JPS5873296A - Dropout compensating circuit - Google Patents

Abstract

PURPOSE:To prevent the deterioration in picture quality such as gneration of tailing, by synthesizing the 1st, 2nd signals and the 3rd signal delayed by a time tau via a delay element from a video signal and obtaining a signal for dropout compensation. CONSTITUTION:When a video signal is inputted from a terminal 1, the 1st signal y1 delayed by (tau-1/2fs, where fs is chrominance carrier frequency) is outputted from the 1st delay element 2. The signal y1 is applied to a delay element 3a to become the 3rd signal y3. The signal y1 is applied to an addition circuit 4 and a phase inverter 5 at the same time. The signal y3 is applied to a delay element 3b further to become the 2nd signal y2 and inputted to an amplifier 7 at the same time. The addition circuit 4 produces a delay signal e1 from the signals y1 and y2, an addition circuit 8 synthesizes signals -y1 and -y2 via phase inverters 5, 6 and a signal 2y3 via an amplifier 7 to obtain a delay signal e2, which is inputted to an LPF9. The signal is inputted to an adder 10 to obtain a signal e3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dropout compensation circuit for video disc players and the like.

Hereinafter, a conventional dropout compensation circuit 111It will be explained using a video disc player as an example. It is generally well known that compensation for dropouts (defects) is accomplished by replacing the defect liA with a signal delayed by one or approximately one horizontal scanning period (IH).

In addition, in a case where a color carrier having a frequency interleap relationship is included in the j+1 x 1 PI signal as in the case of a video signal, if IH delay is applied, the phase of the color carrier of the delayed signal will change. It is also generally well known that it is reversed.

Therefore, the following method has been proposed as a measure to achieve both the IH delay of the luminance signal and the non-inversion of the color carrier phase.

FIG. 1 is a block diagram of a conventional dropout compensation system (b). In the figure, l is a video signal input terminal;
2 is a first delay element with a delay time of <r-V2ts), 3 is a second delay element with a delay time of l/fs, and 4 is a second delay element with a delay time of l/fs.
is an adder circuit. However, here, τ indicates one horizontal scanning period, and fs indicates the color carrier frequency.

When a video signal is input manually from the video signal input terminal l,
The 10th title book 2 outputs the first signal Yi delayed by (τ-fs). The signal y1 of this feeling 1 is
The signal is supplied to the adder circuit 4 and also to the second delay element 3 .

The second delay element 3, which is supplied with the first signal y, delays the video signal by (τ+I/2fS) and generates a second signal y! is output and supplied to the adder circuit 4.

Therefore, the adder circuit 4 supplied with the first & second signals y1 and y generates a delay signal e, ? for dropout compensation consisting of the signals y1 and y, ? :Output.

That is, if the video signal frequency is fs, the sum of the signal y of 1#Il and the second signal y can be expressed as

e, = y, 10y =ε−Jψ(τ−6)+ε−Jω(τ1δ) However.

ω=2πf δ=1. /2rs As shown in this formula, the jl! processed signal e1 is a signal whose amplitude is 2 (2) (πf/f 8 ) and is delayed by τ.Furthermore, the color carrier frequency fsri ,
[8== (2n + 1)/2 r (where n is m) t'', it can be seen that the delayed signal alO color carrier phase is also not inverted.

FIG. 2 is an amplitude-frequency characteristic diagram of the 9M signal e obtained by the circuit of FIG.

As mentioned above, in the conventional dropout compensation circuit,
It was possible to achieve both the d&tn delay of the luminance signal and the non-inversion of the color carrier phase.

However, the effective bandwidth of the luminance signal component in the delay signal e is approximately 14, as can be seen from FIG. That is, in the case of CED, VHD, and the original methods,
The respective bandwidths are approximately 0.76°1, 3, 1, respectively.
．． 8 MHz, which is clearly not sufficient.

Due to this rounding, in the case of the conventional method, for example, in the case of the CED method, undesirable tailing (regret, white beard) will appear in the part of substitution No. 11 (i!I!gN No. eI), etc. One drawback was that quality deteriorated.

