JP3218828B2 - Noise removal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise eliminator for reducing noise contained in a video signal of a camera-integrated VTR or the like.

[0002]

2. Description of the Related Art Conventionally, a recursive filter has been used for the purpose of removing noise from a video signal. In particular, it is essential to reduce the feedback coefficient of the recursive filter in the contour part in order to preserve the contour part. Hereinafter, a conventional noise elimination device configured by a recursive filter will be described.

FIG. 2 is a block diagram showing a conventional noise removing device. In FIG. 2, reference numeral 200 denotes an input terminal of a video input signal, 201 and 202 denote multipliers, 203 denotes a delay element for delaying one horizontal scanning period, 204 denotes an adder, 205 denotes a subtractor, 206 denotes a coefficient controller, and 207 denotes an output. Terminal.

[0004] The operation of the conventional noise elimination apparatus configured as described above will be described below. First, the video input signal that has passed through the input terminal 200 is
(0 ≦ k <1), the output of the multiplier 202 and the adder 2
04 and is output from the output terminal 207. This output signal is delayed by one horizontal scanning period by the delay element 203,
After being multiplied by k (0 ≦ k <1) in the multiplier 202, the adder 2
At 04, it is added to the output of the multiplier 201. At this time, if the value of k is large (for example, 0.8), the addition rate of the output signal delayed by one horizontal scanning period added by the adder 204 is increased. This means that the degree of smoothing is large and the noise reduction effect is large in a flat part. On the other hand, if the value of k is large in the outline, image quality failure such as color blur occurs.

[0005] Then, the difference between the video input signal and the output signal is calculated by a subtractor 205 to detect a contour portion, the contour signal is input to a coefficient controller 206, and the coefficient controller 206 determines the value of the feedback coefficient k in the contour portion. By reducing the size, the image quality breakdown at the contour portion is suppressed. As described above, the noise removal is performed without causing the image quality breakdown in the contour portion.

[0006]

However, in the above-mentioned conventional configuration, two multipliers are required, and when the input signal is used as a color difference signal to remove color noise, the color difference signal component is small at low illuminance and the S / S signal is small. When N is bad, there is a problem that sufficient noise removal is not performed or color bleeding occurs.

The present invention solves the above-mentioned conventional problems, and has a simple structure that does not require a multiplier, and performs noise elimination sufficient to eliminate noise without causing image quality breakdown such as color fringing even at low illuminance. It is intended to provide a device.

[0008]

In order to achieve this object, a noise elimination apparatus according to the present invention comprises a delay element and a first subtraction means.
, Second subtraction means, non-linear processing means, contour detection means
, Storage means, non-linear processing control means, and an output terminal.
And removes noise in the video signal using the color difference signal and the luminance signal.
The noise removing device, wherein the delay element comprises:
The output signal of the subtraction means is delayed by one horizontal scanning period,
The first subtraction means outputs the color difference signal and the output of the delay element.
Subtraction, and the non-linear processing means outputs the output of the first subtraction means.
Force, according to the output of the non-linear processing control means,
The output of the first subtraction means is corrected, and the second subtraction means
The color difference signal is subtracted from the output of the non-linear processing means,
Outputting an output signal to the output terminal and the delay element;
The contour detecting means calculates a luminance contour of the current line from the luminance signal.
Detecting the information, the storage means at least less than the current line.
Also stores the luminance contour information of the previous line,
The control means controls the current line output from the contour detection means.
Brightness contour information and at least the output of the storage means
The nonlinear processing is performed based on the luminance contour information of the previous line.
Output information on whether or not the part is a contour part to the processing means.
You.

[0009]

In this configuration, the outline component can be detected by taking the difference between the input signal and the output signal delayed by one horizontal scanning period by the first subtraction means, and the difference signal is subjected to nonlinear processing by bit shifting and subtraction in the nonlinear processing means. And the second
By subtracting the input signal from the input signal in the subtracting means and using the output as an output signal, a multiplier is not required, and noise can be removed while suppressing image quality failure such as color blur.

[0010]

【Example】

(Embodiment 1) Hereinafter, a noise removing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a noise removing apparatus according to a first embodiment of the present invention.

In FIG. 1, reference numeral 101 denotes a delay element that delays an output signal by one horizontal scanning period, and 102 denotes an input signal input from an input terminal 100, specifically, a video signal or a color difference signal, and an output of the delay element 101. A first subtraction means for performing a subtraction between the signals; a non-linear processing means for non-linearly processing the output of the first subtraction means; and a subtraction between the output of the non-linear processing means and the input signal from the input terminal. The subtraction means 105 is an output terminal for outputting the output of the second subtraction means 104.

The operation of the noise eliminator configured as described above will be described with reference to FIG. FIG. 3A shows the relationship between the input and output of the nonlinear processing means 103. d is an input, f (d) is an output, and th is a threshold. Now, when the absolute value of the input d is smaller than th / 2 (i), when it is smaller than th and larger than th / 2 (ii), t
h, the output is divided into three cases (iii), and the output at that time is kd and k by bit shift and subtraction, respectively.
(Th-d), 0 (k is a value in the range of 0 <k <1, for example, 0.75). By performing the non-linear processing on the input d in this manner, the same effect as that obtained by multiplying the input d by k shown in FIG. 3B is obtained.

