JP3264049B2 - Video signal noise reduction device - Google Patents

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 to reduce the noise of a video signal, such as a video tape recorder, a video camera, a video disk, and a video signal transmission device.

[0002]

2. Description of the Related Art In recent years, a noise reduction apparatus for a video signal has been developed in accordance with an increase in the size and the quality of a color television receiver and an increase in the quality of a video tape recorder. It is regarded as important because it reduces noise generated by insufficient recording and storage conditions with software and reproduces more easily viewable images.

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

FIG. 7 is a block diagram showing a conventional video signal noise reduction apparatus. In FIG. 7, reference numeral 21 denotes a high-pass filtering circuit, which extracts a high-frequency component containing noise and a detailed information signal of the input video signal a and outputs it as a high-frequency luminance signal b. Reference numeral 22 denotes a full-wave rectifier circuit that performs full-wave rectification on the high-frequency luminance signal b and outputs a rectified high-frequency luminance signal c. Reference numeral 23 denotes a sample and hold circuit, which receives a rectified luminance signal c when the noise detection pulse e is input.
And holds the smoothed voltage until the next noise detection pulse e is input, and outputs it as a noise detection voltage d. Reference numeral 24 denotes a noise detection pulse generation circuit which shapes the waveform of the vertical synchronizing signal m so as to exclude portions used for a video signal, a character multiplexed signal, etc., 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, an input luminance signal a is inputted to a high-pass filter circuit 1 and its high-frequency components are separated to obtain a high-pass luminance signal b.
Which is input to the full-wave rectifier circuit 2.
The high-frequency luminance signal b is full-wave rectified by the full-wave rectification circuit 2 to obtain a rectified high-frequency luminance signal c. Next, the rectified high-frequency luminance signal c is input to the sample-and-hold circuit 3 and is subjected to a noise detection pulse e input from the noise detection pulse generation circuit 4 so that the rectified high-frequency luminance signal c during a period in which the pulse is input. At the same time as the pulse disappears, and the smoothed voltage is held, and the noise detection voltage d
Output as The noise detection voltage d is input to a 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 when the noise detection voltage d is reversed, the suppression amount can be automatically reduced or reduced to zero. As a result, An output video signal f is obtained. Note that the noise detection pulse is provided in a vertical synchronization period that is not affected by the effective video signal, thereby enabling accurate noise amount detection.

[0006]

However, in the above configuration, the amount of noise suppression is determined from the high-frequency components of the entire video signal.
When there is a high frequency component of a single frequency, the other high frequency components are suppressed in order to remove the interference, and as a result, there is a problem that the sharpness of the output image is reduced. Was. The present invention is to provide a video signal noise reduction device capable of minimizing the noise.

[0007]

In order to solve the above problems, a noise reduction apparatus for a video signal according to the present invention comprises 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 delay circuit for the video signal, a coring circuit for removing noise,
A full-wave rectifier circuit for determining the amount of noise during the vertical synchronization period,
One that has a horizontal smoothing circuit, a vertical smoothing circuit, a memory circuit, a synchronization separation circuit for controlling the timing of noise amount detection, a timing generation circuit, a gain control circuit for controlling the noise suppression amount, a subtraction circuit, and a clip circuit. It is.

[0008]

According to the present invention, the video signal is first decomposed into a plurality of frequency components by the orthogonal transform circuit, and the amount of noise in the vertical synchronizing period for each of the decomposed frequency components is horizontally transmitted to the full-wave rectifier circuit. , Obtained by a vertical smoothing circuit and stored in a memory circuit, which is used as a 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, noise is removed for each frequency component, and then returned to a video signal by the inverse orthogonal transform circuit and output. By this operation, when a video signal having a beat disturbance, which has been a problem in the past, is input, the noise removal operation is performed only on the frequency component including the frequency of the beat disturbance, and the noise removal of other frequency components is performed. Since no operation is performed, sharpness deterioration as in the related art can be considerably reduced, and noise can be more effectively reduced.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a video signal noise reduction apparatus according to an embodiment of the present invention.

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 denotes a Hadamard transform circuit, which decomposes an input video signal into a plurality of frequency components. Reference numeral 2 denotes an inverse Hadamard transform circuit that combines a plurality of frequency components and returns them to a video signal. Reference numeral 3 denotes a delay circuit that 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,
Small amplitude components containing noise are removed from each frequency component of the output of the Hadamard transform circuit to reduce noise. The coring amount of this circuit is given from the memory circuit 8. 5
Is a full-wave rectifier circuit, which turns the negative part of the output signal of the Hadamard conversion circuit back to positive. 6 is a horizontal smoothing circuit,
For a continuous horizontal period of the vertical synchronization period, each frequency component after full-wave rectification is smoothed and its amount is obtained. Reference numeral 7 denotes a vertical smoothing circuit, which smoothes the output of the horizontal smoothing circuit for the past several fields. 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 valid period. Reference numeral 9 denotes a synchronization separation circuit that separates horizontal and vertical synchronization of an input video signal. Reference numeral 10 denotes a timing generation circuit which determines the timing for performing horizontal smoothing in a vertical synchronization period from each of the horizontal and vertical synchronization signals. The timing of the vertical smoothing circuit and the memory circuit is also determined.

