JP2954541B2 - Image quality improvement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for improving image quality of a television signal by digital image signal processing, and more particularly to an FM signal reflected by a sporadic E layer.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image quality improvement device for improving image quality deterioration of a television signal caused by interference with a television signal due to a modulated wave.

[0002]

2. Description of the Related Art Conventionally, among measures for improving image quality deterioration of a television signal due to interference waves, as an image quality improvement device in a video stage of a receiver, interference is performed by FFT analysis (fast Fourier transform) during a blanking period of a television signal. A device that detects a center frequency of a wave and cuts off a frequency component corresponding to the center frequency by a notch filter has been studied.
[Arada et al .: Television tuner for improved home-use interference,
IEICE Technical Report, EMCJ87-60 (1987)] Also, a discrete Fourier transform operation is performed on a digital signal sequence, and a median filter or an appropriate rank order filter is applied to the Fourier coefficient sequence to disturb waves superimposed on the signal. As a technique for suppressing only an interference wave component in a signal sequence by performing an inverse conversion operation after suppressing a spectrum, there is a signal processing apparatus described in Japanese Patent Application Laid-Open No. Hei 5-327534 by the present applicant.

[0003]

In the former conventional method,
Since the power spectrum of the video signal (desired wave component) is not taken into account, if the frequency component of the video signal at the frequency of the interference wave is sufficiently small, it is possible to remove the interference wave by cutting off the frequency. However, if the frequency component of the video signal is not sufficiently small, the video signal component is also removed, resulting in a waveform distortion in the reproduced image. In addition, a plurality of notch filters are required for a plurality of interference waves, and the circuit scale is large.

On the other hand, in the latter conventional method, the spectral state of the signal component needs to be sufficiently smooth in the vicinity of an arbitrary spectrum in order to remove an interference wave. In general, the spectrum is not smooth. It is also possible to use the smoothness of the temporal change in the spectral shape of the signal component, but it cannot be applied to the removal of an interfering wave that changes smoothly in time, such as an interfering wave by a sporadic E layer. .

Accordingly, an object of the present invention is to provide an image quality improving apparatus which has solved the above problems.

[0006]

In general, the frequency characteristic of an image signal statistically shows a tendency that the amplitude value gradually decreases as the frequency increases.
By integrating the T output and averaging over time, it is possible to estimate the power spectrum of the desired wave component from which the influence of the interfering wave has been eliminated by utilizing the statistical properties of the image signal. That is, contrary to the tendency that the amplitude value gradually decreases as the frequency increases, it is determined that the frequency at which the amplitude value shows a steep peak corresponds to the interference wave component. Further, by utilizing the general property of an image that the time average of the amplitude value is smoothly continuous with respect to the frequency, it is possible to correct the amplitude characteristic including the interference wave component to the amplitude characteristic only of the desired wave component.

It is considered that the magnitude of the image quality deterioration due to the interference wave is determined by the ratio between the amplitude value of the interference wave and the amplitude value of the desired wave at that frequency. Therefore, F of the video signal
By comparing the FT value with the estimated amplitude value of the desired wave, and suppressing only the frequency components whose ratio exceeds the set threshold value, it is possible to suppress only the interference wave having a large influence on the image quality deterioration. According to this method, it is possible to reduce the waveform distortion caused by the interference wave removal without removing the video signal components more than necessary.

Since an interference wave component is suppressed by suppressing the amplitude value in the frequency domain by the FFT, an interference wave elimination filter is not required. Even for a plurality of interfering waves, it is possible to effectively detect and suppress the interfering waves without increasing the circuit scale.

In view of this, the present applicant has proposed a picture quality improving apparatus shown in FIG. 8 in Japanese Patent Application No. 8-205588.
The image quality improvement device described above converts the analog television signal to A /
The digital signal is converted into a digital signal by the D conversion circuit 21, the power spectrum of the video signal calculated by the FFT processing circuit 22 is averaged over time by the integration circuit 23, and further, the smoothing circuit 24
Smoothing of the frequency characteristic removes the interfering wave component from the power spectrum and estimates the power spectrum of the desired wave. The adaptive gain adjustment circuit 26 estimates the estimated value and the video signal after the delay by the delay circuit 25. Based on the result of comparison with the FFT value of
This is an apparatus that improves image quality by selecting and suppressing the amplitude value of T, and outputs an analog television signal through an inverse FFT processing circuit 27 and a D / A conversion circuit 28.

