JP2502865B2 - Video signal noise eliminator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise removing device for removing noise from a luminance signal of a video tape recorder (hereinafter referred to as VTR).

[0002]

2. Description of the Related Art In recent years, VTRs are required to have higher image quality. Under such circumstances, many noise eliminators and the like utilizing line correlation of video signals have been proposed.

A conventional vertical noise eliminator will be described below. 8 and 9 are block diagrams showing the configuration of a conventional noise filter disclosed in Japanese Patent Publication No. 2-3356. In the pre-emphasis circuit shown in FIG. 8, the video signal input to the input terminal 8a is the subtraction circuit 80.
5 is supplied to one of the input terminals, while the adder circuit 801
Through the delay circuit 802. This delay circuit 8
The signal output from 02 is attenuated by a coefficient circuit (attenuation circuit) 803 that multiplies a coefficient K1 (K1 <1) and then supplied to the addition circuit 801, where it is added and synthesized with the video signal from the input terminal 8a. After that, it is supplied to the delay circuit 802 again. Further, the output signal of the delay circuit 802 is a coefficient K2.
It is supplied to the other input terminal of the subtraction circuit 805 through a coefficient circuit 804 that multiplies by. The subtraction circuit 805 has an input terminal 8
The output signal of the coefficient circuit 804 is subtracted from the input video signal from a, and the signal thus obtained is output to the output terminal 8b. The signal output to the output terminal 8b is the delay circuit 8
If the delay time of 02 is 1H (where 1H is one horizontal scanning period), the signals 1H, 2H, ..., nH before in the screen vertical direction are gradually subtracted from the input video signal of the input terminal 8a. The pre-emphasis circuit emphasizes the high frequency component of the spatial frequency in the vertical direction of the screen.

Next, in the de-emphasis circuit shown in FIG. 9, the video signal pre-emphasized by the above pre-emphasis circuit is input to the input terminal 9a and supplied to the adder circuit 901 and the adder circuit 905. The adder circuit 901 adds the signal attenuated by the coefficient circuit 903 and the input video signal to each other, and outputs the resulting signal to the delay circuit 9.
Supply to 02. The delay circuit 902 delays the input signal by the same delay time as the delay time in pre-emphasis, and supplies the input signal to the coefficient circuit 903 and the coefficient circuit 904. Coefficient circuit 9
Reference numeral 03 denotes an attenuator circuit that obtains an attenuated signal by multiplying the signal from the delay circuit 902 by a coefficient L1, and supplies the signal to the adder circuit 901. The coefficient circuit 904 multiplies the output signal of the delay circuit 902 by the coefficient L2 to generate a signal relatively emphasized more than the input video signal level of the input terminal 9a, and adds this signal to the addition circuit 905.
Supply to. The adder circuit 905 adds the input signal from the input terminal 9a and the output signal of the coefficient circuit 904,
It is output from the output terminal 9b as a de-emphasized signal. When the delay time of the delay circuit 902 is 1H, the signal output to the output terminal 9b is 1H, 2H, ..., N in the screen vertical direction with respect to the input video signal of the input terminal 9a.
The signal before H is added little by little, whereby the de-emphasis circuit attenuates the high frequency component of the spatial frequency in the vertical direction of the screen.

As described above, by pre-emphasizing the high frequency component in the vertical direction at the time of recording and attenuating the high frequency component by using the de-emphasis at the time of reproduction, the deterioration of the image quality is suppressed and the high frequency component in the vertical direction is suppressed. It had a configuration to reduce noise components.

[0006]

However, in the above-mentioned conventional configuration, it is necessary to perform two processes of pre-emphasis during recording and de-emphasis during reproduction. In the case of such a configuration, if de-emphasis is applied to a video signal which is not pre-emphasized during recording, the original video signal is intentionally removed and the image quality is deteriorated. .
In addition, there is a problem that the noise removing effect becomes small when trying to improve the deterioration of the image quality by limiting the size of the noise component extracted by the de-emphasis.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a noise eliminator which is introduced only during reproduction to suppress the deterioration of image quality and to improve the noise elimination effect.

