JP2001186378A - Video signal processor and television signal receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video signal processor and a television signal receiver, which appropriately suppress noise components amplified with a video signal by conducting gamma correction and conducting optimum gamma correction without damaging the quality of a picture. SOLUTION: In a gamma correction circuit 100, a selection circuit 117 selects a multiplication coefficient signal showing an amplification rate outputted from multiplication circuits 105 to 108 and 112 to 114. The video signal which is gamma-corrected by a gamma correction characteristic approximately articulated is obtained. Noise suppression quantity corresponding to the divided amplitude level of an input video sigil, which is detected by the amplitude level detection circuit 118, is given to a noise suppression circuit 120 from a correction quantity arithmetic circuit 126. The noise in the video signal outputted from the gamma correction circuit 100 is suppressed in accordance with noise suppression quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing apparatus for a display device such as a television receiver or a personal computer, which is capable of realizing optimal control of gradation and contrast of a display image without deteriorating image quality due to noise. The present invention relates to a television signal receiving device.

[0002]

2. Description of the Related Art In television broadcasting and the like, video signals are transmitted on the assumption that a CRT (cathode ray tube) display device is used as a display device. Therefore, in a television receiver using a CRT display device, assuming that the gamma value of the CRT display device in the gamma correction circuit is 2.2, the gamma correction is canceled from the broadcast station side. Video signals that have been subjected to gamma correction with a gamma value being the reciprocal of 2.2 have been transmitted. In this way,
By setting the total gamma value of the transmitting and receiving system to 1,
In a CRT display device, an original image can be reproduced with a faithful color and gradation.

A curve Γ _CRT in FIG. 3 is a graph showing a gamma characteristic of a CRT display device. However, even if gamma correction is performed according to the curve Γ _CRT , the original image may not be faithfully reproduced when evaluating the image quality in terms of gradation and contrast. Needs to fine-tune the characteristics of the gamma curve.
Recently, CR display devices have been used as display devices for television broadcasting.
It is assumed that a liquid crystal display device is used instead of the T display device. In this case, the gamma characteristic of the liquid crystal display device is C
Unlike the case of the RT display device, the characteristics are as shown by the curve Γ _{LCD in} FIG.

FIG. 3 shows a plasma display panel.
It has a linear correction characteristic like the curve Γ _PD shown in
This is clearly different from the gamma characteristic of the CRT display device. Similarly, in these cases, in order to obtain a faithful image of a television broadcast on a liquid crystal display device or a plasma display panel, the gamma characteristic of the gamma correction as viewed on each display device is set to 1 in each display device. Therefore, it is necessary to optimally control the amplitude level of the video signal in accordance with the level of the input signal. A gamma correction circuit having a variable gamma characteristic is disclosed in, for example, Japanese Patent Application Laid-Open No.
No. 0363.

[0005]

In the above-described conventional gamma correction circuit, the amplitude of the video signal is adjusted so that a linear gradation image can be displayed at the stage of displaying the image of the input video signal on a display device or the like. By amplifying the level according to the amplitude level of this video signal, correction control is performed so that an appropriate reproduced image is obtained for each type of display device. However, noise is also amplified and the image quality of the reproduced image is reduced. There was a problem of deterioration. As described above, there is a problem that the relationship between the adjustment of the gamma characteristic and the noise is a trade-off relationship in which the process of increasing the amplitude level of the video signal is performed in order to improve the gradation performance of the reproduced image. .

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art. By performing gamma correction, a noise component amplified together with a video signal is appropriately suppressed, so that an optimum image quality is not impaired. An object of the present invention is to provide a video signal processing device and a television signal receiving device that can perform gamma correction.

[0007]

In order to achieve the above-mentioned object, the present invention provides a gamma correction characteristic used in a gamma correction means, wherein a gamma correction characteristic corresponding to each division point obtained by dividing the level range of an input video signal into a plurality of divisions. And a straight line between the broken points, and the noise suppression level when the noise signal is suppressed by the noise suppressing unit is set to the break point of the gamma correction characteristic and the amplification factor set for each straight line between the broken points. It is a value according to.

