JP4466454B2 - Video correction device - Google Patents

Description

  The present invention relates to an image correction apparatus.

  FIG. 4 is a block diagram showing a configuration of a conventional video correction apparatus. In FIG. 4, 21 is a first video feature detection unit, 22 is a gain control processing unit, 23 is a first gradation variable gain processing unit, 24 is a second video feature detection unit, 25 is a correction control processing unit, Reference numeral 26 denotes an APL correction control processing unit, and 27 denotes a second gradation variable gain processing unit. As a process often performed in the control method of such a conventional video correction apparatus, an explanation will be given below of a video level correction (generally gamma correction) process.

  The first video feature detection unit 21 detects the level distribution (histogram), average value (abbreviation: APL: Average Picture Level) of the luminance signal Yin of the input image, and the maximum value (MAX) and minimum value (MIN) of the video. To do. Based on this, the video signal is controlled so as to be easy to see when displayed on the video display device (display). Video features such as histogram, APL, MIN, and MAX are processed by the gain control processing unit 22 into data for correcting the tone characteristics of the luminance signal Yin, and the first tone variable gain processing unit 23 according to the level. The gain is given to the luminance signal Yin, and an output signal Yout1 with desired gradation characteristics is obtained. The above is the first step.

  The second video feature detector 24 detects the video feature of the output signal Yout1 of the first gradation variable gain processor 23, and the correction control processor 25 detects the input detected by the first video feature detector 21. Based on the characteristics of the video signal Yin and the video characteristics of the signal Yout1 detected by the second video feature detection unit 24, control data of the second gradation variable gain processing unit 27 is generated. Based on the control data from the correction control processing unit 25, the second gradation variable gain processing unit 27 further corrects the signal Yout1 corrected by the APL correction processing unit 26 and finally outputs a luminance signal output Yout2. To do. The above is the second step.

  FIG. 5 shows one characteristic of the gradation variable gain processing controlled by the variable gain obtained by detecting the histogram of the image in the first step and derived as a result. In FIG. 5, the characteristic of gain = 1 shown by the broken line A corresponds to signal through, and the solid line B shows the characteristic controlled so that the intermediate gray level sinks. In this case, the central part of the amplitude level becomes dark and sinks, and the APL of the first video feature detection unit 21 and the second video feature detection unit 24 that detects the histogram, APL, MIN, and MAX for the video signal. The difference fluctuates on the negative side.

  This circuit includes first and second video feature detection units 21 and 24 that detect the above-described video feature before and after the first grayscale variable gain processing unit 23, so that the first grayscale variable gain is obtained. Evaluation (comparison) of the processing result of the processing unit 23 becomes possible. The aforementioned APL variation is evaluated (compared) by the correction control processing unit 25 and corrected by the APL correction processing unit 26. The correction content can be optimized based on subjective evaluation by displaying an image on a display. For example, if correction is performed in a direction in which there is no APL fluctuation, an APL correction processing unit is set so that the difference in APL is set to “0”. 26 to correct. The characteristics of the correction contents are shown in FIG. The controlled signals C1 and C2 are parallel to the characteristic C0 of gain = 1. In addition, when swinging in one plus / minus direction, it is possible to determine the correction scale in consideration of the magnitude of the difference value of APL.

However, in such a conventional technique, the input signal is simply offset in the APL correction processing unit 26. As a result, the video signal sticks to the dynamic range, and the black and white of the signal component are crushed. There was a problem.
JP 2004-242235 A

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a video correction apparatus capable of effectively reproducing the black and white signal components. It is said.

