JPH0556306A - Adaptive ringing controller - Google Patents

Abstract

PURPOSE:To obtain the suppressing effect of a ringing by making a ringing control means to be non-linear, and to avoid the problem of the blurring of a boundary, or the thickness of a line. CONSTITUTION:In an adaptive ringing controller which is equipped with a ringing detecting circuit 3 which detects the part of the generation of a ringing, and a ringing control circuit 2, and which controls the suppressing amount of the ringing suppressing circuit 2 based on the detected result of the ringing detecting circuit 3, the circuit of an amplitude non-linear characteristic whose frequency characteristic is changed according the amplitude of an input signal is used as the ringing control circuit 2. Thus, when the ringing suppressing amount of the ringing detecting circuit 3 is large, the frequency characteristic which is flat or almost flat is obtained corresponding to the input signal whose amplitude is large, and the frequency characteristic of a smooth filter characteristic is obtained corresponding to the input signal whose amplitude is small. Also, when the ringing amount is small, the frequency characteristic which is flat or almost flat is obtained regardless of the size of the amplitude of the input signal.

Description

Detailed Description of the Invention

[0001]

This invention relates to broadcasting, communication, recording,
The present invention relates to an adaptive ringing suppressing device used to suppress ringing that occurs due to filtering processing performed in a system in which a signal transmission band such as reproduction is limited.

[0002]

2. Description of the Related Art Generally, in a signal transmission system, the transmission band is defined as a standard or specification, and the spectrum of the original signal is wider than the transmission band, so that the band is limited by the filtering process. In order to transmit more information of the original signal, it is necessary to make the cutoff characteristic of the filter steep and reduce the attenuation in the pass band.

However, the steeper the cutoff characteristic of the filter, the more discontinuous the spectrum of the signal to be transmitted, and the ringing at the cutoff frequency, which was not present in the original signal, tends to occur and tends to increase. On the contrary to the above, as the cutoff characteristic of the filter is made gentler in order to reduce the occurrence of ringing, the attenuation amount in the pass band tends to increase and the information amount tends to decrease. Therefore, in the past,
The filter is designed to have an intermediate characteristic in consideration of both the information amount of the transmission signal and the problem of ringing.

For example, in a television video signal, the high frequency spectrum is fine information. The high-frequency information of original signals from cameras and the like has increased due to higher definition and higher image quality of TV images, but the transmission band of video signals in broadcasting is 4.2M.
Since the frequency is set to Hz, there is a limit to achieving higher definition, and if a filter with a sharp cutoff characteristic is used to achieve higher definition, 4.2 MHz ringing increases, which is one of the causes of deterioration of image quality. Becomes On the other hand, if a filter having a gentle cutoff characteristic is used, the occurrence of ringing can be reduced, but the definition is lowered.

FIG. 6 shows 4.2M in a television video signal.
It is a block diagram which shows an example of a structure of the conventional adaptive ringing suppression apparatus which was made to suppress the ringing generate | occur | produced by the band limitation of Hz, and it is a technical report (ITEJ Technical Report Vol.12 No.5, PP. 49
~ 54, PPOE'88-2 Jan. 1988). In FIG. 6, 1 is a luminance signal input terminal, 2 is a ringing suppression circuit, 3 is a ringing detection circuit, and 4 is a luminance signal output terminal. Reference numeral 27 is a low-pass filter (hereinafter referred to as LPF), which has a smooth cutoff characteristic. 28 is a switch.

Next, the operation of the above configuration will be described. The luminance signal Y input from the terminal 1 is input to the LPF 27 of the ringing suppression circuit 2 and one input terminal of the switch 28, and the output of the LPF 27 is the switch 28.
The luminance signal Y input from the other input terminal of the ringing detection circuit 3 is also input to the ringing detection circuit 3 and the switch 28 is controlled by the output signal of the ringing detection circuit 3.

When the ringing detection circuit 3 determines that there is ringing, the switch 28 is set to LPF.
When the ringing is switched to the 27 side and it is determined that there is no ringing, it is switched to the bypass side and output to the output terminal 4.
A steep LPF (not shown) is arranged on the front or rear stage. When it is determined that the ringing is “present”, the LPF 27 and the steep LPF are
Although it has the characteristics of cascade connection,
Since the characteristic of the PF 27 is dominant, the overall characteristic becomes the characteristic of the LPF 27 which is gentle as shown by a in FIG. 7, and the ringing is suppressed. Further, when it is determined that the ringing is “none”, the overall characteristic becomes a steep LPF characteristic as shown in FIG. 7B, and a high-definition image with no attenuation up to 4.2 MHz is obtained. Be done.

FIG. 8 shows a ringing suppressing waveform, FIG. 8A shows a waveform of a luminance signal input to the terminal 1, FIG. 8B shows a waveform of an output signal of the LPF 27 having a gentle characteristic, and FIG.
Is the output waveform of the ringing detection signal, and (d) is the waveform of the luminance signal output from the terminal 4. In the video signal, the portion where the ringing Yl is likely to occur is near the front and rear of the boundary L and the line (from left to right on the screen), and the area thereof is smaller than the entire screen. Therefore, as described above, the fineness is improved as a whole by adaptively performing the gentle filtering process on the ringing portion rather than performing the gentle filtering process on the entire screen.

