JP2003032512A - Video signal contour corrector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gradation corrector which purposes to prevent reflected noises or the collapse of the gradation performance in a gradation part. SOLUTION: The gradation corrector controls a correction value adaptively according to the gradient of a video signal, senses reflected noises, suppresses noises, sharpens the edge of a large amplitude without a deterioration in image quality, and improves the space frequency of a video signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correction device for more clearly correcting a contour of an image by making a rising or falling edge of a portion of a video signal used in a television receiver or the like more sharp, More specifically, the present invention relates to a contour correction device that does not impair the characteristics of the original image by changing the steepening method according to the state of the image signal.

[0002]

2. Description of the Related Art Conventionally, in order to make a contour portion of an image clearer, a contour correction method and a contour correction device for absorbing rising or falling of a contour component corresponding to the image have been put into practical use. There is. FIG. 17 shows a typical example of such a conventional contour correcting device as disclosed in Japanese Patent Publication No. 7-570.
The contour correction device for correcting the contour of the video signal disclosed in Japanese Patent Application Laid-Open No. 09-2009 is shown. As shown in the figure, the contour correction device OEc includes a delay circuit 1, a subtraction circuit 2, a delay circuit 3, a minimum value circuit 4, a delay circuit 5, a subtraction circuit 6, a delay circuit 7, a minimum value circuit 8 and a delay circuit. A circuit 9 and a subtraction circuit 10 are included.

The delay circuit 1 is connected to an external video signal source (not shown) and delays the input video signal a by a first predetermined time P1 to generate a delayed input video signal b. The subtraction circuit 2 has its positive input port connected to the above-mentioned video signal source to receive the video signal a, and its negative input port connected to the delay circuit 1 to receive the delayed input video signal b. . Then, the delayed input video signal b is subtracted from the video signal a to generate the primary differential signal c.

The delay circuit 3 is connected to the subtraction circuit 2 and
The primary differential signal c is input. The delay circuit 3 further delays the input primary differential signal c by a second predetermined time P2 to generate a delayed primary differential signal d.

The minimum value circuit 4 is connected to the subtraction circuit 2 and the delay circuit 3 and receives the primary differential signal c and the delayed primary differential signal d, respectively. Then, the minimum value circuit 4 is
The minimum value of the input first-order differential signal c and delayed first-order differential signal d is taken out to generate a minimum-value first-order differential signal e.

Both the delay circuit 5 and the delay circuit 7 are connected to the minimum value circuit, and the minimum value first-order differential signal e is input. Then, the input minimum value first-order differential signal e is delayed by the delay circuit 5 for the third predetermined time P3,
A first delay minimum value first derivative signal f is generated. Similarly, the minimum first-order differential signal e is output by the delay circuit 7 to the fourth value.
Is delayed by a predetermined time P4 to generate the second delay minimum value first derivative signal h.

In the subtraction circuit 6, the positive side input port is connected to the minimum value circuit 4 and the minimum value first derivative signal e is input,
The negative input port is connected to the delay circuit 5 and the first delay minimum value first-order differential signal f is input. The subtraction circuit 6 calculates the first delay minimum value 1 from the input minimum value first-order differential signal e.
The secondary differential signal f is subtracted to generate the secondary differential signal g.

The minimum value circuit 8 is connected to the subtraction circuit 6 and the delay circuit 7, and receives the secondary differential signal g and the second delayed minimum value primary differential signal h, respectively. Minimum value circuit 8
Takes out the minimum value of the input secondary differential signal g and the second delay minimum value primary differential signal h, and generates a correction signal i.

The delay circuit 9 is connected to the above-mentioned video signal source and receives the video signal a. Then, the delay circuit 9
Generates the delayed input video signal j by delaying the input video signal a by the fifth predetermined time P5.

The subtraction circuit 10 has its positive input port connected to the delay circuit 9 to receive the delayed input video signal j,
The negative side input port is connected to the minimum value circuit 8 and the correction signal i
Is entered. The subtraction circuit 10 subtracts the correction signal i from the input delayed input video signal j to obtain the output video signal k.

Next, with reference to FIG. 18, the contour correcting operation of the video signal of the contour correcting apparatus OEc configured as described above will be described in detail. First, the input video signal a is delayed by the delay device 1 to obtain the delayed video input signal b. The delayed video input signal b is subtracted from the input video signal a by the subtraction circuit 2 to obtain the primary differential signal c. Next, the delay device 3 delays the first-order differential signal c by a first predetermined time as in the delay device 1, and obtains a delayed first-order differential signal d.

Then, the minimum value circuit 4 outputs the primary differential signal c
And one with a smaller absolute value of the delayed first derivative signal d,
The minimum value first-order differential signal e is output. However, if the primary differential signal c and the delayed primary differential signal d have different signs, 0 is output as the minimum value primary differential signal e. This minimum value first derivative signal e always has the same width as the rising or falling time of the contour portion of the input video signal a.

Next, the minimum value first-order differential signal e is supplied to the delay unit 5
And the delay circuit 7 supplies the minimum first-order differential signal e to the third predetermined time P3 and the fourth predetermined time P4, respectively.
Then, the first delay minimum value first derivative signal f and the second delay minimum value first derivative signal h are obtained. The fourth predetermined time P4 is 1/2 of the third predetermined time P3 (P
4 = P3 / 2).

Next, the subtraction circuit 6 subtracts the first delay minimum value first-order differential signal f from the minimum value first-order differential signal e to obtain 2
The second derivative signal g is obtained. The minimum value circuit 8 selects the smaller absolute value of the secondary differential signal g and the second delay minimum value primary differential signal h to obtain the correction signal i. However, the same sign as the second derivative signal g is used. Next, the subtraction circuit 10 obtains the output video signal k by subtracting the correction signal i from the delayed input video signal j. The delayed input video signal j is a signal obtained by delaying the video signal a by the time (fifth predetermined time P5) required for the above arithmetic processing. As a result, the output video signal k is always the rising edge of the contour portion of the input video signal a,
Alternatively, since it has the same width as the fall time, contour correction can be performed without pre-shooting and over-shooting.

