JPH021474B2 - - Google Patents

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 retrace section of the video signal, and these data information signals are separated and reproduced in a reproducing device for various purposes. FIG. 1 is a block diagram showing a conventional 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 the first voltage comparator circuit 4, respectively. The reproduced video signal input to the first gate circuit 3 is an output signal of a first voltage comparison circuit 4, which will be described later.
That is, it is gated by the synchronization signal of the reproduced video signal, and only this gated signal is supplied to the first sample and hold circuit 5. Therefore, in the first sample and hold circuit 5, A in FIG.
As shown in the figure, the voltage at the leading edge of the synchronization signal in the reproduced video signal is held. The signal from the first sample and hold circuit 5 is sent to the first voltage comparator circuit 4.
Based on the signal from the first sample and hold circuit 5, a reference voltage for voltage comparison is created as shown in B of FIG. A voltage comparison is made with a certain reproduced video signal. As a result of this voltage comparison, a signal is output from the first voltage comparator circuit 4 only when the voltage of the reproduced video signal is lower than the reference voltage B, as is clear from FIG. 2a. Since only the synchronizing signal portion (D in Figure 2a) of the reproduced video signal is lower than the reference voltage B, the output signal of the first voltage comparator circuit 4 is lower than the reproduced video signal as shown in Figure 2b. Match the signal's sync signal. Therefore, these circuits operate as a synchronization signal separation circuit, and 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 monomulti circuit 7, where the input pulse signal is delayed so as to match the pedestal portion of the reproduced video signal, as shown in FIG. 2C. The output signal of the monomulti circuit 7 is sent to the second gate circuit 8
Here, the reproduced video signal supplied from the video amplification circuit 2 to the gate circuit 8 is gated, and the second
The reproduced video signal supplied to the sample and hold circuit 9 is substantially limited to only the 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. Each is supplied. The output signal of the operational amplifier 10 is fed back to the negative phase input terminal via the resistor R ₂ 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, data information signals are transmitted on lines 17 and 1 in the case of odd fields.
8, and in the case of an even field, lines 280 and 281, and the outline of the waveform is as shown in Figure 2d, with the synchronization signal level being 40IRE and the data information signal level being 40IRE with reference to the pedestal level C. It is becoming 75IRE. Therefore, the appropriate punching level for the data information signal is the center level of the data information signal, and that level is shown in Figure 2 d.
The result is 37.5 IRE as shown as E. 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
It is necessary to set it to 37.5IRE (E in Figure 2 d),
This can be achieved by setting the values of resistors R ₁ and R ₂ so that R ₁ :R ₂ =40:3.75. In the second voltage comparator circuit 13, the signal from the operational amplifier 10 is used as a reference signal for voltage comparison, and voltage comparison is performed with the input video signal from the video amplifier circuit 2, and when 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, Figure 3a
When an abnormal signal F such as a dropout is mixed into the reproduced video signal as shown in FIG. According to this hold voltage A', the reference voltage for voltage comparison also becomes B', so
The output signal of the first voltage comparison circuit 4 lacks one or more synchronization signals as shown in FIG. 3b, and has a serious drawback as a synchronization separation circuit. 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. The data information signal level is reached, and therefore the hold voltage of the second sample and hold circuit 9 is as shown by 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, changes as shown in E' in FIG. During this period, no signal is output from the second voltage comparator circuit 13, and the data information signal separation function is completely lost. SUMMARY OF THE INVENTION It is an object of the present invention to provide a video signal processing device for sync 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 following explanation will be given based on FIG. 4, but blocks having the same functions as those of the conventional example are given the same numbers and the explanation will be omitted.

Recording media playback devices such as video disc players are usually equipped with dropout detection means for checking dropouts in the playback video signal in order to compensate for dropouts in the playback video signal. A dropout detection signal is input to an 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 dropout detection signal, the output signal is turned off, and when there is no dropout detection signal, the output signal is turned off, and when there is no dropout detection signal, the output signal is turned on. 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. With 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 dropout, the input to the first gate circuit 3 is quickly cut off by the switch 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 5 almost coincides with the leading edge of the synchronization signal of the video signal, as shown in A in FIG. 2a. can be done. Therefore, from the first voltage comparator circuit 4, a synchronized and separated output signal without any dropouts as shown in FIG. can get. Therefore, the output signal waveform of the monomulti circuit 7 becomes as shown in FIG. Therefore, in this case, the hold voltage of the second sample and hold circuit 9 does not become an abnormal voltage as shown in C' in FIG. 3d, but almost matches the pedestal voltage in the reproduced video signal as shown in C in FIG. 2a. do. As a result, the second voltage comparator circuit 13 for data information signal separation
The reference voltage of is exactly the same as when 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. 5 shows another embodiment of the present invention, and as is clear from the comparison with the embodiment of FIG.
2 are combined into one switch circuit 30, and 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 signal processing devices such as video disks and VTRs, dropout detection means can be used to compensate for dropouts in video signals or audio signals, etc. , generally has a dropout detection means, so it is advantageous in terms of cost to use the same detection means, and it is quite possible to use the same 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 video signal for a video signal containing an abnormal signal. Waveform diagram showing the operating state of the conventional processing device and the device according to the present invention, No. 4
This figure is a block diagram showing one embodiment of the video signal processing device according to the present invention, and FIG. 5 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, 7... Mono multi circuit, 10
...Arithmetic amplification circuit, 20...Dropout detection signal input terminal, 21, 22...Switch circuit.

Claims (1)

[Claims] 1 A first sample-hold means to which a reproduced video signal from a recording medium is supplied, samples and holds the voltage at the leading edge of the synchronization signal of the reproduced video signal, and a first sample-hold means that samples and holds the voltage at the leading edge of the synchronization signal of the reproduced video signal; a first voltage comparison means for setting a reference voltage, comparing the voltage with the reproduced video signal, and generating an output signal at a portion of the synchronization signal where the reproduced video signal is lower than the reference voltage; a first gate that is controlled by an output signal of the voltage comparison means and limits the reproduced video signal to be supplied to the first sample and hold means only during the output signal generation period of the first voltage comparison means; means and
delay means for delaying the output signal of the first voltage comparison means to a pedestal section of the video signal;
a second gate means that is controlled by the output signal of the delay means and limits the reproduced video signal to be supplied to the second sample and hold means only during the output signal generation period of the delay means; 1
and an operational amplification means for producing a reference signal for separating the data information signal in the reproduced video signal using the two sample and hold voltage signals from the second sample and hold means, and a reference signal from the operational amplification means. and second voltage comparison means for separating the data information signal by comparing the voltages of the reproduced video signal, the voltage at the leading edge of the synchronization signal in the reproduced video signal from the recording medium. The dropout detection means operates in response to a dropout detection output signal from the dropout detection means that detects the dropout as a dropout when a signal lower than the dropout is generated, and during the period of the dropout detection output signal, the first and second sample hold means A video signal processing device containing an abnormal signal, comprising means for cutting off the first and second gate means so as not to supply the video signal.