  According to a first aspect of the present invention, there is provided a first video feature detection unit that detects a histogram, an average value (APL), a maximum value, and a minimum value, which are level distributions of luminance signals, as a feature amount of an input video signal. A gain control processing unit for generating data for correcting gradation characteristics of the input video signal based on the feature amount detected by the first video feature detection unit; and the gain control for the input video signal. A first gradation variable gain processing section that adjusts the gradation characteristics based on data for correcting the gradation characteristics generated by the processing section and outputs a first corrected video signal; and the first gradation variable gain processing. A second video feature detection unit that detects a histogram, an average value (APL), a maximum value, and a minimum value, which is a level distribution of the luminance signal, as a feature amount of the first corrected video signal output by the unit; , The first video feature detection unit A correction control processing unit that generates control data based on the feature amount of the input video signal detected by the second video feature detection unit and the feature amount of the first corrected video signal detected by the second video feature detection unit; The APL correction processing unit that performs APL correction processing on the corrected video signal of 1 with the control data output from the correction control processing unit, and the video signal that has been subjected to APL correction processing by the APL correction processing unit, A second gradation variable gain processing unit that corrects based on the control data generated by the correction control processing unit and outputs a final corrected video signal, and the APL correction processing unit includes the first correction An adder that generates correction data by adding the correction data obtained in the correction control processing unit to the already corrected video signal, and a preset value for the first corrected video signal. Is limited to a gain that does not cause whiteout by applying the gain when the level of the video signal exceeds a predetermined value, and the gain is applied to the first corrected video signal. When the level of the video signal falls below a predetermined value with respect to the constant gain preset for the side processing unit and the first corrected video signal, blackout is caused by applying the gain when the level falls below a predetermined value. The black side processing unit that raises the gain to the first corrected video signal, the correction data generated by the adder, and the minimum value of the signal generated by the white side processing unit are selected. And a selector that selects the correction data generated in the adder and the maximum value of the signal generated in the black side processing unit, and outputs the selected video signal as the APL corrected video signal. It is characterized by being.

  According to a second aspect of the present invention, in the video correction apparatus according to the first aspect, the APL correction processing unit refers to the histogram obtained by the first video feature detection unit, and there are many histogram distributions with a high input luminance signal level. The white side processing unit that arbitrarily controls the white side inclination and the histogram obtained by the first video feature detection unit are referred to, and the black side inclination is arbitrarily selected when there are many histogram distributions with low input luminance signal levels. And a black side control unit for controlling the control.

  According to the present invention, by appropriately variably setting the gain according to the input signal level of the video signal, it is possible to reduce the blackout and whiteout of the signal component, and the reproducibility of the black and white signal components is effective. Can be done automatically.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  (First Embodiment) FIG. 1 is a block diagram showing a configuration of an APL correction processing unit 26 in a video correction apparatus according to a first embodiment of the present invention. The configuration of the video correction apparatus itself according to the present embodiment is the same as that shown in FIG. 4 as in the conventional example. Among them, the APL correction processing unit 26 has the configuration shown in FIG.

  As shown in FIG. 1, the APL correction processing unit 26 in the video correction apparatus according to the present embodiment includes an adder 10, a white side processing unit 11, a black side processing unit 12, and a selector 13. The adder 10 adds the correction data Y_dat by adding the input luminance signal Yin (same as the first corrected luminance signal Yout1 in FIG. 4) and the correction data dc_in obtained in the correction control processing unit 25 in FIG. obtain. Due to the processing performed in the first gradation variable gain processing unit 23, the APL of the video signal may increase or decrease. In order to deal with this problem, fluctuations in the APL components obtained from the first and second video feature detection units 21 and 24 are analyzed, and correction is performed using correction data dc_in in the direction of suppression.

  The white side processing unit 11 and the black side processing unit 12 generate a signal having an arbitrary inclination with respect to the input luminance signal Yin. The signal obtained by the white side processing unit 11 is Y_siro, and the signal obtained by the black side processing unit 12 is Y_kuro. The selector 13 selects the correction data Y_dat of the input luminance signal, the signal Y_siro obtained by the white side processing unit 11, and the signal Y_kuro obtained by the black side processing unit 12, and outputs them as the luminance signal output Yout.