As described above, in the contour correction device OEc, the minimum value first-order differential signal e and the second delay minimum-value first-order differential signal h are synchronized, and the fourth predetermined time P4 is the third predetermined time. The time is set to half of the time P3, and the first predetermined time P1, the second predetermined time P2, the third predetermined time P3, and the fourth
The predetermined time P4 and the fifth predetermined time P5 are appropriately set according to the contour correction device OEc, and a correction signal i that falls within the rising or falling period of the contour portion of the video signal a can be obtained. Then, by subtracting the video signal a from the correction signal i, the preshoot and overshoot are performed.
Output signal k having a steeper and narrower contour than the input signal can be obtained.

FIG. 19 shows an example of a preferable relationship between the video signal a and the output video signal k in the contour correction device OEc. In the figure, the solid line indicates the input video signal a, and the alternate long and short dash line indicates the output video signal k whose contour has been corrected by the contour correcting device OEc. In the same example, the inclinations of the rising edge and the falling edge of the output video signal k are larger than those of the video signal a. That is, the output video signal k is corrected so that the contour becomes clear as compared with the video signal a. In this way, the contour correction device OEc
In the above, in the case of a so-called contour signal in which the gradation and the intensity of the video signal a change with a predetermined amplitude or more, it can be effectively corrected.

[0017]

However, as shown in FIG.
The preferable example shown in is limited to the case where the inclination of the contour portion of the video signal a is equal to or more than a predetermined value and within a predetermined period. When the gradient of the contour portion of the video signal a is a predetermined value or less (in particular, the gradient changes) and the gradation signal extends for a predetermined period or more, or when the video signal a is a waveform signal according to a specific law, contour correction is performed. The desired result as shown in FIG. 19 is not obtained in the device OEc.

Such a case will be described below with reference to FIGS. 20 and 21. Note that, for the sake of visibility, the circle Ven in FIGS.
The part corresponding to the falling edge part surrounded by is shown.
Also in these drawings, the solid line indicates the video signal a, and the alternate long and short dash line indicates the output video signal k.

First, FIG. 20 shows an example of the video signal a and the output video signal k when the video signal a is a gradation signal that monotonically increases / decreases with a small amplitude. In the contour correction device OEc, the same contour correction as that for a contour signal that sharply changes at a predetermined amplitude or more is performed on a gradation signal that monotonously increases or decreases with a small amplitude. Therefore, if the gradation signal changes the video signal a with a slightly larger amplitude than the surroundings, as in the portion surrounded by the circle Lp in the figure, in the contour correction apparatus OEc, for contour correction, The slope of the output video signal k changes abruptly. However, it is obvious that such contour correction in a gradation signal that changes monotonously is not desirable, assuming that the gradation signal looks like human skin.

Next, in FIG. 21, for example, the peak Po composed of an increasing portion and a decreasing portion where the video signal a is continuous is 1
If there is one, the output video signal k is 2 for the same Po.
It has three mountains Pm and Pe. In this way, the output video signal k has extra peaks Pm as compared with the video signal a, and the characteristics of the video signal a are obviously broken. Therefore,
The present invention provides a contour correction device that solves a problem peculiar to the contour correction device OEc that a contour signal cannot be corrected correctly with respect to a gradation signal or a waveform signal having a peak near a contour portion as described above. The purpose is to clarify the optimum values of the predetermined first time P1, the second predetermined time P2, the third predetermined time P3, the fourth predetermined time P4, and the fifth predetermined time P5. .

[0021]

Means for Solving the Problems and Effects of the Invention The present invention has the following features in order to achieve the above-mentioned objects. A first aspect of the present invention is a contour correction device that processes an input video signal in a unit period corresponding to a pixel to emphasize a contour component of the input signal, and delays the input video signal by 2 times the unit period to obtain 2T. A first delay unit that generates a delayed input video signal; a first subtractor that subtracts the first delayed input video signal from the input video signal to generate a first primary differential signal; 1st order differential signal of 1 to 2 of unit period
2nd delay to generate a 2T delayed first derivative signal
Delay device, a minimum absolute value calculator for generating the minimum value first-order differential signal by selecting the smaller one of the first first-order differential signal and the 2T-delay first-order differential signal, and the lowest-value first-order differential signal Is delayed by twice the unit period to generate a 2T delay minimum value first derivative signal, and a first delay minimum value first derivative signal is subtracted from the minimum delay first derivative signal Se. And a second subtractor for generating a secondary differential signal and a fourth delay device for delaying the minimum value primary differential signal by a unit period to generate a 1T delayed minimum value primary differential signal, and a secondary differential Signal and 1T delay minimum value 1
A second minimum value unit that selects the smaller one of the secondary differential signals to generate the first correction signal, and the first correction signal is calculated by calculating the 2T-delayed primary differential signal based on a predetermined function. The operation unit for generating the correction signal of 2 and the input video signal for the unit period 3
Fifth delayer for delaying by 3 times to delay 3T delay input video signal, and third subtraction for subtracting the second correction signal from the 3T delay input video signal to generate a contour-corrected video signal Equipped with a vessel.

As described above, in the first aspect of the invention, the contour of the video signal is corrected by making the signal waveform of the portion that is monotonically increasing or decreasing monotonically, and the correction value is adjusted by the inclination of the video signal. The contour can be corrected without changing the characteristics of the original image.

A second aspect of the present invention is a contour correction apparatus for processing an input video signal in a unit period corresponding to a pixel to emphasize a contour component of the input signal, wherein the input video signal is set to 2 in the unit period.
First, a 2T delayed input video signal is generated by delaying by a factor of 2
, A first subtractor that subtracts the first delayed input video signal from the input video signal to generate a first primary differential signal, and a first primary differential signal for a unit period. A second delay device that delays by a factor of 2 to generate a 2T delayed first derivative signal;
A minimum absolute value calculator that selects the smaller one of the first primary differential signal and the 2T-delay primary differential signal to generate the minimum primary differential signal, and the minimum primary differential signal in the unit period of 2 4th delaying by a factor of 2 to generate a 2T delay minimum value first derivative signal
, A second subtractor that subtracts the first delayed minimum-value first-order differential signal from the minimum-value first-order differential signal Se to generate a second-order differential signal, and a minimum-value first-order differential signal. A fifth delay unit that delays by a unit period to generate a 1T-delayed minimum-value first-order differential signal; a sixth delay unit that delays an input video signal by a unit period to generate a 1T-delayed input video signal; A third subtractor for subtracting a 1T delayed input video signal from the video signal to generate a second primary differential signal, and a third subtractor for delaying the second primary differential signal by three times the unit period to generate 3T A seventh delayer that generates a delayed input video signal, a second-order differential signal, a 1T delay minimum value first-order differential signal, and a second delayed first-order differential signal are selected to select the smallest one. A second minimum value unit for generating a correction signal and a contour correction is performed by subtracting the first correction signal from the 3T delay input video signal. Comprising a fourth subtractor for generating a video signal.

As described above, in the second aspect of the present invention, the contour of the video signal is corrected by making the signal waveform of the portion that monotonically increases or decreases monotonically, and the original video features are corrected. It is possible to perform contour correction without damaging the characteristics of the original image while suppressing large deformation.

A third invention is the second invention according to the second invention.
Further comprising an eighth delayer that delays the first-order differential signal of 2 by a unit period to generate a 2T-delayed first-order differential signal,
The second second minimum value unit is a second derivative signal, a 1T delay minimum value first derivative signal, a second delayed first derivative signal, and a 2T
It is characterized in that the smallest one of the delayed first-order differential signals is selected to generate the first correction signal.

As described above, the third invention has the same effect as in the second aspect.

According to a fourth aspect of the present invention, in any one of the second aspect and the third aspect of the invention, the first correction signal and the 2T-delayed first-order differential signal are calculated based on a predetermined function to perform the second correction. The fourth subtracter further includes a calculator that generates a signal.
A third subtractor is provided that subtracts the second correction signal from the T-delayed input video signal to generate a contour-corrected video signal. As described above, according to the fourth aspect of the present invention, the contour of the video signal is corrected by making the signal waveform of the portion that is monotonically increasing or decreasing monotonically, and the correction value is adjusted by the inclination of the video signal. Can be adaptively changed to suppress the large deformation of the original image, and the contour can be corrected without losing the characteristics of the original image.

A fifth invention is characterized in that, in any one of the first invention and the fourth invention, the computing unit computes based on a predetermined function according to the gradation of the input video signal. And

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The basic concept of the contour correcting apparatus according to the present embodiment will be described first with reference to the drawings and before being specifically described. The contour correction apparatus OEp1 according to the present embodiment solves the problem of contour correction of gradation signals in the contour correction apparatus OEc described with reference to FIG.

As described above, in the contour correction device OEc, the correction signal i is subtracted from the delayed input video signal j obtained by delaying the input video signal a by the fifth predetermined time P5, and the output video signal k is output. Is generated, the video signal a
However, in the case of a gradation signal in which the gradation changes gradually as a whole, the contour correction (steepening) is excessively performed on the portion having a larger gradation difference than the surroundings, and the contour is originally formed on the portion having no contour. Will occur. In order to prevent this, in the present embodiment, the contour correction amount is adjusted according to the degree of gradation change rather than the gradation difference.

(First Embodiment) A contour correcting device according to a first embodiment of the present invention will be described with reference to FIG. As shown in the figure, the contour correction device OEp1 is
T delay device 101, subtractor 102, 2T delay device 103, minimum absolute value calculator 104, 2T delay device 105, subtractor 10
6, 1T delay device 107, minimum absolute value selector 108, 3T
A delay device 109, a subtractor 110, a 2T delay device 111, and a calculator 112 are included.

The 2T delay device 101 is connected to an external video signal source (not shown), delays the input analog or digital input video signal Sa by 2T period, and delays it by 2T.
The T delay input video signal Sb is generated. The T period in the 2T period is 1 expressed by the input video signal Sa.
It is N times the period GP corresponding to a pixel (N is a natural number).
That is, it can be expressed as T = N · GP. Thus, the T period is a period corresponding to an arbitrary number N of pixels. That is, the 2T period is a 2N pixel period of the input video signal Sa. Then, preferably, the optimum value of N is determined according to the frequency of the input video signal Sa.
However, in this specification, for simplification of description, the case of N = 1 will be described as a typical example unless otherwise specified.

The subtractor 102 has a positive side input port connected to the above-mentioned video signal source to receive the input video signal Sa, and a negative side input port connected to the 2T delay device 101 to input a 2T delay input image. The signal Sb is input. Then, the 2T delayed input video signal Sb is subtracted from the input video signal Sa to generate the first primary differential signal Sc. 2T delay device 1
03 is connected to the subtractor 102 and receives the first first-order differential signal Sc. The 2T delay device 103 further delays the input first primary differential signal Sc by a 2T period to generate a 2T delayed primary differential signal Sd.

The minimum absolute value calculator 104 is a subtractor 102.
And a 2T delay device 103, and the first primary differential signal Sc and the 2T delayed primary differential signal Sd are input respectively. Then, the minimum absolute value calculator 104 receives the input first primary differential signal Sc and 2T delayed primary differential signal Sd.
The minimum value of and is taken out, and the minimum value first-order differential signal Se is generated.

2T delay device 105 and 1T delay device 107
Are both connected to the minimum absolute value calculator 104, and the minimum value 1
The secondary differential signal Se is input. Then, the input minimum value first-order differential signal Se is input to the 2T delay unit 105 to
Delayed by T period, 2T delay minimum value first derivative signal S
f is generated. Similarly, the minimum value first-order differential signal Se is
The 1T delay unit 107 delays by 1T period (one pixel period) to generate the 1T delay minimum value first-order differential signal Sh.

