JP3201449B2 - Image display processing method and apparatus for electronic display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display processing technology for an electronic display (LCD (Liquid Crystal Display Panel), PDP (Plasma Display Panel), etc.) used for a television or the like. And a video display processing method for an electronic display.

[0002]

2. Description of the Related Art When an image based on an input image signal is displayed on an electronic display, for example, a liquid crystal display panel (hereinafter, referred to as LCD) or a plasma display panel (hereinafter, referred to as PDP), the characteristics (gamma characteristics, etc.) of the electronic display are adjusted. And performs predetermined signal processing on the input video signal.

[0003] In this signal processing, for example, input / output characteristic conversion processing for gamma correction is performed on a video signal of a television or the like (RGB digital video signal,
An appropriate image based on the image signal can be displayed on an electronic display.

[0004]

By the way, the above-mentioned electronic displays, especially LCDs and PDPs, generally have a lack of contrast and brightness of the displayed images as compared with other electronic displays, so that good images can be obtained. It is difficult at present.

[0005] Further, in the above-mentioned electronic display, power consumption is kept constant in consideration of life and the like.
For example, when the display image is not entirely bright, that is, when the entire screen is dark, the luminance of the peak of the display image also decreases, and the image quality of the display image decreases, and, for example, a blackout state occurs.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to suppress black and white loss of a displayed image, improve the contrast of a screen, and obtain a high quality image. It is an object of the present invention to provide a video display processing method and apparatus for an electronic display as described above.

[0007]

In order to achieve the above object, the present invention provides a method for converting an input video signal into an input / output characteristic according to the characteristics of an electronic display. creating a histogram by counting the number of pixels each, to obtain a mean value and the variance of the histogram, y = 1/2 · by the average value
((X / c) to the power of γ) (y: output level, x: input level
, C: median, γ: gamma)
In both cases, the above-mentioned y = 1/2 · ((x / c)
Of the input / output characteristic conversion.
For the input video signal
Is input / output characteristic converted .

According to the present invention, first, the number of pixels is counted by the counter for each of the same signal levels of the input video signal based on the luminance signal of the input video signal, and preferably, for each field (or one frame). A histogram of the input video signals (same signal level) is created by summing.

Then, the average value and the variance of the histogram are calculated by the input / output characteristic calculation means,
According to the average value and the variance, y = １ ／ · ((x / c)
Γ power) (y: output level, x: input level, c: median, γ: gamma value), and determine and input / output the median value (the value of x where y =＝) and the gamma value Characteristic data is calculated. The input / output characteristic data is subjected to input / output characteristic conversion (including gamma correction) so that the input video signal can be input to the electronic display.

[0010] For example, the average value is rather small, when it displays the image in a small PDP of da Inami'<br/> Kurenji,
When thus Tsu names in underexposure screen, calculated by the input-output characteristic data for input and output characteristics converting an input video signal is y = 1/2 · has a small median ((x / c) of the γ-th power) As a result, a bright screen is obtained as a whole, and blackout is suppressed.

Also, when the average value is large, that is, when the screen is overexposed, the central value y = y
Since the input / output characteristic data is calculated by ・ · ((x / c) to the power of γ), the loss of black on the screen and the loss of white are suppressed.

Further, when the variance is small, that is, when the contrast of the image is small due to the concentration of the brightness being concentrated at a certain level, the gamma value is increased y = 1/2.
Since the input / output characteristic data is calculated by ((x / c) to the power of γ), an image with good contrast can be obtained.

Further, when the variance is large, the input / output characteristic data is calculated by y = 1/2 · ((x / c) raised to the γ power) where the gamma value is reduced. No video is obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image display processing method and apparatus for an electronic display according to the present invention is characterized in that an average value (APL) of a histogram obtained by counting the number of pixels for each of the same signal levels of an input video signal (RGB digital video signal). It is possible to judge the brightness of the screen from the video level) and its variance (or standard deviation). In other words, paying attention to the fact that the brightness of the screen is reflected in the average value and the variance, When converting the input video signal into an input / output characteristic in order to display the
L and variance (corresponding to the spatial distribution and temporal change of level and hue from the same video signal) and converting the video signal output to the electronic display based on the calculated APL and variance into input / output characteristics Is determined for each field (or one frame).

