JPS6251894A - Drop-out correcting device - Google Patents

Abstract

PURPOSE:To minimize the degradation in picture quality due to drop-out correction by using a signal of 1H before for drop-out correction of a Y signal and suing a signal of 2H before for dro-out correction of color difference signals. CONSTITUTION:A reproduced FM signal is inputted to an FM demodulator 1 and a drop-out detector 2. The FM demodulated signal is inputted to a delay circuit 5a, a horizontal synchronizing signal separating circuit 6, and a switch 8. The horizontal synchronizing signal separating circuit 6 separates HD from the input signal, and it is discriminated whether the present signal is the Y signal or the color difference signal or not by a signal discriminating circuit 7. If it is discriminated that the reproduced signal is the Y signal, the switch 8 is so controlled that the output of the delay line 5a is selected. If it is discriminated that the reproduced signal is the color difference signal, the switch 8 is so controlled that the output of a delay line 5b is selected. Thus, the Y signal is corrected by the signal of 1H before, and the color difference signal is corrected by the signal of 2H before.

Description

[Detailed description of the invention] [Industrial application field] This invention uses two types of color difference signals (hereinafter referred to as CW).

A television signal (hereinafter referred to as TV signal) that is time-axis multiplexed during the horizontal blanking period of a luminance signal (hereinafter referred to as Y signal) is reproduced from a recording medium. The present invention relates to a dropout correction device for a device that uses a dropout correction device.

[Conventional technology]

The format of the TV signal targeted by this invention is shown in FIG.
In the same figure, C"w and C'n are two types of color difference signals (Cw, Cn) compressed on the time axis, and are time-axis multiplexed in the horizontal blanking period of the Y signal. Here, Y The signal may be subjected to time axis compression. Also, HD is a horizontal synchronization signal. In the figure, HD is time axis multiplexed, but frequency multiplexing etc., Y signal or C' The present invention also applies to the case where the signal is multiplexed on the same time axis as the w and C'n signals. Note that IH in the figure represents one horizontal scanning period.

In broadcast VTRs or home VTRs that record and reproduce TV signals that are not line sequential, dropout correction is performed using pre-IH signals that have a high correlation with the lost signal.

On the other hand, a VTR or V [) that reproduces the above TV signal
As a conventional dropout correction method for playback devices such as P (Video Disc Player), there is a method in which when a dropout occurs, it is corrected using a signal 2H earlier (TV Society Technical Report TEBS99-4)
). That is, in this conventional method, the color difference signals C2W, C
' 11 are multiplexed line-sequentially.

FIG. 6 is a schematic block diagram of an apparatus for performing dropout correction according to the conventional method. The figure shows the case where the TV signal is reproduced from a recording medium on which the TV signal is FM-modulated and recorded.
The FM demodulator 2 that demodulates the signal to FM detects the occurrence of dropout from the level of the envelope of the reproduced FM signal, and after matching the timing with the output of the FM demodulator 1, generates a dropout detection pulse (hereinafter referred to as Do pulse). ); 3 is a delay circuit having a delay amount of 2H period; 4 selects either the output of delay circuit 3 or the output of FM demodulator 1 depending on the presence or absence of a DO pulse;
This is a switch that outputs this to the subsequent signal processing circuit.

That is, the signal output to the subsequent signal processing circuit is the output of the FM demodulator 1 when there is no dropout, and is the output of the delay circuit 3 when a dropout occurs. Here, the signal processing circuit converts C'W from the input signal.

This method separates C'n and extends the time axis to restore CW and Cn.

[Problem that the invention seeks to solve]

Since the conventional dropout correction device is configured as described above, even if a dropout occurs in the Y signal portion, it is corrected before 2H. As a result, regarding the Y signal, there was a problem in that the image quality after correction deteriorated compared to the case where dropout correction was performed using the signal before IH, which has a higher correlation than the signal before 2H, for the current signal.

This invention has been made to solve the above-mentioned problems, and provides a dropout correction device that can minimize deterioration in image quality due to correction for Y, C'w, and C'n signals. With the goal.

[Means for solving problems]

The dropout correction device according to the present invention separates a horizontal synchronization signal (HD) from a reproduction synchronization signal, and uses HD as a time axis reference to determine whether the reproduction signal at the present moment is a Y signal or a color difference signal. , the pre-IH signal or the pre-2H signal is selected as the signal used for dropout correction according to the determination result.

[Effect]

In this invention, by switching the signal used for correction according to the position of dropout occurrence, the Y signal is
The previous signal is used for correction, and the color difference signal is corrected using the 2H previous signal.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 and 2 are the same as in FIG. 3, and 5a is an FM detector and a dropout detector, respectively.
Delay circuit 5b delays the output of the demodulator 1 for the IH period; 6 is the delay circuit F;
7 is a horizontal synchronization separation circuit that separates and detects the HD from the output of the M demodulator 1; 7 is a signal discrimination circuit that receives the HD and clock signals and determines whether the current signal is a Y signal or a color difference signal; 8; In accordance with the outputs of the dropout detector 2 and the signal discrimination circuit 7, the signal to be output to the subsequent signal processing circuit is selected from among the output of the FM demodulator 1, the output of the delay circuit 5a, or the output of the delay circuit 5b. It is a switch to select.

