JPS6239997A - video signal reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for reproducing a video signal including a luminance signal and a chroma signal from a recording medium.

[Conventional technology]

In this specification, a video tape recorder of a type in which a luminance signal is FM-modulated, a chroma signal is frequency-converted to its lower frequency range, and frequency multiplexed recording is performed will be described below as an example.

FIG. 5 is a diagram showing a schematic configuration example of a playback system in a conventional video tape recorder, in which 21 is a delay line for one horizontal scanning period, 22 is a dropout detection circuit, and 2
3 is a switch circuit.

The video signal reproduced by the reproduction head 20 is supplied to a bypass filter (HPF) 25 and a low-pass filter (LPF) 26 via a reproduction amplifier 24. The HPF 25 separates the FM modulated luminance signal. When this dropout of the FM modulated luminance signal is detected by the detection circuit 22, the 1 horizontal scanning period delay line (1'HDL)
21 and is supplied to the FM demodulation circuit 27 to obtain a demodulated luminance signal with dropout compensation.

On the other hand, the LPF 26 separates the low-frequency converted chroma signal, which is returned to the original band by the frequency conversion circuit 28, and then the chroma signal is restored via the color killer circuit 29. This color killer circuit 29 operates according to the reproduced color burst signal level and the dropout detection circuit 22.

The demodulated luminance signal and the restored chroma signal described above are mixed in a mixer 60 to obtain an output video signal.

In the device configured as described in -1-, the conventional dropout compensation is such that when the dropout detection circuit 22 detects a dropout in the reproduced FM modulated luminance signal,
The dropout portion is supplemented with only the luminance signal from one horizontal scanning period (hereinafter referred to as 1H) before by using the 1HDL 21 and the switch 23.

[Problem that the invention seeks to solve]

In the video signal playback device using the conventional dropout compensation method as described above, when the dropout is compensated, the compensation part does not have any color on the playback screen, and when viewed as a whole image, it is extremely unnatural. .

This invention was made to solve the conventional problem of unnatural reproduced images, and aims to provide a video signal reproducing device that can obtain good reproduced images even when dropouts occur. aimed to.

[Failure to solve the problem]

The video signal reproducing apparatus according to the invention comprises: means for detecting dropout of the reproduced signal; a delay circuit for delaying the reproduced chroma signal by one horizontal scanning period; means for shifting the phase of the output signal of the delay circuit; and means for replacing the reproduced chroma signal with the output signal of the shifting means in accordance with the output of the detecting means.

[For production]

In this invention, it is possible to use the vertical correlation of the screen to replace a portion where a dropout has occurred in the recorded playback video signal with an effective ROMA signal, and to Since color loss can be prevented, good reproduced images can now be obtained.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a magnetic head, 2 is a reproduction amplifier, 6 is a circuit for demodulating the FM modulated luminance signal, 4, 7-digit 1HDL, and 5.9 are A switch circuit, 6 a circuit for converting the frequency of a chroma signal, 8 an inverting amplifier, 10 a dropout detection circuit, and 11 a mixer.

In the device configured as described above, the reproduced output of the magnetic head 1 is amplified by the amplifier 2, and the FM modulated luminance signal separated by the HPF is sent to the FM demodulation circuit 6 as a low frequency converted chroma signal separated by the LPF. is supplied to frequency conversion circuit B. In addition, the output of amplifier 2 is output by dropout detection circuit 10.
are supplied respectively.

The output signal of the demodulation circuit B is input to one side of the switch circuit 5, and the output signal of the switch circuit 5 is input to the mixer 11 and the IH
Supplied to DL4. In addition, the output of 1HDL4 is used as the other manual power of the switch circuit 5, and when a dropout occurs, the switch circuit 5 is switched by the dropout switching pulse output of the dropout detection circuit 10.
The output signal of IHDL 4 is output as the output of switch circuit 5, and is supplied to mixer 11 and IHDL4.

On the other hand, the output signal of the frequency conversion circuit B is input to one side of the switch circuit 9, and the output signal of the switch circuit 9 is supplied to the mixer 11 and 1 HD L 71c. Also, I
The output of the HDL 7 passes through an inverting amplifier 8 and becomes the other input of the switch circuit 9.

Generally, in a video signal, the frequency components of a luminance signal and a chroma signal are interpolated with each other. That is, it is an odd multiple of the color subcarrier +flu (fH is the horizontal scanning frequency) of the chroma signal, and therefore the phase of the 1H delayed chroma signal and the undelayed chroma signal are reversed. The chroma signal output from the inverting amplifier 8 and the chroma signal output from the frequency conversion circuit 6 match in phase.

When a dropout occurs, the switch circuit 9 is switched by the dropout switching pulse output of the dropout detection circuit 10, and I is output as the output of the switch circuit 9.
The output signal of HDL 7 is output and supplied to mixer 11 and IHDL 7. The outputs of the switch circuits 5 and 9 are mixed in a mixer 11 to obtain an output video signal.

It goes without saying that the two IHDLs 4 and 7 may be of a J:1 type as long as a delay of 1H is possible.

FIG. 2d shows another embodiment of the invention, in which similar components to those in FIG. 1 have been given the same reference numerals.

In this example, after performing dropout compensation, FM demodulation of luminance signal and frequency conversion of chroma signal are performed to restore each of the luminance signal and chroma signal.

Reference numeral 18 denotes a phase shift circuit which compensates for a phase shift caused by delaying the low frequency converted chroma signal by 1H. That is, in a video tape recorder that employs the well-known PI method, the phase of the low frequency conversion chroma signal is inverted every 1H, so the phase shift circuit 181iJ:180
In a video tape recorder that is configured to perform a phase shift (phase inversion) of 100° and employs the well-known PS system, the d1 low frequency conversion chroma signal has a 90° phase shift every 1H. The phase shift circuit is configured to perform a phase shift of 190°.

In addition, it is also possible to perform dropout compensation for the luminance signal before FM demodulation and for the chroma signal after frequency conversion, or to perform dropout compensation for the luminance signal after FM demodulation and for the chroma signal before frequency conversion. Of course it is.

〔Effect of the invention〕

As explained above, the present invention has the advantage that it is possible to obtain a video signal reproducing apparatus that can provide an extremely good reproduced screen even when dropout occurs in the reproduced signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a video signal reproducing device showing one embodiment of the invention, FIG. 2 is a block diagram of a video signal reproducing device showing another embodiment of the invention, and FIG. 6 is a conventional video signal reproducing device. It is a figure showing an example of a device. In the figure, 1 is a magnetic head, 2 is an amplifier, 3 is a dFM demodulation circuit, 4 and 7 are delay circuits, 5 and 9 are switch circuits, and 6
8 is an inverting amplifier, 10 is a dropout detection circuit, an 11-digit mixer, and 18 is a phase shift circuit.

Claims (1)

[Claims] In a video signal reproducing apparatus for reproducing a video signal including a luminance signal and a chroma signal from a recording medium, the apparatus includes a means for detecting a dropout of the reproduced signal, and a means for detecting a dropout of the reproduced chroma signal.
A delay circuit that delays a horizontal scanning period, a means for shifting the phase of an output signal of the delay circuit, and a means for replacing the reproduced chroma signal with the output signal of the shifting means in accordance with the output of the detecting means. A video signal reproducing device characterized by: