JPS61148978A - Drop out compensating system - Google Patents

Abstract

PURPOSE:To compensate the drop out of a composite video signal by devising a signal selecting mean which selects plural drop out compensating signals outputted from a drop out compensating signal generating mean and one of plural signals. CONSTITUTION:If a drop out occurs and if it is in the reproducing cycle of a luminance signal, a timing generating circuit 35 outputs a control signal SB which makes the movable stylus 325 of a switch 32 connect with a stationary terminal 323. In such a way the delayed output from a 1H-delay circuit 39 is supplied to a reproducing-signal processing circuit 42, and the drop out of the luminance signal is compensated by the 1H-delayed output. Likewise, if a drop out occurs in a color difference signal, the delayed output from a 1H- delay circuit 40 is supplied to the circuit 42, and the drop out of the color difference signal is compensated by the 2H-delayed output. Also if a drop out occurs in the control signal, the circuit 35 outputs a control signal SC which, differing from the signal SB, makes an other substitute signal generating circuit 41, and in such a way, the drop out of the control signal is compensated by an all '1' digital data.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention is applicable to, for example, a video tape recorder (hereinafter referred to as a VTR).
The present invention relates to a dropout compensation device in a video signal reproducing device such as a video signal reproducing device.

[Technical background of the invention]

Conventionally, a VTR is equipped with a drop-act compensation device for compensating for a dropout (hereinafter referred to as dropout) of a reproduced signal.

This dropout compensation device utilizes the correlation of video signals to replace a missing portion (hereinafter referred to as a dropout portion) of a video signal with an approximate signal.

FIG. 3 is a circuit diagram showing a conventional dropout compensation device for a video signal reproducing device such as a VTR. A signal picked up by a pickup element such as a rotary head 12 from a recording medium such as a magnetic tape 11 is amplified by a preamplifier 13. The FM luminance signal (FM-modulated luminance signal) included in this amplified output is filtered by a band-pass filter (
BPF) 14 and then demodulated by an FM demodulation circuit 16. Further, the amplified output of the preamplifier 13 is level detected by a level detection circuit 16. Switching signal forming circuit 1
7 determines that a dropout has occurred when the level detection output is below a predetermined level, and outputs a switching signal indicating the drop-act period. When the switch 18 receives a switching signal indicating a dropout period, the IH
The output of the delay circuit 19 is selected, and when this switching signal is not obtained, the demodulated output of the FM demodulation circuit 15 is selected. As a result, the dropout portion of the demodulated output is replaced by the demodulated output from IH (one horizontal scanning period) before, and the demodulated output is supplied to the combining circuit 20. Then, in this synthesis circuit 20, it is synthesized with the color signal provided from the color signal processing circuit 21. Therefore, the composite circuit 20 outputs a composite video signal (composite signal such as a luminance signal, a color signal, a synchronization signal, etc.) whose dropout has been compensated for.

Figure 3 shows an example in which dropout compensation for color signals is not performed. Dropout compensation for color signals can be achieved by inverting the subcarrier phase for each IH, for example, by inverting the subcarrier phase every 1 to 7. Constructed by adding an inverting circuit.

[Problems with background technology]

Incidentally, in recent years, in order to obtain high-quality images, a band compression technique called the MUCH system has been developed in which various signals combined into a composite video signal are band-compressed and transmitted in analog form. In this NUMB method, color difference signals are transmitted in Isf@order. Also, a control signal (digital data) for controlling decoding operations for band compression, etc. is transmitted. Therefore, when compensating for dropouts in the M081 composite video signal, conventional dropout compensation devices cannot be used.

[Purpose of the invention]

This invention was made to deal with the above situation, and M
It is an object of the present invention to provide a dropout compensation device capable of compensating for dropouts of a composite video signal in which luminance signals, line sequential signals, and control signals for controlling these signals are composited in time series, such as the U8E system. purpose.

[Summary of the invention]

The present invention provides a means for determining which signal is currently being reproduced among a plurality of 48 signals inserted in chronological order into a composite video signal, a means for detecting a dropout in the playback output of the composite video signal, and Providing means for generating a dropout compensation signal for each of the plurality of signals,
The reproduction output of the composite video signal and the plurality of dropout compensation signals are selectively output according to the discrimination output of the discrimination means and the detection output of the dropout detection means.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention. In the following description, the case where the present invention is applied to compensation for dropout of a composite video signal of the MUSE system will be described as a representative example.

The composite video signal of the MU8E system is shown in FIG.