Now, the input signal and the 1
When the output signal delayed in the horizontal scanning period is input and the absolute value of the difference output is smaller than th, the nonlinear processing means 1
03, a value equivalent to multiplying the difference output by k shown in FIG. 3 (B) is output, and is subtracted from the input signal by the second subtraction means 104, so that smoothing is performed and noise is removed. Is done. On the other hand, the absolute value of the difference output is t
If h is greater than or equal to h, 0 is output from the non-linear processing means 103, and the input signal is output as it is from the output terminal 105, and the contour is preserved.

Here, the reason why nonlinear processing is performed using the function shown in FIG. 3A will be described. Originally, since the image has line correlation, a small level difference between lines can be considered as noise. Therefore, a threshold value is provided for the difference value between the lines, and if the absolute value of the difference value is larger than the threshold value, it is determined to be a contour portion, and if smaller, the noise is determined to be noise. However, if the non-linear processing is performed using a function as shown in FIG. 3 (C), an image becomes unnatural because it is not smoothed before or after the threshold. Therefore, the output gradually decreases when the difference value exceeds th / 2, and becomes zero at the time of th, whereby the unnaturalness of the processed image can be avoided.

As described above, according to the present embodiment, a large noise removing effect is exhibited in a flat portion, and image quality breakdown such as color blur can be suppressed in a contour portion.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings. In the configuration of the second embodiment, as shown in FIG. 4, a luminance input terminal 401 for inputting a luminance input and a vertical contour component of a luminance signal input from the luminance input terminal 401 are added to the configuration of the first embodiment. A contour detecting unit 402 for detecting and detecting whether the contour is a flat portion or a flat portion, a non-linear processing control unit 403 receiving the output of the contour detecting unit 402 and controlling the non-linear processing unit 103
Has been added.

Now, a luminance signal is input from the luminance input terminal 401, and a luminance contour component is detected by the contour detecting means 402. If the luminance contour component is small, it is determined that the portion is flat.
The non-linear processing control means 403 outputs, for example, 0
Is output. At this time, the nonlinear processing control unit 403 controls the nonlinear processing unit 103 to perform the operation described in the first embodiment. On the other hand, if the luminance contour component is large, the contour detecting means 402 determines that the contour is a contour part, and outputs 1 of a 1-bit signal to the nonlinear processing control means 403.

At this time, the nonlinear processing control means 403
The nonlinear processing means 103 is controlled so that 0 is output from the nonlinear processing means 103. Here, the reason for controlling the nonlinear processing means using the luminance contour signal will be described. Originally,
The color difference signal has a narrow band and the contour is not clear. In addition, when the illuminance of the subject is low, the signal level difference at the contour part becomes small, and the signal does not reach the maximum threshold for performing the non-linear processing.
Color bleeding occurs. Therefore, the outline portion is detected by using the luminance outline signal having a wide band, and the non-linear processing control section 403 controls the non-linear processing section 103 to prevent color blur.

As described above, according to the present embodiment, even when the signal component of the color difference signal is small at the time of low illuminance, noise can be removed while suppressing the image quality breakdown at the outline.

(Embodiment 3) Next, a third embodiment of the present invention will be described with reference to the drawings. The configuration of the third embodiment is different from the configuration of the first embodiment as shown in FIG. 5 in that a luminance input terminal 401 for inputting a luminance input, a vertical contour component is detected from the output of the luminance input terminal 401, Contour detecting means 402 for detecting whether the part is a flat part or a flat part;
A storage unit 501 that processes the output of the contour detection unit 402 and stores the information for at least one horizontal scanning period, and a nonlinear processing control unit 502 that controls the nonlinear processing unit 103 based on the output of the contour detection unit 402 and the output of the storage unit 501. Has been added.

FIG. 6 shows the configuration of the storage means 501. Reference numeral 5010 denotes a delay element for delaying one horizontal scanning period, and reference numeral 5011 denotes a logical operation unit. Hereinafter, the operation of the storage unit 501 when storing luminance contour information for three lines will be described with reference to FIG.

A is the output of the delay element 5010 and represents the luminance contour information of the preceding three lines. If the bit length is 2 bits and there is a luminance contour part one line before, a is 01; It is 11 three lines before. b is the output of the logical operation unit 5011, and a is obtained by delaying b by one horizontal scanning period. c represents the luminance contour information of the current line as an output from the contour detecting means 402, and is 1 for a contour portion and 0 for a non-contour portion.

Now, when c = 0 and a = 00, since there are no contours in the current line and the previous three lines, b = 00, and this is output to the delay element 5010. When c = 0 and a ≠ 00, there is no contour in the current line, and there is a contour in any of the previous three lines, so that b = a + 1,
Output to delay element 5010.

On the other hand, when c = 1, there is an outline in the current line, so b = 01, and this is output to the delay element 5010. By delaying this b by one horizontal scanning period,
It can be stored whether or not a luminance contour portion exists in the line, and if so, what number is closest to the current line when viewed from the current line.