The subtractor 106 has its positive input port connected to the minimum absolute value calculator 104, and has a minimum value first derivative signal S.
e is input, the negative side input port is connected to the 2T delay device 105, and the 2T delay minimum value first-order differential signal Sf is input. The subtractor 106 receives the input minimum value first-order differential signal S
The 2T delay minimum value first derivative signal Sf is subtracted from e to generate a second derivative signal Sg.

The minimum absolute value selector 108 is a subtractor 106.
And the 1T delay unit 107, and the secondary differential signal Sg and the 1T delay minimum value primary differential signal Sh are input, respectively. The minimum absolute value selector 108 takes out the minimum value of the input secondary differential signal Sg and the 1T delay minimum value primary differential signal Sh, and generates a first correction signal Si1.

The 3T delay unit 109 is connected to the above-mentioned video signal source and receives the input video signal Sa. And
The 3T delay unit 109 sets the input second-order differential signal Sg to 3
The 3T delayed input video signal Sj is generated by delaying by the T period.

The 2T delay device 111 is connected to the subtractor 102 and receives the first primary differential signal Sc. Then, the 2T delay device 111 outputs the first primary differential signal Sc to 2
The second delayed primary differential signal Sm is generated by delaying by the T period. The 2T delayed primary differential signal Sd and the second delayed primary differential signal Sm are equivalent. Therefore, the 2T delay device 1
11 may be removed, and the first delayed first-order differential signal d may be input to the calculator 112 instead of the second delayed first-order differential signal Sm.

The calculator 112 is a minimum absolute value selector 108.
And the 2T delay device 111, and respectively connected to the first
The correction signal Si1 of the second delayed primary differential signal Sm and the gradation information Li are input. The arithmetic unit 112 is, uniquely, the first correction signal Si1 and the second delayed first derivative signal S.
It is an adjuster of the first correction signal Si1 that performs a predetermined calculation on m and to generate a second correction signal Ss. That is,
The arithmetic unit 112 and the 2T delay unit 111 realize an adaptive correction function that adaptively adjusts the contour correction amount according to the degree of gradation change rather than the gradation difference, which is the basic concept of the present embodiment. There is.

The calculator 112 is further connected to a video signal gradation indicator (not shown) provided outside, and receives gradation information Li indicating the gradation of the input video signal Sa.
Then, based on the gradation information Li, the first correction signal Si
A further adjusted second correction signal Ss is generated by changing the content of the calculation of the first and second delayed primary differential signals Sm.

The subtraction circuit 10 has three positive input ports.
3T delay input video signal Sj connected to T delay device 109
Is input, the negative side input port is connected to the calculator 112, and the second correction signal Ss is input. The subtraction circuit 10 is
The second correction signal Ss is subtracted from the input 3T delayed input video signal Sj to obtain the first output video signal Sk1.
Thus, the subtractor 110 subtracts the second correction signal Ss from the 3T delayed input video signal Sj to generate the first first output video signal Sk1 in which the contour of the input video signal Sa is corrected. To be done. In this sense
The arithmetic unit 112 determines the contour state of the first first output video signal Sk1 as the second delayed primary differential signal Sm and the gradation information L.
It has a function of adjusting with a two-dimensional term called i.

The operation of the contour correction device OEp1 configured as described above will be described in detail below. Input video signal Sa
Is delayed by the delay device 1 to obtain the 2T-delayed input video signal Sb which is the input video signal Sa delayed by the 2T period (two pixel periods). This 2T delayed input video signal Sb
2, the first primary differential signal Sc is obtained by subtracting from the input video signal Sa.

Next, the 2T delay unit 103 delays the first first-order differential signal Sc for 2T periods to obtain a 2T delay 1
After obtaining the secondary differential signal Sd, the minimum absolute value calculator 104 selects the smaller absolute value of the first primary differential signal Sc and the 2T-delay primary differential signal Sd to select the minimum primary differential signal. S
get e. However, if the first primary differential signal Sc and the 2T delayed primary differential signal Sd have different signs, 0 is output. Further, as the sign, the sign of the first primary differential signal Sc is used. The minimum-value first-order differential signal Se thus obtained always falls within the rising or falling period of the contour portion of the input video signal Sa.

Next, the 2T delay device 105 and the 1T delay device 107 delay the minimum value first-order differential signal Se by 2T period and 1T period, respectively, to obtain a 2T delay minimum first-order differential signal Sf and a 1T delay minimum value first-order. The differential signal Sh is obtained.

Next, the subtracter 106 subtracts the 2T delay minimum value first order differential signal Sf from the minimum value first order differential signal Se,
The second derivative signal Sg is obtained. 2 in the minimum absolute value selector 108
The smaller of the absolute values of the secondary differential signal Sg and the 1T delay minimum value primary differential signal Sh is selected to obtain the first correction signal Si1. However, the same sign as the secondary differential signal Sg is used.

The 2T delay device 111 delays the first first-order differential signal Sc for a 2T period to generate the second delayed first-order differential signal S.
get m. The second delayed primary differential signal Sm is delayed from the input video signal Sa by 3T period.

As described above, the first correction signal Si1 is subjected to the predetermined calculation based on the second delayed first-order differential signal Sm and the gradation information Li by the calculator 112 to obtain the second correction signal Ss. Is generated.