As another conventional example, an adaptive ringing suppression method using an asymmetric coefficient filter is known, as described in Television Society Journal Vol.44, No.6, pp761 to 766 (1990). ing. According to this method, the frequency characteristic can be made steep even in the period in which the ringing is suppressed, and the high frequency signal component does not have to be reduced.

[0010]

Since the conventional adaptive ringing suppressing apparatus is constructed as described above, in the case of the construction shown in FIG. 6, the boundary or line where the ringing is likely to occur is front or rear. However, since the smooth filtering process is performed, there are problems such as a blurred boundary and a thick line. Further, in the case of using the asymmetric coefficient filter, it is necessary to instantaneously switch the two types of asymmetric coefficient filters at the boundary portion, and it is difficult to create the switching signal, and the asymmetric coefficient filter has a large number of taps and is large-scale. Since it is a circuit, there is a problem that the cost becomes high.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to satisfy both contradictory requirements such as suppression of ringing and improvement of definition, and a simple circuit is formed. It is an object of the present invention to provide an adaptive ringing suppressing device that can reduce costs.

[0012]

The adaptive ringing suppressing device according to the present invention is characterized in that, as the ringing suppressing means, one having a non-linear amplitude characteristic between the input and the output is used.

In particular, it is preferable to use one having an amplitude non-linear characteristic in which the frequency characteristic changes according to the amplitude of the input signal.

[0014]

According to the present invention, when the ringing suppression amount of the ringing detection means is large, a frequency characteristic which is flat or nearly flat with respect to an input signal with a large amplitude, and an input signal with a small amplitude is exhibited. The frequency characteristic of the gentle filter characteristic is exhibited. Further, when the ringing suppression amount of the ringing detection means is large, regardless of the magnitude of the amplitude of the input signal, the frequency characteristics exhibit a flat or nearly flat frequency characteristic, and blurring of boundaries and lines is eliminated while eliminating the deterioration of definition. It can be lost.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an adaptive ringing suppressing apparatus according to an embodiment of the present invention. In FIG. 1, 1 to 4 are the same as those of the conventional example shown in FIG. , And the detailed description thereof is omitted.

In FIG. 1, reference numeral 21 denotes a delay circuit for the luminance signal Y, which compensates for the detection signal of the ringing detection circuit 3 being delayed more than the ringing period of the input luminance signal Y. 22 is a non-linear processing circuit that suppresses ringing,
Reference numeral 23 is a delay circuit for the bypass luminance signal, which compensates for the delay of the luminance signal Y by the nonlinear processing circuit 22. 24, 2
Reference numeral 5 denotes a multiplication circuit, and one multiplication circuit 24 applies a ringing control amount k (0 ≦ 0) of the ringing detection circuit 3 to the nonlinear processing signal.
k ≦ 1) is multiplied to output a non-linear processed signal whose amplitude is controlled. The other multiplication circuit 25 multiplies the other ringing control amount (1-k) of the ringing detection circuit 3 by the bypass signal and outputs a bypass signal whose amplitude is controlled. An adder circuit 26 adds the outputs of the two multiplying circuits 24 and 25.

Reference numeral 5 is an input terminal for the chroma signal C, and 6 is a delay circuit for compensating the total delay time until the luminance signal Y input from the terminal 1 is output from the terminal 4. Reference numeral 7 is an output terminal for the chroma signal C. The ringing detection circuit 3 detects the temporal center of the ringing period in the input luminance signal Y, or detects a boundary or a line portion where ringing is likely to occur before and after the input luminance signal Y to obtain a length equal to the ringing period. Only during this period, the ringing control amount k is set to 1, and the other periods are set to 0. The change from 0 to 1, 1 to 0 is a continuous curve. The outputs of the ringing detection circuit 3 are k and (k-1), and the total value of both is constant. That is, k + (1-k) = 1.

FIG. 2 is a diagram showing an example of frequency characteristics of the above-mentioned non-linear processing circuit 22.
%, It is flat, but the smaller the amplitude, the greater the attenuation of high frequency. Also, FIG.
FIG. 4 is a diagram showing an example of the input / output amplitude characteristic of the non-linear processing circuit 22, which has a linear characteristic with respect to direct current but a non-linear characteristic with respect to alternating current. Due to the frequency characteristics shown in FIG. 2 and the input / output amplitude characteristics shown in FIG. 3, a small amplitude and
It can be seen that the high frequency components are suppressed.

The non-linear processing circuit 22 is composed of, for example, an integrated circuit M51494L and a small number of peripheral components shown in its application. Since the principle and the like are well known, detailed description thereof will be omitted.