Therefore, as shown in FIG. 1, the video display processing device of this electronic display uses an input video signal (RG
B digital video signal) by one field, and a RAM for performing input / output characteristic conversion processing (gamma correction or the like) on the delayed video signal.
An input / output characteristic conversion circuit 2 comprising 2a, 2b, 2c, and a luminance signal detection circuit 3 for detecting a luminance signal of an input video signal
And a histogram calculation circuit 4 that counts the number of pixels for each video signal level based on the detected luminance signal and calculates a histogram for each field, and an average value of the calculated histogram, that is, APL (average video level).
And the variance (or standard deviation)
And an input / output characteristic calculation circuit 5 for calculating input / output characteristic data (data for converting a video signal into input / output characteristics) of the input / output characteristic conversion circuit 2 based on the dispersion.

Next, the operation of the video display processing apparatus for an electronic display having the above-mentioned structure will be described in detail with reference to the characteristic diagrams of FIGS.
RGB digital video signal (8
It is assumed that an image based on a bit to 10-bit RGB image signal) is displayed on an electronic display (LCD, PDP, or the like).

At this time, the one-field delay unit 1
A GB digital video signal (hereinafter referred to as an input video signal) is delayed by one field and output to the input / output characteristic conversion circuit 2. On the other hand, the luminance signal detection circuit 3 outputs 6 to 8 bits of data (upper 6 to 8 bits data) of the input video signal.
To detect the luminance signal of the input video signal. The histogram calculation circuit 4 is a counter, and counts the number of pixels for each of the same signal levels of the input video signal based on the detected luminance signal (8-bit data), and sums up each field to create a histogram.

When the input video signal is an NTSC signal, the luminance signal Y detected by the luminance signal detecting circuit 3 is usually Y = 0.30R + 0.59G + 0.11B.
In the present invention, the luminance signal is Ya = R
+ G + B is also possible. That is, the histogram calculation circuit 4 simply counts the number of pixels for each same signal level and creates a histogram of the input video signal.

When the output signal, that is, the signal to be output after converting the input / output characteristics has an 8-bit configuration, it is apparently sufficient that the signal level for generating the histogram is 6 bits to 8 bits.

Further, a pixel block for obtaining the frequency (output level) of the histogram is used when an image based on an NTSC signal is displayed in a general 480 × 680 pixel.
Even if the APL and the variance are calculated with one 2 × 32 pixel block, that is, one pixel of the pixel block as a representative, the histogram obtained by counting the number of pixels for each signal level as described above and the histogram does not change.
Therefore, 1/16 × 1/16 to 1/32 × 1 /
The histogram may be calculated by taking one pixel from 32 pixels.

The input / output characteristic calculation circuit 5 calculates the variance and the A based on the histogram calculated for each field.
In addition to calculating the PL, the γ value (0.1 to 6.0) of the input / output characteristic is determined according to the variance, and the input value at which the output level of the device becomes 1/2 of the maximum according to the APL. (Median value c shown in FIGS. 2 to 5). Further, based on the determined γ value and median value c, data for input / output characteristic conversion is calculated by the following equation 1 and written into each of the RAMs 2a, 2b, 2c of the input / output conversion circuit 2. .

[0022]

(Equation 1) In the above equation 1, y is the output level of the input / output characteristic conversion,
x is the input level of the input / output characteristic conversion, and c is the median value (y = 1
/ 2), and γ means a γ (gamma) value.
In this case, the input / output characteristic calculation circuit 5 temporarily stores the calculated histogram in the internal RAM,
The AM data is taken into the arithmetic processing unit (MPU), and the values of the input / output characteristics (γ value and input value) are calculated according to the above-mentioned constant equation (1).