[0008]

In order to achieve this object, a noise removing apparatus according to the present invention is a signal obtained by delaying a low frequency component of an input signal and a low frequency component of the input signal by 1H (one horizontal scanning period). And a first operation means for performing a calculation to output a first signal, and performing a calculation on the signal delayed by 1H and a signal delayed by 2H for the low frequency component of the input signal, and outputting a third signal. A first control signal by detecting a correlation between a low-frequency component of the input signal, a signal obtained by delaying the low-frequency component of the input signal by 1H, and a signal obtained by delaying the low-frequency component of the input signal by 2H And the second signal fixes the signal level to “0” and outputs the first correlation
A first selection unit that selects any one of the first signal, the second signal, and the third signal as a noise component in a low frequency region with a control signal; A high-frequency component and a signal obtained by delaying the high-frequency component of the input signal by 1H are operated to output a fourth signal, and the signal delayed by 1H and a signal obtained by delaying the high-frequency component of the input signal by 2H. And a second arithmetic means for outputting a sixth signal, a high frequency component of the input signal, a signal obtained by delaying the high frequency component of the input signal by 1H, and a high frequency component of the input signal. Second correlation detecting means for detecting a correlation with the signal delayed by 2H and outputting a second control signal, and a fifth signal being a high frequency component of the input signal, and the second control signal, Which one of the fourth signal, the fifth signal, and the sixth signal And a subtracting means for subtracting the noise component in the low frequency region and the noise component in the high frequency region from a signal obtained by delaying the input signal for a predetermined time. , Has the configuration.

[0009]

According to the present invention, the input signal is divided into the low-frequency region and the high-frequency region by the above-mentioned structure. The correlation between the video signals is detected by using the means for detecting the correlation between the three signals of the
The non-correlation component in the video signal is extracted as a noise component.
Further, in the high frequency region, correlation detection between noise components is performed using a means for detecting the correlation between the high frequency component of the input signal and the signal delayed by 1H and the signal delayed by 2H. Extract only the noise component.

Noise is removed by subtracting the noise component of each band extracted as described above from the signal obtained by delaying the input signal for a predetermined time.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a noise removing apparatus according to the first embodiment of the present invention. In FIG. 1, the video signal input to the input terminal 1a includes a low-pass filter (LPF) 101 and a high-pass filter (HPF).
Is supplied to 102. The output of the low-pass filter 101 is supplied to the comb filter 103, the comb filter 104, and the correlation detection circuit 107, and the respective results are also supplied to the switch circuit 108. Configuration examples of the comb filter 103 and the comb filter 104 are shown in FIGS. 3 and 4, respectively. FIG.
In the above, assuming that the signal input to the input terminal 3a is at the position S1 on the screen shown in FIG. 2, the signal obtained by delaying the input signal by 1H is at the point S2. Therefore, the comb filter 103
Calculates the signal at the S1 point and the signal at the S2 point and outputs the result from the output terminal 3b. In FIG. 4, the input terminal 4a
The signal input from the same as the comb filter 103 is shown in FIG.
S1 point of the signal, the signal delayed by 1H from the input is S2
The signal further delayed by 1H is point S3.
Therefore, the comb filter 104 calculates the signal at the point S2 and the signal at the point S3, and outputs the result from the output terminal 4b.

On the other hand, the output of the high-pass filter 102 is supplied to the comb filter 105, the comb filter 106, and the correlation detection circuit 110, and the respective results are also supplied to the switch circuit 109. The comb filter 105 and the comb filter 106 perform the same processing as that of the comb filter 103 and the comb filter 104, respectively. Delay circuit 111
Delays the input signal from the input terminal 1a and supplies the output to the subtraction circuit 112. Then, the result of the subtraction circuit 112 that receives the outputs of the switch circuit 108, the switch circuit 109, and the delay circuit 111 is output from the output terminal 1b.

The operation of the noise eliminator of the present embodiment constructed as above will be described below.

First, the operation of detecting the noise component in the low frequency region will be described. V input to the input terminal 1a
The low-pass filter 101 extracts only low-frequency components from the reproduction luminance signal of TR, and the TR reproduction luminance signal is input to the comb filter 103, the comb filter 104, and the correlation detection circuit 107.

The comb filter 103 performs a calculation between the input signal and a signal obtained by delaying this signal by 1H, and outputs a non-correlation component. The comb filter 104 performs a calculation between a signal obtained by delaying the input signal by 1H and a signal obtained by further delaying this signal by 1H, and outputs a non-correlation component.

The structure of the correlation detection circuit 107 is shown in FIG.
In the low frequency region, when comparing the energy of the video signal and the energy of the noise component, the energy of the video signal is large. Therefore, in the low frequency region, the component extracted by the low-pass filter is used as a video signal to detect the correlation between the video signals. Specifically, two types of vertical direction correlation detection are performed between the input signal 501, the signal 502 delayed by 1H, and the signal 503 delayed by 1H between the three video signals. The first detection is detection of the strength of correlation between the three signals, and the second detection is detection of which of the signal 501 and the signal 503 has a stronger correlation with the signal 502. The detection result is given to the switch circuit 108 as a control signal.