In other words, in this sense, in the present embodiment, the first correction signal Si1 and the second correction signal S
s, the second delayed first derivative signal Sm, and the gradation information Li
Preferably, the relationships shown in the following equations (1) to (9) are established between the two. Ss = f (Si1, Sm, Li) ... (1) Ss = f (Si1, Li) × f (Sm, Li) ... (2)

From the above equation, as a preferable example when the input video signal Sa has 256 gradations (Li = 256), the second correction signal Ss is expressed as a two-line graph.
That is, the second correction signal Ss takes a value defined by the following equations (3) and (4) according to the value of the second delayed first-order differential signal Sm. Ss = Si1 × Sm / 16 (Sm <= 16) (3) Ss = Si1 (Sm> 16) (4)

The above equations (3) and (4) show an example in which the value of the second delayed first derivative signal Sm is 16 as the threshold value. However, depending on the desired contour correction result, 32 or It can be set to an appropriate value other than 16 called 24. Also,
As defined by the following equations (5), (6), and (7),
The second correction signal Ss may be set so as to be expressed as a three-line graph. Ss = Si1 × Sm / 32 (Sm <= 16) (5) Ss = Si1 / 2 + Si1 * (Sm-16) / 64 (Sm> 16, Sm <= 48) (6) Ss = Si1 (Sm> 48) (7)

Further, the function and the threshold value appropriately determined for the value of the gradation information Li exemplified in the above equations (1) to (7) are stored in the calculator 112 as a table. Then, the arithmetic unit 112 refers to a table stored inside based on the inputted gradation information Li to perform a predetermined arithmetic operation, thereby converting the first correction signal Si1 into the second delayed primary differential signal. The second correction signal Ss is generated by adjusting with Sm.

As an example in which the value of the gradation information Li is different, the following equations (8) and (9) are obtained when the input video signal Sa has 1024 gradations. Ss = Si1 × Sm / 64 (Sm ≦ 64) ... (8) Ss = Si1 (Sm> 64) ... (9) Then, this Ss is the second correction signal Ss and is a subtractor. It is output to 110.

Next, the subtractor 110 subtracts the second correction signal Ss from the 3T-delayed input video signal Sj which is the input video signal Sa delayed by the 3T period, thereby obtaining the first correction signal Ss.
To obtain the first output video signal Sk1. When the first first output video signal Sk1 is a video signal which smoothly and monotonically increases or decreases like a gradation, the first-order differential value (Sm) is given by the above equation (2). Since the gain is determined by the function of, the first first output video signal Sk1 becomes small, and the characteristics of the original input video signal Sa are not lost.

As for the steep contour portion, the first first output video signal Sk1 is always the rising edge of the contour portion of the input video signal Sa, as in the output video signal k in the contour correcting apparatus OEc of the conventional example. Alternatively, since it falls within the falling period, contour correction can be performed without pre-shoot and over-shoot. Note that the functional expressions (1) to (9) and the threshold value with respect to the value of the gradation information Li described above are examples, and the characteristics of the input video signal Sa and the corrected first first value.
According to the characteristics of the display that displays the output video signal Sk1, the various appropriate settings can be made through experiments and the like so that the optimum contour correction result can be obtained.

Next, with reference to FIGS. 2, 3, 4, and 5, the contour correction device OE according to the present embodiment will be described by taking a signal obtained by digitally sampling the input video signal Sa as an example.
The contour correction process based on p1 will be specifically described. 2 and 3 show the contour correction device O according to the present embodiment.
Represents a signal value and a signal waveform processed by Ep1,
4 and 5, the 2T delay unit 111 and the arithmetic unit 112 that provide the adaptive correction function are removed from the contour correction apparatus OEp1, and the subtractor 110 removes the 3T delay input video signal Sj.
Sj-Si obtained by subtracting the first correction signal Si1 from
3 shows signal values and signal waveforms when output as the output video signal Sk1n.

In FIG. 2, reference numerals Sa and S shown in the leftmost column.
b, Sc, Sd, Se, Sf, Sg, Sh, Si, S
m, Ss, Sj, and Sk1 are the above-mentioned input video signal Sa, 2T delayed input video signal Sb, first first-order differential signal Sc, and 2T-delayed first-order differential which are observed in each part of the contour correction apparatus OEp1. Signal Sd, minimum value first derivative signal Se, 2T delay minimum value first derivative signal Sf, second derivative signal Sg, 1T delay minimum value first derivative signal Sh, first correction signal Si1, second delay first order The differential signal Sm, the second correction signal Ss, the 3T delayed input video signal Sj, and the first output video signal Sk1 are shown. And the top line is
The time elapsed after the input video signal Sa is input to the contour correction device OEp1 is represented by a multiple of the period T.
Each time represented by a multiple of the period T is time n × T
(N is a natural number). Then, the values of the corresponding signals at the respective times are shown in each row including the sign of the signal.

Then, FIG. 3 graphically shows changes in the input video signal Sa and the first output video signal Sk1 shown in FIG. 2 on the time axis (horizontal axis) and the gradation axis (vertical axis). Also in FIG. 4, as in FIG. 2, except that the second delayed first derivative signal Sm and the second correction signal Ss are removed, the first output video signal Sk1n is replaced by the first output video signal Sk1n. The signal value is displayed. Then, in FIG. 5, the input video signal Sa and the first output video signal Sk1 shown in FIG.
The change in n is graphically displayed.

Comparing FIG. 3 and FIG. 5, in FIG.
Although the amplitude of the inclination is not constant, it can be seen in FIG. 3 that the amplitude of the inclination is suppressed to be almost constant. This means that the correction of the gradation signal that monotonously increases / decreases with a small amplitude is suppressed, and the characteristics of the original video signal are retained. As a result, the effect of the adaptive correction function based on the degree of change in gradation formed by the 2T delay unit 111 and the arithmetic unit 112 according to the present invention is clear.

(Second Embodiment) The basic concept of the contour correcting apparatus according to the present embodiment will be described first with reference to the drawings and before being specifically described. The contour correction apparatus OEp2 according to the present embodiment is unique to the contour correction apparatus OEc that cannot correctly correct the waveform signal having a peak in the vicinity of the contour portion in the contour correction apparatus OEc described with reference to FIG. Solving the problem is what solves the problem.

