KR100249654B1 - Method for eliminating white noise of a video signal and a video signal white noise eliminating circuit for performing the same - Google Patents

Abstract

Disclosed are a white noise removing method included in a video image input signal, and a white noise removing circuit for performing the same. After the input video image signal passes through the video processor to filter and contour correct the low pass component, the video signal of the low pass component edge-compensated is subtracted from the signal passed through the video processor. In addition, the video image signal is input to the sync separator to separate the video sync signal, the noise level detector detects the noise level on the video sync signal, and considers it as the total noise level, and adjusts the limiter level α using this level. The α value is added and subtracted by the first summer and the third summer. At this time, when the detected noise level of the synchronization signal is large, the width α value of the limiter becomes large. After limiting the subtracted signal, subtract the limiting signal from the subtracted signal, separate the sign (±) signals through a signal separator, add and subtract each of them, and synthesize them, and then contour-correct the pre-synthesized signal. Synthesizing the low pass component video signal removes white noise and outputs a contour corrected low pass video signal. Accordingly, by eliminating the white noise displayed on the screen, the white noise that can be felt during viewing is prevented, thereby forming an improved white noise removing circuit.

Description

White noise cancellation method and white noise cancellation circuit for performing the same

The present invention relates to a white noise removing method and a white noise removing circuit for performing the same. More particularly, the present invention relates to a video image signal input to a system such as a television or a television video cassette recorder (TVCR) system. The present invention relates to a white noise removing method for removing white noise included and a white noise removing circuit for performing the same.

In image processing systems such as televisions or video recorders, one of the important problems is the reproduction of clean images without noise. Normally, screen images provided from broadcasting stations or video tape production companies are likely to introduce unnecessary noise due to image transmission channels or repeated copying. In addition, noise may be introduced into the image information signal during operation of the image signal processing system, and furthermore, the image is also affected by a weak electromagnetic wave while receiving the television image signal.

In general, noise is classified into impulse noise and line noise, and the impulse noise is classified into white noise and black noise. Such noise may occur even when included in an image source or when a low quality film is used in an image processing system, and various measures must be considered to effectively reduce noise components. White noise (white noise) is a video image signal input to a system such as a TVCR contains a lot of noise components that are common, and high frequency noise components of the noise components are displayed in white on the screen.

1A to 1C are diagrams for explaining a conventional method for removing noise of a television signal. As shown in Fig. 1A, a clipper 11 is used for conventional noise cancellation. The clipper 11 does not output a signal having a level smaller than the reference level. That is, the clipper 11 outputs a zero level signal when a signal having a level smaller than the reference level is input. Therefore, when the luminance signal Y including the noise of the same waveform is input as shown in FIG. 1B, the clipper 11 outputs a zero-level signal of the luminance signal Y below the reference level. As shown in the figure, the luminance signal Y 'from which noise included in the low level of luminance is removed is output. However, the noise canceling circuit used in the conventional television has a disadvantage in that it does not remove noise included in the luminance signal at a high level of the luminance signal, that is, a level larger than the reference level of the clipper. Therefore, there is a problem that the clamp level is not adjusted and the high level noise cannot be removed according to the signal level of the noise portion input to the television.

However, the noise canceling circuit used in the conventional television has a disadvantage in that it does not remove noise included in the luminance signal at a high level of the luminance signal, that is, a level larger than the reference level of the clipper. Therefore, there is a problem in that the noise level input to the television cannot remove the high level noise and the clamp level is not adjusted according to the input signal level.

The present invention has been made to solve the problems of the prior art in view of the above point, the first object of the present invention is to detect the noise level of the input video synchronization signal to determine the limiter level and limit the low-pass contour correction To provide a white noise removal method for removing white noise of a video signal.

It is also a second object of the present invention to provide a white noise canceling circuit which is particularly suitable for carrying out the above method.

1A to 1C are diagrams for explaining a back noise removing circuit of a conventional television signal.

2 is a block diagram showing a white noise removing circuit of a television signal according to an embodiment of the present invention.

3 is a diagram for explaining the limiter level determination by detecting the noise level of the television synchronization signal.