Further, in FIG. 1, the same parts as in FIG. 3 are given the same reference numerals.

In FIG. 1, MUa output from the preamplifier 13
The reproduced output of the g-scheme composite video signal is input to the FM demodulation circuit 3. In the composite video signal 4A of the MUSj13 system, each of the signals composited in time series is FM modulated, and these signals are demodulated by the FM demodulation circuit 3.

The output of the FM demodulation circuit 36 is connected to the fixed terminal 3 of the switch 32.
2 and the vertical synchronizing signal separation circuit 33
, these separation circuits, which will be applied to the horizontal synchronization signal separation circuit 34? 3 and 34 are a vertical synchronization signal (vD) and a horizontal synchronization signal (H
D) is separated and applied to the timing generation circuit 35. The horizontal synchronizing signal (HD) is further given to the PLL circuit 36,
The PLL circuit 36 generates a clock pulse (CP) synchronized with the horizontal synchronization signal (HD). This clock pulse (cp) is also manually input to the timing generation circuit 35.

The timing generation circuit 35 receives these three signals (VD),
Which signal is currently being reproduced among the luminance signal, color difference signal (line sequential signal), and control signal that are combined into a composite video signal using (HD), (CP)'i-, in other words, the above three signals It is determined which signal is currently being output from the FM sub-circuit 31.

Furthermore, the amplified output of the preamplifier 13 is transmitted to a level detection circuit 37.
The level is detected by the switching signal generating circuit 3, and the detected output is
8 will be man-powered. When the level of the level detection output is not at a predetermined level, the switching signal generating circuit 38 determines that dropout has occurred, and outputs a switching signal (8*) tl- indicating the period. This switching signal (SA) is input to the timing generation circuit 35.

The timing generation circuit 35 determines whether or not there is a dropout based on the switching signal (SA) K, and if there is a dropout, the movable contact piece 325 of the switch 32 is disconnected according to the determination output of the type of signal currently being reproduced. Outputs a control signal (8B) for switching.

The switch 32 selectively selects the demodulated output of the FM demodulation circuit 31, the delayed output of the IH delay circuits 39 and 40, and the output of the replacement signal generation circuit 4 according to the control signal (8B)K. In addition to the fixed terminal 322 to which the demodulated output of the circuit 31 is applied, there is also a fixed terminal -f- to which the outputs of the lH slow grinding circuits 39, 40 and the replacement signal generation circuit 41 are applied, respectively.
The 01H4 delay circuit 39 having 323, 324, and 321 delays the selected output 11H of the switch 32, and its delayed output is used for dropout compensation of the luminance IS. The IH delay circuit 40 further delays the delayed output of the IH delay circuit 39 by IH, and the delayed output is used for dropout compensation of the color difference signal. These IH delay circuits 3
9.40 is composed of an analog delay circuit using, for example, a CCD (charge-coupled device). In addition to this, for example, it may be configured with a digital delay circuit that is a combination of an analog/digital converter, a digital/analog converter, and a memory.

The output of the replacement signal generator circuit 41 is used as digital data for dropout compensation of the control signal that is combined into the composite video signal. Since this dropout of the control signal cannot be compensated for by signals from one horizontal set line, such as a luminance signal or a color difference signal, such a replacement signal generation circuit 41 is provided, and the content of the replacement signal is For example, is considered to be all digital data. As a result, the reproduced signal processing circuit 42, which will be described later, can determine that a number of numbers are missing when there is digital data of all 1s. In this way, even if complete compensation of the control signal is not performed, in the case of the MUSE method, the same control signal is sent three times, so
Compared to the case where no dropout compensation is performed at all, other accurate control signals can be used to the extent that erroneous portions can be detected reliably, and proper control is possible.

Assuming that no dropout has occurred, the timing generation circuit 32 outputs the control III signal (8a)t- which is connected to the fixed terminal 322 of the switch 32 and the movable contact piece 325f. Thereby, the demodulated output of the FMJ modulation circuit 3 is given to the reproduced signal processing circuit 42 and subjected to predetermined signal processing. On the other hand, if a dropout occurs and this is the regeneration period of the luminance signal, the timing generation circuit 35 causes the switch 32 to
A control signal (SB) for connecting the movable contact piece 325 to the fixed terminal 323 is output. From this K, the delayed output of the IH delay circuit 39 is given to the reproduced signal processing (b) path 42, and the dropout of luminance Δ3 is compensated for by the IH delayed output. Similarly, if there is a color difference signal busy dropout,
The delayed output of the IH delay circuit 40 is applied to the reproduced signal processing circuit 42 (the movable piece 325 of the switch 32 is connected to the fixed terminal 3).
24), the color difference signal dropout is 2H
Compensated with delayed output. Furthermore, if there is a dropout in the control signal, the timing generation circuit 35 outputs the control signal (
In addition to SB), a control signal (Sa)' is output to turn on the replacement signal generation circuit 4. Thereby, dropout of the control signal is compensated for by the all-1 digital data.

