JPH02158282A - Adaptive type noise suppressor - Google Patents

Abstract

PURPOSE:To reduce the appearance of the edge of an object with low level difference between frames as an after-image on a screen by detecting an edge from a video signal of one preceding frame for an input signal, and prohibiting noise suppression in the neighborhood of the edge in the video signal of one preceding frame. CONSTITUTION:The suppressor is comprised of an input terminal 1, a switching circuit 2, a frame memory 3, a delay circuit 4, a first subtraction circuit 5, a fixed memory circuit 3, a second subtraction circuit 7, an edge detection circuit 8, and a detecting signal extension circuit 9. And the edge is detected by the video signal of one preceding frame, and the noise suppression in the neighborhood of the edge in the video signal of one preceding frame is prohibited. In such a way, it is possible to reduce the appearance of the edge of the object generating the low level difference between the frames as the after-image on the screen.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a television receiver.

The present invention relates to a noise suppression device that suppresses noise in a video signal.

[Prior Art] FIG. 10 is a block diagram showing the configuration of a generally considered conventional noise suppression device. In FIG. 1, (1)
is an input terminal for inputting a digital video signal, (3) is a frame memory for delaying the noise-suppressed video signal by one frame, and (5) is a first subtraction circuit, which is input from the input terminal (1). frame memory (3
) is subtracted from the output video signal. (6) is a fixed memory circuit which inputs the difference signal output from the first subtraction circuit (5), converts this signal with non-linear characteristics, and outputs a general press signal. (7) is a second subtraction circuit that subtracts the noise suppression signal output from the fixed storage circuit (6) from the video signal input from the input terminal (1). (10) is an output terminal, which outputs the noise-suppressed video signal output from the subtraction circuit (7) to the outside.

FIG. 11 is a diagram showing the input/output characteristics of a fixed memory circuit in a conventional noise suppression device.

A conventional noise suppression device is configured as described above.

The video signal (101) input from the input terminal (1) is.

It is input to the first and second subtraction circuits (5) and (7). Further, the first subtraction circuit (5) is also inputted with a video signal (102) in which the noise described in f& is suppressed and delayed by one frame. The first subtraction circuit (5) converts the video signal (101) input from the input terminal (1) into the frame memory (
3) Subtract the output video signal (102) from
A minute signal (103) is output. The fixed memory circuit (6) is
The difference signal (103) is inputted, the difference signal is converted with input/output characteristics as shown in FIG.
04).

The second subtraction circuit (7) subtracts the noise suppression signal (104) output from the fixed storage circuit (6) from the video signal (101) input from the input terminal (1), so that the noise is suppressed. A video signal (105) is output. Then, the frame memory <3) stores the video signal (1) in which this noise has been suppressed.
05) is input, and outputs a video signal (102) delayed by one frame and with noise suppressed. In addition, the output terminal (10
) outputs the noise-suppressed video signal (105) to the outside. This suppresses low-level noise mixed into the video signal.

[Problem to be solved by the invention] In the conventional noise suppression device as described above, when one image changes scene, the edges of objects with small level differences between frames appear on the screen as afterimages. was there.

This invention was made to solve this problem, and detects edges from the video signal one frame before the input video signal, and prohibits noise suppression around edges in the video signal one frame before. by or 1
By reducing the amount of noise suppression around edges in the video signal before the frame according to the magnitude of the edge detection signal.

An object of the present invention is to obtain an adaptive noise suppression device that reduces the appearance of edges of objects with small level differences between frames as afterimages on the screen.

[Means for Solving the Problems] An adaptive noise suppression device according to the present invention receives a digital video signal as an input and uses a frame memory.

A noise suppression device that suppresses noise in the video signal using a subtraction circuit and a fixed storage circuit includes an edge detection circuit that detects edges of the video signal, and an edge signal detected by the edge detection circuit that is horizontally and vertically This device includes a detection signal expansion circuit that expands in the direction, and a switch circuit that switches between an input video signal and a noise-suppressed video signal using the output signal of the detection signal expansion circuit.

This is an adaptive noise suppression device according to another invention.

An edge detection circuit that detects edges of the video signal in a noise suppression device that receives a digital video signal and suppresses noise in the video signal using a frame memory, a subtraction circuit, and a fixed storage circuit.

A detection signal expansion circuit that expands the edge signal detected by this edge detection circuit in the horizontal and vertical directions, and an input video signal and a video signal with noise suppressed depending on the magnitude of the output signal of this detection signal expansion circuit. It is equipped with a mixing circuit that makes the mixing ratio variable.

[Operation] In the present invention, edges are detected from the video signal one frame before the input signal, and noise suppression around edges in the video signal one frame before is prohibited.
To reduce the appearance of edges of objects with small level differences between frames as afterimages on the screen.