4A to 4H are waveform diagrams for explaining the operation of each part of the white noise removing circuit of FIG.

FIG. 5 is a flowchart for briefly explaining a method for removing white noise of the circuit shown in FIG.

* Explanation of symbols for main parts of the drawings

11: clipper 110: video processor

120: low pass filter 130: contour correction circuit

210: synchronous separator 220: noise level detector

310: Limiter 410: Signal Separator

140: first subtractor 510: first summer

320: second subtractor 530: second summer

520: third subtractor 540: third summer

α: limiting level of limiter

In order to realize the first object of the present invention, the present invention (a) by receiving a video image signal and subtracting the video signal of the low-pass component and the video signal of the contour-corrected low-pass component subtracted from the video signal of the contour-corrected low-frequency component Providing a subtracted signal; (b) receiving the video image signal and detecting a noise level of the video synchronization signal to provide a limiter level α value; (c) receiving the first subtracted signal and subtracting the limited signal at α level to the first subtracted signal to provide a second subtracted signal; (d) receiving the second subtracted signal and separating the ± signal to provide a (+) signal separated signal and a (−) signal separated signal; And (e) the video having the low frequency component contour-corrected by removing the white noise by receiving the (+) signal separated signal, the (-) signal separated signal, the contour corrected low frequency component video signal and the limiting level α value. It provides a method for removing white noise, characterized in that the step of outputting a signal.

In order to carry out the second object of the present invention, the present invention, the video signal of the low-pass component and the contour-corrected low-band component video input to the video signal and the contour-corrected video signal received through the input terminal (IN) A low pass contour correction unit for subtracting the signal to provide a first subtracted signal; A noise level detector for receiving the video image signal and detecting a noise level of the video synchronization signal to provide a limiter level α value; A limiting unit configured to receive the first subtracted signal and subtract the first limited signal to an α level to provide a second subtracted signal; A limiting unit for providing the second subtracted signal; A signal separation unit configured to receive the second subtracted signal and separate a ± signal to provide a (+) signal separated signal and a (−) signal separated signal; And an output unit configured to receive the (+) signal separated signal, the (−) signal separated signal, and the contour corrected low pass component video signal, and output a video signal of the contour corrected low pass component by removing white noise. Provides a white noise cancellation circuit.

According to the present invention, after the video image signal is filtered through the video processor to filter the low pass component and contour correction, the video signal of the low pass component edge-compensated to the signal passed through the video processor is subtracted. In addition, the video image signal is input to the sync separator to separate the video sync signal, and the noise level detector detects the noise level applied to the video sync signal, regards it as the total noise level, and adjusts the limiter level α using this level. The α value is added and subtracted with this summer and subtractor. At this time, if the noise level of the detected sync signal is large, the width α value of the limiter becomes large. After limiting the subtracted signal, the limiting signal is subtracted from the subtracted signal, and each of the (±) signals is separated through a signal separator, summed and subtracted, and then synthesized.

Therefore, when the video signal of the low-pass component of the contour correction is synthesized to the synthesized signal, white noise is removed to output the video signal of the low-pass component of the contour correction to remove the back noise on the television screen.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in more detail through an embodiment of the present invention.

2 is a block diagram showing a white noise removing circuit of a television signal according to an embodiment of the present invention.

Referring to FIG. 2, the white noise removing circuit according to an exemplary embodiment of the present invention may include a low-pass outline correcting unit 100, a noise level detecting unit 200, a limiting unit 300, a signal separating unit 400, and an output unit. It is made up of 500.

The low pass contour correcting unit 100 includes a video processor 110, a low pass filter 120, an outline correction circuit 130, and a first subtractor 140.

The video processor 110 receives the video image signal 102 and provides the video signal 111 to the low pass filter 120 and the first subtractor 140 through internal processing.

The first subtractor 140 receives the video image signal 102 and performs low pass filtering to provide the low frequency component video signal 121 to the contour correction circuit 130.

The contour correction circuit 130 receives the low frequency component video signal 121 and compensates an edge, thereby providing the contour corrected low frequency component video signal 131 to the first subtractor 140 and the output unit 500. .