It should be noted that it is not possible to determine the value of a portion where the display image is bright (the high-level portion of the input / output characteristics) by the formula shown in the above equation (1). That is, when x = 1, y ≠ 1.

Therefore, in a place where the displayed image is bright, an ellipse which smoothly connects to Equation 1 and smoothly satisfies x = 1 and y = 1, for example, an ellipse shown in Equation 2 below is used. However, the maximum value of x and y is set to 1 (the same applies hereinafter).

[0025]

(Equation 2) In Equation 2, xω and yω denote the center of the ellipse, and a and b denote the diameters in the respective axial directions. Explaining Equation 2, xω and yω are generally selected to be 1 or more.
If = 1, dx / dy = 0 at x = 1, and the input level is smooth near the maximum, and the brightness of the image is saturated.
In this case, xω = 1−x and yω = 1−y−b.

Then, the point connecting Equation 1 and Equation 2 is represented by (x
k, yk), and at this (xk, yk) point, β is an equal value of the gradients dy / dx, dyω / dxω of Equations 1 and 2, and the square of b and a and y are
The shape is as shown in 4,5.

[0027]

(Equation 3)

[0028]

(Equation 4)

[0029]

(Equation 5) The input / output characteristics at and above the point (xk, yk) can be obtained from the equations obtained by substituting the above equations 3 and 4 into the equation 5. Note that the value of the point (xk, yk) may be as large as possible, without saturation of the image in a bright place of the display image, that is, without loss of white.

Therefore, the larger the value of c and the smaller γ, the larger the value of the point (xk, yk), and conversely, the smaller the value of c and the larger γ, the smaller the value of the point (xk, yk). Good. As an example, the equation of y = −Ax + B and Equation 1
Assuming that the intersection with the formula is obtained, A is a value close to 0,
B is preferably about 0.5 to 0.8, so that y = 0.5
At about 0.8, the ellipse is smoothly connected to Equation 1. Note that y may be a fixed value of 0.6 to 0.7.

More specifically, as shown by a broken line in FIG. 2, when the APL is small, that is, when a dark screen is displayed, for example, when a dark image is displayed on a PDP having a small dynamic range, a black portion of the image is displayed. Will be a crushed screen. Therefore, the input / output characteristic calculation circuit 5 reduces the median c of Equation 1 based on the APL of the histogram and calculates the data of the input / output characteristics in the form shown by the solid line in FIG. The calculated data is stored in the RAMs 2a and 2a of the input / output characteristic conversion circuit 2.
b, 2c, and the data of the input / output characteristics is calculated for each field and written to the RAMs 2a, 2b, 2c.

On the other hand, since the input video signal delayed for each field is input to the input / output characteristic conversion circuit 2, the input video signal is converted for each field into the calculated input / output characteristic data (FIG. 2 (indicated by a solid line) to convert input / output characteristics (including gamma correction).

When the input / output characteristic-converted video signal (gamma-corrected 8-bit RGB digital video signal) is input to an electronic display, for example, a PDP, the entire display video becomes brighter and the black portion of the video becomes black. It is possible to reduce crushing, to obtain good image quality, and to improve image contrast.

As shown by the broken line in FIG. 3, when the APL is large, that is, when a bright screen is displayed, for example, when a bright image is displayed as it is on a PDP having a small dynamic range, the image becomes a screen in which the white portion of the image is crushed. Therefore,
The input / output characteristic calculation circuit 5 increases the median c of Equation 1 based on the APL of the histogram and calculates the data of the input / output characteristics in the form shown by the solid line in FIG. Hereinafter, by the same processing as described above, the input video signal is subjected to input / output characteristic conversion (including gamma correction) for each field using the calculated input / output characteristic data (shown by the solid line in FIG. 3).

