JPH03258170A - Noise reduction device - Google Patents

Abstract

PURPOSE:To eliminate noise in a same processing system by delaying each input video signal by one frame, obtaining a difference signal between the input video signal and each delay signal and decomposing the result into a component signal representing the characteristic of the difference signal to extract a noise level signal. CONSTITUTION:When a luminance signal is inputted from a terminal 1, it is A/D-converted by an A/D converter 2, an output digital signal enters a luminance processing system, the signal is supplied to a subtractor 3, from which a signal not including noise component is obtained and stored in a frame memory 4, delayed by one frame and a 2-luminance frame difference signal is obtained from a subtractor 6. The difference is subject to D/A conversion 12 via a Hadamard transformation processing circuit group 21 and a luminance signal resulting from decreasing the noise component from the input signal is outputted. On the other hand, color difference signals B-Y, R-Y are selected by an analog switcher 24, given to the A/D converter 2 and the shared B-Y and R-Y signals are subject to similar processing to the luminance signal and the signal component subtracting the noise component from the input color difference signal is extracted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention reduces noise even in moving images by using field or frame correlation of video signals from televisions, videos, video cameras, etc. In this case, the present invention relates to a noise reduction device that can effectively reduce noise even when the input video signal is a component signal of luminance and color difference signals.

2. Prior Art As a conventional noise reduction device, for example, Japanese Patent Application Laid-open No. 61-1
It is shown in Japanese Patent No. 58574.

FIG. 6 is a block diagram showing a conventional noise reduction device.

In Fig. 6, 1 is an input terminal for a composite video signal, 2 is an A/D converter that converts the composite input video signal from an analog signal to a digital signal, and 3 is an input terminal that has two input signals, one input signal to the other. A subtraction circuit 4 subtracts the input signal from the input video signal, and 4 is a frame memory that delays a signal obtained by reducing noise from the input video signal by one frame.

Since the phase of the color signal of the NTSC color video signal is inverted for each frame, 5 is a color signal phase shift circuit to compensate for this, and the color signal of the composite video signal delayed in the frame memory 4 is phase shifted. Invert. 8 is a subtraction circuit that obtains a frame difference signal by subtracting the input frame-posit video signal and the frame-posit video signal delayed by one frame; 7 is a subtraction circuit that converts the frame difference signal output from the subtraction circuit 6 from a serial digital signal to a parallel digital signal. A serial-parallel conversion circuit 8 performs Hadamard transform, which is orthogonal conversion, on the parallel digital signal output from the serial-parallel conversion circuit 7, and converts the frame difference signal into vertical components, horizontal components,
This is a Hadamard transform circuit that extracts diagonal components. Since the output of the Hadamard transform circuit 8 has a different distribution of noise components and motion components, 9 is a nonlinear processing circuit that extracts the noise components by utilizing this fact. 10 is a Hadamard inverse transform circuit, and the noise signal extracted from the nonlinear processing circuit 9 is obtained by Hadamard transform.
Return to the original time axis by inverse Hadamard transformation. 1
Reference numeral 1 designates a parallel-to-serial conversion circuit that returns a parallel digital signal to the original serial digital signal, and 12 a D/A converter that converts the digital signal into an analog signal. Table 1 is 4fs
The highest point of the energy distribution when Hadamard transform is performed with c sampling and 2×4-order input is indicated with a mark. Each left side of Table 1 shows the pattern of each component, each right side shows the energy distribution, the horizontal axis is the two-dimensional horizontal frequency (unit is (Hz)), and the vertical axis is the two-dimensional vertical frequency (unit is (Hz)). is CHHz/screen height], and screen height is a unit that normalizes the vertical height of a TV screen.) Below is a conventional noise reduction device configured as shown in Table 1 and above. In □, when a composite video signal is input from the input terminal 1, it is converted into a digital signal by the A/D converter 2, and this digital signal passes through the subtracter 3 to subtract the uncorrelated components described below, and the ideal Specifically, it becomes a composite video signal component that does not contain noise components, is stored in the frame memory 4, and is delayed for one frame. Since this video signal delayed by one frame has a color signal phase inverted from that of the one frame signal, the phase is compensated by the chroma invert circuit 5 and only the phase of the color signal is inverted. A subtracter 6 obtains a frame difference signal between two composite video signals having the same chroma phase. Originally, when the input video signal is a still image, this frame difference signal becomes a noise component itself, and noise can be extracted without the need for the circuit described below. However, if the input video signal is a moving image, this frame difference signal will be a signal that is a combination of a signal component with no frame correlation and a noise component.