The first subtractor 140 receives the video signal 111 and the video signal 131 having the contour-corrected low pass component and subtracts the video signal 131 having the contour-corrected low pass component from the video signal 111. The subtracted signal 141 is provided to the limiting unit 300.

The noise level detector 200 is composed of a synchronous separator 210 and a noise level detector 220.

The sync separator 210 receives the video video signal 102 and extracts the sync signal of the video video signal 102 to provide the video sync signal 211 to the noise level detector 220.

The noise level detector 220 receives the video synchronization signal 211 and detects the noise level of the synchronization signal, and considers the noise level as the total noise level and limits the α value to adjust the limiter level. And an output unit 500. At this time, when the noise level of the video synchronization signal output from the noise level detector 220 is large, the width α of the limiter becomes large. Accordingly, as shown in the accompanying drawings, FIG. 3 illustrates the limiter level determination by detecting the noise level via the noise level detector 220 to the video synchronization signal 211 detected through the sync separator 210. You can see a detailed waveform in the drawing.

The limiting unit 300 includes a limiter 310 and a second subtractor 320.

The limiter 310 receives the first subtracted signal and limits the limiter signal to the limiter level α to provide the limiting signal 311 to the second subtractor 320.

The second subtractor 320 receives the first subtracted signal 141 and the limited signal 311 and subtracts the limited signal 311 from the first subtracted signal 141 to the second subtracted signal. 321 is provided to the signal separator 400.

The signal separator 400 is composed only of the signal separator 410. The signal separator 500 receives the second subtracted signal and outputs a signal 411 and a signal 412 separated from the (+) signal according to the (+,-) sign of the signal. 500).

The output unit 500 includes a first summer 510, a third summer 520, a second summer 530, and a third summer 540.

The first summer 510 subtracts a value 411 provided by the (+) signal-separated signal and the noise level detector 200 to subtract the third subtracted signal 521 from the second summer 530. To provide.

The third subtractor 520 subtracts the α value provided from the (-) signal-separated signal and the noise level detector 200 to convert the third subtracted signal 521 to the second summer 530. to provide.

The second summer 530 receives the first summed signal 511 and the third subtracted signal 521 and adds the second summed signal 531 to the third summarizer 540. .

The third summer 540 combines the second summed signal 531 with the contour-corrected low pass component video signal 131 to output the contour-corrected low pass component video signal 541 with white noise removed. do.

4A to 4H are waveform diagrams for explaining the output waveforms of the respective portions and the white noise removing operation in the white noise removing circuit of FIG. 2 which is an embodiment of the present invention.

FIG. 5 is a flowchart for briefly describing a white noise removing method according to an exemplary embodiment of the present invention performed by the white noise removing circuit of FIG. 2.

The video image signal 102 inputted from the input terminal IN to the video processor 110 is processed, so that the video signal 111 as shown in FIG. 4A is converted into a low pass filter 120 and a first subtractor. 140) (step S1).

The video signal 111 input to the low pass filter 120 is low-pass filtered so that the video signal 121 having the low pass component as shown in FIG. 4B is output to the contour correction circuit 130 (step S2).

The low frequency component video signal 121 input to the contour correction circuit 130 is edge-compensated, so that the contour corrected low frequency component video signal 131 as shown in FIG. It is output to the third summer 540 (step S3).

The video signal 111 and the contour-corrected low frequency component video signal 131 are input to the first subtractor 140. The first subtractor 140 subtracts the video signal 131 of the low pass component whose contour is corrected from the video signal 111 to subtract the first subtracted signal 141 as shown in FIG. 4D from the limiter 310 and the second. It is output to the subtractor 320 (step S4).

On the other hand, the video image signal 102 input to the sync separator 210, the video sync signal 211 as shown in Figure 4h is extracted and output to the noise level detector 220 (step S5).

The video synchronizing signal 211 input to the noise level detector 220 senses the noise level of the video synchronizing signal 211, and adjusts the level α of the limiter considering the noise level as the total noise level. This α value is provided to the limiter, the first summer 510 and the third subtractor 520 (step S6).

The first subtracted signal 141 input to the limiter 310 is limited to α level so that the limited signal 311 is output to the second subtractor 320 (step S7).