°Here, the delay circuits 5a and 5b are specifically RAM,
This is realized by a shift register or an analog delay line such as a CCD. The embodiment shown in FIG. 1 is a case where an analog delay line is used, and the delay circuits 5a,
5b is configured with digital circuit elements such as RAM and shift registers, the output of the FM demodulator 1 is supplied to an A/D converter (not shown), and the output of the A/D converter is connected to the delay line 5a, It is input to the horizontal synchronization separation circuit 6 and switch 8. Further, the signal discrimination circuit 7 can be realized, for example, by the configuration shown in FIG. In the figure, reference numeral 9 is a counter whose count value is preset to 0 in the HD and thereafter performs an amplifier counting operation in response to a clock signal, and lO is a comparator which compares the count value Q of the counter 9 with a set value A.

Next, the operation will be explained. FIG. 2 is a diagram showing signal waveforms of each part of the embodiment device of FIG. 1, and FIG.
FIG. 3 is a diagram showing signal waveforms of each part of the signal discrimination circuit 7 shown in the figure.

The reproduced FM signal is transmitted through FM demodulator 1 and dropout detector 2.
is input. The FM demodulated reproduction signal shown in FIG. 2(a) is input to a delay circuit 5a, a horizontal synchronization separation circuit 6, and a switch 8. The horizontal synchronization separation circuit 6 separates HD from the input signal and outputs a positive pulse signal HDP shown in FIG. When FIIr 7 receives HDP, as shown in FIG. 4(C), it continues counting up after setting the count value of counter 9 to 0. It is determined whether the current signal is a Y signal or a color difference signal as shown in FIG. The time is the Y signal.

Here, when the Do pulse is output during the period from time t1 to t2 as shown in FIG. 2(d), the signal discrimination circuit 7 discriminates that the reproduced signal is the Y signal during this period, so
Switch 8 is controlled to select the output of delay line 5a. As a result, the switch 8 during the period from time t1 to t2
The output becomes the signal shown in FIG. 2 (Q), which is obtained by correcting the signal in FIG. Also, from time t3 to t
If dropout occurs during the period 4, that is, the color difference signal period, it is corrected by the output of the delay circuit 5b, which is a signal extended by the 2H period shown in FIG. 2(C). moreover,
Like the period from time t5 to t7, the color difference signal period and Y
If dropout occurs over the signal period, the color difference signal period from time t5 to t6 is corrected with the signal from 2H earlier, that is, the output of the delay circuit 5b, and the Y signal period from time t6 to t7 is corrected by the signal from before IH. , that is, it is corrected by the output of the delay circuit 5a.

In this way, with this actual dropout device, if a dropout occurs during the Y signal period, it is corrected with the signal before IH, and when a dropout occurs during the color difference signal period, it is corrected with the signal 2H before. Therefore, when correcting dropout of the Y signal, it is possible to perform correction using a signal with a higher correlation than in the past, and image quality deterioration due to correction can be minimized.

Note that although the above embodiment shows a case where dropout correction is performed after FM demodulation, the present invention can be similarly applied to a case where correction is performed in a state before full JIA, and the same effects as in the above embodiment can be obtained. .

Further, in the above embodiments, an FM modulation signal is considered as a reproduced signal, but the modulation method is not limited to FM. Furthermore, the configuration of the signal discrimination circuit is not limited to that shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, dropout correction is performed using the pre-IH signal for the Y signal and the 2-color difference signal.
Since this is done using the pre-H signal, the two types of color difference signals are time-axis compressed, and when playing back the TV signal that is time-axis multiplexed with the Y signal line-sequentially, image quality deterioration due to dropout correction is avoided. It is effective in minimizing the

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of a dropout correction device according to an embodiment of the present invention, FIG. 2 is a diagram showing timing charts of signals in each part of the circuit of the device, and FIG.
FIG. 4 is a diagram showing a timing chart for explaining its operation; FIG. 5 is a diagram showing the format of signals handled by the present invention; FIG. The figure is a block diagram of a conventional dropout correction device. 2... Dropout detector, 5a, 5b... Delay circuit, 6... Horizontal synchronization separation circuit, 7... Signal discrimination circuit, 8... Switch. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) Detecting the occurrence of dropouts in a dropout correction device in a device that reproduces a television signal in which two types of color difference signals are line-sequentially time-axis compressed and time-axis multiplexed during the horizontal blanking period of the luminance signal. a dropout detector for separating the horizontal synchronization signal from the reproduced signal; a horizontal synchronization separation circuit for separating the horizontal synchronization signal from the reproduction signal; and receiving the output of the horizontal synchronization separation circuit to determine whether the reproduction signal at the present moment is a color difference signal or a luminance signal. a signal discrimination circuit; a delay circuit that outputs a signal from one horizontal scanning period before and two horizontal scanning periods before the reproduced signal; , or select the reproduced signal from two horizontal scanning periods ago, and if a dropout occurs in the luminance signal, correct the luminance signal using the signal from one horizontal scanning period ago, and if dropout occurs in the color difference signal. and signal selection means for correcting the color difference signal using a signal from two horizontal scanning periods ago.