A method for obtaining only the noise component from this frame difference signal will be described below. This frame difference signal is converted from a serial digital signal to a parallel digital signal by a serial-parallel converter 7, and a Hadamard transform circuit 8 converts the frame difference signal into a low frequency component, a vertical component, a horizontal component, etc. in the TV signal band. Assuming that we sampled with 4f so above, now,
Assuming that a two-dimensional Hadamard transformation with a transformation order of 4×2 is performed, an energy distribution appears centered on the Nass vector component as shown in Table 1. In this case, one pattern of input picture elements is as shown in FIG. 7, and the input is as follows: Xaa=l□::Porridge::N:X:I 01. (1
). The conversion output of the 2×4 Hadamard transform is F2
4, then F2-=H2・X2a・H4...(3) According to the above formula,
The Hadamard transform output F24 is obtained from the 4×2-order input picture element X24. Here, Fss”Fsa of equation (2)
and F+s"F+a are F■ to FII3 and F in Table 1.
ll”F1a. Also, H2°H4 is as follows.

The output from the Hadamard transform circuit 8 is a converted output of eight components, and as described above, these eight component outputs appear in the vicinity of each frequency, and the energy is distributed around the spectral components shown in Table 1 described above.

On the other hand, since noise has no correlation, it is almost equally distributed among the eight component frequencies of the output of the Hadamard transform circuit 8.

As is well known, the noise level at the output of the Hadamard transform circuit 8 corresponds to the noise level of the input signal, so only small-level noise components can be extracted from each of these components through the nonlinear processing circuit 9. . Since each component extracted by this nonlinear processing circuit 9 is obtained by Hadamard transform, it is returned to the original time axis by passing through Hadamard inverse transform circuit 10, and a parallel digital noise signal is obtained here. Become.

The parallel-to-serial conversion circuit 11 converts the parallel digital noise signal into a serial digital signal similar to the input form. The signal obtained here is one in which only the noise component is extracted from the frame difference signal that has no frame correlation, and is supplied to the subtraction circuit 3 as described above, and is removed from the input video signal by subtracting the noise component from the input video signal. A digital video signal will be obtained. The digital video signal is then converted into the original analog signal by the A/D converter 12 and output.

A noise reduction device using such a method can reduce noise without producing afterimages not only in still images but also in moving images when inputting a composite video signal.

Problems to be Solved by the Invention The noise reduction device described in the conventional example can reduce noise without producing an afterimage even when inputting a composite video signal and not only in still images but also in moving images.

However, the above-mentioned apparatus has a problem in that the input video signal is limited to only a composite signal.

In view of this, an object of the present invention is to provide a noise reduction device that reduces noise in component input video signals as well as in composite video signals.

Means to solve problems In order to achieve the above object, the present invention provides a luminance signal.

When the color difference signal is independently A/D converted and sampled, the color difference signal is sampled at a frequency different from the sampling frequency of the luminance signal. By changing the sampling frequency depending on the input signal in this way, the frequency-dependent part of the Hadamard transform is adjusted to the bandwidth of the luminance signal and the bandwidth of the chrominance signal, and the noise of the chrominance signal is reduced using the same noise reduction circuit as that for the luminance signal. Perform removal.

Effect With the above configuration, noise components can be extracted from signal components that have no frame correlation by Hadamard transform of the frame difference signal of composite input video and nonlinear processing. In the case of input signals that originally have different frequency bandwidths, such as a luminance signal and a chrominance signal, the frequency band of each component when subjected to Hadamard transform can be changed by sampling the luminance signal and chrominance signal in separate frequency bands. It is possible,
Noise reduction can be performed on the luminance signal and color signal using the same processing circuit.

