JPS62250789A - Color video signal reproducing device - Google Patents

Abstract

PURPOSE:To compensate a dropout with least deterioration of a picture with a simple circuit constitution by providing a baseband signal dropout copensating means to compensate the dropout of a baseband signal converted from a chroma signal by a converting means. CONSTITUTION:A reproduced brightness signal separted from a reproduced composite video signal by a HPF 4 is supplied to a dropout detecting circuit 16. If the variation of an envelope is detected in the circuit 16, switch change over pulses of a high level are outputted to respective changeover switches 8, 18a and 18b until the variation is nullified to turn the connection of the switches to H-side. Accordingly, the outputs of the switches 8, 18a and 18b come to be respective 1H preceding signals that is delayed for one horizontal scanning period by 1H delay circuits 9, 19a and 19b during the time dropouts are happening. In such a way, a signal including a dropout is interpolated by a 1-H preceding signal, then outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application in Library Business The present invention relates to a color video signal reproducing apparatus for reproducing color video signals from a recording medium.

[Conventional technology]

Conventionally, for example, on the playback side of a VTR, compensation for dropouts that occur during playback of a recording medium has been performed as described below.
This was done only for the recorded luminance signal.

FIG. 2 is a diagram showing a schematic configuration of a reproduction side of a VTR including a luminance signal dropout correction circuit as a conventional example.

In FIG. 2, a magnetic head 1 is connected to a magnetic tape (not shown).
The reproduced composite video signal written by the aelb is supplied to the changeover switch 2. The changeover switch 2 is operated by a head switching pulse generated according to the rotation period of the magnetic heads 1a and 1b, which are rotating heads, to switch between side A and B in the figure.
The reproduction composite video signal reproduced by the magnetic heads 1a and 1bK is switched to the reproduction amplifier 3.
supply to. Note that the control switch 2 is designed to be switched every 1/60 seconds when compatible with NTSC television signals, for example.

The signal amplified by the regenerative amplifier 3 is passed through a bypass filter (HPF) 4 and a low pass filter (LPF) 5.
, is supplied to a well-known frequency control (AFC) circuit 6, and BP
The reproduced luminance signal is separated by F4, and the reproduced chroma signal is separated by LPF5.

After the reproduced luminance signal is demodulated by the FM demodulation circuit 7, it is sent to the l horizontal scanning period (IH) delay circuit 9 and the mixer 10 via the changeover switch 8, which is normally connected to the L side in the figure. is supplied to

10,000, the reproduced chroma signal has been subjected to low frequency conversion, and a well-known frequency conversion circuit 11 and a bandpass filter (
BPF) 12 restores the original chroma signal form, that is, a signal modulated by subcarrier fsc (3.58 MHz), and then supplies it to the mixer 10. The AFC circuit 6, the phase control (APC) circuit 13, and the side frequency conversion circuit 14 are well-known circuits, and the frequency conversion circuit 1
1 to generate a time-base corrected signal that is used when performing the well-known frequency conversion.

The luminance signal and chroma signal processed as described above and supplied to the mixer 10 are added in the mixer 10 and output as a reproduced composite video signal.

Here, the operation when dropout occurs will be explained.

In FIG. 2, when a dropout occurs during playback of a magnetic tape, the reproduced brightness signal at that portion causes a sudden level fluctuation in the envelope, and the dropout detection circuit 16
If a level fluctuation of this envelope is detected, it is assumed that a dropout has occurred in that portion, and a dropout detection pulse is output to the changeover switch 8.

When the dropout detection pulse is input, the changeover switch 8 is connected to Hllll in the diagram for one horizontal scanning period, and I
The luminance signal from one horizontal period before, delayed by the H delay circuit 9, is supplied to the mixer 10 via the changeover switch 8, and the luminance signal in the portion where dropout has occurred is compensated by the luminance signal from one horizontal scanning period before. will be done.

[Problem that the invention seeks to solve]

As described above, dropout compensation has conventionally been performed on luminance signals, but dropout compensation as described above has not been performed on chroma signals for reasons described later.

In other words, the above-mentioned dropout compensation corrects a signal in which a dropout has occurred using a correlated signal with a different time axis, and is based on the premise that an IH delay circuit or a one-frame period delay circuit is used. It has become.

