JPH0317435B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention relates to a so-called video signal reproducing device such as a video disc player or a video tape recorder, and particularly relates to a video signal, an audio signal, etc. contained in a reproduced video signal. The present invention relates to an improvement of a dropout correction circuit for correcting dropout.

<Prior art> Video signal reproducing devices applied to video disc players, video tape recorders, etc.
There is one shown in the figure. In this video signal reproducing device, a recorded signal reproduced from a recording medium such as a video disk is converted into a reproduced video signal by an FM demodulator 2.
Demodulates FM. In this case, the recorded signal reproduced from the recording medium is a so-called double FM modulation signal in which an audio signal is superimposed on a video FM signal, so the FM demodulator 2
The reproduced video signal demodulated in is a video signal (composite video signal) superimposed using the audio FM signal as a carrier. and,
The reproduced video signal output from the FM demodulator 2 is passed through a low-pass filter 4 to remove noise contained in the reproduced video signal. The reproduced video signal from which noise has been removed passes through the next-stage de-emphasis circuit 6, passes through the audio FM carrier cut filter circuit 28, and a video signal is extracted, and the extracted video signal is sent to the switching circuit 14 of the dropout correction circuit 10'. At the same time as being input, a part of the reproduced video signal is also input to the audio FM demodulator 8 and demodulated into an audio signal. The video signal input to the switching circuit 14 is transmitted through a glass delay line or CCD (Charge-
The signal is input to a luminance/color signal separation circuit 22 which includes a delay circuit 12 having a delay element such as a coupled device, an adder 24, and a subtracter 26. The video signal is separated into a brightness signal and a color signal by this brightness/color signal separation circuit 22, and the brightness signal is sent to the next stage brightness signal processing circuit 30, and the color signal is sent to the color signal processing circuit 32. .

On the other hand, when a dropout occurs in a part of the video signal output from the FM demodulator 2 due to a defect in the recording medium or a malfunction on the recording or playback side, the dropout is detected by the dropout detection circuit 20. A dropout detection pulse is output from the circuit. This dropout detection pulse is input to the switching circuit 14 and the audio correction circuit 34, respectively. The switching circuit 14 switches the connection in response to the dropout detection pulse, and returns the video signal delayed by one horizontal scanning period in the delay circuit 12 to the delay circuit 12 again, thereby converting the video signal in which the dropout has occurred into the returned video. Correct the dropout by replacing the signal. At the same time, the dropout detection pulse output from the dropout detection circuit 20 is transmitted to the audio correction circuit 34.
This also allows the audio correction circuit 34 to mute the audio signal, perform sample hold, reduce the amount of companding for noise reduction, or combine the switch circuit and delay circuit. The dropout that occurs in the audio signal is corrected by replacing the dropout portion with the video signal immediately before the dropout occurs (for example, see Japanese Patent Application Laid-Open No. 143310/1983).

In this way, conventional video signal playback devices
In either case, dropout correction is performed individually in separate circuits for the video and audio signals, so separate delay circuits, etc. are required for each system, resulting in a large number of circuit components. There is a drawback.

<Object of the Invention> The present invention has been made in view of the above-mentioned problems, and the present invention has been made in view of the above-mentioned problems. In addition, the output of the delay circuit is used to simultaneously compensate for the dropouts of the video signal and the audio signal. The purpose is to reduce the number of circuit components such as delay circuits.

