JPH027773A - noise reduction device - Google Patents

Abstract

PURPOSE:To decrease the increase in after-image even if noise reduction is increased by utilizing a difference of points to be subjected to noise reduction and also plural points in the vicility and discriminating the correlation between fields so as to reduce noise. CONSTITUTION:The 1st delay device 7 comprising n-set of delay elements 701-70N to obtain a difference among plural points in the vicinity of a point, an expansion ROM 14 outputting a digital data stored in advance in response to (n+1) sets of digital data from n-set of delay elements of the 1st delay device 7 and the 1st subtractor 4 and deciding the noise reduction, and the 2nd delay device 8 comprising m-set of delay elements 801-80M are provided to the noise reduction device. Then surer local discrimination of stationary part and moving part is applied from the correlation data of plural points and the noise reduction is decided by the result of discrimination. Thus, even if larger noise reduction is obtained from the stationary part, the after-image of the moving part is suppressed smaller than a conventional device.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a noise reduction device for reducing noise components of a video signal.

2. Description of the Related Art In recent years, advances in semiconductor technology have led to lower semiconductor prices, and it has become possible to relatively easily process video signals using digital technology.

One of them is a device that uses field memory and uses correlation between fields to reduce noise in a video signal.

An example of the above-mentioned conventional noise reduction device will be described below with reference to the drawings. FIG. 3 shows a conventional noise reduction device using field correlation. .

In Figure 3, 1 is an A/D converter, 11 is an A/D converter, and 11 is an A/D converter.
/D Analog video signal input to converter, 1
2 is a digital signal output from the A/D converter. 2 is a D/A converter, 21 is a D/A
Digital signal input to the converter, 22 is D/
A This is an analog video signal output from converter 2. 3 is a field memory, which delays the video signal by one field. 4 is the first subtractor;
A one field delay signal is subtracted from the digital signal 12 in the field memory 3. 6 is a ROM which determines the amount of noise reduction.

θ is a subtracter 4. The operation of the conventional noise reduction device configured as described above will be explained below. First, an input analog video signal 11 is converted into a digital signal 12 by an A/D converter 1.

This converted digital signal 12 is input to the subtracter 4, and the difference between it and the data one field before from the field memory 3 is calculated and output to the ROM 5.

Subtraction by the subtractor 40 is obtained by inputting the sum of the two's complement of the data input to the minus terminal of the subtractor 4 and the summed data input to the plus terminal of the subtractor 4 to the full adder. There is. The ROM 6 has the characteristics shown in FIG. 4, and when the absolute value of the difference between the data output from the subtracter 4 is small, that is, when the correlation between fields is large, the ratio of the input data to the output data is K. If the absolute value is large (larger than L), it is assumed that there is movement, and K is set to O to avoid an afterimage, and noise reduction is not performed. The pig output from ROM 5 is reduced to 17 6
The difference between the data from the A/D converter 1 inputted to the negative terminal 62 and inputted to the positive terminal 61 is determined, the noise is reduced, and the result is outputted from the output terminal T-63. The output terminal 63 ('i) is input to the D/A converter 2 and is also input to the two-yield memory 3, and is used again after one field.
The digital signal 21 input to the analog video signal 2
2 and output.

Problems to be Solved by the Invention However, in the above configuration, the correlation between fields is determined and noise reduction is performed only based on the difference between the points at which noise reduction is to be performed. It is difficult to distinguish, and if you try to improve the noise reduction effect in the necessary areas, the afterimage will increase in the moving parts and the image will become unnatural, so in actual use it will not be possible to obtain a significant improvement effect. I had an issue.

In view of the above problems, the present invention performs noise reduction by determining the correlation between fields by using not only the point at which noise reduction is to be performed, but also the difference between a plurality of points in the vicinity of that point,
It is an object of the present invention to provide a noise reduction device that makes the difference between a stationary part and a moving part more clear, and that causes less increase in afterimages even when the amount of noise reduction is increased.

Means for Solving the Problems In order to solve the above problems, the noise reduction device of the present invention has n
a first delay device consisting of delay elements;

an expansion ROM that outputs digital data stored in advance in response to n+1 digital data from the n individual delay elements of the first subtracter and the first delay device and determines the amount of noise reduction; and a second delay device consisting of m individual delay elements between the second subtracter of the ADC and the second subtracter of the ADC.