Next, the operation of the above configuration will be described with reference to the waveform chart shown in FIG. The ringing suppression device of the above-described embodiment utilizes the property that the ringing amplitude is as small as about 10% or less compared to the boundary or line amplitude. As shown in the waveform of the output Ys of the non-linear processing circuit 22 of FIG. 4B, a fine amplitude component having a small amplitude and a high frequency included in the input luminance signal Y _IN of FIG. Although the information Ya and the ringing Yl are suppressed, the sharpness of a portion having a large amplitude such as the boundary L is hardly impaired and blurring does not occur. Also, although not shown, in the case of a line, the width of the line does not become so thick although the ringing before and after the line is suppressed. Therefore, the output luminance signal Y _OUT from the output terminal 4 is
As shown in (f), Y _OUT = k · Ys + (1−k) · Yb, where (0 ≦ k ≦ 1).

When the ringing detection circuit 3 determines that there is no ringing, k = 0, and FIG.
The bypass signal Yb shown in (c) is selected. Further, when the ringing detection circuit 3 determines that the ringing is “present”, k = 1, and the nonlinear processing signal Ys shown in FIG. 4B is selected. In the change region from 0 to 1 or from 1 to 0, the mixing ratio of the bypass signal Yb and the non-linear processing signal Ys changes smoothly. As described above, the ringing detection circuit 3 selects the non-linear processing signal Ys only during the ringing period, so that the output luminance signal Y
_{In OUT} , the fine information Ya existing in the other period is the bypass signal Yb, the same amplitude as the input luminance signal Y _IN is maintained, and the fineness is not deteriorated.

When the amplitude of the boundary or line is as small as 20%, for example, the boundary or line in the output of the non-linear processing circuit 22 is blurred or thick. Before and after a boundary or a line with a small amplitude, the ringing amplitude is very small, for example, 20% or less, so that the ringing detection circuit 3 in which the threshold is set is determined to have “no ringing”. In this case, the bypass signal Yb is selected and output to the terminal 4, so that the boundaries and lines are not blurred.

In the above embodiment, the output signal of the ringing detection circuit 3 changes the mixing ratio of the bypass signal Yb and the non-linear processing signal Ys, but FIG.
As described above, the non-linearity of the non-linear processing circuit 22 may be directly controlled by the output signal of the ringing detection circuit 3, and the same effect as that of the above-described embodiment can be obtained.

[0024]

As described above, according to the present invention, since the ringing suppressing means is made non-linear, not only the ringing suppressing effect but also the problem that the boundary is blurred or the line becomes thick as seen in the conventional example. Can be avoided.
Further, the non-linear processing circuit can be composed of a small-scale integrated circuit and a small number of external parts, and in the case of a system in which two types of asymmetric coefficient filters are instantaneously switched at the boundary portion as in the conventional example. There is no technical difficulty in comparison, and the overall structure can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an adaptive ringing suppression device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of frequency characteristics of a non-linear processing circuit used in an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an example of input / output amplitude characteristics of a nonlinear processing circuit used in an embodiment of the present invention.

FIG. 4 is a signal waveform diagram for explaining the operation of the present invention.

FIG. 5 is a block diagram showing the configuration of an adaptive ringing suppression device according to another embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional adaptive ringing suppression device.

FIG. 7 is an explanatory diagram of conventional frequency characteristics.

FIG. 8 is a signal waveform diagram for explaining the operation of the configuration of FIG.

[Explanation of symbols]

 2 Ringing suppression circuit (ringing suppression means) 3 Ringing detection circuit (ringing detection means) 22 Non-linear processing circuit

[Procedure amendment]

[Submission date] December 3, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

[0014]

According to the present invention, when the ringing suppression amount of the ringing detection means is large, a frequency characteristic which is flat or nearly flat with respect to an input signal with a large amplitude, and an input signal with a small amplitude is exhibited. The frequency characteristic of the gentle filter characteristic is exhibited. In addition, when the ringing suppression amount of the ringing detection means is small , regardless of the magnitude of the amplitude of the input signal, the frequency characteristic is flat or close to flat, and blurring of boundaries and lines is prevented while eliminating the deterioration of definition. It can be lost.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

When the amplitude of the boundary or line is as small as 20%, for example, the boundary or line in the output of the non-linear processing circuit 22 is blurred or thick. Before and after the boundary or line having a small amplitude, the ringing amplitude is very small, for example, 2% or less, and therefore, the ringing detection circuit 3 in which the threshold is set determines that there is no ringing. In this case, the bypass signal Yb is selected and output to the terminal 4, so that the boundaries and lines are not blurred.

Claims (2)

[Claims] 1. A ringing suppressing means and a ringing detecting means for detecting a location of occurrence of ringing, wherein the ringing suppressing amount of the ringing suppressing means is controlled based on a detection result of the ringing detecting means. In the adaptive ringing suppressing device, the ringing suppressing means has a non-linear amplitude characteristic between input and output. 2. The adaptive ringing suppressing device according to claim 1, wherein the ringing suppressing means has an amplitude non-linear characteristic in which a frequency characteristic changes according to an amplitude of an input signal.