JPS58220584A - Processor for video signal containing abnormal signal - Google Patents

Abstract

PURPOSE:To operate stably even for a reproduction video signal including an abnormal signal, by blocking a signal outputted from a voltage comparison circuit according to the abnormal signal by a switching circuit to prevent the hold of abnormal voltage. CONSTITUTION:If a voltage comparison circuit 4 outputs according to an abnormal signal, it is blocked to enter a gate circuit 3 by a switching circuit 21 to prevent the hold of the abnormal voltage in a sample holding circuit 5, and the hold voltage in the circuit 5 is almost agreed with the end of a synchronous signal of a video signal. Therefore, a synchronous signal with no lack is obtained from the comparison circuit 4. By the output of switching circuits 21 and 22, namely the output signal of a monostable multivibrator circuit 7, only a pedestal part is supplied to a sample hold circuit 9 as a sample. Thus, the hold voltage of the circuit 9 does not become the abnormal voltage and almost agrees with the pedestal voltage. As a result, the reference voltage of a voltage comparison circuit 13 for separating an information signal becomes the same as that in the case where no abnormal signal is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal processing device for separating a synchronization signal of a video signal using a voltage comparison method and for separating data information signals such as address information included in the video signal. In particular, it is an object of the present invention to provide a video signal processing device that operates stably even for video signals including abnormal signals due to dropouts and the like. In video information recording and reproducing systems such as video discs, data information signals such as address information are recorded in the vertical blanking interval of the video signal, and these data information signals are separated and reproduced in a reproducing device for various purposes. FIG. 1 is a schematic diagram showing a conventional example of a video signal processing device that performs synchronization signal separation and data information separation using voltage comparison means. A video signal reproduced from a recording medium such as a video disk is inputted from an input terminal 1 to a video amplification circuit 2, and after being amplified here, the output signal is sent to a first gate circuit 3 and a first voltage comparator circuit. 4 respectively.

The reproduced video signal input to the first gate circuit 3 is gated by the output signal of the first voltage comparator circuit 4, which will be described later, that is, the synchronization signal of the reproduced video signal, and only this gated signal is sent to the first sample hold. supplied to the circuits. Therefore, in the first pull-hold circuit 6, the voltage at the leading edge of the synchronization signal in the reproduced video signal is held as shown in FIG. 2A (7)A. The signal from the first sample and hold circuit 6 is supplied to the first voltage comparator circuit 4, where the signal from the first sample and hold circuit 6 is also input as shown in B of FIG. A reference voltage for voltage comparison is created, and the voltage is compared with another input signal, the reproduced video signal. As a result of this voltage comparison, the voltage of the reproduced video signal is 1 less than the reference voltage B. However, as is clear from FIG. D) in Figure a, the output signal of the first voltage comparison circuit 4 matches the synchronization signal of the reproduced video signal as shown in Figure 2.Therefore, these circuits operate as a synchronization signal separation circuit. The output synchronization signal is supplied to the output terminal 6.

The output pulse signal of the first voltage comparator circuit 4 is also input to the mono multi-circuit 7, where it receives an input pulse signal as shown in FIG. 2C. is delayed to match. The output signal of the monomulti circuit 7 is input to the second gate circuit 8, which gates the reproduced video signal supplied from the video amplifier circuit 2 to the gate circuit 8, and supplies it to the second sample hold circuit 9. To substantially limit a reproduced video signal to only a pedestal section. Therefore, the hold voltage of the second sample and hold circuit 9 becomes the voltage C shown in FIG. 2a. The hold voltage of the second sample and hold circuit 9 is applied to the positive phase input terminal of the operational amplifier 10, and the hold voltage of the first sample and hold circuit 5 is applied to the negative phase input terminal of the operational amplifier 10 via the resistor R1. Supplied.

The output signal of the operational amplifier 10 is fed back to the negative phase input terminal via the resistor R2, and is also supplied to the second voltage comparison circuit 13 as a reference signal for voltage comparison. Taking the VHD system, which is a video disc system, as an example, the data information signal is on lines 17 and 1 in the case of an odd field.
8, and lines 280 and 28 for even fields.
1, and the outline of its waveform is as shown in FIG. 2d, with the pedestal level C as a reference, the synchronizing signal level being 40 IRE, and the data information signal level cuff being 5 IRH. Therefore, the center level of the data information signal is suitable for the sharpness of the data information signal, and the level is 3γ, 5IRE as shown as E in Fig. 2d.
becomes. Therefore, for example, when separating VHD data information signals, the output signal level of the operational amplifier 10,
That is, the comparison reference signal of the second voltage comparison circuit 13 is
．． 5IRE (E in Figure 2d), which requires the values of resistors R and R2 to be R1:R2=40:3.75.
This can be achieved by setting the following. In the second voltage comparison circuit 13, the signal from the operational amplifier 10 is used as a reference signal for voltage comparison, and the voltage is compared with the input video signal from the video amplifier circuit 2, and the input video signal exceeds the reference signal level. A signal is output only when the data information signal is separated as shown in FIG. 2e. This separated data information signal is processed by a subsequent data information signal processing circuit via an output terminal 14. However, as shown in FIG. 3a, when an abnormal signal F such as a dropout is mixed into the reproduced video signal, the first sample held circuit 5 holds the abnormal signal voltage at a voltage such as A', and this Since the reference voltage for voltage comparison becomes B' in accordance with the hold voltage A', the output signal of the first voltage comparison circuit 4 lacks one or more synchronizing signals as shown in FIG. As a synchronous separation circuit, it has serious drawbacks. Furthermore, at this time, the output signal of the mono multi-circuit 7 becomes as shown in FIG. 3C, and as a result, in the case of the example shown in FIG. Therefore, the hold voltage of the second sample and hold circuit 9 becomes as shown at C' in FIG. 3d. Therefore, the output signal of the operational amplifier 10 when an abnormal signal occurs, that is, the reference signal of the second voltage comparator circuit 13, is E in FIG. 3a.
In the worst case, the second voltage comparator circuit 13 outputs no signal at all for a certain period of time after the abnormal signal occurs, and the data information signal separation function is completely lost. It has the following drawbacks. SUMMARY OF THE INVENTION An object of the present invention is to provide a video signal processing device for synchronization signal separation, data information signal separation, etc., which eliminates these drawbacks and operates stably even on reproduced video signals including abnormal signals.