The gamma correction means includes a breakpoint level setting means for setting a level value of a plurality of breakpoints of the gamma correction characteristic approximated by a broken line, and a breakpoint multiplication coefficient setting means for setting a multiplication coefficient of the breakpoint. A plurality of first multiplying means for multiplying, for each breakpoint, a level value set by the breakpoint level setting means and a multiplication coefficient set by the breakpoint multiplication coefficient setting means; A plurality of multiplication coefficients for calculating, as a multiplication coefficient, a slope of a straight line between the respective break points of the gamma correction characteristic from the level value of the break point set by the level setting means and the multiplication coefficient set by the break point multiplication coefficient setting means; Calculating means, a plurality of second multiplying means for multiplying the input video signal by a multiplication coefficient obtained by the plurality of multiplication coefficient calculating means, and the level of the input video signal is any of a break point or a range between the break points. Amplitude level detecting means for detecting whether or not to belong, based on the result detected by the amplitude level detecting means, the plurality of first multiplying means and the plurality of second multiplying means corresponding to the input video signal, Selecting means for selecting any one of the output signals as a gamma-corrected video signal and outputting the selected signal, and the noise suppressing means selects the output signal based on a result detected by the amplitude level detecting means. And a noise suppression amount generating means for generating a noise suppression amount according to the multiplication coefficient used in the first or second multiplying means, wherein the noise of the gamma-corrected video signal is suppressed in accordance with the noise suppression amount. It was made.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a video signal processing device and a television signal receiving device according to an embodiment of the present invention. In the figure, 10
0 is a gamma correction circuit, 104 is a noise suppression amount generation circuit,
Reference numerals 105 to 114, 117 and 118 denote internal circuits of the gamma correction circuit, 105 to 108 denote multiplication circuits, and 109 to 1
11 is a gain operation circuit, 112 to 114 are multiplication circuits, 1
17 is a selection circuit, 118 is an amplitude level detection circuit, 120
Is a noise suppression circuit, and 123, 124, 126, and 127 are internal circuits of the noise suppression amount generation circuit 104.
Is an S / N detection circuit, 124 is a limiter, 126 is a correction amount calculation circuit, 127 is an addition circuit, 128 is a display device of a television receiver, _Tr is a noise suppression level input terminal,
T _s is the slice level input terminal, T _i is the video input terminal,
T _p is the break point level input terminal, T _g is the break point gain input terminal, T _o is the video output terminal.

Hereinafter, the operation of this embodiment will be described.
Digital video signal received television broadcast in unillustrated receiver a predetermined signal processing is quantized been made is inputted from the video input terminal T _i to the gamma correction circuit 100. Digital video signal subjected to gamma correction for canceling the gamma characteristic of the display device 128 by the gamma correction circuit 100 is input to the noise suppression circuit 120, outputs the noise component is suppressed to the display device 128 from the video output terminal T _o Is done.

Hereinafter, the operation of the gamma correction circuit 100 will be described. FIG. 2 is a graph showing a gamma correction curve approximated by a polygonal line of a gamma correction circuit 100 for correcting a gamma characteristic of a display device. The calculation process for gamma correction will be described with reference to FIG. Video input terminal T _i
The level range of the input digital video signal is 0,
a1, a2, a3,..., an, a (n + 1) (n is an integer). That is, this signal level is the level of the input video signal at each break point of the gamma correction characteristic of the polygonal line approximation. Hereinafter, the signal level = 0 is referred to as the origin, and the signal levels a1 to an for dividing the level range are respectively referred to as These break points are referred to as a1 to an.

[0012] Origin 0, the value at each break point of the break point a1~ a (n + 1) (Level) 0, a1~ a (n + 1) is input from the break point level input terminal T _p. Then, the level setting value of the origin 0 is input to the multiplication circuit 105 and stored and held. The level set value of the break point a1 is input to the multiplication circuit 106,
It is stored. Further, the level set value of the break point a2 is input to the multiplication circuit 107 and stored and held. Break point a3
Is input to the multiplication circuit 108 and stored. Similarly, although not shown in FIG. 1, the level set value of the break point a (n) is also input to a multiplication circuit having the same circuit configuration and stored.

Each of the multiplication circuits 105 to 108 described above
To the., Multiplication coefficient β0 inputted from crossover gain input terminal _{T g, β1, β2, β3} , ··· are supplied. First, a multiplication coefficient β0 is supplied to the multiplication circuit 105. In this embodiment, since the starting point of the break point is the origin (input value: 0), a value of 0 is output from the multiplication circuit 105 regardless of the set value of the multiplication coefficient β0.