FIG. 2 is a diagram illustrating the input / output characteristics of the APL correction processing unit 26 in FIG. As shown in FIG. 2, the white side processing unit 11 sets a start point up_stp of the inclination with respect to the input signal level. From this point, an arbitrary straight line Y_siro is obtained with the slope gain as up_k. Similarly, the black side processing unit 12 sets an inclination start point dc_blev with respect to the input signal level. From this point, an arbitrary straight line Y_kuro is obtained by setting the slope gain to lo-k. The selector 13 selects the minimum value of the correction data Y_dat of the input luminance signal and the signal Y_siro obtained by the white side processing unit 11 (Equation 1),
Yout = min (Y_siro, Y_dat) (Equation 1)
The maximum value of the correction data Y_dat of the input luminance signal and the signal Y_kuro obtained by the black side processing unit 12 is selected (Expression 2).

Yout = max (Y_kuro, Y_dat) (Equation 2)
In this way, the luminance signal output Yout corrected by the APL correction processing unit 26 is obtained.

  Further, when the correction data Y_dat of the input luminance signal swings positive with respect to the input video signal Yin, only the processing by the white side processing unit 11 is performed, and when the correction data Y_dat swings negative, only the processing by the black side processing unit 12 is performed. It can also be used limited to.

  When the value of dc_in obtained by the correction processing control unit 25 is large and the value of the correction data Y_dat is negatively offset, the video is blacked out. At this time, blackening can be suppressed by performing the processing on the black side as shown in Formula 2. Further, when the value of the correction data Y_dat is offset to a plus value, the image is totally faded. At this time, the white side reproducibility can be improved by performing the white side processing as shown in Equation (1).

  As described above, according to the video correction apparatus of the present embodiment, the APL correction processing unit 26 performs the above-described correction control processing based on the detection values of the first and second video feature detection units 21 and 24. Thus, it is possible to improve the reduction in the contrast feeling of the image that can occur without losing gradation.

  (Second Embodiment) An image correction apparatus according to a second embodiment of the present invention will be described. The overall configuration of the second embodiment is the same as that of the conventional example shown in FIG. 4, and the internal configuration of the APL correction processing unit 26 is the same as that of the first embodiment shown in FIG. However, the APL correction processing unit 26 adaptively performs the same control as in the first embodiment based on the histogram detected by the first video feature detection unit 21.

  In the present embodiment, the APL correction processing unit 26 operates as follows. The first gradation variable gain processing unit 23 performs gradation variable gain processing based on the histogram detected by the first video feature detection unit 21 shown in FIG. With this process, the image may appear to float and appear to be white. Therefore, in the present embodiment, the detected histogram information is given to the APL correction processing unit 26, and when the histogram distribution with a high input luminance signal level is large, the white side processing unit 11 in FIG. 1 controls the white side inclination. And make a straight line that will lie down. By doing so, the reproducibility of the gradation on the white side can be improved. Similarly, when there are many histogram distributions with low input luminance signal levels, the black side processing unit 12 in FIG. 1 controls the black side inclination to create a straight line that lays down the inclination, thereby adjusting the black side gradation. Reproducibility can be improved and black float can be suppressed.

  As described above, according to the second embodiment, a video signal with a high contrast feeling can be obtained by controlling the tilt in conjunction with the characteristics of the video signal.

  (Third Embodiment) An image correction apparatus according to a third embodiment of the present invention will be described. The overall configuration of the third embodiment is the same as that of the conventional example shown in FIG. 4, and the internal configuration of the APL correction processing unit 26 is the same as that of the first embodiment shown in FIG. However, the APL correction processing unit 26 is characterized by adaptively performing the same control as in the first embodiment based on the MIN and MAX detected by the first video feature detection unit 21.

  In the present embodiment, the APL correction processing unit 26 operates as follows. The minimum value MIN and the maximum value MAX of the video luminance signal detected by the second video feature detection unit 24 shown in FIG. 4 are given to the APL correction processing unit 26, and the input luminance signal Yin (in FIG. 4) When the value of the correction data Y_dat for the first corrected luminance signal Yout1) is smaller than MAX, the white side processing unit sets the output value of the APL correction process to the maximum value of the dynamic range or a desired value. 11, a straight line Y_siro is generated. Further, when the value of the correction data Y_dat of the input luminance signal Y_in is larger than MIN, the black side processing unit 12 generates a straight line Y_kuro so that the output value of the APL correction processing becomes zero or a desired value.