According to the above-described configuration, the present invention uses the second delay device to determine the center point at which noise reduction is to be performed, and uses the first delay device to obtain the difference between a plurality of points in the vicinity of that point. It is possible to obtain the correlation of not only a single point but also multiple points in the vicinity of that point at the same time, and from the correlation data of these multiple points, it is possible to more reliably distinguish between stationary and moving parts, and this discrimination result can be used to reduce noise. Since the amount of noise is determined, even if a larger amount of noise reduction is obtained in a still part, it is possible to suppress image noise in a moving part to be smaller than before.

Embodiments Hereinafter, noise reduction apparatuses according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a noise reduction device according to an embodiment of the present invention, and FIG. 2 is a detailed diagram showing an example of the expansion ROM in FIG. 1. The same parts as in FIG. 3 are given the same numbers. The explanation will be omitted.

In Figure 1, 1 is an A/D converter (hereinafter referred to as ADC).
), D/A converter (hereinafter referred to as DAC),
3 is a field memory, 4 is a first subtracter, 6 is a second subtractor, 7 is a first delay device for obtaining the difference between a plurality of points in the vicinity of a certain point, and 701 to 7ON are first delay devices. n delay elements forming a delay device element; 8 is a low-noise, second delay device for determining the center point at which scanning is to be performed; 801 to 80M are m delay elements forming a second delay device 8; 14 is an expansion ROM, 141 is an expansion ROM 140 manual group, and 142 is an output of the expansion ROM 14.

Further, in Fig. 2, 91 to 9 (N+1) are n range detectors, 191 to 19 (N+1) are the inputs of each range detector, 291 to 29 (N+1) are the outputs of each range detector, 10 is a logical multiplier, 101 is an input of the logical multiplier 10, 102 is an output of the logical multiplier 10, 11
111 is an input selected when the control input is "true"; 112 is an input selected when the control input is "false"; 113 is a data selector switch output;
114 is the control input of the data changeover switch, 12 is the ROM
, 121 is the input of ROM12, 122 is the output of ROM12, 13 is ROM, 131 is the input of ROM13, 132
is the output of ROM1s.

The operation of the noise reduction device configured as described above will be explained below using the same text and FIG. 2.

First, in FIG. 1, an analog video signal 11 input to the ADCl is converted into a digital signal 12, and a subtracter 4 calculates the difference with the signal one field before, and outputs it to the first delay device 7. Same as before.

Next, the first delay device element is composed of n individual delay elements 701 to 7ON connected in cascade, and the total
It has a delay time of i. Then, the configuration is such that the outputs of the five individual delay elements 701 to 7ON can be taken out with i=1. Here, the time of the delay element is calculated as follows:
It only needs to be the period of the sampling clock, and the delay element can be easily configured with a flip-flop. If the points are close to the top and bottom of the screen, one line worth of memory is required.

On the other hand, the signal from the ADC 1 is input to the second delay device 8. The second delay device is composed of m individual delay devices 801 to soM connected in cascade, and has a total delay time of τi.

This is to correct the delay in data at the point where noise reduction is to be performed by the first delay device it7. By setting m = n/2, it is possible to obtain data symmetrically at points in the vicinity of the point at which noise reduction is to be performed.

With the above configuration, it is possible to obtain the difference between the point at which noise reduction is to be performed and the points in its vicinity. These obtained differences are input to the expansion ROM 14, where the amount of noise reduction is determined and output to the second reducer 6. and by the second subtractor 6, the second delay device 8
The difference between the data from the expansion ROM 14 and the data from the expansion ROM 14 is determined to reduce noise. The subsequent operations are the same as before.

However, the delay time of the field memory 3 is longer than the delay time of the second delay device 8! It must be shorter by τi (1-'I).

Next, the operation of the expansion ROM 14 will be explained.

FIG. 2 is an example of a detailed diagram of the expansion ROM 14.