The multiplication circuit 106 similarly receives and stores the value a1 of the break point a1 and stores the multiplication coefficient β1
Is multiplied by the value a1 of the break point a1, and as a result,
The value of β1 · a1 is output. Further, the multiplication circuit 107 receives and stores the value a2 of the break point a2, multiplies the set value of the multiplication coefficient β2 by the value a2 of the break point a2,
The resulting value of β2 · a2 is output. Furthermore,
In the multiplication circuit 108, the value a3 of the break point a3 is input and stored, and the value of the multiplication coefficient β3 is multiplied by the value a3 of the break point a3. As a result, the value of β3 · a3 is output. Similarly, the value an of the breakpoint an is also multiplied by the value of the multiplication coefficient βn by the multiplication circuit having the same circuit configuration, and as a result, βn · a (n) is output. Note that the multiplication coefficient β0
Ββ (n + 1) are set at the origin 0 and each break point a1 to a (n
It is also an amplification factor for amplifying the signal level of the video signal in (+1).

Next, the operation of the gain calculation circuits 109 to 111 will be described. Each gain operation circuit 109 to 111
Then, the values of the multiplication coefficients β01 to βn (n + 1) representing the inclination of the straight line portion between the origin 0 and each of the break points a1 to a (n + 1) are calculated. As shown in FIG. 2, the slope of the straight line between the origin 0 and the break point a1 is β01, the slope of the straight line between the break points a1-a2 is β12, the slope of the straight line between the break points a2-a3 is β23, and the break point a3 The slope of the straight line between −a4 is β34,.
The slope of the straight line between −a (n + 1) is βn (n + 1).

In the gain operation circuit 109, the multiplication circuit 105
, The input signal of the value of a1 and the output signal of the value of β1 · a1 of the multiplication circuit 106 are input and held, and as shown in the following equation, the signal between the origin 0 and the break point a1 Is calculated and output.

[0017]

(Equation 1)

The value β01 is input to the multiplication circuit 112 and used as a multiplication coefficient.

The gain calculation circuit 110
A value β12 representing the inclination of the straight line between the break points a1 and a2 is calculated and output according to the following equation.

[0020]

(Equation 2)

[0021] The value β12 is input to the multiplier circuit 113 is used as a multiplication factor of the image signal input from the video input terminal T _i. Here, when the level a of the input video signal satisfies a1 <a <a2, the multiplication circuit 1
From 13,

[0022]

(Equation 3)

Is output as a gamma-corrected video signal. The second term on the right side of the above equation is a DC component, and is generated by the multiplication circuit 113 using the above-described coefficients.

Similarly, the gain calculation circuit 111 calculates and outputs a value β23 representing the inclination of the straight line between the break points a2 and a3 according to the following equation. β23 = (β3 · a3-β2 · a2) / (a3- a2) This value Beta23 is input to the multiplier circuit 114 is used as a multiplication factor of the image signal input from the video input terminal T _i. Here, the level a of the input video signal is a
When 2 <a <a3, the multiplication circuit 114 outputs

[0025]

(Equation 4)

Is output as a gamma-corrected video signal. Note that the second term on the right side of the above equation is also a DC component, and is generated by the multiplier circuit 114 using each of the above coefficients.

Similarly, the break point ai-a (i + 1) (i is 3) in the gain operation circuit subsequent to the gain operation circuit 111
The value βi (i + 1) representing the slope of the straight line between the above integers) is calculated and output. Then, as shown in FIG.
(n) and the value βn (n +
1) is also calculated by the following exactly same arithmetic expression.

[0028]

(Equation 5)

When the level a of the video signal input from the video input terminal T _i satisfies an <a <a <a (n + 1), the multiplication circuit supplied with the value βn (n + 1)

[0030]

(Equation 6)

Is output as a gamma-corrected video signal. Note that the second term on the right side of the above equation is also a DC component, and is generated by the above-described multiplier using the above-described coefficients.

[0032] the amplitude level detection circuit 118, as shown in FIG. 4, the origin 0 is broken point information inputted from the break point level input terminal T _p, the value of each break point a1~ a (n + 1) Is input and stored. Then, the amplitude level detection circuit 118, the level of the digital video signal input from the video input terminal T _i is the origin 0, the break point a1 to a (n +
The signal is decoded by being compared with the value of 1), and is output as a decoded signal indicating which of the origin 0 and the level range determined by the values of the break points a1 to a (n + 1). This decode signal is input to the selection circuit 117 as a control signal, and one of the output signals of the multiplication circuits 105 to 108 and 112 to 114 is selected and output according to the amplitude level of the input video signal. That is, the selection circuit 117
Are calculated according to the control signal output from the amplitude level detection circuit 118 as follows.
To 114 are selected and output.