Here, interference by the sporadic E layer does not always occur but tends to occur during the daytime from spring to summer. That is, the time rate at which interference occurs is 1
Few throughout the year. Even under such conditions, the video signal itself (main line) is always
In the method of Japanese Patent Application No. 8-205588 passing through an inverse FFT processing circuit, a high-precision FF is used to maintain the quality of a video signal.
T, requires inverse FFT processing.

On the other hand, the FFT and inverse FFT processing are so-called linear transformations, in which a video signal (main line) is handled only in a time domain signal form, only an interference wave is detected in a frequency domain, and the detected interference wave is converted into a time signal. The method of converting into a signal of the area and subtracting it from the video signal (main line) can expect the same effect as the method of Japanese Patent Application No. 8-205588.
Since the T and inverse FFT processes are applied only to the interfering wave, the FFT and inverse FFT processes do not need to be so high in precision as compared with Japanese Patent Application No. 8-205588, and the device scale can be reduced.

[0012] The invention according to claim 1 is a decomposing means for decomposing a video signal into frequency components and outputting the same, an integrating means for obtaining and outputting a time average of the output of the decomposing means, and an output of the integrating means with respect to the frequency. Smoothing means for smoothing, and comparing means for comparing the output of the integrating means and the output of the smoothing means under a preset condition to detect the frequency of the interference wave,
Interference signal estimating means for estimating the spectral intensity for the frequency of the interference signal based on the output of the comparing means; reconstructing means for reconstructing the interference signal estimation means output into a time-domain interference signal; and And subtracting means for subtracting the interference signal.

[0013] The invention according to claim 2 is based on claim 1.
Wherein the decomposition means is a fast Fourier transform processing circuit, and the reconstructing means is an inverse fast Fourier transform processing circuit.

The invention according to claim 3 is the invention according to claim 1 or 2, wherein the integrating means accumulates the output of the decomposing means for each frequency component over a period T using one delay element; A coefficient of 1 is added to the signal after the accumulation.
/ T for multiplying and outputting the result.

Further, according to a fourth aspect of the present invention, in the first or second aspect, the integrating means includes an adder to which the output of the decomposing means is input, and one delay element for delaying the output of the adder. Means for multiplying the output of the delay element by an attenuation coefficient k (k is a positive real number less than 1) and supplying the result to the adder;
Means for multiplying the adder output by a coefficient 1-k and outputting the result.

Further, according to a fifth aspect of the present invention, in the first or second aspect, the integrating means includes T-1 delay elements connected in cascade for sequentially delaying the output of the decomposing means; An adder for adding the outputs of the delay elements, and means for multiplying the output of the adder by a coefficient 1 / T and outputting the result.

Further, according to a sixth aspect of the present invention, in the first or second aspect, the smoothing means outputs an average value of frequency components near the frequency to be smoothed in the output of the integrating means. There is a feature.

According to a seventh aspect of the present invention, in the first or second aspect, the comparing means is arranged such that the output of the integrating means multiplies the output of the smoothing means by a preset first threshold value. The frequency when the output of the integrator is larger than the predetermined value and the output of the integrator is larger than a preset second threshold value is determined as the frequency of the interference wave and output.

According to an eighth aspect of the present invention, in the seventh aspect, the comparing means further comprises one or two frequencies obtained from the decomposing means adjacent to both sides of the frequency determined as the interference wave. Is also determined to be the frequency of the interference wave.

According to a ninth aspect of the present invention, in the first or second aspect, the interfering wave estimating means relates to the frequency of the interfering wave detected by the comparing means and outputs the output of the decomposing means to the output of the smoothing means Is output as the spectrum intensity of the frequency of the interference wave.

According to a tenth aspect of the present invention, in the first or second aspect, the interfering wave estimating means relates to a frequency of the interfering wave detected by the comparing means, and outputs an output of the decomposing means to a spectrum intensity of the frequency. Is output.

Further, according to an eleventh aspect of the present invention, in the first or second aspect, the interfering wave estimating means relates to a frequency of the interfering wave detected by the comparing means, and outputs from the integrating means output to the smoothing means output. Is output as the spectrum intensity of the frequency of the interference wave.

In a twelfth aspect of the present invention, in the first or second aspect, the interference wave estimating means relates to a frequency of the interference wave detected by the comparing means, and outputs an output of the integration means to the frequency of the interference wave. Is output as the spectrum intensity.