Using the luminance contour information a up to three lines before and the luminance contour information c of the current line stored by the above method,
By controlling the non-linear processing control means 403, the output of the non-linear processing means 103 is set to 0 for four lines if there is a luminance contour portion, and the color blur is more reliably prevented without performing smoothing.

As described above, according to the present embodiment, even when the signal component of the color difference signal is small at the time of low illuminance, noise can be removed while suppressing the image quality breakdown at the outline.

(Embodiment 4) Next, a fourth embodiment of the present invention will be described with reference to the drawings. The configuration of the fourth embodiment is, as shown in FIG. 8, composed of a delay element 801 for delaying the output signal and the output of the luminance contour information generating means 802 by one horizontal scanning period, an output of the luminance contour detecting means 402 and a delay element 801. A luminance contour information generating unit 802 that newly generates luminance contour information from a luminance contour information output, the input terminal 100 described in the third embodiment, and the first subtraction units 102 and 10.
4, a nonlinear processing means 103, a luminance input terminal 401, a contour detection means 402, a nonlinear processing control means 502, and an output terminal 105.

The operation of the noise eliminator configured as described above will be described. FIG. 9 shows a signal delayed by the delay element 801. Luminance contour information indicating at least the number of lines before the luminance contour exists at the MSB side of the video signal is inserted. This delay element 80
Only the video signal from 1 is output to the first subtraction means 102,
The luminance contour information is output to the nonlinear processing control means 502 and the luminance contour information generating means 802. The luminance contour information generating means 802 performs the same operation as the logical operation unit 5011 in the third embodiment, newly generates luminance contour information, and
Output to Other operations are the same as in the third embodiment.

As described above, according to the present embodiment, even when the signal component of the color difference signal is small at the time of low illuminance, it is possible to perform noise removal while suppressing the image quality breakdown at the outline.

Although k = 0.75 in the first embodiment, other values may be selected (however, values obtained by bit shift and subtraction). Further, in the third embodiment, the number of storage lines is three, but another number of lines may be selected. However, in this case, the number of bits of the luminance contour information is the number of bits according to the number of storage lines. Further, in the fourth embodiment, the luminance contour information is represented by the M of the video signal.
Although inserted on the SB side, it is not limited to this and may be inserted in another place.

[0031]

As described above, according to the present invention, the difference signal between the output signal delayed by one horizontal scanning period and the input signal is subjected to non-linear processing by bit shift and subtraction, and then subtracted from the input signal and output. And a noise elimination device capable of eliminating noise without using a multiplier and suppressing image quality deterioration such as color fringing.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a conventional noise elimination device.

3A is a diagram showing a relationship between an input and an output of the nonlinear processing means in the first embodiment. FIG. 3B is a diagram showing a relationship between the input and an apparent feedback coefficient k. FIG. FIG. 9 is a diagram showing an input / output relationship of a non-linear processing unit for comparison with the embodiment.

FIG. 4 is a block diagram of a noise removing apparatus according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a noise removing device according to a third embodiment of the present invention.

FIG. 6 is a block diagram of a storage unit according to a third embodiment of the present invention.

FIG. 7 is a flowchart showing the operation of the logical operation unit;

FIG. 8 is a block diagram of a noise removing apparatus according to a fourth embodiment of the present invention.

FIG. 9 is a diagram showing a signal delayed by the delay means.

[Explanation of symbols]

 Reference Signs List 100 input terminal 101 delay element 102 first subtraction means 103 nonlinear processing means 104 second subtraction means 105 output terminal

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yukihiro Tanizoe 1006 Kazuma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-69269 (JP, A) JP-A-61 JP-A-228792 (JP, A) JP-A-58-96484 (JP, A) JP-A-59-83492 (JP, A) JP-A-2-181590 (JP, A) JP-A-5-160671 (JP, A) JP-A-4-315391 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 9/64 H04N 5/21

Claims (2)

(57) [Claims] And 1. A contour detection unit, a nonlinear processing control means, storage means, a delay element, a first subtraction means, second subtracting means, the color difference signals and a luminance signal and a nonlinear processing means a noise removing apparatus for removing noise of a video signal by using the contour detecting unit, the current line from the luminance signal is the luminance contour information extracted whether contour, before Symbol storage means, current single luminance contour information up past one line before the luminance contour information line that already stored
And encodes the result into one horizontal scanning period.
The nonlinear processing control means outputs the luminance contour information of the current line.
From the information and the output of the storage means whether or not the contour portion exists
The delay element outputs the output signal of the second subtraction means after delaying by one horizontal scanning period, and the first subtraction means subtracts and outputs the color difference signal and the output of the delay element. The non-linear processing means, when the contour portion does not exist in the extraction result of the non-linear processing control means, outputs the output result of the first subtraction means by performing non-linear processing, if there is, stops the output, The noise removing device according to claim 2, wherein the second subtraction unit subtracts the output result of the non-linear processing unit from the color difference signal and outputs the result. 2. The noise removing apparatus according to claim 1, wherein said storage means stores information indicating the presence of a luminance contour a predetermined number of lines before the current line.