An object of the present invention is to eliminate the drawbacks of the prior art as described above, and to provide a delayed signal for dropout compensation that is delayed by a time and has no color carrier phase inversion, and that It is an object of the present invention to provide a dropout compensation circuit that can provide a much improved effective bandwidth of a luminance signal component compared to the conventional one.

In order to achieve the above object, the present invention provides the above-mentioned first
S? and second signals y and y and a third signal newly generated according to the present invention and delayed by a predetermined delay time τ at a ratio of 1:1:2 to obtain delayed signals e, Furthermore, in the present invention, in order to achieve the above object, the M extended signal e is passed through a filter that stops the passage of the color signal component contained in this signal f:tm, and the above-mentioned formula (
It was decided to combine it with the M extended signal e1 shown in 1) to generate a delayed signal for dropout compensation.

Hereinafter, the present invention will be explained in detail using the drawings.

The third i+ill is a block diagram showing an embodiment of the dropout compensation circuit of the present invention. In the same figure, 3m
, 3b are d extension elements each having an M delay time of 1/zrs, 5 and 6 are phase inverters, 7 is an amplifier with double gain, and 8.
10 is an adder circuit, and 9 is a low pass filter (LPF).

In this figure, the same parts and the same parts as in FIG. 1 are indicated by the same reference numerals. In addition, FIGS. 4(a) and (b) show the 3rd #
At-Amplitude-Frequency III diagram for illustrative purposes.

When a video signal is input manually from video signal input terminal 1,
1st j! ! As explained in FIG.
, is output.

This first signal y1 divides the second delay element 3 in FIG. 1 into two, and connects the second delay element 3 in series! l! The delay elements 3a, 3
It is supplied to the element 31 in the previous stage of b. At the same time, the first signal y1 is also supplied to the addition IEJ@4sp and the phase inverter 5.

A circle! is supplied to the delay element 3a. 181 signal 3'tt
By passing through the element 3a, yc becomes a third signal ys. 1g! The J-induced signal y is the delay element 3 of the next stage.
b and amplification Wk7, respectively. The third signal y3 supplied to the main child 3b becomes the second signal y by passing through the element 3b, and the addition circuit 4s? and phase inverter 6, respectively.

As is clear from the above description, as in the case of the conventional example shown in FIG. A delayed signal alt- is generated and supplied to the adder circuit 10 at the next stage.

Next, the first & second signals yp and yy supplied to the aforementioned phase inverters 52 and 6, respectively, and the amplifier 7
The third signal y supplied to the above-mentioned nine phase inverters, 6's? and an amplifier 7, respectively, and then input to an adder circuit 8.

-YI+"Fm
+2 and 2y3) are combined, and a second I!1 extended signal 14 having a waveform as shown in Figure #s4 (1) is output.This second delayed signal el is When expressed as a formula, it becomes like formula (2).

6m = 21s'! t)'! −jωτ−ε−jω(τ−δ)−ε−jω(τ+δ)−
2ε ”'21s @+ Next, this $2 delay signal e!kura, cutoff frequency af
e is added to the aforementioned nine-first delay signal e in the addition circuit 410 via the LPF 9 (the part shown by the solid line in FIG. 4(a) (LPF 9 that passes only F). As a result, the addition circuit As the output signal of 10, a −嬌 signal (hereinafter referred to as replacement reach a signal) e having a waveform as shown in FIG. 4(b) is used.
l will be monked.

In other words, the replacement II! The extended signal e1 is the LP11
' In the passband (f(fc)), the waveform given by equation (3) is 9, and on the other hand, in the stopband of the LPF 9 (
fife), the waveform becomes J as required by equation (4).

e3”' @, + el= 2ε−Jωτ 10999
0000.6090. (3) As can be seen from the above explanation, this is referred to as spacing. In order to combine the first and second delayed signals e1 and el to obtain a defect-free replacement illumination signal 3 for the color signal, the second
Delay of 1g issue e! must be prevented from passing through the color signal components contained in the filter.

Therefore, the WJi cutoff frequency fc is the replacement a! It is necessary to set it near the lower limit of the bandwidth required for transmission of the multiplied signal 1 color signal.