There are (N+1) input signals 191 to 19 (N+1), of which all but the M4-1st (N>M) input signal are input to the respective range detectors 91 to 9 (N+1). Here, when the absolute value of the difference ε is smaller than or equal to a certain constant value Ln, that is, when Ln≦ε≦+Ln, “true” is output to each of the outputs 291 to 29 (N+1). The outputs of the respective range detectors are then input to the logical multiplier 1o. Here, a logical product is calculated, and this logical product is output to the data changeover switch 11. The logical product that is output becomes "true" only when the differences from one field before at points near tr are all smaller than a certain value Ln. The signal is then input to the control input terminal 114 of the data changeover switch 11. On the other hand, the m+1-th input is input to the ROM12 and ROM13.

ROM12 and ROM13 are similar to conventional ROMs. ROM12 has the value of K set to a large value and has the characteristic of a large amount of noise improvement.
The value of K is set to a smaller value, and the amount of noise improvement is suppressed. The output of each ROM is input to the data changeover switch 11.

The data selector switch 11 is set to R when the control input is “true”.
The output of OM12 is selected and the data of ROM12 is output, and if the control input is "false", the output of ROM13 is selected and the data of ROM13 is output. In other words, extended RO
M14 operates to select the output of ROM 12 and increase the amount of noise improvement when the correlation between fields is strong even at nearby points, and to select the output of Rolls and suppress the amount of noise improvement when the correlation is weak.

As described above, according to this embodiment, the first delay device 7 composed of n delay elements is used to obtain the difference between a plurality of points in the vicinity of a certain point, and the center point at which noise reduction is to be performed is determined. A second delay device 8 consisting of m delay elements 801 to soM between the ADCl and the second subtracter 6 for
As M14, n (in this example, n=2) range detectors 91°92 and two 80M12, 13 with different characteristics.
By providing a logical multiplier 10 that obtains the logical product of the respective range detectors 91 and 92, and a data changeover switch 11 that selects the output of each ROM according to the output of the logical multiplier 10, a more reliable field can be obtained. It is possible to detect the correlation between images, and even when trying to obtain a large noise reduction effect, the afterimage of moving parts can be suppressed to be smaller than before.

Note that as an embodiment of the expansion ROM 14, it is also possible to have a configuration in which the number of ROMs is three or more, a plurality of logical multipliers are used, and the correlation is finely determined to select the optimal ROM.

Effects of the Invention As described above, the present invention provides a first delay device comprising n delay elements for obtaining a difference between a plurality of points in the vicinity of a certain point;
an expansion ROM that outputs digital data stored in advance in response to n+1 digital data from the n individual delay elements of the first subtracter and the first delay device and determines the amount of noise reduction; A large noise reduction effect can be obtained by providing a second delay device consisting of m delay elements between the ADC and the second subtractor for determining the center point at which noise reduction is to be performed. Even when moving, afterimages in moving parts can be kept smaller than before.
It is possible to obtain an excellent effect such that the image is less likely to look unnatural.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a noise reduction device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a detailed configuration example of an expansion ROM, FIG. 3 is a block diagram of a conventional noise reduction device, and FIG. 4 is an input/output characteristic diagram of the ROM. 1...ADC12...DACls...
...Field memory, 4...First subtractor, 5...ROMθ...Second subtractor, 7...First subtractor Delay device, 8... Second delay device, 9... Range detector, 10...
...Logic product, 11...Data changeover switch,
12゜13...ROM, 14...Expansion ROM0 Agent's name Patent attorney Toshi Nakao and one other person Figure/--ADC (Akame) Vno

Claims (1)

[Claims] an A/D converter that converts an input video signal into digital data and outputs the digital data; a D/A converter that converts the input digital data into a video signal and outputs the digital data;
a field memory that delays and outputs digital data input to the A/D converter by at least one field; and a first field memory that outputs the difference between the digital data from the A/D converter and the digital data delayed by the field memory. a subtracter, and a first delay device that delays the digital data from the first subtracter by connecting n delay elements cascaded to the output of the first subtractor to delay the digital data by a certain time τi and output the resultant output; an expansion ROM that outputs digital data stored in advance in response to n+1 digital data from the n individual delay elements of the first subtracter and the first delay device and determines the amount of noise reduction; Digital data from the A/D converter is stored for a certain period of time ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼τi (m is a positive integer)
a second delay device for outputting the digital data after delaying the data by the amount of time; and a second subtracter for outputting the difference between the digital data from the second delay device and the digital data from the expansion ROM to the D/A converter and the field memory. A noise reduction device characterized by comprising: