JPH10257356A - Noise-removing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noise-removing device which has both the effect for suppressing an afterimage of moving part and a noise-removing effect in a comparatively simple circuit configuration. SOLUTION: In a noise removing device having cyclic noise removing circuits 2-6 and continuous noise removing circuit 9 based on intra-field or intra-frame processing, this device is provided with a motion detecting means 5 for detecting the moving amount of signal at the cyclic noise-removing circuit and a cyclic amount control means 4 is provided for controlling the cyclic amount through the moving amount, detected by this motion detecting means 5. Furthermore, the noise-removing circuit based on intra-field or intra-frame processing is provided with a noise-removing amount control means 29 for controlling the noise-removing amount through the moving amount which is detected by the motion detecting means 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal noise elimination apparatus, and more particularly to a noise elimination apparatus that eliminates the effect of an afterimage in a moving image portion of a video signal.

[0002]

2. Description of the Related Art In a recursive noise elimination apparatus which removes noise by averaging output signals processed in the past, an afterimage occurs in a moving image portion due to its configuration. Conventionally, the afterimage in the moving image portion has been unavoidable, and the noise removal effect has been emphasized, and the noise removal has been abandoned to some extent, or the noise removal has been performed only in the stationary portion.

FIG. 5 is a circuit block diagram of a conventional cyclic noise elimination device. In FIG. 5, reference numeral 101 denotes a video signal input, and 107 denotes an output after noise removal. The difference between the video signal input from the input terminal 101 and the past processed image signal output from the field or frame memory 106 is calculated by the adder 102, and the difference signal is input to the multiplier 104 and the motion detector 105. Is done. At a pixel position where the level of the difference signal is larger than the set value, the motion detector 105 determines the pixel as a motion part, and sets the value of K related to the multiplier of the multiplier 104 to 0.
It has a function to control it to approach.

[0004] The difference signal multiplied by the multiplier 104 is added to a past output signal output from the field or frame memory 106 and output as an output 107.

As shown in FIG. 5, in such a cyclic noise elimination device, the value of K is set to the maximum value in the stationary portion, and the noise elimination effect is maximized. In addition, the value of K is 0 in a portion determined to be a motion, and the noise removing effect is completely lost. The occurrence of an afterimage depends on the performance of the motion detector 105.

[0006]

As described above, in the conventional cyclic noise elimination apparatus, since an addition process is performed with a past image signal, an afterimage is generated in a moving portion. Therefore, conventionally, noise removal was abandoned in the moving part.

SUMMARY OF THE INVENTION It is an object of the present invention to solve this problem and realize a noise elimination device having a relatively simple circuit configuration and having both an effect of suppressing an afterimage of a moving part and a noise elimination effect.

[0008]

In order to achieve the above object, the present invention removes noise by averaging a current signal and a previously processed output signal stored in a memory on a field or frame basis. A noise detection circuit that detects a signal motion amount in the cyclic noise elimination circuit and a noise elimination circuit having a noise elimination circuit that performs subsequent field or intra-frame processing. Means for controlling the amount of repetition based on the amount of motion detected by the means, and a noise removal circuit for controlling the amount of noise removal based on the amount of motion detected by the motion detection means in the noise removal circuit by the field or intra-frame processing. Volume control means.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a noise elimination device according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of a noise elimination device according to the present invention. In this embodiment, a cyclic noise elimination circuit block (hereinafter referred to as a cyclic noise reducer)
And a noise removing circuit block (hereinafter referred to as a field or intra-frame processing noise reducer) by coring processing for removing noise by field or intra-frame processing. The coring process is a function of suppressing an output to 0 by regarding an input signal having a certain level or less as noise.

The cyclic noise reducer and the field or intra-frame processing noise reducer are connected in cascade, and a portion determined to be stationary by the motion detector is subjected to noise reduction by the cyclic noise reducer. On the other hand, in the field or intra-frame processing noise reducer, the coring dead band width is set to 0 for a portion determined to be still by the motion detector, and no processing is performed.

In addition, in the portion determined to be motion by the motion detector, the value of K is set to 0 in the cyclic noise reducer and no noise is removed, and the noise is determined to be motion in the field or intra-frame processing noise reducer. Noise removal is performed on the portion by setting the dead band width due to coring to the maximum value.