First, when (input amplitude level) = 0,
The output signal of the multiplication circuit 105 is selected and output. next,
When 0 <(input amplitude level) <(a1), the output signal of the multiplication circuit 112 is selected and output. When (input amplitude level) = a1, the output signal of the multiplication circuit 106 is selected and output. (A1) <(input amplitude level) <(a
In the case of 2), the output signal of the multiplication circuit 106 is selected and output. When (input amplitude level) = a2, the output signal of the multiplication circuit 107 is selected and output, and (a2) <
When (input amplitude level) <(a3), the multiplication circuit 10
7 is selected. When (input amplitude level) = a3, the output signal of the multiplication circuit 108 is selected and output. Similarly, when (input amplitude level) = an, an output signal of the multiplication circuit corresponding to the break point an is selected and output, and (an) <(input amplitude level) <(a)
In the case of (n + 1)), the output signal of the multiplication circuit whose slope βn (n + 1) is used as a multiplication coefficient is selected and output.

As described above, the gamma correction circuit 100
As shown in FIG. 2, a video signal that has been gamma-corrected based on a gamma correction characteristic approximated by a polygonal line is output from a quantized digital video signal input from a video input terminal T _i . Then, by appropriately setting the values of the breakpoints a1 to a (n + 1) and the values of the multiplication coefficients β0 to β (n + 1), different gamma characteristics as shown in FIG. Applicable to display devices in common. The gamma-corrected video signal is input to the noise suppression circuit 120.

The noise suppression circuit 120 suppresses the noise component amplified by the gamma correction circuit 100 together with the level amplification of the input video signal as described below.
The degree of noise suppression in the noise suppression circuit 120 is determined by the DC control value input from the noise suppression amount generation circuit 104. The noise suppression amount generation circuit 104
A / N detection circuit 123, a limiter 124, a correction amount calculation circuit 126, and an adder 127, and a set value for suppressing noise is input from a noise suppression level input terminal _Tr . This setting value means that the noise suppression amount is large if the value is large, the noise suppression amount is small if the value is small, and the noise suppression is not performed if the value is zero. The set value is, for example, a DC value “2”. This set value “2” is input to the limiter 124.

The S / N detection circuit 123 is supplied with a video signal input from the video input terminal T _i, and extracts noise from a synchronizing signal portion having a cycle much longer than the cycle of the noise of the video signal. Integrates and outputs the integrated value as a noise level value. This noise level value corresponds to the average value of noise superimposed on the video signal. This noise level value signal is input to the other input terminal of the limiter 124.

The limiter 124 controls S / S so as not to exceed the set value input from the noise suppression level input terminal _Tr.
The noise level value input from the N detection circuit 123 is restricted. For example, if the noise level value detected by the S / N detection circuit 123 is “1”, this noise level value is smaller than the set value “2” input from the noise suppression level input terminal _Tr. So limiter 124
, The output value “1” of the S / N detection circuit 123 is output as it is. The output signal of limiter 124 is added to adder 127
Is input to one of the input terminals.

[0038] Figure 5 is a block diagram showing an internal circuit configuration of the correction amount calculating circuit 126, comparator circuit of 501 to 508 the same configuration, the selection circuit 510, T _a is the amplification factor input terminal, T _c is selected Control input terminal. FIG. 6 is a conversion characteristic graph showing the input / output characteristics of the comparison circuit inside the correction amount calculation circuit 126. The operation of the correction amount calculation circuit 126 will be described below with reference to these drawings.

In FIG. 5, a break point gain input terminal T _g
(FIG. 1) Origin 0, each break point a1 to a (n +
1), the origin 0 calculated by the gain calculation circuits 109 to 111 (FIG. 1) and the like, and the linear portion between the break points a1 to a (n + 1). the multiplication coefficient β01~βn representing the slope (n + 1) via an amplification factor input terminal T _a, also, are input to the respective comparator circuits 501 to 508 by the slice level SL through the slice level input terminal T _s .