As shown in FIG. 6, the contour correcting apparatus OEp2 according to the present embodiment is the contour correcting apparatus O shown in FIG.
At Ep1, the minimum absolute value selector 108a is replaced with the minimum absolute value selector 108b, the 2T delay unit 111 and the arithmetic unit 112 are removed, and the 1T delay unit 113,
A subtractor 114 and a 3T delay circuit 115 are newly added and configured. The newly provided 1T delay device 113, subtractor 114, and 3T delay circuit 115 have a contour correction function that suppresses contour correction processing that causes the waveform of the input video signal Sa to be deformed. Not for the device.

That is, the input video signal Sa input from the video signal source is subtracted by the subtractor 102, the subtractor 102, the 2T delay device 103, the minimum absolute value calculator 104, and the 2T delay device 10.
5, the subtractor 106, and the 1T delay device 107
In the same manner as in the contour correction device OEp1, the subtracter 106 and the 1T delay device 107 output the secondary differential signal Sg and the 1T delay minimum value primary differential signal Sh to the minimum absolute value selector 108b, respectively. It

The 1T delay device 113 newly provided in the contour correction device OEp2 is connected to the video signal source,
The input video signal Sa is input. Then, the 1T delay device 1
13 is 1T after delaying the input video signal Sa by 1T period.
The delayed input video signal Sn is generated.

The subtractor 114, like the subtractor 102,
The positive side input port is connected to the above-mentioned video signal source to input the input video signal Sa, and the negative side input port is connected to the 1T delay unit 113 to input the 1T delayed input video signal Sn. Then, the subtractor 114 subtracts the 1T delayed input video signal Sn from the input video signal Sa to generate a second primary differential signal Sp. The 3T delay circuit 115 is connected to the subtractor 114 and receives the second primary differential signal Sp. The 3T delay circuit 115 delays the second primary differential signal Sp by a 3T period to generate a second delayed primary differential signal Sq, and outputs it to the minimum absolute value selector 108b.

The minimum absolute value selector 108b is the subtractor 10
Second derivative signal Sg input from 6 and 1T delay device 10
1T delay minimum value first-order differential signal Sh input from
The minimum value of the second delayed first-order differential signal Sq input from the 3T delay circuit 115 is extracted and used as the first correction signal Si2.
To generate. Note that the minimum absolute value selector 108a according to the first exemplary embodiment uses two input signals (secondary differential signal Sg).
And 1T delay minimum value first derivative signal Sh), the minimum absolute value selector 108b has three input signals (second derivative signal Sg, 1T delay minimum value first derivative signal S).
The difference is that the minimum value of h and the second delayed primary differential signal Sq) is taken. Naturally, the first correction signal Si1 output from the minimum absolute value selector 108a and the minimum absolute value selector 108b
The possible values of the first correction signal Si2 output from are different.

Contour correction device OEp constructed as described above
The contour correction operation of No. 2 will be described in detail. 2T
The operation from the delay device 101 to the minimum absolute value selector 108b is the same as the operation in the contour correction apparatus OEp1 already described, and therefore description thereof will be omitted.

The 1T delay unit 113 sets the input video signal Sa to 1
After delaying for T period, 1T delayed input video signal Sn is obtained.
The subtractor 114 subtracts the 1T delayed input video signal Sn from the input video signal Sa to obtain a second primary differential signal Sp.
The 3T delay circuit 115 outputs the second primary differential signal Sp to 3T.
A second delayed primary differential signal Sq delayed for a period is obtained. The smallest absolute value selector 108 selects the one having the smaller absolute value of the secondary differential signal Sg, the 1T delay minimum value primary differential signal Sh, and the second delayed primary differential signal Sq to obtain the first correction signal Si2. . However, the same sign as the secondary differential signal Sg is used.

Next, the subtracter 110 delays the first correction signal Si2 by 3T period to obtain the input video signal S.
The first correction signal Si2 is obtained by subtracting from the 3T delayed input video signal Sj which is a. The output video signal k and the contour correction device OE in the above-described contour correction device OEc
Similarly to the first output video signal Sk1 at p1,
Since the correction signal Si2 is always within the rising or falling period of the contour portion of the input video signal Sa (a), the contour correction can be performed without pre-shooting and over-shooting. Further, it solves the problem that the output video signal becomes different from the characteristics of the input video signal (the pattern of increase / decrease) with respect to the pattern of a certain video signal.

Next, FIG. 7, FIG. 8, FIG. 9, FIG.
With reference to FIG. 1 and FIG. 12, the contour correction processing by the contour correction apparatus OEp2 according to the present embodiment will be specifically described by taking a signal obtained by digitally sampling the input video signal Sa as an example.

7 and 8 show the signal value and the signal wave waveform processed by the contour correcting apparatus OEp2 according to the present embodiment, and FIGS. 9 and 10 show the contour correcting apparatus O.
Ep2 to 1T delay 113, subtractor 114, and 3
The processing when the T delay circuit 115 is removed is shown. In this case, the minimum absolute value selector 108b has the second delay 1
Since the secondary differential signal Sq is not input, the minimum absolute value selector 108b outputs the first correction signal Si1 to the subtractor 110 instead of the first correction signal Si2. As a result, in the subtractor 110, the input video signal Sa delayed for 3T period
Then, the first correction signal Si1 is subtracted from the 3T delayed input video signal Sj, which is the 3T delay input video signal Sj, to generate the first correction signal Si2n. 9 and 10 show the signal value and the signal waveform at this time.

Comparing FIG. 8 and FIG. 10, the first correction signal Si2n in FIG. 10 has two peaks of increase / decrease, but the first correction signal Si2n in FIG. Correction signal Si2
, The peak of increase / decrease is suppressed to the same one as the input video signal Sa. As described above, the present embodiment shows that the problem that the characteristics of the input video signal Sa is destroyed is solved. As described above, the effect of the deformation suppressing function that suppresses the contour correction for deforming the waveform of the input video signal Sa provided by the 1T delay device 113, the subtractor 114, and the 3T delay circuit 115 is clear.

