JPH0738784A - Noise reducing device for video signal - Google Patents

Abstract

PURPOSE:To provide the noise removing device of a video signal in which the deterioration of the sharpness of a video at the time of removing a noise can be reduced, and a noise removing capability against beat interference or the like can be excellent. CONSTITUTION:The video signal is resolved into plural frequency components by a Hadamard transformation circuit(orthogonal transformation circuit) 1, the noise amounts of a vertical synchronizing period are obtained by a full-wave rectifying circuit 5 and horizontal and vertical smoothing circuits 6 and 7 for each resolved frequency component, and the result is stored in a memory circuit 8 as the noise detection amounts of each frequency component. The noise detection amounts are gain-controlled by a gain control circuit 12, and added to a coring circuit 4 as the noise removing amounts, and noise removal is operated to each frequency components. Afterwards, the video signal is restored by an inverse Hadamard transformation circuit (inverse orthogonal transformation circuit) 2, and outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a television receiver,
The present invention relates to a video signal noise reduction device used for reducing the noise of a video signal, such as a video tape recorder, a video camera, a video disk, a video signal transmission device.

[0002]

2. Description of the Related Art In recent years, a noise reduction apparatus for video signals has been used in a weak electric field region of television broadcasting and a part of video due to an increase in size and image quality of a color television receiver and an increase in image quality of a video tape recorder. It is emphasized to reduce noise caused by insufficient software recording and storage conditions and to reproduce easier-to-see images.

Conventionally, a video signal noise reduction device has been used which automatically controls the noise suppression amount and the contour correction amount according to the amount of high frequency components in the vertical blanking period of the video signal. . An example of the above-described conventional video signal noise reduction device will be described below with reference to the drawings.

FIG. 7 is a block diagram of a conventional video signal noise reduction apparatus. In FIG. 7, reference numeral 21 is a high-pass filtering circuit, which takes out a high-frequency component containing noise of the input video signal a and a detailed information signal and outputs it as a high-luminance signal b. Reference numeral 22 denotes a full-wave rectification circuit, which full-wave rectifies the high-frequency luminance signal b and outputs a rectified high-frequency luminance signal c. Reference numeral 23 is a sample and hold circuit which, when the noise detection pulse e is input, rectifies the luminance signal c of that portion.
Is held and the smoothed voltage is held until the next noise detection pulse e is input, and it is output as the noise detection voltage d. Reference numeral 24 denotes a noise detection pulse generation circuit, which shapes the waveform of the vertical synchronization signal m so as to exclude a portion used for a video signal, a character multiplex signal or the like, and outputs it as a noise detection pulse e. Regarding the luminance signal noise suppression device configured as described above,
The operation will be described.

First, the input luminance signal a is input to the high-pass filtering circuit 1 and its high-frequency components are separated to obtain a high-frequency luminance signal b.
And is input to the full-wave rectifier circuit 2.
The full-wave rectification circuit 2 full-wave rectifies the high-frequency luminance signal b to obtain a rectified high-frequency luminance signal c. Next, the rectified high band luminance signal c is input to the sample and hold circuit 3, and the noise detection pulse e input from the noise detection pulse generation circuit 4 causes the rectified high band luminance signal c during the period in which the pulse is input. Is smoothed, and the smoothed voltage is held at the same time when the pulse disappears.
Output as. The noise detection voltage d is input to the noise suppression circuit 5 similar to the conventional example, and controls the noise suppression amount of the input luminance signal a input to this circuit. That is, when the noise detection voltage d is large (there is a lot of noise), the noise suppression amount can be increased, and in the opposite case, the suppression amount can be decreased or automatically controlled to zero. As a result, The output video signal f is obtained. It should be noted that the noise detection pulse is provided during the vertical synchronization period that is not affected by the effective video signal, so that the noise amount can be accurately detected.

[0006]

However, in the above configuration, the noise suppression amount is determined from the entire high frequency component of the video signal, and for example, beat interference to the video,
When there is a high frequency component of a single frequency, the whole other high frequency component is suppressed in order to remove the interference, and as a result, the sharpness of the output image is lowered. It was It is intended to provide a video signal noise reduction device capable of minimizing the noise.

[0007]

In order to solve the above problems, a video signal noise reduction apparatus according to the present invention has an orthogonal transform circuit (Hadamard transform circuit) for decomposing a video signal into a plurality of frequency components. An inverse orthogonal transform circuit (inverse Hadamard transform circuit) for returning a plurality of frequency components to a video signal, a video signal delay circuit, a coring circuit for removing noise,
A full-wave rectifier circuit for obtaining the amount of noise in the vertical synchronization period,
Horizontal smoothing circuit, vertical smoothing circuit, memory circuit, sync separation circuit for controlling timing of noise amount detection, timing generation circuit, gain control circuit for controlling noise suppression amount, subtraction circuit, clip circuit Is.

