JPH02181590A - Chroma noise reduction circuit - Google Patents

Abstract

PURPOSE:To remove vertical directional color blurring by obtaining the OR between a conventional noncorrelation detection pulse and a 1H delayed noncorrelation detection pulse and turning off a switching circuit using the OR pulse as a new noncorrelation detection pulse. CONSTITUTION:When noncorrelation is detected, a noncorrelation detection pulse S5, which is the same as that in a conventional example, is generated in a noncorrelation detection pulse generation circuit 7, and a 1H delayed pulse S6 is generated from the pulse S5 in a 1H delay circuit 9. Further, in an OR circuit 10, a pulse S7 is generated by obtaining the OR between the two pulses S5 and S6. The pulse S7 becomes the new noncorrelation detection pulse to turn off a cyclic loop switching circuit 5, and no chroma signal component to be the cause of the vertical directional color blurring appears in a signal S4 to be outputted from an adder 4. Thus, the vertical directional color blurring caused by a cyclic type noise reduction circuit can be removed.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to two horizontal scanning periods (hereinafter referred to as
This paper relates to a chroma noise reduction circuit for signals with line correlation.

(Prior art) Conventionally, as a technology to improve the image quality of video equipment, a composite color video signal is subjected to a luminance/chroma signal valve 11 (Y/C separation), and then the luminance signal is passed through a comb filter for luminance noise reduction. For the chroma signal, -dan,
Color difference signal (B-Y).

(RY) to eliminate the influence of phase, and then pass it through a comb filter for chroma noise reduction.

In the above-mentioned comb filter for noise reduction, the signal amplitude doubles when two scanning lines with line correlation are added, but since noise is generated randomly, the amplitude is multiplied by ff. This takes advantage of the property that it can only become .

FIG. 3 shows an example of a chroma noise reduction circuit for NTSC signals. Inside the dotted line is a chroma comb filter 11 which is constructed using the above-mentioned properties and is known for boat fishing, and which is comprised of a 1H delay circuit 12 and an adder 13.

Input terminal 1 is supplied with a chroma signal with 1H line correlation such as an NTSC signal (here, chroma signal refers to a color difference signal demodulated after luminance and chroma signals are separated). . Then, the difference component between the input signal delayed for one day by the 1H delay circuit 12 and the original signal is taken by the subtracter 2, amplified by the limiter amplifier 3 (where K is a cyclic coefficient), and then by the adder 4. It constitutes a cyclic chroma noise reduction circuit that adds to the original signal. In this type of chroma noise reduction circuit,
A switch circuit 5 is arranged in a circular loop, and this switch circuit 5 is turned off when there is no correlation, so that color blurring in the vertical direction does not occur when there is no correlation. The detection at the time of non-correlation is a non-correlation detection signal of the luminance signal Y (Y-
The same operation as the non-correlation detection of the luminance signal is performed using the VD) signal. That is, the non-correlation detection circuit 6 detects a difference signal (Y
-YD), and when the mother of the difference signal is greater than a predetermined value, a non-correlation detection pulse is output from the next stage non-correlation detection pulse generation circuit 7, and the switch circuit 5 is turned off with this pulse. .

FIG. 4 explains the state of the chroma signal in each part of the circuit shown in FIG. 3. The input chroma signal S1 is a signal containing noise as shown in the figure. Arrow A indicates that the correlation between the chroma signals has disappeared at this point. The signal S2 is the input chroma signal S1
2 and shows a signal delayed by one day. The difference between this signal S2 and the original signal S1 becomes a signal S3, which is determined by the limiter amplifier 3 and added to the input signal S1 to become a signal S4. In this case, the non-correlation detection pulse S5 is output at time A to turn off the cyclic loop, so that the vertical 1H color blur caused by the cyclic noise reduction circuit does not occur in the signal S4. Therefore, there is no problem even if the signal S4 is input again to the cyclic noise reduction circuit.

Note that the output signal $6 is a signal obtained by adding signals S1 and S2 to have an amplitude of 172.

In this way, in the NTSC system in which the chroma signal has daily line correlation, vertical color fringing at the time of non-correlation can be removed.