In this example, the slice level SL value is
As shown in FIG. 4, the values are ternary. Specifically, as shown in FIG. 4, SL0 = 0.8, SL0 = 1.5, and SL0 = 2.5. In each of the comparison circuits 501 to 508, the above-described multiplication coefficients β0 to β (n + 1) and β01 to βn (n + 1) are compared with these three slice levels SL0 to SL2, and the comparison is performed. The result is output as a quaternary decoded value of 0-3.

That is, in the comparison circuit 501, as follows:
The level of the multiplication coefficient β0 and the slice levels SL0 to SL2 is determined, and a decoding value 0 is output when the multiplication coefficient β0 is 0 ≦ β0 ≦ SL0, and a decoding value 1 is output when SL0 <β0 ≦ SL1. , SL1 <β0 ≦ SL2, a decoded value 2 is output, and when SL2 <β0, a decoded value 3 is output. The value of the multiplication coefficient β0 is “0” as described above.
Therefore, the comparison circuit 501 outputs the decode value “0”.

In order to facilitate the following description, specific numerical values will be assigned to the multiplication coefficients β0 to β (n + 1) and the multiplication coefficients β01 to βn (n + 1). That is, as shown in FIG. 4, β1 = 2.4, β2 = 1.8, β3 = 1.4,.
, Βn = 0.9, β (n + 1) = 0.7, and the multiplication coefficients indicating the slope of the straight line between the break points are β01 = 2.8, β12 = 2.3, β23 = 1.6,. , Βn
It is assumed that (n + 1) = 0.7. Therefore, in the comparison circuit 502, since the multiplication coefficient β01 = 2.8, this value is SL2 <β01, and the converted value 3 is output. Similarly, the decode values are output from the comparison circuits 503 to 508 in the same manner.

The control signal output from the amplitude level detection circuit 118 (FIG. 1) and used for controlling the selection circuit 117 is supplied to the correction amount calculation circuit 126 by the selection control input terminal T.
_The input from _c is used for selection control of the selection circuit 510. Thus, in the gamma correction circuit 100 in FIG. 1, the selection circuit 117 includes the multiplication circuits 105 to 108,
When any one of the output signals 112 to 114 is selected,
This output is supplied with the same multiplication coefficient as the multiplication coefficient supplied to the selected multiplication circuit.
The output decode value of any one of .about.508 is selected by the selection circuit 510 and output as a noise suppression correction amount.
FIG. 4 shows the value of the noise suppression correction amount for each multiplication coefficient.

In FIG. 1, the noise suppression correction amount output from the correction amount calculation circuit 126 as described above is
27 is input to the other input terminal. Adder 127
Then, the noise suppression value “1” output from the limiter 124 and the noise suppression correction amount from the correction amount calculation circuit 126 are added, and the added value is supplied to the noise suppression circuit 120 as a noise suppression level. . The noise suppression circuit 120 suppresses the noise of the video signal from the gamma correction circuit 100 according to the noise suppression level output from the adder 127. FIG. 4 shows the value of the noise suppression level in this case.

As described above, the noise suppression level output from the adder 127 is determined by multiplying coefficients β0 to βnβ (n +
1) When the values of β01 to βn (n + 1) are large,
When the gain of the video signal in the gamma correction circuit 100 is large, the amount of noise suppression is large, and when the gain of the video signal is small, the amount of noise suppression is small. In other words, when gamma correction is performed by the gamma correction circuit 100, the noise suppression amount is increased in a greatly amplified portion of the input video signal, and the noise suppression amount is also reduced in a small amplified portion. As described above, by providing the noise suppression amount in the noise suppression circuit 120 in accordance with the amplification factor of the video signal gamma-corrected in the gamma correction circuit 100, the S / N ratio of the entire video signal is improved, and Since noise is also suppressed at the suppression level according to the amplification factor of the video signal assigned according to the level of the input video signal at the time of gamma correction, optimal noise suppression is possible. The video signal that has been subjected to gamma correction by the gamma correction circuit 100 and the gradation and contrast are optimally controlled, and the noise has been optimally suppressed by the noise suppression circuit 120 is output from the video output terminal T _o to the display device 128. Is output. Therefore, on the display device 128, an image faithful to the original image whose gradation and contrast have been adjusted is displayed.