[0008]

According to the present invention, according to the above-described configuration, first, the video signal is decomposed into a plurality of frequency components by the orthogonal transformation circuit, and the noise amount in the vertical synchronization period is divided horizontally by the full-wave rectification circuit for each of the decomposed frequency components. , The result obtained by the vertical smoothing circuit is stored in the memory circuit, and this is used as the noise detection amount for each frequency component. The noise detection amount gain-controlled by the gain control circuit is added to the coring circuit as a noise removal amount to remove the noise for each frequency component, and then the inverse orthogonal transform circuit returns it to the video signal for output. With this operation, when a video signal with beat interference, which has been a problem in the past, is input, the noise removal operation is performed only on the frequency component that contains the frequency of the beat interference, and the noise removal of other frequency components is performed. Since no operation is performed, deterioration of sharpness as in the past can be considerably reduced, and noise can be reduced more effectively.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A video signal noise reduction apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a video signal noise reduction apparatus according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 is a Hadamard conversion circuit, which decomposes an input video signal into a plurality of frequency components. Reference numeral 2 denotes an inverse Hadamard transform circuit, which functions to combine a plurality of frequency components and return them to a video signal. A delay circuit 3 delays the DC component of the output of the Hadamard transform circuit and matches the timing with other frequency components. 4 is a coring circuit,
Noise is reduced by removing small-amplitude components containing noise from each frequency component of the output of the Hadamard transform circuit. The coring amount of this circuit is given from the memory circuit 8. 5
Is a full-wave rectifier circuit, which folds the negative part of the output signal of the Hadamard converter circuit to positive. 6 is a horizontal smoothing circuit,
The frequency components after full-wave rectification are smoothed for a constant horizontal period in which the vertical synchronization period continues, and the amount thereof is obtained. A vertical smoothing circuit 7 smoothes the output of the horizontal smoothing circuit during the past several field periods. Reference numeral 8 denotes a memory circuit, which functions to keep the output of the vertical smoothing circuit at a constant value during the vertical effective period. Reference numeral 9 denotes a sync separation circuit, which separates horizontal and vertical syncs of the input video signal. Reference numeral 10 denotes a timing generation circuit, which determines the timing of horizontal smoothing in the vertical synchronization period from the horizontal and vertical synchronization signals. Also, the timing of the vertical smoothing circuit and the memory circuit is determined.

Each of the configurations 4 to 8 is provided for each frequency component except for the DC component. The operation will be described with reference to FIG.

First, the input video signal a is input to the Hadamard transform circuit 1 and decomposed into frequency components by Hadamard transform. FIG. 2 shows a specific circuit diagram of Hadamard transform, and the example of FIG. 2 shows a case where division into four frequency components is performed. F (0) is a direct current component,
(1) to F (3) represent high frequency components. After performing the full-wave rectification, the horizontal smoothing circuit 6 smoothes the output signal e of the full-wave rectification circuit in the portion of the vertical synchronization period excluding the horizontal synchronization. When there is essentially no noise, the result of this smoothing becomes almost 0, but when there is noise (such as a weak electric field broadcast signal), a noise amount corresponding to that is shown. In order to stabilize the operation, the horizontal smoothing circuit output f is smoothed with the noise amount from several fields before in the vertical smoothing circuit 7.

The smoothed signal g is input to the memory circuit 8 so as to maintain a constant value during the vertical effective period. The output signal h of the memory circuit 8 is input to the coring circuit 4, and the output signal d of each Hadamard conversion circuit is cored by using the output signal h as a coring amount to remove noise. This operation is performed for each frequency component. That is, the noise amount for each frequency component obtained in the vertical synchronization period is
It is operated by setting the coring amount (noise removal amount) of the coring circuit between the fields. After that, the output signal i of the coring circuit and the signal c obtained by delaying the DC component b by the delay circuit 3 are input to the inverse Hadamard conversion circuit, and the output video signal m from which noise has been removed is restored by the inverse Hadamard conversion. FIG. 3 shows a specific circuit diagram of the inverse Hadamard transform, and an output video signal can be obtained by performing addition and subtraction on each frequency component. FIG. 4 is a waveform diagram showing the operation of each part during the vertical synchronization period. The timing of noise amount detection in the vertical synchronization period is determined by the synchronization separation circuit 9 and the timing generation circuit 10, and is performed by the detection pulse 1.