According to a thirteenth aspect of the present invention, in the second aspect, the video signal is sampled at four times the frequency of the color subcarrier, and one horizontal line including a blanking period is sampled at 910 points. In the case of an NTSC television signal, the fast Fourier transform circuit and the inverse fast Fourier transform circuit each have a block length of 1024 points, and 114 bits from the beginning of the blanking period of the horizontal line located next to the horizontal line of the signal to be processed. By taking in points and generating 1024 samples, fast Fourier transform processing and inverse fast Fourier transform processing are performed for each horizontal line of the signal to be processed.

According to a fourteenth aspect of the present invention, in the seventh or eighth aspect, when the video signal is an NTSC television signal, the comparing means centers on the DC and chrominance subcarrier frequencies of the video signal. , Up to ± 1
It is characterized in that a predetermined frequency section in the range of 00 kHz is determined not to be an interference wave in any case.

[0026]

FIG. 1 is a block diagram showing an embodiment of an image quality improving apparatus according to the present invention in a television receiver. In FIG. 1, a is an input analog television signal, which is a composite signal such as NTSC, or a luminance signal or a color difference signal after Y / C (luminance / color difference) separation. Reference numeral 1 denotes an A / D (analog / digital) conversion circuit for converting an analog input signal into a digital signal. When the input signal to the A / D conversion circuit 1 is a composite signal, a digital Y / C separation circuit can be provided before the output of the A / D conversion circuit 1. b is a digital composite signal, a digital luminance signal, or a digital color difference signal. The digital television signal used in the following description refers to any of these signals.

The video signal digitized by the A / D conversion circuit 1 passes through a delay circuit 9 as a video signal (main line).
The interference wave signal i is subtracted by the subtracter 10 and the D / A conversion circuit 11 returns to the analog video signal. Here, the delay circuit 9
Is for correcting the delay of the interference signal i with respect to the video signal (main line).

Reference numeral 2 denotes an FFT (Fast Fourier Transform) processing circuit for converting a time-series digital television signal into a frequency-series signal, and decomposes an input signal into frequency components.
Output. One block of FFT is converted to one block of television signal.
By corresponding to a line or an integral multiple of one line, a boundary of a block in which block distortion is easily recognized can be prevented from being provided within an effective pixel range of a television signal. One horizontal line sampled at four times the frequency of the color sub-carrier and including a blanking period (about 16% of the whole) is 91
When one line of an NTSC television signal sampled at 0 points corresponds to one block of FFT, when the block length of FFT and inverse FFT is set to 1024 in circuit design, the remaining 114 points are filled with zero. Since a sudden level change occurs, it is not preferable. Therefore, consecutive ones that start within the blanking period included in the horizontal line of the signal to be processed and end within the blanking period of the next horizontal line located next.
By generating 024 samples, it is possible to realize an FFT circuit and an inverse FFT circuit that use one horizontal line as a conversion interval. At this time, a total of 114 points in the blanking period are converted twice. c is FFT
An output signal of the processing circuit, which is an input signal to the integrating circuit 3 and the delay circuit 5.

The integration circuit 3 calculates a time average of the FFT output signal c. The input signal to the integration circuit 3 is an amplitude value or a function of the amplitude value (for example, the square of the amplitude value).
If the output of the FT processing circuit 2 is a complex number, it is converted to an amplitude value at the first stage of the integration circuit. Three examples of the integrating circuit 3 are shown in FIGS. In FIGS. 2, 3 and 4,
An example in which the amplitude value for each frequency is sequentially input as the input signal c (frequency sweep) is shown in FIG.
Reference numeral 16 denotes a delay element for one block of the n-point FFT.

In FIG. 2, the switch 11 is connected to the 0 side in the first block of the integration period, and connected to the delay element 15 in the second and subsequent blocks.
, The input signal c is accumulated for each frequency component. The integration is completed when the accumulation for the input signal c over the T blocks is completed.
Are multiplied by a coefficient of 1 / T and output as an output signal d via the switch 14. During accumulation, the switch 14 is connected to the delay element 16 side, and the previous integration result is output as the output signal d.

FIG. 3 shows a second embodiment of the integration circuit. The output of the adder 19 is delayed by the delay element 15 without using a switch, and the attenuation coefficient k (k is less than 1) is output by the coefficient unit 17. Is multiplied by the real number) and added to the input signal c to continuously obtain an integrated output. The integrated output is multiplied by a coefficient 1-k by a coefficient unit 18 and output as an output signal d. Things.