As is well known, the color carrier frequency f8 is K, C
ED, VHD, optical O6 method - 1.53M each
Hz, 2.56 MHz, and 3.58 MHz, but regardless of which method is used, the bandwidth is within a range of ±0.5 MHz centered on the color carrier frequency fS.

Therefore, for example, in the case of the CED method, the cutoff frequency fc is desirably set to about 1.1 MHz K.

In this way, by setting the cutoff frequency fc of the LPF 9, the delay signal e for the luminance signal is generated, the color carrier phase is not inverted, and the delay signal e for the luminance signal is
It is possible to obtain a replacement M extension signal e1 which is greatly improved compared to the above.

In addition, in FIG. 3, the signals y1 and )'mt"l
im inverted and added with signal 2Yx, but
As shown in FIG. 5, the phase inversion fiS is deleted, the delayed signal 6+ (i.e., -a of the signals y1 and y!) is manually inverted by the phase inverter 6, and the output is the signal of jli3. y
Even if we add and synthesize the signal 2'/s which is doubled from 1,
Exactly the same delayed signal ezt- as before can be obtained.

That is, it is clear that a similar replacement M signal signal e can be obtained from the ll1ll path Cζ shown in FIG.

It is clear.

In addition, in the above explanation, the predetermined delay time (τ) is
Although the explanation has been given as H, in some cases it may be necessary to take into account delays in other circuits (not shown) and set it to IH or lower. In addition, although the LPF was used in the above embodiment, a fluorescent band rejection filter (BWF) was used instead.
k may also be used, I! ! The spreading element may be made of COD or the like. Furthermore, add phase inversion 6 and multiplier tgl&
It is also clear that it can be composed by including it in 8.

It is also obvious that the same result can be obtained by multiplying the first and second signals Vt& and yts- by 1/2 instead of doubling the signal Xs of j43.

Before, first, second and third signals) '++3'! and y can be extracted as tap outputs, and in some cases, these signal outputs can be used to configure a comb filter.

Furthermore, the entire embodiment shown in FIG. 3 and FIG.
It is also obvious that it can be configured by an IC including D and the like.

As is clear from the above AI description, the present invention provides a horizontal scanning period of 4 g, a non-inverted color carrier phase, and an effective band of the brightness IfL reconnaissance component, which is even more effective than that of the conventional method. j11 for improved dropout compensation
A signal e1 can be obtained. As a result, the present invention has the effect of preventing deterioration of image quality such as the occurrence of trailing, which was a drawback of the conventional technology.

[Brief explanation of drawings]

@Figure 1 is a block diagram of a conventional dropout compensation circuit 1gll11, Figure 2 is an amplitude-frequency characteristic diagram for explaining Figure 1, and Figure 3 is a block diagram showing an embodiment of the dropout compensation circuit of the present invention. Figure, 7I! J4 figure (&) (b) is the 311i! 2. Vibration-single-frequency wave ridge timing diagram,
1ml! FIG. 5 is a block diagram showing an embodiment of the droop-out compensation Igl path of the present invention. l...Video signal manual notification, 2.3m, 3b...Delay element, 4.8. IO... Adder circuit, 5.6... Phase inverter, 7... Increase III! Vessel, 9...LPF, Patent Attorney Michihito Hiraki

Claims (3)

[Claims] (1) means for outputting a first signal 48 in which the input signal is delayed by (r-1/2ts) when the T1 color carrier frequency ridges are each indicated by f8 for a predetermined delay time; means for outputting a second signal extended by force number k (t+1/2 fs); means for outputting the signal of the stud 3 delayed by the delay time τ; means for combining the signals Is1 and s2 to output the first delayed signal e; and the m 1 % signal whose phase is inverted. 2 signal and the previous 2 3rd signal are combined and the mackerel 2 j! ! Nobu 111
means for outputting a signal; a filter for blocking the passage of a color signal component included in the delayed signal e2 of the -origin 2;
A dropout compensation circuit comprising: means for adding the output of the filter to the lth delay signal e1. (2) The dropout compensation circuit according to claim 1, wherein the filter is a low-pass filter, and the cutoff frequency thereof is set to a value lower than the color carrier frequency. (3) The filter is a filter that is KI&determined to block the passage of color signal components included in the second 11 signal e. Dropout compensation circuit as described.