed for a second predetermined time by passing through the low-pass filter (low-pass filter) 8, and then is supplied to the signal switching circuit 9 and also to the comparator IO.

In the comparator lO, the output d is compared with a predetermined reference voltage Vref which is higher than the white peak level in the reproduced video signal α and near that level, and the dropout detection signal component included in the output d is detected, and the signal detection output e is The signal is output and supplied to the pulse width stretching circuit 11. In the pulse width stretching circuit 11, the extinction time, that is, the trailing edge of the signal detection output e is delayed by a third predetermined time longer than the second predetermined time, and a correction command signal f consisting of a pulse having a width nine times wider than the signal detection output e is generated. is output. This correction command signal f is supplied to the control input terminal of the signal switching circuit 9. This signal switching circuit 9, the output g of 9LPF8
and one of the reproduced video signals α is selectively outputted, resulting in video output 5.

In addition, in order to match the phase of the chroma signal in the video output signal 1 when switching is performed by the signal switching circuit 9, the time difference between the composite 1 video signal α and the output σ of the LPF 8 is determined by the IH ratio (/c = 3 The number of stages in the CCD 5 and the signal delay time in the LPF 8 are set so that fc becomes .58■k). This signal delay time is
Because the subcarrier frequency in the NTSO television system is set to an odd multiple of 7 of that of the horizontal synchronization signal, the phase difference with respect to the horizontal synchronization signal shifts by 180 degrees every horizontal synchronization period. That's what I do.

In the above configuration, if there is a dropout in the reproduced RF signal, the level of the reproduced video signal α obtained by FM demodulating the reproduced RF signal decreases significantly as shown in pulses i and j in Figure 2, and pulse noise occurs. do. On the other hand, when the dropout detection circuit 2 detects a dropout, the dropout detection circuit 2 detects a dropout during a period T1 during which the dropout exists, as shown in FIG.
*At T2, a dropout detection signal consisting of a high level signal is output. When this dropout detection signal and the reproduced video signal α are supplied to the adder circuit 3, the level of the output C of the adder circuit 3 is sufficiently higher than the white peak level VF of the reproduced video signal a. C
is a signal having a waveform as shown in FIG. 2C, which includes a dropout detection signal component in periods 'r and #'r2. When this output C is supplied to OOD 5, CC
The output d of D5 becomes a signal in which a dropout detection signal component exists in each of the periods 'r3e and 'r after the period Tl and T2, and the waveform of the output d is as shown in the figure (
(g) as shown in (g). The dropout detection signal component at the output d is detected by being compared with the reference voltage vref in the comparator 10, and a signal detection output e as shown in FIG. In the width stretch circuit 11, the occurrence time is almost the same as the signal detection output e, and the time width is the same as the signal detection output e.
Therefore, a correction command signal f that is longer by the third predetermined time T5 is output. On the other hand, the output g of LPF 8 is the output d of COD 5.
Since it is obtained by delaying the second predetermined time T6, which is shorter than the third predetermined time T5, the output g is as shown in CG in the same figure.
The period of existence of the dropout detection signal component in is included in the period of existence of the correction command signal f. When the correction command signal f is supplied to the control input terminal of the signal switching circuit 9 and the reproduced video signal α is selectively output as the video output instead of the output Q, the video output 5 is output as shown in FIG. can be made into a signal without any waveform disturbance due to dropout, and dropout compensation can be performed.

As described in detail above, the dropout compensation device according to the present invention delays the reproduced video signal including the dropout detection signal component and then detects the dropout detection signal component to generate a correction command signal. Even if there is a dropout, a plurality of corresponding correction command signals are outputted to ensure dropout compensation.

Further, the dropout compensation device according to the present invention performs dropout compensation by synthesizing the reproduced video signal containing the dropout detection signal component at a level higher than the white peak level during the period in which dropout exists.
Supplying the playback video signal to the sync separation circuit: erroneous sync signal due to dropout due to °? ? It is possible to prevent death. □

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram showing the operation of each part of the apparatus shown in FIG. Explanation of symbols of main parts 1... FM restorer 2... Dropout detection circuit 3... Addition circuit 4... Correction means 5 ・
COD 7/VOO Applicant Universal Pioneer Co., Ltd. Agent Patent Attorney Motohiko Fujimura)

Claims (4)

[Claims] (1) an FM demodulator that performs FM demodulation of a reproduced RF signal and outputs a reproduced video signal; a dropout detection circuit that generates a dropout detection signal when a dropout of the reproduced RF signal occurs; a signal synthesizing means for synthesizing the dropout detection signals and outputting a signal having a level equal to or higher than a predetermined level during the period in which the dropout detection signal exists; and a first delay for delaying the output of the signal synthesizing means for a first predetermined time. means for detecting a dropout detection signal component included in the output of the first delay means, selectively outputting the reproduced video signal during at least the period in which the dropout detection signal component exists, and detecting the dropout detection signal component included in the output of the first delaying means; 1. A dropout compensating device comprising: a correcting means for performing dropout correction by selectively outputting the output of one delay means. (2) The first delay means is a variable delay element that corrects the time axis of the reproduced video signal by changing the delay time according to the time axis error.
Dropout compensator as described in section. (3) The signal synthesizing means comprises an adding circuit that adds the dropout detection signal made of positive pulses and the reproduced video signal.
Dropout compensator as described in section. (4) The correction means converts the output of the first delay means into a second delay means.
a second delay means for delaying a predetermined period of time; and a second delay means for separating and extracting the dropout detection signal component included in the output of the first delay means, and performing dropout for a period longer than a third predetermined period of time by separating and extracting the dropout detection signal component included in the output of the first delay means. a dropout correction command signal generation circuit that outputs a correction command signal; and a signal switch that selectively outputs either the output of the second delay means or the reproduced video signal according to the dropout correction command signal. 2. A dropout compensating device according to claim 1, comprising a circuit.