As described above, in the present embodiment, the gamma correction circuit 100 divides the gamma correction characteristic into a plurality of levels of a video signal, forms a break point at each of these split points, and forms a straight line between the split points. Along with the approximation, a desired amplification factor is set for each of these division points and between the division points,
The input video signal is amplified and output according to this amplification factor.
The correction amount calculation circuit 126 generates a noise suppression level corresponding to the division points and the amplification factor set between the division points. The noise suppression circuit 120 suppresses the noise of the divided gamma-corrected video signal in accordance with the noise suppression level with respect to the video signal including the noise signal having a different amplitude depending on the signal level by the gamma correction. The noise signal can be suppressed without deteriorating the quality of the video signal as much as possible. Therefore, optimal gamma correction is performed on the input video signal, and noise is suppressed satisfactorily. With the display device 128, it is possible to obtain an image with optimal gradation and contrast without deterioration in image quality.

As described above, in the correction amount calculation circuit 126, the noise signal is optimally suppressed by increasing the noise suppression level where the multiplication coefficient is large, but the signal level of the video signal displayed on the display device 128 is reduced. Comparing the low part image and the high part image, when the same level of noise is added to these parts, even if such a video signal is amplified by the gamma correction circuit 100 at the same amplification rate, the signal level is low. The noise added to the portion where the signal level is low and displayed dark is more noticeable than the noise added to the portion where the image is displayed bright and high.

Therefore, the correction amount calculation circuit 126 may further increase the noise suppression amount for a portion where the signal level of the video signal is low and supply the noise suppression amount to the adder 127. By performing such control in the correction amount calculating circuit 126, noise is conspicuous by increasing the amplification factor and performing gamma correction. In particular, the noise reduction effect is enhanced in an image portion having a low signal level, and the image quality is improved. Can be displayed on the display device 128.

FIG. 7 is a block diagram showing another embodiment of the video signal processing apparatus according to the present invention. In FIG. 7, reference numeral 701 denotes an outline emphasis circuit provided at a stage subsequent to the noise suppression circuit 120. Only the point provided is different from the above-described embodiment. As described above, in order to sufficiently exhibit the noise suppressing effect, the noise suppressing circuit 12
When the noise suppression level supplied to 0 is increased, particularly, the noise signal is sufficiently suppressed. On the other hand, for example, in an image representing grass, in a small amplitude portion where the signal level of the video signal is low, Due to the decrease in the amplitude level of the high-frequency component due to the above-described noise suppression processing by the noise suppression circuit 120, the frequency characteristics of the high-frequency component of the display video in this portion deteriorate, resulting in an image that is slightly blurred.

Therefore, in this embodiment, in FIG.
An outline emphasis process is performed by a contour emphasis circuit 710 provided at a subsequent stage of the noise suppression circuit 120 so that the video signal supplied from the noise suppression circuit 120 is further emphasized with a contour portion degraded by the noise suppression circuit 120. Do. For this reason, the contour emphasizing circuit 710 extracts the high-frequency component of the contour portion from the input video signal, and when the high-frequency component is sufficiently suppressed by the noise suppressing circuit 120, the high-frequency component is extracted. The band component is sufficiently amplified and added to the outline of the video signal. In this case, the degree to which the high-frequency component of the contour portion has been suppressed by the noise suppression circuit 120 can be detected by the same method as the correction amount calculation circuit 126.
The amplification factor of the suppressed high frequency component is also calculated by the correction amount calculating circuit 12.
When the amount of noise suppression obtained in step 6 is large, the high-frequency component is further suppressed, and thus the high-frequency component is amplified at an amplification factor according to the amount of noise suppression.

By doing so, sufficient noise suppression can be performed on the video signal, and the high-frequency component of the outline of the video signal can be sufficiently retained. Therefore, it is possible to display an image in which the noise signal is sufficiently suppressed on the display device while maintaining the high frequency characteristics of the gamma-corrected image signal. In the above description, the video signal input from the video input terminal T _i is used as a television broadcast reception signal. However, other video signals such as a personal computer video signal and a video camera output video signal may be used. Is also good.

[0052]

As described above, according to the present invention, the gamma correction characteristics of the gamma correction means are obtained by dividing a predetermined level range of an input video signal into a plurality of parts, and setting the division points as break points. The noise suppression level when suppressing the noise of the video signal gamma-corrected by the gamma correction means is approximated by a polygonal line consisting of a straight line connecting the points, and the amplification level assigned to each of the division points and divisions Since the value is determined according to the rate, the input video signal is optimally gamma-corrected and the noise component is appropriately suppressed, so that the optimal gamma correction can be performed without deteriorating the quality of the image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a video signal processing device according to the present invention.