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

First, an input video signal a is input to a Hadamard transform circuit 1 and decomposed into frequency components by Hadamard transform. FIG. 2 shows a specific circuit diagram of the Hadamard transform, and the example of FIG. 2 shows a case where division into four frequency components is performed. F (0) is a DC component, and F (0)
(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 for a portion of the vertical synchronization period other than the horizontal synchronization. When there is essentially no noise, the result of this smoothing is almost 0, but when there is noise (a broadcast signal of a weak electric field or the like), the amount of noise is shown accordingly. The horizontal smoothing circuit output f is smoothed by the vertical smoothing circuit 7 with the noise amount from several fields before in order to stabilize the operation.

The smoothed signal g is input to the memory circuit 8 so as to maintain a constant value during the vertical valid 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 transform circuit is cored using the output signal h as a coring amount to remove noise. This operation is performed for each frequency component. That is, the amount of noise for each frequency component obtained in the vertical synchronization period is
The coring circuit is operated as the coring amount (noise removal amount) of the coring circuit between the fields. Thereafter, 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 transform circuit, and are returned to the output video signal m from which noise has been removed by the inverse Hadamard transform. FIG. 3 is a specific circuit diagram of the inverse Hadamard transform, and an output video signal can be obtained by performing addition and subtraction for each frequency component. FIG. 4 is a waveform diagram showing the operation of each part during the vertical synchronization period. The timing of detecting the amount of noise during 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 l.

As described above, according to this embodiment, 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, A delay circuit, a coring circuit for removing noise, a full-wave rectifier circuit for determining the amount of noise in a vertical synchronization period, a horizontal smoothing circuit, a vertical smoothing circuit, a memory circuit,
By providing a sync separation circuit and a timing generation circuit to control the timing of noise detection, if 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 for the frequency components that are not performed, and the noise removal operation for the other frequency components is not performed.Thus, the deterioration of sharpness as in the past can be considerably reduced, and the noise can be more effectively reduced. You can do it.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram of a video signal noise reduction device according to a second embodiment of the present invention. In FIG. 5, reference numeral 11 denotes a first coring circuit, which removes a small amplitude component of an output signal of the full-wave rectifier 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. Other configurations are the same as those of the first embodiment. The second coring circuit of the present 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, when detecting the noise amount during the vertical synchronization period, in order to solve this disadvantage that even a clean signal has some noise and the output of the horizontal smoothing circuit has some value, in this embodiment, The first coring circuit is inserted into the output signal e of the full-wave rectifier circuit 5 to remove this noise component. Also, 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 that the value obtained by multiplying the output h of the memory circuit 8 by several times is the coring value h ′ Thus, it was found that more effective noise reduction can be achieved.
Therefore, the gain control circuit 12 is provided to realize a noise reduction amount according to the gain setting value.

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

Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a block diagram showing a video signal noise reduction apparatus according to a third embodiment of the present invention. In FIG. 6, reference numeral 13 denotes a subtraction circuit, which subtracts a constant subtraction value from the output value of the memory circuit. Numeral 14 denotes a negative clipping circuit which, when the output value of the subtraction circuit 13 becomes negative, clips that portion to zero. That is, 13
As a result, the value smaller than the subtraction value among the output values of the memory circuit is removed. 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 with a coring amount.

The other structure is the same as that 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.

As described in the second embodiment, since the output value of the horizontal smoothing circuit does not become 0 even with a clean signal, in the present embodiment, the output value of the memory circuit becomes 0 with a clean signal. The adjustment is performed by the subtraction circuit 13 and the negative clip circuit 14. Thereafter, gain control is performed by the gain control circuit 12 so as to obtain a desired noise reduction amount, and the coring amount of the coring circuit 4 is determined.

As described above, according to the present embodiment, the detection of the noise amount in the vertical period is more accurately performed by the subtraction circuit 13 and the negative clip circuit 14, and the desired noise reduction amount is determined by the gain control circuit 12. By making the selection possible, a more effective noise reduction device can be provided.

In the above embodiment, the orthogonal transform circuit is a Hadamard transform circuit, but may be a discrete cosine transform, a Fourier transform or the like.