However, as is well known, the chroma signal is a signal modulated by the subcarrier fsc that is interleaved with the repetition frequency fn of the horizontal scanning f-line, so the chroma signal of the video signal in which the dron one dropout has occurred If you try to compensate for this by dropout compensation as described above, even if you simply replace the chroma signal delayed by one horizontal scanning period with the chroma signal that caused the dropout, it will not be possible to perform processing such as phase inversion of the delayed chroma signal. Unless this is done, the continuity of the subcarrier fsc will not be maintained,
Further, if the timing of the delay is even slightly shifted, this causes a change in hue, resulting in a problem in that a completely different color is restored.

For the reasons mentioned above, it is very difficult to perform dropout compensation using a delay circuit in the case of the L rechroma signal, unlike the luminance signal, and therefore the rechroma signal dropout compensation has not been performed in this way.

The present invention has been made in view of the above problem, and an object of the present invention is to provide a color video signal reproducing apparatus that is capable of performing dropout compensation with a simple configuration and with little deterioration in image quality.

A color video signal reproducing apparatus of the present invention includes a reproducing means for reproducing a color video signal from a recording medium, and a luminance signal and a chroma signal, respectively, from the color video signal reproduced by the reproducing means. a separating means for separating; a converting means for converting the chroma signal separated by the separating means into a baseband signal;
a luminance signal dropout compensating means for detecting a dropout of the luminance signal separated by the separating means and compensating for the luminance signal in which the dropout has occurred;
The baseband signal dropout compensation means compensates for the dropout of the baseband signal converted from the chroma signal by the conversion means.

[For production]

With the above configuration, dropout compensation of the chroma signal can be easily performed when converting the chroma signal into a baseband signal.

〔Example〕

The present invention will be explained below using examples.

FIG. 1 shows a V to which the present invention is applied as an embodiment of the present invention.
1 is a diagram showing a schematic configuration of a dropout compensation circuit of 'rR. Components equivalent to those in FIG. 2 are given the same reference numerals.

In FIG. 1, similarly to FIG. 2, a reproduced composite video signal is reproduced from a magnetic tape (not shown) by a magnetic head 1a + 1b and amplified by a reproduction amplifier 3, and is separated into HP F4. The reproduced luminance signal is supplied to the dropout detection circuit 16 and F M :
lJ! After being demodulated in the modulation circuit 7, the signal is supplied to the changeover switch 8.

Furthermore, since the reproduced chroma signal separated by the LPF 4 from the reproduced composite video signal has been low-frequency converted, it is returned to a normal chroma signal by the same method as shown in FIG. 2 and then supplied to the color difference signal demodulation circuit 17. Ru.

The color difference signal demodulation circuit 17 demodulates the manually generated chroma signal into color difference signals of R-Y and B-Y, which are demodulated and generated R-Y.

The B-Y color difference signal is supplied to changeover switches 18a and 18b.

Here, the changeover switches 8.18a and 18b are normally connected to the L side in the figure, the luminance signal is supplied to the mixer 10 via the changeover switch 8, and the color difference signal R-Y
, B-Y are supplied to the chroma signal modulation circuit 20 via changeover switches 18a and 18b.

The chroma signal modulation circuit 20 modulates the input color difference signals R-Y and B-Y into the original chroma signal form, and the chroma signal generated in this way is sent to a mixer. 10, mixed with the luminance signal, and output as an output composite video signal.

The brightness signal output from the changeover switch 8 is supplied to the mixer 10 and also to the KIH delay circuit 9, where the brightness signal is delayed for one horizontal scanning period and then output to the changeover switch 8.
is supplied to the H side of In addition, the changeover switches 18a, 18
The R-Y signal and the B-YOr signal output from the b-processing are supplied to the chroma signal modulation circuit 20, and the R-Y signal is input to the I
The B-Y signal is transferred to the IH delay circuit 1 by the H delay circuit 19a.
9b, the output of the IH delay circuit 19a is supplied to the H side of the changeover switch 18a, and the output of the IH delay circuit 19b is supplied to the H side of the changeover switch 18b.