When the input / output characteristic-converted video signal (gamma-corrected 8-bit RGB digital video signal) is input to an electronic display, for example, a PDP, the brightness of the entire display video is suppressed and the white color is reduced. Good image quality without crushing can be obtained, and the image contrast can be improved.

Further, as shown by the broken line in FIG. 4, when the histogram variance is small, that is, when the brightness is concentrated at a certain level, for example, when a bright image is displayed as it is on a PDP with a small dynamic range, The screen has low contrast. Therefore, the input / output characteristic calculation circuit 5 calculates the input / output characteristic data in which the γ value of Equation 1 is increased based on the variance of the histogram in the form shown by the solid line in FIG. This data is stored in the RAM of the input / output characteristic conversion circuit 2.
2a, 2b, 2c, and the input / output characteristic calculation circuit 5 calculates data of the input / output characteristics for each field and writes the data to the RAMs 2a, 2b, 2c.

In the following, the input video signal is converted (including gamma correction) by the same processing as described above using the calculated input / output characteristic data (shown by the solid line in FIG. 3) for each field.

As shown by the dashed line in FIG. 5, when the histogram variance is large, that is, when the brightness is spread over a wide range of levels, for example, when a bright picture is displayed as it is on a PDP with a small dynamic range, black and black are displayed. The screen is such that the white part is crushed. Therefore, the input / output characteristic calculation circuit 5 reduces the γ value of Equation 1 based on the variance of the histogram and calculates the data of the input / output characteristics in the form shown by the solid line in FIG.

Thereafter, by the same processing as described above, the input video signal is subjected to input / output characteristic conversion (including gamma correction) for each field using the calculated input / output characteristic data (shown by the solid line in FIG. 3).

When an input video signal (gamma-corrected 8-bit RGB digital video signal) whose input / output characteristics have been converted as described above is input to an electronic display, for example, a PDP, the black and white portions of the displayed video are less likely to be lost. As a result, good image quality can be obtained, and the contrast can be improved.

In addition, since the display image is naturally expanded in white and black by varying the γ value, the image quality is further improved.

Actually, data of the input / output characteristics obtained by combining FIGS. 2 to 5 is calculated, and the input video signal is converted into the input / output characteristics by the data of the input / output characteristics.

As described above, a histogram of the input video signal (RGB digital video signal) is created for each field from the luminance signal of the input video signal (RGB digital video signal).
The PL (average video level) and the variance are calculated, and based on the APL and the variance, the c (median value) of Equation 1 is varied, or the γ value is varied to calculate the input / output characteristic data.

For example, in the case of a dark screen, c
By reducing the (median value) and suppressing blackout, a good image can be obtained, the contrast of the image can be improved, and a high image quality can be obtained.

Also, when the screen is bright, the APL is increased to suppress underexposure, so that a good image can be obtained and the contrast of the image can be improved.

Further, when the contrast of the screen is reduced by concentrating the brightness at a predetermined level, a good image can be obtained by increasing the γ value and increasing the contrast of the screen.

Further, when the lightness and darkness are not concentrated at a certain level and are dispersed, a good image can be obtained by reducing the γ value and reducing the underexposure and underexposure. .

In the above embodiment, one of the input video signals
Input / output characteristic data of the input / output characteristic conversion circuit 2 is calculated for each field, and input / output characteristic conversion (including gamma correction) of the input video signal is performed for each field. Data of input / output characteristics may be obtained. In this case, if each circuit is configured to be able to process each frame, the same operation and effect as those of the above embodiment can be obtained.