In this other invention, edges are detected from a video signal one frame before the input signal, and the amount of noise suppression around edges in the video signal one frame before is reduced in accordance with the magnitude of the edge detection signal. This reduces the appearance of edges of objects with small level differences between nine frames as afterimages on the screen.

[Embodiment] FIG. 1 is a block diagram showing the configuration of a noise suppression device according to an embodiment of the present invention.

(1) is an input terminal for inputting digital video signals.

(2) is a switch circuit that switches between the video signal input from the input terminal (1) and the noise-suppressed video signal output from the second subtraction circuit (7).

(3) is a frame memory whose input side is connected to the switch circuit (2), and delays the video signal in which the TA sound has been suppressed by one frame. (4) is a delay circuit,
Adjust the delay amount of the video signal output from the frame memory (3). (5) is a first subtraction circuit that subtracts the video signal output from the delay circuit (4) from the video signal input from the input terminal (1). (6) is a fixed storage circuit to which the difference signal output from the first subtraction circuit (5) is input.

This signal is converted with nonlinear characteristics and a noise suppressed signal is output. (7) is a second subtraction circuit, which has an input terminal (1
) The noise suppression signal output from the fixed storage circuit (6) is subtracted from the video signal input from the fixed storage circuit (6).

(8) is an edge detection circuit, which is a frame memory (3
) detects edges in the horizontal and vertical directions of the video signal output from the video signal. (9) is a detection signal expansion circuit that expands the edge detection signal output from the edge detection circuit (8) in the horizontal and vertical directions. (10) is an output terminal, which outputs the noise-suppressed video signal output from the switch circuit (2) to the outside.

In the adaptive noise suppression device configured as above,
The video signal (201) input from the input terminal (1) is
It is input to the switch circuit (2) and the first subtraction circuit (5). The first subtraction circuit (5) also receives a video signal (202
> is also input. The first subtraction circuit (5) has an input terminal (
1) from the video signal (201) input from the delay circuit (
4) Subtracts the output video signal (202) and outputs a difference signal (203>).The fixed storage circuit (6) inputs the difference signal (203) and, as in the conventional example, The difference signal is converted with the input/output characteristics as shown, and outputted as a noise suppression signal (204).The second subtraction circuit (7) converts the video signal (201) input from the input terminal (1) into a fixed storage circuit. (6) The noise suppression signal (20
4) and a noise-suppressed video signal (205) is output. The switch circuit (2) receives an edge detection signal (209) output from a detection signal extension circuit (9) which will be described later.
If there is an edge detection signal (209), the video signal (201
) and if there is no edge detection signal (209),
The noise-suppressed video signal (205) output from the second subtraction circuit (7) is selected. This is then stored as a noise-suppressed video signal (206) in the frame memory (3).
) and the output terminal (10). The frame memory (3) delays the noise-suppressed video signal (206) by one frame, and outputs a one-frame delayed, noise-suppressed video signal (207). The edge detection circuit (8) receives the video signal (20
7) Detect horizontal and vertical directions.

For example, a circuit as shown in FIG. 2 can be considered as this circuit. Video signal (207) output from frame memory (3)
is a 1-line delay circuit (801) and an adder circuit (80
3) is input. This one line delay circuit (801) delays the video signal (207) by one line and outputs the video signal (301) as shown in FIG. 4(b). The 1-line delay circuit (802) delays the video signal (301) output from the 1-line delay circuit (801) by 1 line, and outputs the video signal (302) as shown in FIG. 4(c). The addition circuit (803) is.

The video signal (207) and the video signal (302> output from the 1-line delay circuit (802>) are added, and the result shown in FIG. 4(d) is
A video signal (303) as shown in FIG.

The 1/2 times circuit (804) multiplies the video signal (303) outputted from the adder circuit (803) by 1/2, as shown in FIG. 4(e).
A video signal (304) as shown in FIG.