The switch circuit 108 uses the output of the comb filter 103 as a first signal, fixes the second signal at "0", and outputs the output of the comb filter 104 as a third signal from the correlation detection circuit 107. One signal is selected from the three signals by the control signal a of 1. The first signal is selected when it is determined that the video signals 501 to 503 have a strong correlation, and in particular, the signals 501 and 502 have a strong correlation. The selection of the third signal is performed by the video signal 50.
The correlation between 1 to 503 is strong, and especially the signal 50
This is the case where it is determined that the correlation between 2 and 503 is strong. In the case of such detection, the result output by the calculation performed between the video signals having stronger correlation, that is, the non-correlation component between the video signals is extracted as the noise component. The second signal is selected when it is determined that the correlation between the video signals is weak, and the noise component is set to “0” without performing calculation with other signals.
And The component extracted as described above is the noise component mixed in the low frequency region of the signal input to the input terminal 1a, and is input to the subtraction circuit 112.

Next, the operation of detecting the noise component in the high frequency region will be described. The high-pass filter 102 extracts only the high-frequency component of the VTR reproduction luminance signal input to the input terminal 1a, and the high-frequency component is input to the comb filter 105, the comb filter 106, and the correlation detection circuit 110.

The comb filter 105 performs an operation between the input signal and a signal obtained by delaying this signal by 1H, and outputs a strongly correlated component. Comb filter 10
In 6, an operation is performed between a signal obtained by delaying the input signal by 1H and a signal obtained by further delaying this signal by 1H, and a component having a strong correlation is output.

The configuration of the correlation detection circuit 110 is shown in FIG.
In the high frequency region, comparing the energy of the video signal and the energy of the noise component, the energy of the noise component is large. Therefore, in the high frequency region, the component extracted by the high-pass filter is used as a noise component, and correlation detection is performed between the noise components. Specifically, the input signal 601
Then, two types of vertical direction correlation detection are performed between the three signals, that is, the signal 602 delayed by 1H and the signal 603 delayed by 1H. Since noise correlation detection is performed here, the signs of the signals 601 and 603 are inverted and converted into a noise component region. The first detection is 3
The second detection is detection of which noise component of the signal 601 and the signal 603 has a stronger correlation with the signal 602.
The detection result is given to the switch circuit 109 as the control signal b.

The switch circuit 109 controls the correlation detection circuit 110 using the output of the comb filter 105 as the fourth signal, the output of the high pass filter 102 as the fifth signal, and the output of the comb filter 106 as the sixth signal. One signal is selected from the three signals by the signal b. The selection of the fourth signal is performed when it is determined that the noise components among the signals 601 to 603 have a strong correlation, and in particular, the noise components of the signals 601 and 602 have a strong correlation. Also the 6th
The signal is selected when it is determined that the noise components among the signals 601 to 603 have a strong correlation, and in particular, the noise components of the signals 602 and 603 have a strong correlation. In the case of such detection, the result of calculation between noise components having stronger correlation is extracted as a noise component. In the selection of the fifth signal, it is determined that the correlation between the noise components is weak, and when the calculation with other components is performed at this time, the correlation component of the video signal is mixed. The output is directly output as a noise component. The signal extracted in this way is a noise component mixed in the high frequency region of the signal input to the input terminal 1a, and is input to the subtraction circuit 112.

The subtraction circuit 112 subtracts the noise components detected in the two bands from the output signal of the delay circuit 111,
A reproduction luminance signal from which noise is removed is output.

As described above, according to the present embodiment, the input signal is divided into the low frequency region and the high frequency region, and in the low frequency region, the correlation detection in the vertical direction is performed between the video signals to obtain the high frequency region. In the area, vertical correlation detection is performed between noise components. In this way, by discriminating the original video signal and the noise component in each band, only the noise component can be extracted, and the noise can be removed while suppressing the image quality deterioration.

FIG. 7 is a block diagram of a noise eliminator showing a second embodiment of the present invention. In the figure, first, the video signal input from the input terminal 7a is supplied to the 1H delay circuit 701, and this output is further supplied to the 1H delay circuit 702. The input signal from the input terminal 7a and the outputs of the 1H delay circuits 701 and 702 are the low pass filters 703 to 705 and the high pass filters 710 to 71, respectively.
2 respectively. Low pass filters 703 and 7
The output of 04 is input to the subtraction circuit 706, and the result is supplied to the switch circuit 709. The outputs of the low pass filters 704 and 705 are input to the subtraction circuit 707,
This result is also supplied to the switch circuit 709. The switch circuit 709 selects an output based on the control signal a from the correlation detection circuit 708 which performs correlation detection with the outputs of the low-pass filters 703 to 705, and supplies the output to the subtraction circuit 718.

On the other hand, the outputs of the high pass filters 710 and 711 are input to the subtraction circuit 713, and the result is supplied to the switch circuit 716. In addition, the high pass filter 71
The outputs of 1 and 712 are input to the subtraction circuit 714, and the result is also supplied to the switch circuit 716. Switch circuit 7
16 selects an output based on the control signal b from the correlation detection circuit 715 which performs correlation detection with the outputs of the high pass filters 710 to 712, and subtracts the output from the subtraction circuit 71.
Supply to 8.