As detailed above, this embodiment determines the type of signal currently being played, and selects between the playback output and the dropout compensation output prepared for each type of signal according to this discrimination output and dropout detection. I made a selection based on
It is possible to compensate for dropouts in composite video signals of systems such as the MULE system.

In addition, since the dropout of the color difference signal is compensated for by the 2H delay output, there is no possibility that two types of color difference signals will be mixed, unlike when compensation is performed by the IH delay output. The invention is not limited to the previous embodiments.

For example, in a MULE system composite video signal, the horizontal synchronization signal (HD) is also the lfM 7I# signal.

Therefore, compensation for the dropout of the horizontal synchronization signal (HD) may also be performed by using a 2H delayed output.In addition, in the M08g method, the polarity of the frame pulse is inverted every horizontal eclipse period. Therefore, in order to compensate for the second horizontal 71: eclipse period, the inverted signal for the first horizontal scanning period may be used.

As with the control signal, frame pulse compensation may be performed by using the output of a replacement signal generation circuit provided separately, instead of using the reproduced output. Similarly, in order to improve the waveform, dropout compensation for the 1-horizontal open period signal is provided with a separate dedicated replacement signal generation circuit, without using the reproduced output, and even if the output of this circuit is used. In addition, in the above explanation, the case where the signal after PM demodulation is delayed and the dropout compensation signal t-4 is generated is explained, but F
The signal before M demodulation may be delayed. Tsumafi
, dropout compensation may be performed before FM demodulation. In this case, a glass delay line, for example, can be used as the delay means.

Furthermore, by providing a flywheel effect to the PLL circuit 36 and timing generation circuit 35, normal timing can be obtained even if the vertical synchronization signal (VD) or horizontal synchronization signal (HD) is lost due to dropout. can.

Furthermore, the 2H delay output may be obtained from the 2H delay circuit instead of from the series connection of the two LH delay circuits 39 and 40.

In addition, the pupil of the lH delay circuit 39 and 40 may not cover the entire horizontal set meal period, but may cover only the necessary time width. It may be possible to use a signal between the two.

The present invention is also applicable to dropout compensation devices for video signal reproducing devices other than VTRs, such as video disc players.

〔Effect of the invention〕

According to the present invention, as in the MUaB system, a luminance signal, a line sequential signal, a system for controlling these signals/signals, a 4M signal, or a dropout compensation for a composite video signal that is composited in time series. It is possible to provide a dropout compensator that allows this.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, and FIG.
The figure shows a composite video signal of the MUSFJ system, and FIG. 3 is a circuit diagram showing a conventional dropout compensation device. 11...Magnetic tape, 12...7 degrees to rotation, 13.
...Preamplifier, 31...FM demodulation circuit, 32...
Suiso 1ch, 33... Vertical synchronization signal separation circuit, 34...
...Horizontal synchronization signal separation circuit 1.75...Timing generation circuit, 36...PLL circuit, 37...Level detection circuit, 38...Switching signal generation circuit, 39.40...
lH delay circuit, 4... Replacement signal generation circuit, 42...
・Reproduction signal processing circuit O Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 ゛

Claims (1)

[Scope of Claims] An image that reproduces a composite video signal from a recording medium on which a composite video signal in which a luminance signal, a line sequential signal, and a control signal of these luminance signals and line sequential signals are composited in time series is recorded. In the signal reproducing device, a reproducing means for reproducing the composite video signal from the recording medium, and a signal discriminating means for determining whether the signal currently being reproduced by the reproducing means is one of the luminance signal, line sequential signal, or control signal. and dropout detection means for detecting drop-up out of the reproduced output of the reproduction means, and dropout compensation signal generation means for generating dropout compensation signals for each of the luminance signal, line sequential signal, and control signal. , a plurality of signals including a reproduction output of the reproduction means and a plurality of dropout compensation signals output from the dropout compensation signal generation means according to the discrimination output of the signal discrimination means and the detection output of the dropout detection means. A dropout compensation device comprising signal selection means for selecting one of the signals.