FIG. 4 shows a third embodiment of the integration circuit.
-1 delay elements 31-1 to 31-T-1 are connected in cascade, and the input signal c and the addition result of each delay element output are multiplied by a coefficient unit 13 by a coefficient of 1 / T. The average value over the T block immediately before c is output continuously.

Reference numeral 4 in FIG. 1 denotes a smoothing circuit, which removes an interfering wave component from the average frequency characteristic over T blocks in the output signal d of the integrating circuit 3 and estimates the average frequency characteristic only of the desired wave component. . FIGS. 5 and 6 show two embodiments of the smoothing circuit 4. FIG.

FIG. 5 shows that the comparison / selection circuit 32 compares the frequency component d0 of the signal d to be smoothed with the average value d1 of N frequency components adjacent to the frequency, and sets a third preset value. When the frequency component d0 to be smoothed exceeds the threshold value and exceeds the average value d1, the frequency component d0 is replaced with the average value d1 (otherwise, the frequency component d0 is not replaced), and the output signal e is smoothed. And d0 and d1 are generated by N delay elements 33 for one point, an adder 34, and a coefficient unit 35 having a 1 / N coefficient.

FIG. 6 shows an embodiment in which the input signal d is sequentially input from a frequency component corresponding to a low frequency (frequency sweep). As the frequency characteristic of the video signal becomes higher, the frequency characteristic corresponds to the higher frequency. Utilizing the property that the amplitude value decreases, the output signal e obtained by delaying the output of the comparison / selection circuit 32 by the delay element 33 for one point, that is, 1
The frequency component to be smoothed is compared with the frequency component to be smoothed, that is, the signal d, and the frequency component to be smoothed, that is, one signal d exceeds the fourth threshold value set in advance. If the frequency component of the lower frequency is larger than the signal e, that frequency component (signal d)
Is replaced with the frequency component (signal e) of one lower frequency (in other cases, it is not replaced), thereby smoothing can be performed. If the threshold value is set to 0 (or 1), the smoothing characteristic becomes monotonic and non-increasing. This method is particularly effective when handling television signals other than composite signals. FIG. 6 shows an example in which the delay element 33 is inserted immediately after the comparison / selection circuit 32. However, the delay element 33 is inserted in the feedback loop of the comparison / selection circuit 32 so that no delay occurs in the output of the smoothing circuit. You can also.

Reference numeral 5 in FIG. 1 denotes a delay circuit, which outputs an output signal f for compensating a delay amount between the output c of the FFT processing circuit 2 and the output e of the smoothing circuit 4. Reference numeral 6 denotes a comparison circuit which multiplies the output e of the smoothing circuit 4 by a preset first threshold value and compares it with the output d of the integration circuit 3. Further, the output d of the integration circuit 3 is compared with a second threshold value set in advance. When K is a first threshold value and δ is a second threshold value, the output d of the integration circuit 3 is equal to or more than K times the output e of the smoothing circuit 4, and the comparison circuit 6 When the output d of No. 3 is larger than δ, this frequency is determined as the frequency g of the interfering wave and output.

FIG. 7 is a spectrum of a television signal which has been disturbed by two FM broadcast waves. The output c of the FFT processing circuit 2, the output d of the integration circuit 3, and the output e of the smoothing circuit 4 are shown in FIG. This is an example of the display. Here, the horizontal axis represents frequency, and the vertical axis represents spectrum intensity expressed on a logarithmic scale. It can be seen that the spectrum intensity changes greatly with frequency by simply performing the FFT processing on the video signal, but the change is reduced by integration. In addition, the integrated output has a remarkable peak, which is an interference wave. The integrated output is smoothed to detect this interference wave. By smoothing, the peak of the interference wave disappears, and the spectrum changes to a smoother spectrum. From FIG. 7, it can be understood that the interference wave can be detected by comparing the integrated output and the smoothed output.

In FIG. 1, reference numeral 7 denotes an interference wave estimating circuit for estimating and outputting the spectrum intensity of the interference wave detected by the comparison circuit 6 with respect to the frequency g. The four methods shown in Table 1 can be considered using the frequency g of the interference wave detected by the comparison circuit 6 as an input. If the output symbols d, e, f, and h are used as the spectrum intensities at the frequency g, the operations of the comparison circuit 6 and the interference wave estimation circuit 7 are as shown in Table 1.

[0039]

[Table 1]

Since the judgment of the interference wave in the comparison circuit 6 is made based on the ratio of the output d of the integration circuit 3 to the output e of the smoothing circuit 4, it is easy to make an erroneous detection if both have small values. For this reason, when the absolute amplitude of the spectrum intensity is small, it is necessary not to be an interference wave. A second threshold δ is provided for this purpose.