The delay circuit 717 delays the input signal from the input terminal 7a and supplies the output to the subtraction circuit 718. The subtraction circuit 718 includes a switch circuit 709 and a switch circuit 716.
The output of the delay circuit 717 is subtracted, and the result is output from the output terminal 7b.

The noise eliminator having the above structure will be described below. First, the signal input from the input terminal 7a is supplied to the 1H delay circuits 701 and 702, and
An H delay signal and a 2H delay signal are obtained. Then, noise detection is performed after the three signals are divided into low frequency regions and high frequency regions by the low pass filters 703 to 705 and the high pass filters 710 to 712, respectively.

In the low frequency region, the low pass filter 703 is used.
The outputs from ˜705 are input to the correlation detection circuit 708 to detect the correlation. This detection is the same as the detection by the correlation detection circuit 107 of the first embodiment. In addition, a subtraction circuit 706 that performs subtraction with the outputs of the low pass filters 703 and 704.
The subtraction circuit 707 that performs subtraction with the outputs of the low-pass filters 704 and 705 corresponds to the comb filter 103 and the comb filter 104 of the first embodiment, respectively.

Similarly, in the high frequency region, the outputs of the high pass filters 710 to 712 are input to the correlation detection circuit 715,
Correlation detection is performed. This detection is the same as the detection of the correlation detection circuit 110 of the first embodiment. Similarly, the subtraction circuit 7
13 and 714 correspond to the comb filter 105 and the comb filter 106, respectively.

As described above, in the second embodiment, the input video signal is delayed and then divided into the low band and the high band to perform noise detection. The detection operation in each band is the same as that of the first embodiment. is there. In this embodiment, many delay circuits required for the processing of the comb filter and the correlation detection circuit in the first embodiment can be reduced to two, and the device can be realized at low cost.

The present invention is not limited to the above embodiment, but various modifications can be made.

[0033]

As described above, according to the present invention, the input signal is divided into two bands and the vertical correlation is detected in each band, so that the original video signal and the noise component can be accurately discriminated. Since it is possible to remove only the noise component, it is possible to obtain a noise removal effect higher than that of the related art without deteriorating the image.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a noise removing device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining the operation of the comb filter according to the first embodiment.

FIG. 3 is a block diagram showing a configuration of a comb filter according to the first embodiment.

FIG. 4 is a block diagram showing a configuration of a comb filter according to the first embodiment.

FIG. 5 is a block diagram showing a configuration of a correlation detection circuit in the first embodiment.

FIG. 6 is a block diagram showing a configuration of a correlation detection circuit according to the first embodiment.

FIG. 7 is a block diagram showing a configuration of a noise removing device according to a second embodiment of the present invention.

FIG. 8 is a block diagram showing the configuration of a conventional noise eliminator.

FIG. 9 is a block diagram showing a configuration of a conventional noise eliminator.

[Explanation of symbols]

101,703-705 Low-pass filter 102,710-712 High-pass filter 103-106 Comb filter 107,110,708,715 Correlation detection circuit 108,109,709,716 Switch circuit 111,717 Delay circuit 112,706,707,713 , 714, 718 Subtraction circuit 701, 702 1H delay circuit

Claims (1)

(57) [Claims] 1. A low-frequency component of an input signal and a signal obtained by delaying the low-frequency component of the input signal by 1H (1 horizontal scanning period) to output a first signal, and the signal delayed by 1H. And a low-frequency component of the input signal delayed by 2H for performing a calculation to output a third signal, a low-frequency component of the input signal and a low-frequency component of the input signal of 1H 2H between the delayed signal and the low frequency component of the input signal
First correlation detecting means for detecting a correlation with the delayed signal and outputting a first control signal, and the second signal fixing the signal level to "0",
A first selection unit that selects one of the first signal, the second signal, and the third signal as a noise component in a low frequency region by the first control signal; The high frequency component of the input signal and the high frequency component of the input signal are 1
An operation is performed with the H-delayed signal to output a fourth signal, and an operation is performed with the 1H-delayed signal and the high-frequency component of the input signal delayed by 2H to output a sixth signal. Second calculating means, a high frequency component of the input signal, a signal obtained by delaying the high frequency component of the input signal by 1H, and a high frequency component of the input signal by 2H
Second correlation detecting means for detecting a correlation with the delayed signal and outputting a second control signal; and the fifth signal being a high frequency component of the input signal,
Second selecting means for selecting one of the fourth signal, the fifth signal, and the sixth signal as a noise component in a high frequency region by the second control signal, and the input A noise removing device comprising: a subtraction unit that subtracts a noise component in the low frequency region and a noise component in the high frequency region from a signal delayed by a predetermined time.