<Structure of the Invention> In order to achieve the above-mentioned object, the present invention is characterized in that an audio signal is superimposed on a video FM signal and stored in a double FM modulated state on a recording medium such as a video disk or a video tape. A video signal reproducing device for reproducing a recorded signal, comprising: an FM demodulator 2 for FM demodulating the recorded signal reproduced from the recording medium as a reproduced video signal (a signal obtained by superimposing a video signal and an FM audio signal);
It has a brightness/color separation circuit 22 that performs brightness/color separation of the reproduced video signal output from the FM demodulator 2, and an audio FM demodulator 8 that extracts only the FM audio signal from the reproduced video signal and demodulates it. The luminance/color separation circuit 22 includes a delay circuit 12 that delays the reproduced video signal by one horizontal scanning period (1H), an adder 24 and a subtracter 26 that add and subtract the outputs before and after passing through the delay circuit 12. On the other hand, a dropout detection circuit 20 detects a dropout of the reproduced video signal output from the FM demodulator 2 and outputs a dropout detection pulse.
and between the FM demodulator 2 and the delay circuit 12,
A first switching circuit 14 is provided that switches the output of the FM demodulator 2 to the output of the delay circuit 12 in response to the dropout detection pulse, and a first switching circuit 14 is provided between the FM demodulator 2 and the audio FM demodulator 8. , a second switching circuit 18 is provided for switching the output of the FM demodulator 2 to the output of the delay circuit 12 in response to the dropout detection pulse.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 is a circuit diagram of a video signal reproducing apparatus according to the present invention, and parts corresponding to those of the conventional example shown in FIG. 2 described above are given the same reference numerals. In FIG. 1, reference numeral 1 denotes a video signal reproducing device, 2 an FM demodulator that performs FM demodulation of a recorded signal reproduced from a recording medium as a reproduced video signal, and 4 an FM demodulator included in the reproduced video signal demodulated by the FM demodulator. 6 is a de-emphasis circuit, and 8 is an audio FM demodulator that demodulates the audio signal from the reproduced video signal. In the first part
A bandpass filter (not shown) for extracting the FM audio signal is provided, so that only the FM audio signal is extracted from the reproduced video signal and then demodulated into an audio signal.
10 is a dropout correction circuit. This dropout correction circuit 10 converts the reproduced video signal into 1
A delay circuit 12 that delays by the horizontal scanning period, a movable contact 14a connected to the input side of this delay circuit 12, a de-emphasis circuit 6, and both individual contacts 14b, 14 connected to each output side of the delay circuit 12, respectively.
a first switching circuit 14 comprising a first switching circuit 14, an amplifier 16 that amplifies the output signal of the delay circuit 12, a movable contact 18a connected to the input side of the audio FM demodulator 8, a low-pass filter 4, and a movable contact 18a connected to the output side of the amplifier 16, respectively. It is comprised of a second switching circuit 18 having two connected individual contacts 18b and 18c, and a dropout detection circuit 20 that detects a dropout of the reproduced video signal output from the FM demodulator 2 and outputs a dropout detection pulse. Reference numeral 22 denotes a luminance and chrominance signal separation circuit that separates the reproduced video signal into luminance and chrominance signals, and this circuit includes the delay circuit 12, an adder 24, and a subtracter 26. 28 is a filter circuit for removing the audio FM signal included in the luminance signal output from the adder 24 constituting the luminance/color separation circuit 22; 30 is a luminance signal processing circuit; and 32 is a chrominance signal processing circuit.

In the video signal reproducing apparatus 1 having such a configuration, in a normal reproduction state in which dropout correction is not necessary, the first and second switching circuits 14 and 18 are switched to the first switching circuit.
In the connection state shown in the figure. Therefore, first, a recorded signal reproduced from a recording medium such as a video disk is converted into a reproduced video signal (video signal) by the FM demodulator 2.
The FM signal is demodulated into a superimposed signal with the FM audio signal. The demodulated playback video signal is filtered by a low-pass filter 4 to remove noise contained in the playback video signal. Then, the reproduced video signal from which noise has been removed is sent to the luminance and color signal separation circuit 22 via the next-stage de-emphasis circuit 6, one fixed contact 14b of the first switching circuit 14, and the movable contact 14a.
At the same time, part of the reproduced video signal is also input to the audio FM demodulator 8 via the low-pass filter 4, one fixed contact 18b of the second switching circuit 18, and the movable contact 18a. The audio FM demodulator 8 extracts only the FM audio signal from the reproduced video signal using a bandpass filter for extracting the FM audio signal, and then demodulates it into an audio signal. The reproduced video signal input to the luminance and color signal separation circuit 22 is as follows:
The signal is input to the adder 24 and the subtracter 26 either directly or after being delayed by one horizontal scanning period in the delay circuit 12 . As a result, the reproduced video signal is separated into a luminance signal and a chrominance signal on which the audio FM signal is superimposed. The luminance signal separated by the adder 24 is sent to the next-stage luminance signal processing circuit 30 after the audio FM signal contained in the luminance signal is removed by a filter circuit 28 at the next stage. Further, the color signal separated by the subtracter 26 is sent to the color signal processing circuit 32, and the audio FM included in the color signal is filtered by a bandpass filter for passing the color signal provided in the color signal processing circuit 32. The signal is removed. Therefore, in the end, a luminance signal and a color signal that do not include the audio FM signal are obtained.