The methods (1) to (4) in Table 1 were verified by trial production of an apparatus, or good results were obtained. For the value of K, K = 2 gave good results when the spectral intensity has units of amplitude.

In the vicinity of the direct current and the color subcarrier, the spectrum has a sharp peak having a shape similar to that of the interference wave. In order to prevent this part from being erroneously detected as an interfering wave, it is determined that it is not an interfering wave under any condition in the vicinity of the direct current and the vicinity of the color subcarrier, especially in a section of a predetermined frequency within a range of ± 100 kHz from each center. There is a need to.

Further, in FIG. 7, the peak is steep but has a slight width. The above-described detection method cannot detect all frequencies up to both ends of this width. This measure is performed as follows. That is, the width of one or two spectrums adjacent to both sides of the FFT frequency determined to be the interference wave is expanded, and this frequency is also determined to be the frequency of the interference wave. By doing this,
It has been confirmed that there is a further improvement effect.

Reference numeral 8 denotes an inverse FFT processing circuit, which performs an inverse FFT process only on the interference wave h output from the interference wave estimation circuit 7 to convert the interference wave into a time-domain signal i. The disturbing wave converted into the signal in the time domain is subtracted by the subtracter 10 from the delayed main video signal to obtain a video signal j from which the disturbing wave has been removed. If this is converted back to an analog signal by the D / A conversion circuit 11, a clear analog video signal k from which an interference wave has been removed can be obtained.

[0045]

As described above, according to the present invention,
By adopting a method of selecting the frequency of the interfering wave to be suppressed from the video signal, it is possible to suppress only the interfering wave having a large influence on the image quality deterioration.

Therefore, according to the present invention, it is possible to reduce the waveform distortion of the video component caused by the interference wave removal by the conventional method without removing the video signal component more than necessary. The improvement in image quality is large even when compared to.

Further, by performing the suppression operation in the FFT area, an expected improvement in image quality can be obtained without increasing the circuit scale even for a plurality of interference waves.

Further, as compared with the signal processing apparatus described in JP-A-5-327534 using a median filter and a rank order filter, a temporal average spectrum can be obtained by the integration means, and a signal such as a video signal can be obtained. It is possible to instantaneously improve the image quality of a signal whose spectrum is not smooth. In particular, it is characterized by a high image quality improvement effect on temporally continuous interference waves.

Further, conventionally, this kind of picture quality improving device is composed of a demodulation stage of an antenna system, that is, a high frequency stage, and it has been difficult to reduce the circuit scale and the size of the device. Since the device can be used, and furthermore, digital signal processing can be used, cost reduction by mass production is expected, and it can be easily mounted on a home receiver. Further, it is also possible to connect and use the conventional image quality improvement device in the high frequency stage in cascade, and in this case, it is possible to configure a higher performance image quality improvement device.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an apparatus for improving image quality of interference of a television signal according to the present invention.

FIG. 2 is a diagram showing a first embodiment of the integration circuit of FIG. 1;

FIG. 3 is a diagram showing a second embodiment of the integration circuit of FIG. 1;

FIG. 4 is a diagram showing a third embodiment of the integration circuit of FIG. 1;

FIG. 5 is a diagram showing a first embodiment of the smoothing circuit of FIG. 1;

FIG. 6 is a diagram showing a second embodiment of the smoothing circuit of FIG. 1;

FIG. 7 is a diagram showing a spectrum of a video signal mixed with an interference wave.

FIG. 8 is a block diagram of an image quality improving device in Japanese Patent Application No. 8-205588.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 A / D conversion circuit 2 FFT processing circuit 3 Integrating circuit 4 Smoothing circuit 5, 9 Delay circuit 6 Comparison circuit 7 Interference wave estimation circuit 8 Inverse FFT processing circuit 10 Subtractor 11 D / A conversion circuit

Continuing on the front page (72) Inventor Kenichi Tsuchida 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Japan Broadcasting Research Institute (72) Inventor Atsushi Fukuda 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Inside the Broadcasting Research Institute (72) Inventor Kazumasa Kobayashi 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Within the Broadcasting Research Institute (56) References JP-A-3-136475 (JP, A) JP-A-5- 327534 (JP, A) JP-A-6-311399 (JP, A) JP-A-63-142778 (JP, A) JP-A-62-290270 (JP, A) JP-A-10-51663 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 5/21