FIG. 4 is a block diagram showing an embodiment of a video signal processing device according to the present invention. The explanation will be given below with reference to FIG. 4, but the blocks having the same functions as those of the conventional example are given the same numbers and the explanation will be omitted. A signal from a means for detecting dropout in a reproduced signal from a recording medium is input to a dropout detection signal input terminal 20, and this signal is supplied to switch circuits 21 and 22, respectively. The output signals of the first voltage comparator circuit 4 are also supplied to the switch circuits 21 and 22, and when there is a Cff7 pullout detection signal, the switch circuits are cut off, and when there is no signal, the switch circuits are switched to a conductive state. The output signal of the switch circuit 21 is supplied to the first gate circuit 3, and the output signal of the switch circuit 22 is supplied to the monomulti circuit 7. By adopting such a configuration, even if an output signal is generated from the first voltage comparator circuit 4 in response to an abnormal signal such as a pull-out, the input to the first gate circuit 3 is cut off by the switch 1-inch circuit 21. Therefore, it is possible to prevent an abnormal voltage from being held in the first sample and hold circuit 5, and the hold voltage of the first sample and hold circuit 6 is set at the top of the synchronization signal of the video signal as shown in A in FIG. 2a. It is possible to make them almost match. Therefore, from the first voltage comparator circuit 4, a synchronized separated output signal without any dropout as shown in FIG. is obtained. Therefore, the output signal waveform of the mono multi circuit 7 becomes as shown in FIG. Therefore, in this case the ratio 2
The hold voltage of the sample and hold circuit 9 does not become an abnormal voltage as shown in C' in FIG. 3d, but substantially matches the pedestal voltage in the reproduced video signal as shown in C in FIG. 2a. As a result, the reference voltage of the second voltage comparator circuit 13 for data information signal separation becomes exactly the same as in the case where no abnormal signal occurs, and data information signals can be stably separated. As described above, according to the present invention, it is possible to provide a video signal processing device for synchronization separation, data information signal separation, etc., which operates stably with a very simple configuration even for video signals including abnormal signals.

FIG. 6 shows another embodiment of the present invention, and as is clear from comparison with the embodiment of FIG. 4, the switch circuits 21 and 22 are combined into one switch circuit 3o, The rest is the same as the embodiment shown in FIG. Note that dropout detection means can be specially installed for the circuit configuration of the present invention, but
In order to compensate for dropout of video signals or audio signals, signal processing devices such as the , and it is quite possible to use both in terms of performance. Furthermore, it is possible to select whether the voltage comparator circuit used in the conventional example and the embodiment of the present invention generates an output signal when the reproduced video signal exceeds or falls below the reference voltage. It is clear that can be arbitrarily selected depending on the circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional example of a video signal processing device.
FIG. 2 is a waveform diagram showing the operating state of the video signal processing device shown in FIG. 1, and FIG. 3 is a waveform diagram showing the operating state of the conventional device for video signal processing for a video signal containing an abnormal signal and the device according to the present invention. , FIG. 4 is a block diagram showing one embodiment of the video signal processing device according to the present invention, and FIG. 6 is a block diagram showing another embodiment of the video signal processing device according to the present invention. 1...Video signal input terminal, 2...Video amplification circuit, 3.8...Gate circuit, 4.13...
...Voltage comparison circuit, 5,9...Sample hold circuit, 6.14...Output terminal, End...
...mono multi circuit, 10...--arithmetic amplification circuit, 20...dropout detection signal input terminal,
21.22...Switch circuit. Name of agent: Patent attorney Toshio Nakao and one other person (Figure 2)

Claims (1)

[Claims] first and second sample and hold means to which a reproduced video signal from a recording medium is supplied and hold the voltage of the reproduced video signal in a sample manner; a first voltage comparing means for setting a voltage, comparing the voltage with the reproduced video signal, and generating an output signal when the reproduced video signal exceeds or falls below the reference voltage; and the first sample. a first gate means for limiting the reproduced video signal supplied to the hold means to only the output signal generation period of the first voltage comparison means; and a delay for delaying the output signal of the first voltage comparison means by a certain time width. and a second gate means for limiting the reproduced video signal supplied to the second sample and hold means only to the output signal generation section of the delay means, and a second gate from the first and second sample and hold means. operational amplification means for creating a reference signal for separating the data information signal in the reproduced video signal using two size hold voltage signals; A video signal processing device comprising a second voltage comparison means for separating the data information signals by comparison, which operates in response to a signal from the means for detecting a dropout in a reproduced signal from the recording medium. and means for conducting or cutting off the signal from the first voltage comparing means supplied to the first gate means.