FIG. 5 shows an example of a circuit in which the chroma noise reduction circuit that performs non-correlation detection described above is used for PAL signals. The circuit configuration is N as explained in Figure 3.
This is similar to the case of the TSC signal, except that a 2Hi extension circuit 14 is used instead of the delay circuit 12 used in the case of NTSC.

This is because the PAL signal is a signal that has 2H line correlation with respect to the chroma signal.

FIG. 6 explains the state of the chroma signal in each part of the circuit of FIG. 5. The input chroma signal S1 is a signal containing noise as shown in the figure. Arrow A indicates that the correlation between the chroma signals has disappeared at this point. Signal S2 is the input chroma signal S1 that is output to 2H delay circuit 1.
4, showing a signal delayed by 21''. The difference between this signal S2 and the original signal S1 becomes a signal S3, the amount of return is determined by the limiter amplifier 3, and it is added to the input signal S1 to become a signal S4. In this case, the non-correlation detection pulse S5 is output at time A and turns off the cyclic loop by -H.
Since the signal @33 is delayed by 2 days unlike the case of NTSC, when the switch circuit 5 that was once turned off is turned on in the next 1H, a chroma signal that causes vertical color blurring appears in the signal S4. Put it away. Then, this signal S4 will now circulate through the cyclic noise reduction circuit,
Vertical color fringing occurs in the output signal S6 due to the cyclic noise reduction circuit. Note that the output signal S6
shows the signal S1 and 82 added together and the amplitude thereof set to 172.

In this way, the PA with 2-day line correlation of the chroma signal
In the L method, if a non-correlation detection method similar to that used in the NTSC method is used, vertical color fringing during non-correlation cannot be completely removed.

(Problems to be Solved by the Invention) As described above, in the conventional cyclic noise reduction circuit for Oma signals that performs non-correlation detection,
In the case of signals with H correlation, there is a problem in that the cyclic loop cannot be completely turned off when there is no correlation, resulting in vertical color blurring.

Therefore, the present invention is intended to eliminate the above problems.
Even in the case of signals with 2H line correlation such as PAL signals, the chroma noise reduction circuit can completely turn off the cyclic loop at the time of non-correlation and eliminate vertical color fringing caused by the cyclic rise reduction circuit. The purpose is to provide the following.

[Structure of the Invention] (Means for Solving the Problems) Therefore, the present invention provides a cyclic chroma noise reduction circuit for a zero signal having 2H line correlation, such as a PAL signal, to reduce the non-conformance of a luminance signal. detect correlations,
means for creating a non-correlation detection pulse; means for delaying the non-correlation detection pulse from the means by one day; and OR means for ORing the non-correlation detection pulse and the one-day delayed non-correlation detection pulse; The present invention is characterized by comprising a switch means for controlling the cyclic loop in the cyclic chroma noise reduction circuit by the output pulse of the OR means.

(Operation) In this invention, the conventional non-correlation detection pulse and the non-correlation detection pulse delayed by 1H are logically summed, and the logical sum pulse is used as a new non-correlation detection pulse to turn off the switch circuit. The circulating chroma signal component, which causes vertical color fringing, is no longer returned to the input side of the chroma noise reduction circuit, making it possible to eliminate vertical color fringing.

(Example) The present invention will be described below based on the example shown in the drawings.

FIG. 1 is a block diagram showing a chroma noise reduction circuit according to an embodiment of the present invention.

The embodiment shown in this figure shows a cyclic chroma noise reduction circuit for a chroma signal with two-day line correlation, such as a PAL signal, and the same components as in FIG. 5 are denoted by the same reference numerals. be.

1 is the chroma signal input terminal, 2 is the subtractor, 3
is a limiter amplifier, 4.13 is an adder, 5 is a switch circuit, 6 is a luminance signal non-correlation detection circuit, 7 is a non-correlation detection pulse generation circuit, 8 is an output terminal for the O signal, 11 is a chroma comb filter , 13 is an adder, and 14 is a 2-day M delay circuit. Compared to the conventional example, the means for generating a non-correlation detection pulse for turning off the switch circuit 5 is different. l! It is the same in that a non-correlation detection pulse of the chroma signal is created using non-correlation detection of the i-degree signal, but this conventional non-correlation detection pulse is delayed by 1H using a 1-day delay circuit, and is compared to before the 1H delay. OR circuit 1 of both pulses after one day delay
0, and the output pulse is used to turn off the switch circuit 5 as a new non-correlation detection pulse at the time of non-correlation.