Next, with reference to FIG. 11 and FIG. 12, a problem that is still unsolved in the contour correcting apparatus OEp2 according to the present embodiment will be described. FIG. 11 shows the value of each signal in the contour correction device OEp2 as in FIG. However, in FIGS. 11 and 12, time T
When an input video signal Sa having a discontinuous gradation that can be clearly seen in No. 11 is input, as shown in FIG. 12, there is originally only one peak of increase / decrease at time T11, which is the first output video. In the signal Sk2, two peaks occur at times T12 and T14. To solve this problem,
The contour correction device according to the third embodiment of the present invention is proposed below.

(Third Embodiment) Referring to FIG. 13,
A contour correction device according to a third embodiment of the present invention will be described. Contour correction device OEp according to the present embodiment
3 is 3 in the contour correction device OEp2 shown in FIG.
A 2T delay device 116 is newly provided in parallel with the T delay circuit 115. The minimum absolute value selector 108b is replaced with the minimum absolute value selector 108c.

That is, the 2T delay unit 116 is the subtractor 114.
And the second primary differential signal Sp is input.
Then, the 2T delay device 116 delays the second primary differential signal Sp by a 2T period to generate a 2T delayed primary differential signal Sr, which is output to the minimum absolute value selector 108c. As a result, the 1T delay minimum value first-order differential signal Sh, the second delayed first-order differential signal Sq, and 2 are input to the minimum absolute value selector 108c.
Three signals of the T-delay primary differential signal Sr are input, the minimum value of these three signals is selected, the first correction signal Si3 is generated, and the first correction signal Si3 is output to the subtractor 110.

The minimum absolute value selector 108b according to the second embodiment has three input signals (secondary differential signal S
g, 1T delay minimum value first derivative signal Sh and second delay first derivative signal Sq), the minimum absolute value selector 108c has four input signals (second derivative signal). Sg, 1T delay minimum value first derivative signal Sh, second delay first derivative signal Sq, and 2T delay first derivative signal Sr)
The difference is that it takes the minimum value of. Naturally, the minimum absolute value selector 1
08c outputs the first correction signal Si3 and the minimum absolute value selector 108b outputs the first correction signal Si3.
In 2, the possible values are different.

Contour correction device OEp constructed as described above
The contour correction operation of No. 3 will be described in detail. As described above, the 2T delay unit 116 generates the 2T delayed first-order differential signal Sr, the minimum absolute value selector 108c generates the first correction signal Si3, and the subtractor 110 generates the first 3T delayed input video signal Sj. The operation is the same as that of the contour correction apparatus OEp2 except that the first output video signal Sk3 is generated by subtraction of the correction signal Si3.

In the delay unit 116, the second primary differential signal Sp
Is delayed by 2T to obtain a 2T delayed first-order differential signal Sr. The minimum absolute value selector 108 has a second derivative signal Sg,
The 1T delay minimum value primary differential signal Sh, the second delayed primary differential signal Sq, and the 2T delayed primary differential signal Sr having smaller absolute values are selected to obtain the first correction signal Si3. However,
As the sign of the first correction signal Si3, the same sign as that of the secondary differential signal Sg is used.

Next, the subtractor 110 subtracts the first correction signal Si3 from the 3T delayed input video signal Sj, which is the input video signal Sa delayed by the 3T period, to obtain the first correction signal Si3.
The output video signal Sk3 of is obtained. First output video signal Sk
3 always falls within the rising or falling period of the contour portion of the input video signal Sa, the preshoot,
Contour correction can be performed without overshoot.

Further, the problem that the output video signal becomes different from the characteristics of the input video signal (increase / decrease pattern) with respect to the pattern of the input video signal Sa is solved. By adding the 2T delayed first-order differential signal Sr in addition to the second delayed first-order differential signal Sq, it becomes possible to further retain the characteristics of the input video signal with respect to the pattern of the video signal.

Next, with reference to FIGS. 14 and 15, the result of the contour correction processing according to the present embodiment applied to the digitally sampled input video signal Sa will be described. When FIG. 15 is compared with FIG. 12 described above, the output video signal Sk2 in FIG. 12 has two peaks of increase / decrease, but the output video signal Sk3 in FIG.
The peak of increase / decrease is suppressed to the same one as the input video signal Sa. As described above, the present embodiment shows that the problem that the characteristics of the video signal are destroyed is further solved.

(Fourth Embodiment) Referring to FIG. 16,
A contour correction device according to a fourth embodiment of the present invention will be described. Contour correction device OEp according to the present embodiment
4 is configured by combining the contour correction device OEp1 shown in FIG. 1 and the contour correction device OEp3 shown in FIG. In other words, the contour correction apparatus OEp4 is different from the contour correction apparatus OEp3 in the 2T delay unit 111 of the contour correction apparatus OEp1.
And the arithmetic unit 112 is added. As a result, it has the features of both the contour correction apparatus OEp1 and the contour correction apparatus OEp3.

As described above, in the first embodiment of the present invention, the contour of the video signal is corrected by making the signal waveform of the portion where the monotone increase or the monotonous decrease is sharp, and further the video signal. It is possible to adaptively change the correction value according to the inclination of and to perform contour correction without losing the characteristics of the original image.

Further, in the second and third embodiments, the contour of the video signal is corrected by making the signal waveform of the monotonically increasing or monotonically decreasing portion steep, and the original video features are On the other hand, it is possible to correct the contour without damaging the characteristics of the original image while suppressing the large deformation.

Furthermore, in the fourth embodiment, the contour of the video signal is corrected by making the signal waveform of the portion that is monotonically increasing or decreasing monotonically, and the correction value is adjusted by the inclination of the video signal. It is possible to adaptively change the contour of the original image without compromising the characteristics of the original image while suppressing the large deformation of the original image.

[Brief description of drawings]

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

FIG. 2 is a diagram showing values of various signals processed in the contour correction apparatus shown in FIG.

FIG. 3 is a diagram comparatively showing an input video signal and an output video signal in the contour correction device shown in FIG.