Claims (14)

(57) [Claims] 1. Decomposition means for decomposing a video signal into frequency components for output, integration means for obtaining and outputting a time average of the output of the decomposition means, and smoothing for smoothing the output of the integration means with respect to frequency. Means, comparing means for comparing the output of the integrating means and the output of the smoothing means under predetermined conditions to detect the frequency of the interference wave, and estimating the spectrum intensity for the frequency of the interference wave based on the output of the comparison means. Interfering wave estimating means, reconstructing means for reconstructing the output of the interfering wave estimating means into an interference signal in a time domain, and subtracting means for subtracting the interfering wave signal from the video signal. Image quality improvement device. 2. An image quality improving apparatus according to claim 1, wherein said decomposition means is a fast Fourier transform processing circuit, and said reconstruction means is an inverse fast Fourier transform processing circuit. 3. The signal processing device according to claim 1, wherein the integrating means accumulates the output of the decomposing means for each frequency component over a period T using one delay element, and adds a coefficient to the signal after the accumulation is completed. Means for multiplying and outputting 1 / T. 4. The delay circuit according to claim 1, wherein the integration means includes an adder to which the output of the decomposition means is input, one delay element for delaying the output of the adder, and an attenuation coefficient added to the output of the delay element. An image quality improving apparatus, comprising: means for multiplying k (k is a positive real number less than 1) to the adder; and means for multiplying the adder output by a coefficient 1-k and outputting the result. 5. The method according to claim 1, wherein the integrating means adds the T-1 delay elements connected in cascade that sequentially delay the output of the decomposing means, the output of the decomposing means and the outputs of the delay elements. An image quality improving apparatus comprising: an adder; and means for multiplying an output of the adder by a coefficient 1 / T and outputting the result. 6. The image quality improvement method according to claim 1, wherein said smoothing means is means for outputting an average value of a frequency component adjacent to a frequency to be smoothed in said output of said integrating means. apparatus. 7. The comparing means according to claim 1, wherein the output of the integrating means is larger than a value obtained by multiplying the output of the smoothing means by a preset first threshold value, and An image quality improving apparatus characterized in that a frequency when the output of the integration means is larger than a second threshold value set in advance is determined as the frequency of the interference wave and output. 8. The interfering wave according to claim 7, wherein the comparing means further includes one or two frequencies obtained from the decomposing means adjacent to both sides of the frequency determined as the interfering wave, respectively. An image quality improvement device characterized by determining that: 9. The disturbance wave estimating means according to claim 1, wherein the disturbance wave estimating means calculates a value obtained by subtracting the output of the smoothing means from the output of the decomposing means with respect to the frequency of the disturbance wave detected by the comparing means. An image quality improving device for outputting as a spectrum intensity of a frequency of 10. The interference wave estimating means according to claim 1, wherein the interference wave estimating means outputs the output of the decomposing means as a spectrum intensity of the frequency of the interference wave with respect to the frequency of the interference wave detected by the comparing means. Characteristic image quality improvement device. 11. The interfering wave according to claim 1, wherein the interfering wave estimating unit calculates a value obtained by subtracting the output of the smoothing unit from the output of the integrating unit with respect to the frequency of the interfering wave detected by the comparing unit. An image quality improving device for outputting as a spectrum intensity of a frequency of 12. The interference wave estimating means according to claim 1, wherein the interference wave estimating means outputs the output of the integrating means as a spectrum intensity of the frequency of the interference wave with respect to the frequency of the interference wave detected by the comparing means. Characteristic image quality improvement device. 13. The NTSC television signal according to claim 2, wherein the video signal is sampled at four times the frequency of the color subcarrier, and one horizontal line including a blanking period is sampled at 910 points. The fast Fourier transform circuit and the inverse fast Fourier transform circuit,
Each block length is set to 1024 points, and 1024 consecutive samples starting from the blanking period included in the horizontal line of the signal to be processed and ending within the blanking period of the horizontal line located next to the horizontal line of the signal to be processed are defined as: An image quality improving apparatus characterized by performing a fast Fourier transform process and an inverse fast Fourier transform process for each horizontal line of the processing target signal by generating the signal. 14. The method according to claim 7, wherein when the video signal is an NTSC television signal, the comparing means preliminarily sets the frequency of a DC and a chrominance subcarrier of the video signal in a range of ± 100 kHz at the maximum. An image quality improving apparatus characterized in that a section of a determined frequency is determined not to be an interference wave in any case.