The subtraction circuit (805) converts the video signal (301) output from the 1-line delay circuit (801) into a 1/2 times circuit (80
4) Subtract the output video signal (304) from the fourth
An edge signal (305) as shown in Figure (f) is output. Vertical machining/sodging is detected by the operation of the circuits (801) to (805) described above. 1 sample delay circuit (80
6) is delay assimilation for alignment with horizontal edge detection, which will be described later, and delays the edge signal (305) output from the subtraction circuit (805) by one sample, and outputs the edge signal (306). Next, the one-sample delay circuit (807) delays the video signal (301,) output from the one-line delay circuit (801) by one sample, resulting in a video signal (307,) as shown in FIG. 5(b). ) is output. 1
The sample delay circuit (808) is a one-sample delay circuit (808).
07) is delayed by one sample to produce a video signal (308) as shown in Figure 5(c).
Output. The adder circuit (809) is a one-line delay circuit (
The video signal (301) output from the 1-sample delay circuit (801) and the video signal (308) output from the 1-sample delay circuit (808)
), and the video signal (3
09) is output. 17' The double circuit (810) converts the video signal (309) output from the 5 adder circuit (809) into 1
/2 times the video signal (310
) is output. The subtraction circuit (811) extracts 1 from the video signal (307) output from the 1 sample delay circuit (807).
The video signal (310) output from the y2x circuit (810)
), the edge signal (3
Outputs 1,1>. The above-mentioned times n (807) to (811
) to detect edges in the horizontal direction. (7) The fixed memory circuit (812) includes a 1-sample retard circuit (
The edge signal (306) outputted from the subtractor circuit (806), for example, the edge signal shown in FIG.
For example, an edge signal as shown in FIG. 6(e) is input.

The fixed storage circuit (812) determines the presence or absence of edges in the horizontal and vertical directions using threshold values as shown in FIGS. 6(a) and 6(c). Then, edges in the horizontal and vertical directions as shown in FIG. 6(b) and (d) are detected, and the logical sum of these is taken as an edge detection signal (208>), which is output as the zero-order detection signal. The expansion circuit (9) expands the edge detection signal (208) output from the edge detection circuit 1 (8) in the horizontal and vertical directions and outputs it to the switch circuit (2) as an edge detection signal (209). For example, the circuit configuration may be as shown in Figure 3.Edge detection circuit (
The edge detection signal (208> output from 8) is input to the 1-line delay circuit (901) and the OR circuit (903>.
208) is delayed by one line, and the edge detection signal (401) is
Output.

1 line delay circuit (902> is 1 line delay circuit (90
The edge detection signal (401) output from 1) is delayed by one line, and an edge detection signal (402) is output. The OR circuit (903) receives the edge detection signal (208), the edge detection signal (401) output from the 1-line delay circuit (<901), and the edge detection signal (402) output from the 1-line delay circuit (902). ) are input, the logical sum of these is taken, and an edge detection signal <403) is output. The edge detection signal (403) outputted from the OR circuit (903) is output from the primary OR circuit (903) in which an edge detection signal expanded in the vertical direction is obtained by the operation of the circuits (901) to (903) described above. ) and OR circuit (906)
is input. The 1-sample delay circuit (904) receives the output signal (40) from the OR circuit (903).
3) is delayed by one sample, and an edge detection signal (404) is output. The 1 sample delay circuit (905) receives the edge detection signal (4) output from the 1 sample delay circuit <904).
04) is delayed by one sample, and the edge detection signal (405) is
Output. OR circuit <906) is. OR circuit (903
), an edge detection signal (404''I) output from the 1-sample delay circuit (904), and an edge detection signal <405) output from the 1-sample delay circuit (905). are input, their logical sum is taken, and an edge detection signal (209) is output. By the operation of the circuits (904) to (906) described above, an edge detection signal expanded in the horizontal direction is obtained. When the edge detection signal (209> is input to the circuit (2), the switch circuit (2) operates as described above, and there is an edge signal, the output terminal (10) is connected to the input terminal (1).
If there is no edge signal, the noise-suppressed video signal output from the second subtraction circuit (7) is output. Further, the delay circuit (4) compensates for the delay time of the edge detection circuit (8) and the detection signal expansion circuit (9).

Also, by providing a mixing circuit (2a) as shown in Fig. 7 in place of the switch circuit (2), it is possible to reduce the appearance of edges of objects with small level differences between frames on the screen as afterimages, as described above. can. In this case, if the edge detection signal (209) is large, the output terminal (10) outputs the video signal (201) input from the input terminal (1).
A video signal (206) with a large mixing ratio and a reduced amount of noise suppression is output, and an edge detection signal (209) is output.
If is small, the mixing ratio of the noise-suppressed video signal (205) output from the second subtraction circuit (7) is increased to output a video signal (206>) in which the amount of noise suppression is increased.

Furthermore, in the case of another embodiment, the maximum value circuit (903a), (906
a) is provided. In this case, the fixed memory circuit (
The edge signal (306) output from the 1-sample delay circuit (806) is input to 812), and the edge signal (311) output from the subtraction circuit (811) is also input. The fixed storage circuit (812>) stores a horizontal edge signal (306).

Take the maximum value of the vertical edge signal (311).

For example, an operation is performed in which an edge signal is converted with input/output characteristics as shown in FIG. 9, and an edge detection signal (208) is output.