FIG. 4 is a diagram showing a value of a signal processed in a state where the adaptive correction function is disabled in the contour correction apparatus shown in FIG.

5 is a diagram comparatively showing an input video signal and an output video signal in the contour correction device in the state shown in FIG.

FIG. 6 is a block diagram showing a configuration of a contour correction device according to a second embodiment of the present invention.

7 is a diagram showing values of various signals processed by the contour correction device shown in FIG.

8 is a diagram comparatively showing an input video signal and an output video signal in the contour correction apparatus shown in FIG.

9 is a diagram showing a value of a signal processed in a state in which the deformation suppressing function is canceled in the contour correction device shown in FIG.

10 is a diagram comparatively showing an input video signal and an output video signal in the contour correction device in the state shown in FIG.

11 is a diagram showing values of signals relating to processing of an input video signal having a discontinuity in the contour correction device shown in FIG.

12 is a diagram comparatively showing an input video signal and an output video signal in the contour correction device in the state shown in FIG.

FIG. 13 is a block diagram showing a configuration of a contour correction device according to a third embodiment of the present invention.

14 is a diagram showing values of various signals processed by the contour correction device shown in FIG.

FIG. 15 is a diagram comparatively showing an input video signal and an output video signal in the contour correction device shown in FIG.

FIG. 16 is a block diagram showing a configuration of a contour correcting device according to a fourth embodiment of the present invention.

FIG. 17 is a block diagram showing a configuration of a conventional contour correction device.

FIG. 18 is a waveform diagram of various signals processed in the contour correction device shown in FIG. 17.

FIG. 19 is an explanatory diagram showing a contour correction result for a video signal having a contour portion having a density gradient of a predetermined value or more by the contour correction device shown in FIG.

FIG. 20 is an explanatory diagram showing a result of the contour correction performed on the video signal having the gradation portion having the density gradient of a predetermined value or less by the contour correction device shown in FIG.

FIG. 21 is an explanatory diagram showing a contour correction result for a video signal having a peak near a contour portion by the contour correction device shown in FIG. 18;

[Explanation of symbols]

OEc, OEp1 to OEp4 contour correction device 1, 3, 5, 7, 9 delay circuit 2, 6, 10 subtraction circuit 4, 8 Minimum value circuit 101, 103, 105, 111, 116 2T delay device 102, 106, 110, 114 Subtractor 104 Minimum absolute value calculator 107,113 1T delay device 108 Minimum absolute value selector 109,115 3T delay device 112 arithmetic unit

Claims (5)

[Claims] 1. A contour correction device for processing an input video signal in a unit period corresponding to a pixel to emphasize a contour component of the input signal, wherein the input video signal is delayed by twice the unit period. Delay unit for generating a 2T delayed input video signal, and a first subtractor for subtracting the first delayed input video signal from the input video signal to generate a first primary differential signal And a second delayer for delaying the first primary differential signal by twice the unit period to generate a 2T-delayed primary differential signal, the first primary differential signal and the 2T delay A minimum absolute value calculator that selects a smaller one of the first-order differential signals to generate a minimum-value first-order differential signal; A third delay device for generating a value first-order differential signal, and the minimum value first-order differential signal A second subtractor that subtracts the first delayed minimum-value first-order differential signal from the signal Se to generate a second-order differential signal; and delays the minimum-value first-order differential signal by the unit period for 1T. A fourth delay unit for generating a first-order differential signal with a minimum delay value; A minimum value calculator, a calculator for calculating the first correction signal with the 2T-delayed first-order differential signal based on a predetermined function, and generating a second correction signal; A fifth delayer for delaying the 3T delay input video signal by delaying it by 3 times, and a second delay signal subtracted from the 3T delay input video signal to generate a contour-corrected video signal. A contour correction device comprising a subtractor of 3. 2. A contour correction device for processing an input video signal in a unit period corresponding to a pixel to emphasize a contour component of the input signal, wherein the input video signal is delayed by twice the unit period. Delay unit for generating a 2T delayed input video signal, and a first subtractor for subtracting the first delayed input video signal from the input video signal to generate a first primary differential signal And a second delayer for delaying the first primary differential signal by twice the unit period to generate a 2T-delayed primary differential signal, the first primary differential signal and the 2T delay A minimum absolute value calculator that selects a smaller one of the first-order differential signals to generate a minimum-value first-order differential signal; A fourth delay device for generating a first-order differential signal of the value; A second subtractor that subtracts the first delayed minimum-value first-order differential signal from the signal Se to generate a second-order differential signal; and delays the minimum-value first-order differential signal by the unit period for 1T. A fifth delayer for generating a first-order differential signal with a minimum delay value; a sixth delayer for delaying the input video signal by the unit period to generate a 1T delayed input video signal; 1T delay A third subtractor that subtracts an input video signal to generate a second primary differential signal, and a 3T delay by delaying the second primary differential signal by three times the unit period A seventh delayer for generating an input video signal; a secondary differential signal; a 1T delay minimum value primary differential signal; A second minimum value unit for generating a correction signal of the first auxiliary signal from the 3T delayed input video signal. Signal by subtracting a contour correcting device comprising a fourth subtractor for generating a contour correction video signal. 3. An eighth delayer for delaying the second primary differential signal by twice the unit period to generate a 2T-delayed primary differential signal, further comprising: The bin is the second derivative signal, 1T
The first correction signal is generated by selecting the smallest one among the delay minimum value first derivative signal, the second delay first derivative signal, and the 2T delay first derivative signal. The contour correction device according to claim 2. 4. An arithmetic unit for calculating the first correction signal with the 2T-delayed first-order differential signal based on a predetermined function to generate a second correction signal, the fourth subtraction 4. The device according to claim 2, further comprising a third subtractor that subtracts the second correction signal from the 3T delayed input video signal to generate a contour-corrected video signal. The contour correction device according to. 5. The contour according to claim 1, wherein the arithmetic unit performs an arithmetic operation based on a predetermined function according to the gradation of the input video signal. Correction device.