Embodiment Φ- FIG. 1 shows a circuit diagram of a noise reduction device according to a first embodiment of the present invention. In Figure 1, 1 to 6
The steps up to 1 are the same as 1 to 6 shown in FIG. 6, and have the same function. Reference numeral 21 is a seven-series/parallel conversion circuit shown in FIG. 2; 8 is a Hadamard transform circuit; 9 is a nonlinear processing circuit; and 10 is a Hadamard transform circuit. 11 is a circuit configuration including a series of processing of a parallel/serial conversion circuit, and 7 to 11 are similar circuits to 7 to 11 shown in FIG. 6, and have the same function. 22 is an input terminal for the color difference signal B-Y, 23 is an input terminal for the color difference signal RY, and 24 is an analog switcher 25 which sequentially inputs the color difference signals B-Y and RY. This is a selector that divides the output of the input signal into B-Y and RY similar to the input signal.

Table 2 shows the highest points of the energy distribution when 2fsc sampling and Hadamard transformation of 2×4-order input are performed. The left side of Table 2 shows the input pattern of each component. Each right side shows the energy distribution, where the horizontal axis is the two-dimensional horizontal frequency and the vertical axis is the two-dimensional vertical frequency.

The operation of the noise reduction device of this embodiment configured as described above will be described below. When a luminance signal is input as a component signal from the input terminal 1, the A/D converter 2 outputs 4 f,, (3f,).

), and the analog signal is converted to a digital signal. This signal enters a luminance signal processing system, and passes through a subtracter 3 to subtract non-correlated components, which will be described later, and ideally becomes a luminance signal component that does not contain noise components.

Table 2 This luminance signal component is stored in frame memory 4 and 1
After being delayed for a frame, a subtracter 6 obtains a frame difference signal between the two luminance signals. This frame difference signal is
The signal is a combination of a signal component with no frame correlation and a noise component. This frame difference signal enters the Hadamard transform processing circuit group 21, is converted from a serial digital signal to a parallel digital signal by a serial-parallel converter 7, and is converted into a frame difference signal by a Hadamard transform circuit 8 into a low frequency component, a longitudinal frequency component, and a vertical frequency component. component, horizontal frequency component, etc. Now, 4f. (3f, .), and the transform order of the Hadamard transform is a 4×2 two-dimensional Hadamard transform as shown in FIG. 7, as in the conventional example. An energy distribution appears centered around the spectral components shown in the table. The output from the Hadamard transform circuit 8 is a converted output of 8 components having 8 types of frequency characteristics, and since these 8 component outputs are sampled at 4f3° as described above, an energy distribution appears in the vicinity of each frequency. On the other hand, since noise has no correlation, it is almost evenly distributed within the frequency distribution of the eight components output from the Hadamard transform circuit 8. As is well known, the noise level at the output of the Hadamard transform circuit 8 corresponds to the noise level of the input signal, so only small-level noise components can be extracted from each of these components through the nonlinear processing circuit 9. . Since each component extracted by this nonlinear processing circuit 9 is obtained by Hadamard transform, it is returned to the original time axis by passing through Hadamard inverse transform circuit 10, and a parallel digital noise signal is obtained here. Become. The parallel-to-serial conversion circuit 11 converts the parallel digital noise signal into a serial digital signal similar to the input form. The signal obtained here is one in which only the noise component is extracted from the frame difference signal that has no frame correlation, and is supplied to the subtraction circuit 3 as described above, and is removed from the input luminance signal by subtracting the noise component from the input luminance signal. A digital luminance signal will be obtained. The digital video signal is then converted into the original analog signal by the A/D converter 12 and output.

Next, processing of color difference signals, which are component signals, will be described. B-Y and R-Y are input terminals 22.2, respectively.
Input from 3, 1/4f with analog switcher.

[The color difference signals B-Y and RY are sequentially selected at sec1 intervals. In the A/D converter 2, the output from the analog switcher is 4f.

(a case of 3f3° is also considered) is sampled, and the analog signal is converted into a digital signal. The digital signal output from the A/D converter is passed through the selector 25 to 1/4 f.

[By distributing the output from the A/D converter 2 into two types of output at the timing of sec, B-Y, R-Y
into digital signals. Assigned B-Y, R
-Y is input to a B-Y signal processing system and a R-Y signal processing system, which are separate circuit systems that perform the same processing as the luminance signal processing system. The BY signal processing system and the RY signal processing system perform the same digital signal processing as the previously described luminance signal processing system.