[0024]

As described above, the present invention provides 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, coring circuit for removing noise, full-wave rectifier circuit for obtaining the amount of noise during 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 for controlling the amount of noise suppression, a subtraction circuit, and a clipping circuit, when a video signal having a beat disturbance, which has conventionally been a problem, is input, the frequency of the beat disturbance is input. The noise removal operation is performed only on the frequency components that include the, and the noise removal operation on the other frequency components is not performed.
The conventional deterioration of sharpness can be considerably reduced, and noise can be more effectively reduced.

[Brief description of the 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 transform circuit in FIG. 1;

FIG. 3 is a circuit diagram of the inverse Hadamard transform circuit in FIG. 1;

FIG. 4 is a waveform chart of a noise reduction device for a video signal 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 video signal noise reduction device according to a third embodiment of the present invention.

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

[Description of Signs] 1 Hadamard transform circuit 2 Inverse Hadamard transform circuit 3 Delay circuit 4 Coring circuit 5 Full-wave rectifier circuit 6 Horizontal smoothing circuit 7 Vertical smoothing circuit 8 Memory circuit 9 Synchronous separation circuit 10 Timing generation circuit 11 First core Ring circuit 12 Gain control circuit 13 Subtraction circuit 14 Negative clip circuit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-53-17222 (JP, A) JP-A-4-172876 (JP, A) JP-A-63-20970 (JP, A) JP-A-7- 15631 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 5/21

Claims (3)

(57) [Claims] 1. An M × N-order orthogonal transform circuit for dividing an input video signal into M points in the horizontal direction and N lines in the vertical direction, and converting the signals in this area into frequency components. A full-wave rectifier circuit for full-wave rectification of each frequency component for each frequency component excluding a DC component, a horizontal smoothing circuit for smoothing each full-wave rectified signal during a vertical blanking period, A vertical smoothing circuit for smoothing the output signal of the circuit over several fields, a memory circuit for holding the vertically smoothed result until the next field, and a positive / negative clip level for the output signal of the memory circuit, and the output of the orthogonal transform circuit A coring circuit that clips and removes the small amplitude components of the signal is provided. The output signal and the DC component of each coring circuit are input, and the original video signal is An M × N inverse orthogonal transform circuit for inversely transforming an input video signal, a sync separation circuit for separating a sync signal of an input video signal, and a timing for connecting the output of the sync separation circuit to generate horizontal smoothing and vertical smoothing timings A noise reduction device for a video signal, comprising a generation circuit. 2. An M × N-order orthogonal transformation circuit for dividing an input video signal into M points in the horizontal direction and N lines in the vertical direction, and converting the signals in this area into frequency components. A full-wave rectifier circuit for performing full-wave rectification of each frequency component for each frequency component excluding a DC component, a first coring circuit for removing small-amplitude components of each of the full-wave rectified signals, A horizontal smoothing circuit for smoothing the output signal of the coring circuit during the vertical blanking period, a vertical smoothing circuit for smoothing the output signal of the horizontal smoothing circuit over several fields, and the result of the vertical smoothing in the next field. A gain control circuit for adjusting the amplitude of the output of the memory circuit to a preset gain according to a desired noise reduction effect, and a memory control circuit for controlling the output of the gain control circuit. A second coring circuit for clipping and removing small-amplitude components of each frequency component with a signal having a positive / negative clip level; an output signal and a DC component of each of the second coring circuits as inputs; An M × N inverse orthogonal transform circuit for inversely converting a frequency component signal into an original video signal, a sync separation circuit for separating a sync signal of an input video signal, and an output of the sync separation circuit,
A noise reduction apparatus for a video signal, comprising: a timing generation circuit that generates horizontal smoothing and vertical smoothing timings. 3. An M × N-order orthogonal transformation circuit for dividing an input video signal into M points in the horizontal direction and N lines in the vertical direction, and converting the signals in this area into frequency components. A full-wave rectifier circuit for full-wave rectification of each frequency component for each frequency component excluding a DC component, a horizontal smoothing circuit for smoothing each full-wave rectified signal during a vertical blanking period, A vertical smoothing circuit for smoothing the output signal of the circuit over several fields, a memory circuit for holding the vertically smoothed result until the next field, a subtraction circuit for subtracting a constant value from the output signal of the memory circuit, and a subtraction output A clip circuit that clips a negative component of the signal to zero, a gain control circuit that adjusts the output of the clip circuit to a preset gain according to a desired noise removal effect, And a coring circuit for clipping and removing small amplitude components of the output signal of the orthogonal transform circuit with the output signal of the gain control circuit being a positive and negative clip level, and inputting the output signal and the DC component of each coring circuit, An M × N inverse orthogonal transform circuit for inversely converting the signals of those frequency components to the original video signal, a sync separation circuit for separating a sync signal of the input video signal, and an output of the sync separation circuit, A noise reduction apparatus for a video signal, comprising: a timing generation circuit that generates horizontal smoothing and vertical smoothing timings.