When one image undergoes a scene change by any of the operations in the embodiments described above, edges of objects with small level differences between frames are prevented from appearing on the screen as afterimages.

[Effects of the Invention] As described above, the present invention provides a noise suppression device that receives a digital video signal as input and suppresses noise in the video signal using a frame memory, a subtraction circuit, and a fixed storage circuit. An edge detection circuit that detects edges, a detection signal expansion circuit that expands the edge signal detected by this edge detection circuit in the horizontal and vertical directions, and the output signal of this detection signal expansion circuit suppresses the input video signal and noise. Edges are detected using the video signal from the previous frame, and suppression of noise around edges in the video signal from the previous frame is prohibited, so that the level of noise between frames is small. This has the effect of reducing the appearance of edges of objects with differences on the screen as afterimages.

As explained above, the other invention is a noise suppression device that receives a digital video signal as input and suppresses noise in the video signal using a frame memory, a subtraction circuit, and a fixed storage circuit, and detects edges of the video signal. and a detection signal expansion circuit that expands the edge signal detected by the edge detection circuit in the horizontal and vertical directions.

It is equipped with a mixing circuit that changes the mixing ratio of the input video signal and the noise-suppressed video signal according to the magnitude of the output signal of the detection signal expansion circuit, and detects edges from the video signal one frame before. , since the amount of noise suppression around edges in the video signal one frame before is reduced in accordance with the magnitude of the edge detection signal, the same effect as described above can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an adaptive noise suppression device according to an embodiment of the present invention, and FIG. 2 is an edge detection circuit (
8), FIG. 3 is a configuration block diagram of the detection signal expansion circuit (9) in FIG. 1, FIGS. 4 to 6 are operational waveform diagrams of each part in FIG. FIG. 8 is a block diagram of the configuration of an adaptive noise suppression device according to another embodiment of the invention; FIG. 8 is a block diagram of the detection signal expansion circuit (9) of FIG. 7;
The figure is an input/output characteristic diagram of the fixed memory circuit (812) in Figure 2,
Figure 10 is a block diagram of the configuration of a conventional noise suppression device.
FIG. 1 is an input/output characteristic diagram of a fixed memory circuit in a conventional noise suppression device. In the figure, (1)...input terminal, (2)...switch circuit, (2a>...mixing circuit, (3)...frame memory, (4)...delay circuit, (5)... )...1st
subtraction circuit, (6)...fixed memory circuit, (7)...
Second subtraction circuit, (8) . . . edge detection circuit. (9), (9A)...detection signal expansion circuit, (10)...
...This is an output terminal. In addition, the same reference numerals in each figure indicate the same or corresponding parts. (f) Eng/Njii Otsu+(311n -J“”““”
′"""]111.,1-...1111.-[""゛"1.-111111-1'""'Lr--8 Figure 1, Case Indication Patent Application Sho No. 63-311977 No. 2, Name of the invention Adaptive noise suppression device 3, Relationship with the case of the person making the amendment Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Representative of Mitsubishi Electric Corporation person's will
Mamoru Ki, late 4, agent address: 4Wj Marunouchi Building, 2-4-1 Marunouchi, Chiyoda-ku, Tokyo (]) Column 6 of detailed explanation of the invention in Mei aI, contents of amendment (1) Page 12 of the specification Line 9 “1 sample delay circuit (s
oe), is corrected as "1 sample delay circuit (806) J." (2) "Detection signal expansion circuit (9) J" is corrected as "detection signal expansion circuit (9^)" in the 12th to 13th lines of page 18 of the same book. to correct. (3) Correct the drawings in Figures 7, 8, and 10 as shown in the attached sheet. Plot 8 Atsushi Shinga Law Circuit

Claims (2)

[Claims] (1) In a noise suppression device that receives a digital video signal as input and suppresses noise in the video signal using a frame memory, a subtraction circuit, and a fixed storage circuit, an edge detection circuit that detects an edge of the video signal; A detection signal expansion circuit that expands the edge signal detected by the edge detection circuit in the horizontal and vertical directions; and a switch circuit that switches between the input video signal and the noise-suppressed video signal using the output signal of the detection signal expansion circuit. An adaptive noise suppression device characterized by comprising: (2) A noise suppression device that receives a digital video signal and suppresses noise in the video signal using a frame memory, a subtraction circuit, and a fixed storage circuit, including an edge detection circuit that detects an edge of the video signal; A detection signal expansion circuit that expands the edge signal detected by the edge detection circuit in the horizontal and vertical directions, and an input video signal and a noise-suppressed video signal depending on the magnitude of the output signal of this detection signal expansion circuit. An adaptive noise suppression device comprising: a mixing circuit that varies the mixing ratio of the noise suppressing device.