The two color difference signals input to the B-Y processing system and the R-Y processing system pass through a subtracter 3 to subtract non-correlated components, which will be described later, and ideally become color difference signal components that do not contain noise components. Become. This color difference signal is stored in a frame memory 4 and delayed for one frame, and a subtracter 6 obtains a frame difference signal of the color difference signal. This frame difference signal is a signal that is a combination of a signal component with no frame correlation and a noise component. This frame difference signal enters the Hadamard transform processing circuit group 21, and is converted from a serial digital signal to a parallel digital signal by the serial-parallel converter 7.The frame difference signal is converted into a low frequency component, a longitudinal frequency component, and a vertical frequency component by the Hadamard transform circuit 8. component, horizontal frequency component, etc. These color difference signals are 4f. (3f3° is also considered), but the number of data is set to 172 by the selector, so B-Y,
The RY color difference signal is 2f. (If the sampling frequency of the A/D converter is 3f, then the sampling frequency is 1.5f.). Now, assuming that the Hadamard transform has a two-dimensional Hadamard transform of 4×2 order as in the conventional example, the output of the Hadamard transform circuit is the second one on the B-Y, R-Y color difference signal band. An energy distribution appears centered around the spectral components shown in the table. In this case, one pattern of input picture elements is as shown in FIG. The output from the Hadamard transform circuit 8 is a converted output of eight components with eight types of frequency characteristics.
As mentioned above, the component output is the input color difference signal of 2f. Since it is sampled at , an energy distribution appears near each frequency. On the other hand, since noise has no correlation, it is almost evenly distributed within the frequency distribution of the eight components output from the Hadamard transform circuit 8.

As is well known, the noise level at the output of the Hadamard transform circuit 8 corresponds to the noise level of the input signal, so only small-level noise components can be extracted from each of these components through the nonlinear processing circuit 9. . Since each component extracted by this nonlinear processing circuit 9 is obtained by Hadamard transform, it is returned to the original time axis by passing through Hadamard inverse transform circuit 10, and a parallel digital noise signal is obtained here. Become.

The parallel-to-serial conversion circuit 11 converts the parallel digital noise signal into a serial digital signal similar to the input form. The signal obtained here is one in which only the noise component is extracted from the frame difference signal that has no frame correlation, and is supplied to the subtraction circuit 3 as described above, and by subtracting the noise component from the input color difference signal, a noise-free R -Y, B -Y digital color difference signals are obtained. And A/D
A converter 12 converts the digital color difference signal into the original analog signal and outputs it.

In this embodiment, the color difference signals B-Y and RY are sampled using the same A/D converter, but as shown in FIG. 4, the A/D converter is connected to each input terminal. have,
You can also think of ways to sample independently.

FIG. 5 shows a circuit diagram of a noise reduction device according to a second embodiment of the present invention. In Figure 5, 1 to 6
The steps up to 1 are the same as 1 to 6 shown in FIG. 6, and have the same function. 21 is a serial/parallel conversion circuit shown in Fig. 2, and 8 is a serial/parallel conversion circuit.
is a Hadamard transform circuit, 9 is a nonlinear processing circuit, and 10 is an inverse Hadamard transform circuit. Reference numeral 11 denotes a circuit configuration that performs a series of processes in the parallel/serial conversion circuit, and circuits 7 to 11 are similar to circuits 7 to 11 shown in FIG. 6, and have the same functions. 22 is a G signal input terminal, 23 is a B signal input terminal, and 28.27 is a G signal.

This is the output terminal for the B signal.

The operation of the noise reduction device of this embodiment configured as described above will be described below. Input terminal 1.22.2
3, RGB signals are input as component signals. 4f, by each A/D converter 2 assuming that each band of the RGB signals is the same. (3f, .) is sampled and converted from an analog signal to a digital signal. This signal enters a luminance signal processing system, and passes through a subtracter 3 to subtract non-correlation components, which will be described later, and ideally becomes RGB signal components that do not contain noise components. Each of these RGB signal components is stored in the frame memory 4.
The subtracter 6 obtains a frame difference signal between the two RGB signals. This frame difference signal is a signal that is a combination of a signal component with no frame correlation and a noise component. This frame difference signal enters the Hadamard transform processing circuit group 2, and is serially connected to
A parallel converter 7 converts the serial digital signal into a parallel digital signal, and a Hadamard transform circuit 8 separates the frame difference signal into a low frequency component, a vertical frequency component, a horizontal frequency component, etc.