On the other hand, dropouts may occur in a portion of the playback video signal (a signal in which a video signal and an FM audio signal are superimposed) output from the FM demodulator 2 due to a defect in the recording medium or a malfunction on the recording or playback side. When a dropout occurs, a dropout is detected by the dropout detection circuit 20, and a dropout detection pulse is output from the dropout detection circuit 20. This dropout detection pulse is input to first and second switching circuits 14 and 18, respectively. First and second switching circuits 14,1
8 switches the connection in response to the dropout detection pulse, so that the movable contact 14a of the first switching circuit 14 is connected to the other fixed contact 14c, and the second switching circuit 18
The movable contacts 18a are respectively connected to the other fixed contacts 18c. As a result, the delay circuit 12
The reproduced video signal delayed by the horizontal scanning period is the first
The signal is fed back from the other fixed contact 14c of the switching circuit 14 to the delay circuit 12 via the movable contact 14a. Therefore, the reproduced video signal in which dropout has occurred is replaced by the fed-back reproduced video signal, and the replaced reproduced video signal is separated into a luminance signal and a chrominance signal, which are separated by the luminance and chrominance signal separation circuit 22. The output luminance signal and color signal have dropout corrected. Further, the reproduced video signal delayed by one horizontal scanning period in the delay circuit 12 is amplified in the amplifier 16 and then transferred to the second switching circuit 1.
The signal is also input to the audio FM demodulator 8 via the other fixed contact 18c and movable contact 18a. Therefore, the reproduced video signal (signal in which the video signal and FM audio signal are superimposed) in which dropout has occurred is delayed by one horizontal scanning period (1H) before being fed back to the audio FM demodulator 8. (This signal is also a signal in which a video signal and an FM audio signal are superimposed). In other words, just before the dropout occurred (1H before)
playback video signal. Since the reproduced video signal replaced in this way is applied to the audio FM demodulator 8, the audio FM demodulator 8 extracts only the FM audio signal from the replaced reproduced video signal using its internal bandpass filter, and then outputs the audio signal. demodulates to .

Here, the no-signal part where the dropout occurred is
Audio as is without replacing the signal from 1H before.
If the signal is demodulated by the FM demodulator 8, it becomes noise, but if it is replaced with the reproduced video signal 1H earlier, noise can be avoided. Also,
Audio signals around 1H have little correlation with each other compared to video signals, but for a short period of 1H, even if a signal with little correlation is replaced with a signal from 1H before, the reproduced audio signal can be changed. This can prevent listening difficulties to some extent. Therefore, dropout of the audio signal is also corrected at the same time.

<Effects of the Invention> According to the present invention, a delay circuit provided in a luminance/color separation circuit that performs luminance/color separation on a reproduced video signal before separating it into a video signal and an audio signal and demodulating it is used for dropout compensation. Moreover, by supplying the output of the delay circuit to the first and second switching circuits, respectively, the dropout of the video signal and the audio signal can be compensated for at the same time. For this reason, conventionally,
This provides excellent effects such as being able to reduce the number of circuit components such as delay circuits that are provided separately to compensate for dropouts in the video signal and audio signal.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows a conventional example. Both FIG. 1 and FIG. 2 are circuit diagrams of a video signal reproducing apparatus. DESCRIPTION OF SYMBOLS 1... Video signal reproducing device, 2... FM demodulator, 8... Audio FM demodulator, 10... Dropout correction circuit, 28... Filter circuit.

Claims (1)

[Claims] 1. An audio signal is superimposed on a video FM signal on a recording medium such as a video disk or video tape, and
A video signal reproducing device that reproduces a recorded signal stored in an FM modulated state, the recorded signal reproduced from the recording medium as a reproduced video signal (a signal in which a video signal and an FM audio signal are superimposed). FM demodulator 2 that demodulates FM and this
It has a brightness/color separation circuit 22 that performs brightness/color separation of the reproduced video signal output from the FM demodulator 2, and an audio FM demodulator 8 that extracts only the FM audio signal from the reproduced video signal and demodulates it. The luminance/color separation circuit 22 includes a delay circuit 12 that delays the reproduced video signal by one horizontal scanning period (1H), an adder 24 and a subtracter 26 that add and subtract the outputs before and after passing through the delay circuit 12. On the other hand, a dropout detection circuit 20 detects a dropout of the reproduced video signal output from the FM demodulator 2 and outputs a dropout detection pulse.
and between the FM demodulator 2 and the delay circuit 12,
A first switching circuit 14 is provided that switches the output of the FM demodulator 2 to the output of the delay circuit 12 in response to the dropout detection pulse, and a first switching circuit 14 is provided between the FM demodulator 2 and the audio FM demodulator 8. . A video signal reproducing apparatus comprising a second switching circuit 18 for switching the output of the FM demodulator 2 to the output of the delay circuit 12 in response to the dropout detection pulse.