As described above, according to this embodiment, an orthogonal transformation circuit for decomposing a video signal into a plurality of frequency components, an inverse orthogonal transformation circuit for returning the plurality of decomposed frequency components to a video signal, and a video signal Delay circuit, coring circuit for removing noise, full-wave rectification circuit for determining noise amount in vertical synchronization period, horizontal smoothing circuit, vertical smoothing circuit, memory circuit,
By providing a sync separation circuit and timing generation circuit for controlling the timing of noise amount detection, when a video signal with beat interference, which has been a problem in the past, is input, the frequency of the beat interference is included. The noise removal operation is performed only on the frequency components that are generated, and the noise removal operation on the other frequency components is not performed. Therefore, the deterioration of sharpness as in the past can be significantly reduced, and noise can be reduced more effectively. It will be possible.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a block diagram of a video signal noise reduction apparatus according to the second embodiment of the present invention. In FIG. 5, reference numeral 11 is a first coring circuit, which removes a small amplitude component of the output signal of the full-wave rectification circuit. Reference numeral 12 denotes a gain control circuit, which can arbitrarily set the gain of the noise amount h which is the output signal of the memory circuit. The other structure is similar to that of the first embodiment. The second coring circuit of this embodiment corresponds to the coring circuit of the first embodiment.

The operation of the video signal noise reduction device configured as described above will be described below with reference to FIG.

First, in order to solve the problem that the output of the horizontal smoothing circuit has some value when a noise amount is detected during the vertical synchronization period, even a clean signal has some noise, in this embodiment, The first coring circuit is inserted in the output signal e of the full-wave rectifier circuit 5 to remove this noise component. Further, if the noise amount detection value itself in the vertical synchronization period is used as the coring value of the second coring circuit 4, the noise removal effect is not sufficient, so a value obtained by multiplying the output h of the memory circuit 8 by several times is used as the coring value h ′. It was found that the noise reduction can be performed more effectively by setting
Therefore, the gain control circuit 12 is provided to realize the noise reduction amount according to the gain setting value.

As described above, according to the present embodiment, the first coring circuit 11 detects the noise amount in the vertical period more accurately, and the gain control circuit 12 selects the desired noise reduction amount. By making it possible,
Therefore, a highly effective noise reduction device can be provided.

A third embodiment of the present invention will be described below with reference to the drawings. FIG. 6 is a block diagram of a video signal noise reduction apparatus according to the third embodiment of the present invention. In FIG. 6, 13 is a subtraction circuit, which subtracts a constant subtraction value from the output value of the memory circuit. Reference numeral 14 denotes a negative clipping circuit, which clips the portion when the output value of the subtraction circuit 13 becomes negative to zero. That is, 13
By means of 14 and 14, a value smaller than the subtraction value is removed from the output values of the memory circuit. Reference numeral 12 is a gain control circuit, which can arbitrarily set the gain of the output signal of the negative clip circuit, and sends it to the coring circuit 4 by coring it.

The other structure is the same as that of the first embodiment. The operation of the video signal noise reduction apparatus configured as described above will be described below with reference to FIG.

As described in the second embodiment, the output value of the horizontal smoothing circuit does not become 0 even with a clean signal. Therefore, in this embodiment, the output value of the memory circuit is a clean signal and the output value becomes 0. Adjustment is made by the subtraction circuit 13 and the negative clip circuit 14. After that, the gain control circuit 12 performs gain control so as to obtain a desired noise reduction amount, and determines the coring amount of the coring circuit 4.

As described above, according to the present embodiment, the subtraction circuit 13 and the negative clipping circuit 14 detect the noise amount in the vertical period more accurately, and the gain control circuit 12 determines the desired noise reduction amount. By making the selection possible, it is possible to provide a more effective noise reduction device.

Although the orthogonal transform circuit is the Hadamard transform circuit in the above embodiments, it may be a discrete cosine transform, a Fourier transform or the like.

[0024]

As described above, according to the present invention, an orthogonal transform circuit for decomposing a video signal into a plurality of frequency components, an inverse orthogonal transform circuit for returning the decomposed plurality of frequency components to a video signal,
Video signal delay circuit, noise canceling coring circuit, full-wave rectification circuit for determining the amount of noise in the vertical synchronization period, horizontal smoothing circuit, vertical smoothing circuit, memory circuit, and for controlling the timing of noise amount detection Sync separation circuit,
By providing a timing generation circuit, a gain control circuit that controls the amount of noise suppression, a subtraction circuit, and a clipping circuit, when a video signal with beat interference, which has been a problem in the past, is input, the frequency of the beat interference is input. The noise removal operation is performed only on the frequency components that include, and the noise removal operation on the other frequency components is not performed.
It is possible to considerably reduce the deterioration of sharpness as in the past, and it is possible to more effectively reduce noise.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of a Hadamard conversion circuit in FIG.

FIG. 3 is a circuit diagram of an inverse Hadamard transform circuit in FIG.