The operation of the circuit shown in FIG. 1 when dropout occurs will be described below.

w, HP from the reproduced composite video signal in Figure 1
The reproduced luminance signal separated by F4 is supplied to a dropout detection circuit 16. The reproduced brightness signal is FM
Since this is a modulated signal, if a dropout occurs during playback, the signal in the part where the dropout has occurred will be generated as a sudden level change in the envelope, so the dropout detection circuit 16 will detect this change in the envelope. If this occurs, it is determined that a dropout has occurred in that portion, and a high level switching pulse is output to each changeover switch 8.18a, 18b until the envelope change returns to its original state. Each of the changeover switches 8.18a and 18b switches the connection to the H side in the figure during the period when the no-repel switch changeover pulse is input.

As a result of the above operation, during the period when dropout occurs, each changeover switch 8.18a, 18b outputs each pre-IH signal delayed by one horizontal scanning period by IH delay circuits 9.19a, 19b. The signal in which dropout has occurred is interpolated with the signal before IH and output.

Then, each signal for which dropout compensation has been performed at 5Jl' is processed in the same manner as in the normal playback described above, and then
Output is output as a composite video signal.

As explained above, it is possible to convert the reproduced chroma signal into a color difference signal whose information is less affected by phase changes, and it is also possible to easily realize dropout compensation for the chroma signal as well. .

Further, in this embodiment, the dropout detection circuit detects the occurrence of dropout only in the reproduced luminance signal, and the signal via the delay circuit is used accordingly. By doing so, it is possible to solve the problem that occurs when a dropout detection circuit is provided for each of the reproduced luminance signal, the RY signal, and the BY signal.

In other words, if a dropout detection circuit is provided for each of the reproduced luminance signal, R-Y signal, and B-Y signal, and each delay circuit is independently switched and controlled, all dropout detectors will be affected when a dropout occurs. Dropouts are not always detected, and a signal that has been corrected for dropout and a signal that has not been corrected for dropout occur at the same time, and these signals have a large phase shift and are not matched, so the output composite at the time of restoration This is because the video signal deteriorates. In addition, if a dropout detection circuit is provided for each signal source, it should be noted that even if a dropout is detected in any one of the dropout detection circuits, all dropout detection circuits will perform dropout correction processing. The above problem can be solved by generating control pulses.

Furthermore, in this embodiment, dropout compensation is performed using an IH delay circuit, etc., assuming that the signal one horizontal scanning period ago has the highest correlation with the current signal, but the present invention is not limited to this. The image quality after dropout compensation should be further improved by using a delay circuit of one field or one frame period, or by controlling the amount of delay of the delay circuit according to the correlation of the image signals handled. I can do it.

In addition, in this embodiment, the dropout compensation is performed by demodulating the chroma signal into a color difference signal, but the present invention is not limited to this. Needless to say, it is also possible to perform out correction.

Further, although the present embodiment has been explained using a VTR, the present invention is not limited to this, and the present invention can also be applied to a reproducing device such as a video disc device.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a color video signal reproducing apparatus that is simple in structure and capable of performing dropout compensation with little deterioration in image quality.

[Brief explanation of drawings]

FIG. 1 shows a VT to which the present invention is applied as an embodiment of the present invention.
FIG. 2 is a diagram showing a general F@m configuration of a dropout compensation circuit of R; FIG. 2 is a diagram showing a schematic configuration of a reproduction side of a VTR including a luminance signal dropout correction circuit as a conventional example. 8.18a, 18b... changeover switch, 16...
Dropout detection circuit, 17... Color difference signal demodulation circuit, φ*19a*l9b...1 horizontal scanning period delay circuit, 20... Chroma signal modulation circuit.

Claims (1)

[Claims] a reproduction means for reproducing a color video signal from a recording medium;
separation means for separating a luminance signal and a chroma signal from the color video signal reproduced by the reproduction means; a conversion means for converting the chroma signal separated by the separation means into a baseband signal; luminance signal dropout compensating means for detecting dropout in the luminance signal and compensating for the luminance signal in which the dropout has occurred;
and baseband signal dropout compensating means for compensating for dropouts in the baseband signal converted from the chroma signal by the converting means in accordance with a dropout detection state of the luminance signal dropout compensating means. color video signal reproducing device.