JPS6144300Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for compensating dropout of a playback signal in a video playback device or the like, and for example, to a dropout compensation circuit for compensating an audio signal.

2. Description of the Related Art A so-called video disk reproducing device is being developed, in which a rotating recording medium (video disk) on which video and audio signals are recorded is mounted and the recorded signals are reproduced. In such a video disc playback device, a video disc is placed on a turntable, and playback is performed in such a way that a pickup traces the recorded lines of the disc.
There is a risk that the pick-up signal may be missing due to scratches, dirt, etc. on the disk. The present invention was developed in order to cope with the above-mentioned circumstances, and aims to provide a dropout compensation circuit that can compensate for the dropout period and reduce abnormal noise when a dropout occurs in an audio signal, etc. .

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. First, it is assumed that the audio signal compensated by the dropout compensation circuit of the present invention is recorded on a disk as, for example, a stereo signal FM-modulated with two subcarriers. A television signal containing such a stereo signal is picked up by a pickup means of a video disc playback device and applied to an input terminal 11 shown in FIG. This input terminal 11 is connected to a frequency separation circuit 12. The video signal output terminal of this frequency separation circuit 12 is connected to the video signal detector 13.
The audio signal output terminal is connected to first and second audio carrier separation circuits 14 and 15.
Output terminals of the separation circuits 14 and 15 are connected to first and second FM demodulators 16 and 17, respectively, and output terminals of the FM demodulators 16 and 17 are connected to first and second de-emphasis circuits 18 and 19, respectively. connected to.

The output terminal of the first de-emphasis circuit 18 is connected to a first inverter circuit 20 and also to a first synthesis circuit 26 . Further, the output terminal of the second de-emphasis circuit 19 is connected to a second inverter circuit 21 and also to a second synthesis circuit 27 .

The output terminals of the first and second inverter circuits 20 and 21 are connected to the first and second switch circuits 2, respectively.
Connected to 2 and 23. The output terminal of the first switch circuit 22 is connected to the second synthesis circuit 2.
7 and also the second switch circuit 23
The output terminal of is connected to the first synthesis circuit 26. The first and second combining circuits 2
Output terminals 28 and 29 of 6 and 27 are respectively led out as stereo audio signal output terminals. and,
A control signal output terminal of a dropout detection circuit 24 is connected to the control terminals of the first and second switch circuits 22 and 23.

The dropout compensation circuit of the present invention is constructed as described above. Next, the operation will be explained with reference to FIG. First, it is assumed that an FM modulated signal having a dropout period T as shown in FIG. 2a is introduced to the input terminal 11. In the operation of this signal other than the dropout period T, the frequency separation circuit 12 separates the video signal and the audio signal. Since the audio signal is a stereo signal and is modulated by two subcarriers that are close to each other to the extent that they do not interfere with each other, the first and second audio carrier separation circuits 1
4 and 15, the signal is separated into left and right signals. The outputs of the first and second audio carrier separation circuits 14 and 15 are transmitted to first and second FM demodulators 16 and 17, respectively.
added to. The audio signals demodulated by the first and second FM demodulators 16 and 17 are applied to the first and second de-emphasis circuits 18 and 19, respectively, and expanded, and the output of each circuit 18 and 19 is , are derived via the second synthesis circuits 26 and 27.

Next, when the dropout period T begins, a pulse as shown in FIG. The signal waveform shown in Figure 2b is the output after FM detection and demodulation of the signal shown in Figure 2a (with a part of the audio carrier missing) (the audio carrier is unmodulated), and is the output of the de-emphasis circuit. 18, 19. This circuit 1
The signals from 8 and 19 are respectively inverted by inverter circuits 20 and 21 and also applied to combining circuits 26 and 27, as shown in FIG. 2d.

The outputs of the inverter circuits 20, 21 are applied to switch circuits 22, 23 which are gated by a dropout detection circuit 24.

As a result, the first and second combining circuits 26 and 27 synthesize the signals shown in FIG. 2b and d, respectively, so the outputs of each circuit 26 and 27 are shown in FIG. 2e. A signal with almost no noise can be obtained.

In this way, according to the present invention, when a dropout occurs, a signal with an opposite phase to the noise signal obtained from the FM demodulator is created, and both signals are combined and output. It is possible to eliminate abnormal noise when dropping out. In addition,
Although the above embodiment has been described in the case of a stereo signal, the invention is not limited to this, and the present invention can also be applied to a case where a disc or the like on which multi-recording (Japanese and English, etc.) is used is used. Furthermore, the dropout detection method in the dropout detection circuit can be implemented by using a detection circuit or by directly using the signal shown in FIG. 2b.

As described above, the present invention can provide a dropout compensation circuit that can compensate for a dropout period and reduce abnormal noise when a dropout occurs.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the dropout compensation circuit of the present invention, and FIGS.
This is an example of a signal waveform shown to explain the operation of the main part of the circuit shown in the figure. 12... Frequency separation circuit, 13... Video signal detection circuit, 14, 15... First and second audio carrier separation circuits, 16, 17... First and second FM demodulators, 18, 19... ...First and second de-emphasis circuits, 20,21...First and second inverter circuits, 22,23...First and second switch circuits, 24...Dropout detection circuit, 26,2
7...First and second synthesis circuits, 28, 29...Output terminals.

Claims (1)

[Claims for Utility Model Registration] A dropout detection circuit for detecting dropout of an input video signal, a demodulation circuit for demodulating an FM modulated signal included in the input video signal, and an inverter to which the output of the demodulation circuit is supplied. a signal inverting means including a series connection of a circuit and a switch circuit, controlling the switch circuit by a detection output from the dropout detection circuit, and inverting and extracting the output of the demodulation circuit at the time of dropout; A dropout compensation circuit comprising: a synthesis circuit for synthesizing the output and the output of the signal inverting means.