In FIG. 1, reference numeral 1 denotes an input terminal of a video signal, and reference numeral 11 denotes an output terminal of a video signal from which noise has been removed. The cyclic noise reducers are adder 2 and adder 3
, A multiplier 4, a motion detector 5, and a field or frame memory 6. The field or intra-frame processing noise reducer includes a low-pass filter 7, a high-pass filter 8, a coring processor 9, and an adder 10.

Here, an embodiment of the internal configuration of the motion detector 5 will be described with reference to FIG. In FIG.
Is an input terminal to the motion detector 5. This input terminal 21
The output of the adder 2, which is a difference signal between the video input signal 1 of FIG.

From this difference signal, a low-pass filter 22
Then, the high-frequency noise is removed, and is converted into a positive value by the absolute value circuit 23 and input to the comparator 25. The other input 24 of the comparator 25 receives a preset comparison level. The value of this comparison level is set so that the difference level of the part that is determined to be a moving part exceeds the comparison level.

The output of the comparator 25 is a 1-bit signal, and 1 is output in a portion determined to be moving and 0 is output in a portion determined to be stationary. The output of the comparator 25 is input to a low-pass filter 26. When the low-pass filter 26 has seven taps, the output of the low-pass filter 26 has three bits, and it is detected how many pixels among the seven surrounding pixels have been determined to be moving.

The output of the low-pass filter 26 is input to a decoder 27. The decoder 27 outputs an output 28 as a value of K corresponding to the output of the motion detector 5 in FIG. 1 in accordance with the 3-bit output of the low-pass filter 26.

In this decoder 27, the output of the low-pass filter 26 is 0, 1, 2, 3, 4, 5, 6,
7, the corresponding outputs are １ ／, ８, ８, ４, ４, ８, 1
/ 8, 0 is output. The function of this decoder 27 is ROM
It can be realized by associating input and output numerical values by using a logic circuit. With this level correspondence, motion determination is performed smoothly, and deterioration of image quality due to abrupt noise removal can be suppressed.

In FIG. 1, the output of the motion detector 5 is input to a multiplier 4 and a coring processor 9. A high-pass filter 8 is provided in front of the coring processing unit 9 so that the coring process is performed only on the high-frequency component, thereby suppressing the fluctuation of the DC component.

The low-pass filter 7 extracts a low-frequency signal from which noise is not removed. Therefore, low-pass
The filter 7 and the high-pass filter 8 have complementary characteristics, and are returned to flat frequency characteristics by the adder 10.

[0020] Here, the transfer function H2 of the transfer functions H1 and high-pass filter 8 of the low-pass filter 7 are each ^{H1 = (1 + Z -1)} 2/4 H2 = (1-Z -1) 2/4.

The coring processing section 9 is provided with a dead zone for setting the output level to 0 with respect to a certain level range of the input signal, and controls the range of this dead zone by the output of the motion detector 5.

In the example of FIG. 1, the following is set according to the value of K. For example, the output of the high-pass filter 8 is 8 bits and has 256 gradations, and the value of K is 、,
When the values are 3/8, 1/4, 1/8, and 0, the ranges of the dead zones correspond to 0, 2, 5, 7, and 10, respectively.
That is, when K = １ ／, it is considered that the stationary part is completely stationary. In that case, the recursive noise reducer produces the most effect, and the dead zone of the coring processing unit 9 becomes 0 and the coring processing is performed. The effect of noise removal by the processing does not occur. When K = 0, it is considered to be a completely moving part, and there is no effect of the cyclic noise reducer, but the dead zone of the coring processing unit 9 is 10 at the maximum, and the noise removal effect of this part is Be the largest.

In the intermediate stage, the processing effect of the cyclic noise reducer and the processing effect of the coring noise reducer are mixed. In this way, by switching between the two noise reducers smoothly in a stepwise manner, it is possible to prevent the image quality from deteriorating due to a sudden change.

The low-pass filter 7 and the high-pass filter
By changing the configuration of the filter 8, it is also possible to separately set the frequencies at which the processing effect of the recursive noise reducer and the processing effect of the field or intra-frame processing noise reducer occur.