  In the present embodiment, as described above, when the value of the correction data Y_dat for the input luminance signal Yin is smaller than MAX, the APL correction processing unit 26 sets the output value of APL correction processing to the maximum value of the dynamic range or the desired value. By generating a straight line Y_siro in the white side processing unit 11 so as to obtain a value to be obtained, the reproducibility of the white side gradation is enhanced. Further, when the correction data Y_dat is larger than MAX and a little more gradation is desired on the white side, the desired gradation can be obtained by performing the white side control. Similarly, when the value of the correction data Y_dat of the input luminance signal Y_in is larger than MIN, the black side processing unit 12 generates a straight line Y_kuro so that the output value of the APL correction process becomes zero or a desired value. Therefore, the reproducibility of the black side gradation can be improved. In addition, when the value of the correction data Y_dat is smaller than MIN and more gradation is desired on the black side, the desired gradation can be obtained by performing control on the black side.

  As described above, according to the present embodiment, a video signal with a high contrast feeling can be obtained by controlling the tilt in conjunction with the characteristics of the video signal.

The block diagram which shows the structure of the APL correction process part in the video correction apparatus of the 1st Embodiment of this invention. The graph which shows the characteristic of the APL correction process part in the said 1st Embodiment. The graph which shows the characteristic of the APL correction process part in the video correction apparatus of the 3rd Embodiment of this invention. The block diagram which shows the structure of a general video correction apparatus. The graph which shows the characteristic of the gradation variable gain process part in a common image correction apparatus. The graph which shows the characteristic of the conventional APL correction process part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Adder 11 White side process part 12 Black side process part 13 Selector 21 1st image | video feature detection part 22 Gain control process part 23 1st gradation variable gain process part 24 2nd image | video feature detection part 25 Correction control part 26 APL correction processing unit 27 Second gradation variable gain processing unit

Claims (2)

A first video feature detection unit that detects a histogram, which is a level distribution of a luminance signal, an average value (APL), a maximum value, and a minimum value, as a feature amount of an input video signal;
A gain control processing unit that generates data for correcting a gradation characteristic of the input video signal based on the feature amount detected by the first video feature detection unit;
A first gradation variable gain processing unit that adjusts the gradation characteristic based on data for correcting the gradation characteristic generated by the gain control processing unit and outputs a first corrected video signal for the input video signal When,
A histogram, average value (APL), maximum value, and minimum value, which are level distributions of luminance signals, are detected as feature amounts of the first corrected video signal output from the first gradation variable gain processing unit. A second video feature detection unit,
Control data is generated based on the feature amount of the input video signal detected by the first video feature detection unit and the feature amount of the first corrected video signal detected by the second video feature detection unit. A correction control processing unit;
An APL correction processing unit that performs an APL correction process on the first corrected video signal according to control data output from the correction control processing unit;
A second gradation variable gain processing unit that corrects an APL correction processed video signal by the APL correction processing unit based on control data generated by the correction control processing unit and outputs a final corrected video signal And
The APL correction processing unit
An adder that generates correction data by adding correction data obtained in the correction control processing unit to the first corrected video signal;
A constant gain preset for the first corrected video signal is limited to a gain that does not cause whiteout by applying the gain when the level of the video signal exceeds a predetermined value. A white-side processing unit that applies the gain to the first corrected video signal;
A certain gain preset for the first corrected video signal is raised to a gain that does not cause blackout by applying the gain when the level of the video signal falls below a predetermined value. A black side processing unit for applying the gain to the first corrected video signal;
Select the correction data generated in the adder and the minimum value of the signal generated in the white side processing unit, and select the correction data generated in the adder and the maximum value of the signal generated in the black side processing unit And a selector that outputs the video signal after the APL correction processing. The APL correction processing unit refers to the histogram obtained by the first video feature detection unit, and a white side processing unit that arbitrarily controls the white side inclination when there are many histogram distributions with high input luminance signal levels; And a black side control unit that refers to the histogram obtained by the first video feature detection unit and arbitrarily controls the black side inclination when there are many histogram distributions with low input luminance signal levels. Item 2. The image correction apparatus according to Item 1.

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