FIG. 2 is a characteristic diagram showing a specific example of a gamma correction characteristic in the embodiment shown in FIG.

FIG. 3 is a characteristic diagram showing gamma characteristics of different types of display devices.

FIG. 4 is a table showing specific examples of numerical values of signals in the embodiment shown in FIG. 1;

FIG. 5 is a circuit diagram showing a specific example of a correction amount calculation circuit in FIG. 1;

FIG. 6 is a diagram illustrating an operation of the correction amount calculation circuit illustrated in FIG. 1;

FIG. 7 is a block diagram showing another embodiment of the video signal processing device according to the present invention.

[Explanation of symbols]

Reference Signs List 100 gamma correction circuit 104 noise suppression amount generation circuit 105 to 108, 112 to 114 multiplication circuit 109 to 111 gain calculation circuit 117 selection circuit 118 amplitude level detection circuit 120 noise suppression circuit 123 S / N detection circuit 124 limiter 126 correction amount calculation circuit 127 adder circuit 128 display unit T _r noise suppression level input terminal T _s slice level input terminal T _i video input terminal T _p crossover level input terminal T _g crossover gain input terminal T _o video output terminal

Continued on the front page (72) Inventor Haruki Takada 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Digital Media System Division of Hitachi, Ltd. F-term in Hitachi Digital Media System Division (Reference) 5C021 PA12 PA17 PA58 PA67 RB00 RB03 RB07 XA34 XB03 YA01 5C058 AA01 AA06 AA11 BA13 BA25 BA33 BB25 5C082 AA02 BA41 CA11 DA51 MM10

Claims (5)

[Claims] 1. A gamma correction means for performing gamma correction processing on an input video signal, and a noise suppression means for performing noise suppression processing for suppressing a noise component of the video signal output from the gamma correction means. The gamma correction characteristic of the gamma correction unit is approximated by a broken line corresponding to a broken point corresponding to each of the division points obtained by dividing the level range of the input video signal into a plurality of parts and a straight line between the broken points. A video signal processing apparatus, wherein a noise suppression level when suppressing a noise signal is a value corresponding to an amplification factor set for each break point of the gamma correction characteristic and a straight line between the break points. 2. The method according to claim 1, wherein the gamma correction unit includes: a breakpoint level setting unit that sets a level value of the plurality of breakpoints of the gamma correction characteristic approximated by a broken line; and a breakpoint multiplication that sets a multiplication coefficient of the breakpoint. Coefficient setting means, for each break point, a plurality of first multiplication means for multiplying the level value set by the break point level setting means and the multiplication coefficient set by the break point multiplication coefficient setting means, From the level value of the break point set by the break point level setting means and the multiplication coefficient set by the break point multiplication coefficient setting means, a slope of a straight line between the break points of the gamma correction characteristic is defined as a multiplication coefficient. A plurality of multiplication coefficient calculation means for calculating; a plurality of second multiplication means for multiplying the input video signal by the multiplication coefficient obtained by the plurality of multiplication coefficient calculation means; Occasionally Amplitude level detection means for detecting which of the break point or the range between the break points belongs to, and the plurality of first signals corresponding to the input video signal based on a result detected by the amplitude level detection means. Selecting means for selecting an output signal of any one of the multiplying means and the plurality of second multiplying means as a gamma-corrected video signal, and outputting the selected signal, wherein the noise suppressing means comprises: the amplitude level detecting means. A noise suppression amount generation unit that generates a noise suppression amount according to a multiplication coefficient used by the first or second multiplication unit selected by the selection unit based on a result detected by the selection unit. 2. The video signal processing apparatus according to claim 1, wherein noise of the video signal that has been gamma-corrected according to the following equation is suppressed. 3. The video signal processing apparatus according to claim 2, wherein said noise suppression amount generating means further increases the noise suppression amount for a video signal having a low signal level. 4. An image processing apparatus comprising: a contour emphasizing unit for emphasizing a contour of the video signal output from the noise suppressing unit; the contour emphasizing unit emphasizing the image signal with an emphasis degree corresponding to the noise suppression amount in the noise suppressing unit. 4. The video signal processing apparatus according to claim 1, wherein the reduction of the contour level by said noise suppressing means can be compensated. 5. A television signal receiving apparatus comprising the video signal processing apparatus according to claim 1.