FIG. 3 shows a circuit block diagram of such an example. In FIG. 3, the recursive noise reducer exerts its noise reduction effect in all frequency bands of the video signal, but the noise reducer by coring process performs noise reduction only for the high-frequency signal passing through the high-pass filter 38. Generates a removal effect. Here, low-pass filter 3
7 and the transfer function H4 of the high-pass filter 38 are the transfer function H of the low-pass filter 7 of FIG.
1 and highpass transmission filter 8 function H2 same respectively as ^{H3 = (1 + Z -1)} 2/4 H4 = (1-Z -1) is ^2/4.

By doing so, the frequency band of the noise reduction effect can be set for each of the noise reducers, and the noise reduction effect can be more appropriately optimized.

Next, an embodiment of a noise eliminator provided with a noise reducer by horizontal and vertical coring processing in addition to a noise reducer for processing in a field or in a frame will be described with reference to a circuit block diagram of FIG. I do.

In FIG. 4, reference numeral 51 denotes a video signal input terminal, and reference numeral 65 denotes a video signal output terminal from which noise has been removed. 5A is a block of a cyclic noise reducer, 5B is a block of a noise reducer by horizontal coring processing, and 5C is a block of a noise reducer by vertical coring processing. The cyclic noise reducer 5A includes an adder 52, an adder 55, and a multiplier 53.
And a motion detector 54 and a field or frame memory 56.

Also, noise and noise due to horizontal coring processing
The reducer 5B includes a low-pass filter 57, a high-pass filter 58, a coring processing unit 59, and an adder 60. Transfer function H5 and transfer function H of low-pass filter 57 and high-pass filter 58
6 They Like ^{H5 = (1 + Z -1)} 2/4 H6 = (1-Z -1) of FIG. 1 and FIG. 3 is a ^2/4.

The noise and noise generated by the vertical coring process
The reducer consists of a low-pass filter 61 and a high-pass filter.
Filter 62, coring processing unit 63, adder 64
It is composed of Transfer function H7 and transfer function H8 lowpass filter 61 and high pass filter 62 is ^{H7 = (1 + Z -H)} 2/4 H8 = (1-Z -H) 2/4. Here, H is the horizontal synchronization pulse period.

The recursive noise reducer block 5A of FIG. 4 and the noise reducer block 5B of the horizontal coring process perform exactly the same functions as the embodiment of FIG. On the other hand, in the noise reducer block 5C by the vertical coring processing, the vertical frequency is separated by the low-pass filter 61 and the high-pass filter 62, and the high-pass
The vertical high frequency component separated by the filter 62 is subjected to noise removal by a coring processing unit 63. By this processing, noise continuing in the vertical direction can be removed by coring processing.

The coring processing unit 63 is the same as the horizontal coring processing unit 59, and has the cyclic noise reducer block 5.
The dead band width is controlled by the K value 66 from the A motion detector 54. In this case, the correspondence of the dead zone width to the value 66 of K is set independently of the horizontal coring processing unit 59 so that the effect of noise removal is optimized.

With the above configuration, the noise elimination device of the present invention provides a noise reduction device that performs a coring process or the like on a field or an intra-frame processing noise even for a moving part which has given up noise elimination by the cyclic noise reducer.・
Noise can be reduced by the reducer.

On the other hand, in the field or intra-frame processing noise reducer, the signal component is slightly lost, but if this processing is performed on the entire screen, the frequency characteristics will be degraded. Since the sensitivity of the moving part is lower than that of the stationary part, if the field or intra-frame processing noise reducer operates only in the moving part as in the present invention, the stationary part is the noise in the recursive noise reducer. No signal loss occurs due to the elimination, and only the moving parts that are difficult to detect with the human eye are subjected to noise processing using a field or intra-frame processing noise reducer with no afterimages and loss of signal components. Therefore, there is no afterimage and no deterioration in image quality is observed.

Also, MPEG (Moving Picture coding)
Expert Group) For a video signal that has been subjected to the encoding process proposed by the authors, random noise that is likely to occur in the stationary part is removed by a cyclic noise reducer, and blocks that are likely to occur in the moving image part With respect to noise, noise can be removed by a field or intra-frame processing noise reducer, and high-frequency noise components generated at an edge portion of block processing such as MPEG can be removed to improve image quality.