[0049]

As described above, the present invention relates to a video display processing method and apparatus for an electronic display which converts an input video signal into input / output characteristics in accordance with the characteristics of the electronic display to display a video. Input video signal (RG
A histogram is created by counting the number of pixels for each signal level based on the luminance signal of the B digital video signal), and an average value (APL; average video level) and variance (or standard deviation) of the histogram are calculated. the input-output characteristics of a video signal to be output to the display for each field (or one frame), AP, thus calculated,
Based on the L and distributed, by which is adapted determine the input-output characteristic data for the input-output characteristic conversion, for example it is an electronic di play small PDP such dynamic range, underexposure of the displayed image, white Reduce crushing,
In addition , the contrast of the displayed image can be improved,
As a result, a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic partial block diagram of a video display processing device of an electronic display showing one embodiment of the present invention.

FIG. 2 is a schematic input / output characteristic diagram for explaining the operation of the video display processing device shown in FIG.

FIG. 3 is a schematic input / output characteristic diagram for explaining the operation of the video display processing device shown in FIG. 1;

FIG. 4 is a schematic input / output characteristic diagram for explaining the operation of the video display processing device shown in FIG. 1;

FIG. 5 is a schematic input / output characteristic diagram for explaining the operation of the video display processing device shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1 field delay part 2 I / O characteristic conversion circuit 2a, 2b, 2c RAM 3 Luminance signal detection circuit 4 Histogram calculation circuit 5 I / O characteristic calculation circuit

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G09G 5/10 G09G 3/20 H04N 3/00-13/00

Claims (4)

(57) [Claims] When an input video signal is subjected to input / output characteristic conversion in accordance with characteristics of an electronic display, a histogram is created by counting the number of pixels for each signal level based on the luminance signal of the input video signal. And the variance of y = １ ／ · ((x / c) to the γ power) (y: output level, x: input level, c: median, γ: gamma value) The median is determined, and the variance is used to make y = 1 /
2. A gamma value of ((x / c) to the power of γ) is determined to obtain data for the input / output characteristic conversion, and the input video signal is input / output characteristic converted based on the data. Image display processing method for an electronic display. 2. When an input video signal is converted into input / output characteristics in accordance with the characteristics of an electronic display, a histogram is created by counting the number of pixels for each signal level based on the luminance signal of the input video signal. And the variance of y = 1/2 · ((x / c) to the γ power) (y: output level, x: input level, c: median, γ: gamma value) The median is determined, and the variance is used to make y = 1 /
A gamma value of 2. ((X / c) to the power of γ) is determined to obtain data for the input / output characteristic conversion, and in a high-level portion of the input video signal, the y = １ ／.・
The data for the input / output characteristic conversion is obtained by using an elliptic equation that is smoothly connected to ((x / c) to the γ-th power), and the input video signal is input / output characteristic converted by each of these data. An image display processing method for an electronic display, comprising: 3. A video display processing method for an electronic display for converting an input video signal into input / output characteristics in accordance with characteristics of the electronic display, wherein the input video signal is delayed by one field or one frame while the input video signal is delayed. , And a histogram formed by counting the number of pixels for each signal level based on the luminance signal is created for each of the fields or frames, and the average value and variance of the histogram are calculated. The data for the input / output characteristic conversion is determined according to the average value and the variance, and the one field or one data is determined using the determined data.
A video display processing method for an electronic display, wherein input / output characteristics of a video signal delayed by a frame are converted. 4. An image display processing apparatus for an electronic display for converting an input image signal into an input / output characteristic in accordance with characteristics of the electronic display, the delay means for delaying the input image signal by one field or one frame; A luminance signal detecting means for detecting a luminance signal of a video signal; and a histogram calculating means for calculating, for each field or frame, a histogram obtained by counting the number of pixels for each signal level of the video signal based on the luminance signal. And an input / output characteristic calculating means for calculating an average value and a variance of the histogram, calculating data for the input / output characteristic conversion in accordance with the average value and the variance, and data of the calculated input / output characteristics. The input / output characteristic conversion of the video signal delayed by the delay means according to the characteristics of the electronic display. Image display processing apparatus of the electronic display, characterized in that it comprises input and output characteristics converting unit that.