Now, sampling is performed at 4f, , (3f, .), and the transformation order of the Hadamard transform is a 4×2 two-dimensional Hadamard transform as shown in Figure 6, as in the conventional example, so the RGB signal is An energy distribution appears on the band centered around the spectral components shown in Table 2. Hadamard conversion circuit 8
The output from is a converted output of 8 components having 8 types of frequency characteristics, and these 8 component outputs are 4f, as described above. Since it is sampled at , an energy distribution appears near each frequency. On the other hand, since noise has no correlation, it is almost evenly distributed within the frequency distribution of the eight components output from the Hadamard transform circuit 8. As is well known, the noise level at the output of the Hadamard transform circuit 8 corresponds to the noise level of the input signal, so only small-level noise components can be extracted from each of these components through the nonlinear processing circuit 9. . Since each component extracted by this nonlinear processing circuit 9 is obtained by Hadamard transform, it is returned to the original time axis by passing through Hadamard inverse transform circuit 10, and a parallel digital noise signal is obtained here. Become. Parallel-serial conversion circuit 1
1, the parallel digital noise signal is converted into a serial digital signal similar to the input form. The signal obtained here is one in which only the noise component is extracted from the frame difference signal having no frame correlation, and as mentioned above, it is supplied to the subtraction circuit 3, and the noise is removed by subtracting the noise component from each input RGB signal. This results in a digital luminance signal that is different from the original one. The digital video signal is then converted into the original analog signal by the A/D converter 12 and output.

As described in detail, according to the present invention, even when the input video signal is a plurality of component signals, simply changing the sampling frequency of each input signal changes the frequency band handled by Hadamard transform, and the energy distribution with respect to frequency can be changed. are also different. Therefore, by changing the sampling frequency for converting a digital signal into an analog signal for each signal component of the component signal, it is possible to produce the effect of noise removal using the same processing system.

FIG. 1 is a block diagram of a noise reduction device according to a first embodiment of the present invention, and FIG. 2 is a block diagram of a Hadamard transform processing circuit group 21 in FIG.
3 is a block diagram of the apparatus of the first embodiment, and FIG. 7 is an input pattern diagram of the luminance signal of the conventional example and the first embodiment.

1... Signal input terminal, 2.31... A/D converter, 3, 6... Subtractor, 4... Frame memory, 5... Color signal phase shift circuit, 7... Series-parallel conversion circuit, 8... Hadamard conversion circuit,
9... Nonlinear processing circuit, 10... Hadamard inverse conversion circuit, 11... Parallel-serial conversion circuit, 1
2, 32... D/A converter, 13... Output terminal, 21... Hadamard transform processing circuit group, 22
...B-Y signal input terminal, 23...R-Y signal input terminal, 24...Analog switcher-25...Selector, 26...B-Y output terminal, 27...
・RY output terminal.

Claims (5)

[Claims] (1) A noise reduction device that processes a plurality of component video signals through independent noise removal means, the noise removal means including means for delaying each input video signal by one frame, and a means for delaying each input video signal by one frame; It consists of a subtraction circuit for obtaining a difference signal from a video signal, a signal feature extraction means for decomposing the difference signal into signal components representing the characteristics, and a means for extracting a noise level signal from the output of the signal feature extraction means, A noise reduction device characterized in that each of the noise removal means performs the same processing. (2) A noise reduction device that quantizes a plurality of component video signals at independent frequencies and then passes them through independent noise removal means, the noise removal means delaying the input video signal by one frame; a subtraction circuit that obtains a difference signal between the input video signal and the delayed video signal; a signal feature extractor that decomposes the difference signal into signal components representing features; and a noise level signal from the output of the signal feature extractor. 1. A noise reduction device comprising: means for extracting a noise, and wherein the processing by each of the noise removal means is the same except for the processing frequency. (3) The noise reduction device according to claim 2, wherein the plurality of component input video signals are a luminance signal and two color difference signals. (4) The noise reduction device according to claim 2, wherein the plurality of component input video signals are a luminance signal and two color difference signals, and the frequency for processing the two color difference signals is lower than the frequency for processing the luminance signal. . (5) Claim 2 characterized in that the plurality of component input video signals are a luminance signal and two color difference signals, and the frequency at which the two color difference signals are processed is an integer fraction of the frequency at which the luminance signal is processed. Noise reduction device as described.