The first subtracted signal 141 and the signal 311 limited to the α level are input to the second subtractor 320, and the signal 311 limited to the α level is subtracted from the first subtracted signal 141. The second subtracted signal 321 as shown in FIG. 4E is output to the signal separator 410 (step S8).

The second subtracted signal 321 input to the signal separator 410 is a signal 411, in which a positive signal is separated according to a (±) sign, is output to the first summer 510, and a negative signal is separated. The received signal 412 is output to the third subtractor 520. The signal 411 separated from the positive signal inputted to the first summer 510 and the α value 221 provided from the noise level detector 220 are summed so that the first summed signal 511 is second summed. It is output to the machine 530. In addition, the third subtractor 520 subtracts the α value 221 provided from the noise level detector 220 from the input (-) signal-separated signal 412 to subtract the third subtracted signal 521 to the second summer. Output to step 530 (step S9).

The first summed signal 511 and the third subtracted signal 521 inputted to the second summer 530 are summed so that the second summed signal 531 as shown in FIG. 4F is third summed. It is output to the machine 540 (step S10).

The second summed signal 531 input to the third summer 540 and the video signal 131 of the contour-corrected low pass component are summed (step S11) to remove noise as shown in FIG. 4G. The video signal 541 of the contour corrected low pass component is output to the output terminal 103 (step S12).

As a result, the video image signal 102 input from the input terminal IN is subjected to video processing, contour correction after filtering the low frequency component of the video signal 111, and low contour corrected from the video signal 111. First subtract the video signal of the component. In addition, the video synchronization signal 211 of the video image signal 102 is extracted, and the video synchronization signal 211 passes through the noise level detector 220 to detect the noise level that is applied to the video synchronization signal 211 and the whole Consider noise level. The limit level α value 221 is adjusted using the noise level, and the limit value 310 is provided to the limiter 310, the first summer 510, and the third summer 520. After performing the function of limiting the first subtracted signal 141 to the α level, the signal separator 500 is second subtracted from the first subtracted signal 141 by the second subtracted signal 311. The signals are separated from each other and output to the first summer 510 and the third summer 520 according to the sign of the corresponding signal to add and subtract, and then add and subtract the signals from the noise level detector 220 to the first summer 510. The second value is added, the α value is subtracted by the third summer 520, and the first summed signal 511 and the third subtracted signal 521 are second summed by the second summer 530. When combined with the video signal 131 of the low-pass component whose contour is corrected to the second summed signal 531, the video image signal 541 from which white noise is removed is output. Therefore, it is possible to obtain an improved image quality by removing the white noise that comes upon viewing.

As described above, according to the present invention, the video signal input signal is subtracted from the low-end video signal contour correction to the signal of the video processor, the noise level of the synchronously separated signal is detected to adjust the limiter level and limit Inputting a value added to the sum and subtractor, subtracting the limited signal to the subtracted signal, subtracting and adding the signal through a signal separator, and synthesizing the low-pass video signal corrected to the summed signal and displayed on the screen By removing the white noise, an effect of reducing the back noise included in the television signal can be obtained.

Although this invention was demonstrated concretely by the said Example, this invention is not restrict | limited by this, A deformation | transformation and improvement are possible within the range of common knowledge of a person skilled in the art.

Claims (11)