FIG. 2 explains the state of the chroma signal in each part of the circuit shown in FIG. 1. The chroma signal S1 supplied as an input is a signal containing noise as shown. Arrow A
indicates that the correlation between the chroma signals has disappeared at this point. The input signal S1 passes through the 2-day delay circuit 14 and
A delayed signal S2 is obtained. This signal S2 and original signal S1
The difference between them becomes a signal S-3, which is determined by the limiter amplifier 3 and added to the input signal S1 by the adder 4.

In this case, when non-correlation is detected at time A, the non-correlation detection pulse creation circuit 7 creates the same non-correlation detection pulse S5 as in the conventional example, and the 1)-till extension circuit 9 generates the non-correlation detection pulse S5 from the pulse S5. A pulse S6 delayed by one day is created. Then, the OR circuit 10 generates a pulse S7 by ORing the two pulses S5 and S36. Since this pulse S7 becomes a new non-correlation detection pulse that turns off the switch circuit 5 of the circular loop, no chroma signal component that causes vertical color blurring appears in the signal S4 output from the adder 4. . By the way, the chroma signal component that normally causes color blurring will appear for many days as long as it is a cyclic noise reduction circuit, but as long as the cyclic coefficient K is not too large, the chroma signal component that causes color blurring will appear for many days, as in this method. If you cancel the patrol,
The size has been reduced to a level where there is no problem in practical use. Note that the output signal S8 is obtained by adding the signals S1 and 82 and increasing the imaging width by 1.
72 is shown.

In this way, even for chroma signals with two-day line correlation, such as PAL signals, the vertical color blur caused by the cyclic noise reduction circuit can be removed while improving the performance of chroma signal noise removal. be able to.

[Effects of the Invention] As described above, according to the present invention, even in the case of a signal with two-day line correlation, such as a PAL signal, the cyclic loop is completely turned off at the time of non-correlation, and the cyclic noise reduction circuit is activated. It is possible to eliminate vertical color bleeding caused by

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing a chroma noise reduction circuit according to an embodiment of the present invention, FIG. 2 is an explanatory diagram illustrating the states of chroma signals in each part of the circuit shown in FIG. Figure 4 is a block diagram showing an example of a conventional chroma noise reduction circuit, Figure 4 is an explanatory diagram explaining the state of chroma signals in each part of the circuit in Figure 3, and Figure 5 is a chroma noise reduction circuit showing another conventional example. FIG. 6 is an explanatory diagram illustrating the state of the chroma signal in each part of the circuit shown in FIG. DESCRIPTION OF SYMBOLS 1...Input terminal, 2...Subtractor, 3...Limiter amplifier, 4.13...Adder, 5...
... Switch circuit, 6... Non-correlation detection circuit, 7...
Non-correlation detection pulse creation circuit, 8... Output terminal, 9... 1 day delay circuit, 10...
OR circuit, 11...Chroma comb filter, 14...
・2-day delay circuit. Agent: Patent attorney: Nori Chika, Ken Shu, Hiroshi Uji? 0
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Claims (1)

[Claims] A chroma signal having a correlation between two horizontal scanning lines supplied as an input is output by adding a signal delayed by two horizontal scanning periods and the original signal, and a signal delayed by the two horizontal scanning periods and the original signal are outputted. In a cyclic chroma noise reduction circuit that subtracts a signal and adds the difference component to the original signal via a cyclic loop, means for detecting decorrelation of a luminance signal and creating a decorrelation detection pulse; means for delaying the non-correlation detection pulse by one horizontal scanning period; OR means for ORing the non-correlation detection pulse and the non-correlation detection pulse delayed by one horizontal scanning period; and means for turning on and off the cyclic loop. A chroma noise reduction circuit comprising: switch means controlled by an output pulse from the OR means.