[0036]

As described above, according to the first aspect of the present invention, noise is removed by averaging a current signal and a previously processed output signal stored in a memory on a field or frame basis. Motion detection means for detecting the amount of signal motion in the cyclic noise elimination circuit in a noise elimination device having a recursive noise elimination circuit and a subsequent noise elimination circuit by field or intra-frame processing; And a noise amount control means for controlling a noise amount based on the motion amount detected by the motion amount detected by the motion amount detected by the motion detection means. Means is provided. In this way, by providing the cyclic noise elimination circuit and the noise elimination circuit by the field or intra-frame processing, the cyclic type noise elimination circuit is not accompanied by the deterioration of the frequency characteristic in a portion having a small amount of motion according to the amount of motion of the signal. Uses a noise elimination circuit, uses a noise elimination circuit by field or intra-frame processing that does not generate an afterimage in a part with a large amount of motion, and combines the effect of suppressing the afterimage of a moving part with the noise elimination effect with a relatively simple circuit configuration It is possible to realize a noise removing device having the same.

According to a second aspect of the present invention, the noise elimination circuit based on intra-field or intra-frame processing includes a noise elimination circuit based on horizontal coring processing. This makes it possible to remove a signal of a certain level or less as noise in the horizontal processing, thereby realizing noise removal that does not generate an afterimage even in a moving part.

The invention according to claim 3 is characterized in that the noise elimination circuit based on intra-field or intra-frame processing includes a noise elimination circuit based on vertical coring processing. As a result, a signal having a certain level or less can be removed as noise in the processing in the vertical direction, and noise removal that does not generate an afterimage even in a moving part can be realized.

According to a fourth aspect of the present invention, the noise elimination circuit based on intra-field or intra-frame processing includes a noise elimination circuit based on horizontal coring processing and a noise elimination circuit based on vertical coring processing. This allows
Signals of a certain level or less can be removed as noise by horizontal and vertical processing, and noise removal that does not generate an afterimage even in a moving part can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a noise elimination device according to the present invention.

FIG. 2 is a block diagram showing an example of a motion detector used in the noise elimination device of FIG. 1;

FIG. 3 is a block diagram of another embodiment of the noise elimination device of the present invention.

FIG. 4 is a block diagram of another embodiment of the noise elimination device of the present invention.

FIG. 5 is a block diagram of a conventional example of a noise removing device.

[Explanation of symbols]

1, 31, 51... Input terminals, 2, 3, 10, 32, 3
3, 40, 60, 64 Adder, 4, 34 Multiplier, 5, 35, 54 Motion detector, 6, 36, 56
... field or frame memory, 7, 22, 2
6, 37, 57, 61 ... low-pass filter, 8, 3
8, 58, 62 ... high-pass filter, 9, 39, 5
9, 63 ... coring processing unit, 11, 41, 65 ...
Output terminal, 21: Motion detector input terminal, 23: Absolute value circuit, 24: Comparison level input, 25: Comparator, 27: Decoder, 5A: Cyclic noise reducer block, 5B: Block of noise reducer by horizontal coring processing, 5C ... Block of noise reducer by vertical coring processing.

Continuation of the front page (72) Inventor Shoji Shiomoto 6-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (4)

[Claims] 1. A cyclic noise elimination circuit for averaging a current signal and a previously processed output signal stored in a memory on a field or frame basis to remove noise, A noise removal device having a noise removal circuit by processing, wherein: a movement detection means for detecting a movement amount of a signal in the cyclic noise removal circuit; and a recursive amount control for controlling the recursive amount based on the movement amount detected by the motion detection means. A noise elimination device comprising: a noise elimination control unit for controlling the noise elimination amount by the motion amount detected by the motion detection unit in the noise elimination circuit by the field or intra-frame processing. . 2. The noise eliminator according to claim 1, wherein the noise elimination circuit based on the intra-field or intra-frame processing includes a noise elimination circuit based on a horizontal coring process. 3. The noise eliminator according to claim 1, wherein the noise elimination circuit based on the intra-field or intra-frame processing includes a noise elimination circuit based on a vertical coring process. 4. The noise elimination circuit according to claim 1, wherein the noise elimination circuit based on the intra-field or intra-frame processing includes a noise elimination circuit based on a horizontal coring process and a noise elimination circuit based on a vertical coring process. apparatus.