(a) receiving a video image signal and subtracting the contour-corrected low pass component video signal and the video signal from the contour-corrected low pass component video signal to provide a first subtracted signal; (b) receiving the video image signal and detecting a noise level of the video synchronization signal to provide a limiter level α value; (c) receiving the first subtracted signal and subtracting the limited signal at α level to the first subtracted signal to provide a second subtracted signal; (d) receiving the second subtracted signal and separating a ± sign to provide a (+) signal separated signal and a (−) signal separated signal; And (e) the video having the low frequency component contour-corrected by removing the white noise by receiving the (+) signal separated signal, the (-) signal separated signal, the contour corrected low frequency component video signal and the limiting level α value. White noise removal method comprising the step of outputting a signal. The method of claim 1, wherein the step (a) comprises: (a-1) receiving the video image signal and providing a signal; (a-2) receiving the video signal and performing low pass filtering to provide a low frequency component video signal; (a-3) receiving a low frequency component video signal and compensating an edge to provide an edge corrected low frequency component video signal; And (a-4) subtracting the contour-corrected low-frequency component video signal from the video signal to output a first subtracted signal. The method of claim 1, wherein the step (b) comprises: (b-1) receiving the video image signal and providing a video synchronization signal as a synchronization signal; And (b-2) receiving the video image signal, detecting a noise level of the video synchronization signal, and outputting a limiter level α value. The method of claim 1, wherein the step (c) comprises: (c-1) receiving the first subtracted signal and limiting to the limiter level α to provide a limited signal; And (c-2) subtracting the limit signal at the? Level from the first subtracted signal to output a second subtracted signal. The method of claim 1, wherein the step (e) comprises: (e-1) receiving the sum of the (+) signal-separated signal and the limiting level alpha value and adding them to provide a first summed signal; (e-2) receiving and subtracting the (-) signal separated signal and the limiting level α value to provide a third subtracted signal; (e-3) receiving the first summed signal and the third subtracted signal and adding the sums to provide a second summed signal; And (e-4) inputting the contour corrected low pass component video signal and the second summed signal to add up to remove white noise to output a contour corrected low pass component video signal. How to remove noise. The contour-corrected low frequency component video signal 131 and the video signal 111 of the contour corrected low frequency component are subtracted from the video image signal 102 input from the input terminal IN. A low pass contour correction unit 100 for providing a first subtracted signal 141; A noise level detector (200) for receiving the video image signal (102) and detecting a noise level of the video synchronization signal (211) to provide a limiting level α value 221; A limiting unit 300 for receiving the first subtracted signal 141 and subtracting the signal 311 limited to the α level from the first subtracted signal 141 to provide a second subtracted signal 321. ; A signal separator 400 for receiving the second subtracted signal 321 to separate a ± sign to provide a (+) signal separated signal 411 and a (−) signal separated signal 412; And receiving the (+) signal-separated signal 411, the (-) signal-separated signal 412, and the contour-corrected low pass component video signal 131 to remove white noise, And an output unit (500) for outputting a video signal (541). The apparatus of claim 6, wherein the low-pass contour correcting unit comprises: a video processor 110 for receiving a video image signal 102 and outputting a video signal 111; A low pass filter 120 for low pass filtering the video signal 111 and outputting a low pass component video signal 121; An outline correction circuit 130 for edge-compensating the low pass component video signal 121 to output a contour corrected low pass component video signal 131; And a first subtractor 140 for outputting a first subtracted signal 141 by subtracting the video signal 131 of the low pass component whose contour is corrected from the video signal 111. . The apparatus of claim 6, wherein the noise level detecting unit comprises: a sync separator 210 for providing a video sync signal 211 from the video image signal 102; And a noise level detector (220) for sensing the noise level of the video synchronization signal (211) to provide a limiter level [alpha] value. The limiter of claim 6, wherein the limiting unit comprises: a limiter 310 for receiving the first subtracted signal 141 and limiting the limiter level to a limiter level α according to the noise level of the noise level detector 220; And a second subtractor 320 for outputting the second subtracted signal 321 by subtracting the signal 311 limited to the α level from the first subtracted signal 141. Circuit. The signal separating unit 400 receives the second subtracted signal 321 and separates a (±) signal to separate a (+) signal and a (-) signal. White noise canceling circuit, characterized in that it comprises a signal separator (410) for providing a signal (412). The method of claim 6, wherein the output unit 500 is configured to output the first summed signal 511 by receiving the sum of the (+) signal-separated signal 411 and the limiter level α value 221 and adding the sum. A first summer 510; A third subtractor 520 for receiving and subtracting the separated signal 412 and the limiter level α value 221 to provide a third subtracted signal 521; A second summer 530 for receiving the first summed signal 511 and the third subtracted signal 521 and adding the sum and providing a second summed signal 531; And a third summer outputting the contour corrected low pass component video signal 541 by inputting and combining the contour corrected low pass component video signal 131 and the second summed signal 531 to remove white noise. 540, characterized in that the white noise removing circuit.

Images