FIG. 4 is a waveform diagram of the video signal noise reduction device according to the first embodiment of the present invention.

FIG. 5 is a block diagram of a video signal noise reduction device according to a second embodiment of the present invention.

FIG. 6 is a block diagram of a noise reduction device for video signals according to a third embodiment of the present invention.

FIG. 7 is a block diagram of a conventional noise reduction device.

[Explanation of symbols]

 1 Hadamard conversion circuit 2 Inverse Hadamard conversion circuit 3 Delay circuit 4 Coring circuit 5 Full wave rectification circuit 6 Horizontal smoothing circuit 7 Vertical smoothing circuit 8 Memory circuit 9 Sync separation circuit 10 Timing generation circuit 11 First coring circuit 12 Gain control Circuit 13 Subtraction circuit 14 Negative clip circuit

Claims (3)

[Claims] 1. An M × N-order orthogonal transformation circuit for dividing an input video signal into a region of M points in the horizontal direction and N lines in the vertical direction and converting the signal in this region into frequency components, and the conversion signal of this conversion signal. For each frequency component except the DC component, a full-wave rectifier circuit that full-wave rectifies each frequency component, a horizontal smoothing circuit that smoothes each full-wave rectified signal during the vertical blanking period, and this horizontal smoothing circuit. A vertical smoothing circuit that smoothes the output signal of the circuit over several fields, a memory circuit that holds this vertically smoothed result until the next field, and a positive and negative clip level for the output signal of this memory circuit, and the output of the orthogonal transformation circuit. A coring circuit that clips and removes small amplitude components of the signal is provided, and the output signal and DC component of each coring circuit are input, and the original video signal is output from the signals of those frequency components. M × N-order inverse orthogonal transform circuit for inverse transforming into a signal, a sync separation circuit for separating a sync signal of an input video signal, and timing for generating horizontal smoothing and vertical smoothing timings connected to the output of this sync separating circuit. A noise reducing device for a video signal, comprising: a generating circuit. 2. An M.times.N-order orthogonal transformation circuit for dividing an input video signal into a region of M points in the horizontal direction and N lines in the vertical direction and converting the signal in this region into frequency components, and the conversion signal of this conversion signal. For each frequency component excluding the direct current component, a full-wave rectification circuit that full-wave rectifies each frequency component, a first coring circuit that removes a small amplitude component of each full-wave rectified signal, and the first The horizontal smoothing circuit that smoothes the output signal of the coring circuit in the vertical blanking period, the vertical smoothing circuit that smoothes the output signal of this horizontal smoothing circuit over several fields, and the result of this vertical smoothing in the next field. Memory circuit that holds the output of this memory circuit, a gain control circuit that adjusts the amplitude of the output of this memory circuit to a preset gain according to the desired noise removal effect, and the output of this gain control circuit. A second coring circuit that clips signals to positive and negative clipping levels and clips and removes small amplitude components of each frequency component is provided, and an output signal of each second coring circuit and a direct current component are input, and those It is connected to an M × N-order inverse orthogonal transform circuit for inversely converting a signal of a frequency component into an original video signal, a sync separation circuit for separating a sync signal of an input video signal, and an output of this sync separation circuit,
A noise reduction device for a video signal, comprising: a timing generation circuit for generating timings of horizontal smoothing and vertical smoothing. 3. An M × N-order orthogonal transform circuit for dividing an input video signal into an area of M points in the horizontal direction and an N line in the vertical direction and converting the signal in this area into frequency components, and a conversion signal of this converted signal. For each frequency component excluding DC component, full-wave rectification circuit that full-wave rectifies each frequency component, horizontal smoothing circuit that smoothes each full-wave rectified signal during the vertical blanking period, and this horizontal smoothing circuit. Vertical smoothing circuit that smoothes the output signal of the circuit over several fields, memory circuit that holds this vertically smoothed result until the next field, subtraction circuit that subtracts a constant value from the output signal of this memory circuit, and subtraction output A clipping circuit for clipping the negative component of the to zero, and a gain control circuit for adjusting the amplitude of the output of the clipping circuit to a preset gain according to the desired noise removal effect, The output signal of the gain control circuit is set to positive and negative clipping levels, and a coring circuit that clips and removes the small amplitude component of the output signal of the orthogonal transformation circuit is provided, and the output signal and DC component of each coring circuit are input, Connected to the output of this synchronization separation circuit, and an M × N-order inverse orthogonal conversion circuit that inversely converts the signals of these frequency components into an original video signal, a synchronization separation circuit that separates the synchronization signal of the input video signal, A noise reduction device for a video signal, comprising: a timing generation circuit for generating timings of horizontal smoothing and vertical smoothing.