CN101778230B - Control method of liquid crystal display television automatic backlight adjusting speed - Google Patents

Abstract

The invention relates to the liquid crystal display television (LCD TV) terminal application technology, in particular to a control method of LCD TV automatic backlight adjusting speed. The technical problems to be solved by the invention are to provide a control method of LCD TV automatic backlight adjusting speed and solve the problem that when the traditional technology is used to perform LCD TV automatic backlight adjustment, the picture is easy to flicker. The key points of the technical scheme can be summarized as follows: the gray histograms of current frame and previous frame, and the average luminance value of current frame image are obtained; the difference degree between the two gray histograms is calculated; and the backlight adjusting speed is determined according to both average luminance value of current frame image and scene state of the stored previous frame image. The beneficial effects of the invention are as follows: the flickering phenomenon during LCD TV automatic backlight adjusting is reduced and the picture quality is better.

Description

The control method of liquid crystal display television automatic backlight adjusting speed

Technical field

The present invention relates to LCD TV terminal applies technology, relate to a kind of control method of liquid crystal display television automatic backlight adjusting speed specifically.

Background technology

Current most liquid crystal TV set all possesses scalable function backlight, both can improve contrast according to picture material to backlight the automatically adjusting of liquid crystal display screen, can arrive purpose of energy saving again, is therefore adopted widely.At present in the liquid crystal TV set automatic backlight adjustment mode, it mostly is the adjustment backlight that mean flow rate (APL) according to picture and relevant image parameter are carried out automatically, yet when the adjustment of automatic backlight, when dynamic image content changes, if it is improper to governing speed backlight and amplitude control, picture has the phenomenon of " flicker ", makes the user watch the program apparent time that discomfort is arranged.

Summary of the invention

Technical problem to be solved by this invention is: propose a kind of control method of liquid crystal display television automatic backlight adjusting speed, solve conventional art in the liquid crystal TV set automatic backlight is adjusted, picture is the problem of flicker easily.

The present invention solves the problems of the technologies described above the technical scheme that is adopted: the control method of liquid crystal display television automatic backlight adjusting speed may further comprise the steps:

A. obtain the grey level histogram of present frame grey level histogram and former frame image, and the average brightness value of current frame image;

B. calculate the diversity factor between above-mentioned two grey level histograms;

C judges the scene variable condition of current frame image, if current frame image is quick scene change, and execution in step d then; If current frame image is scene change, then execution in step e at a slow speed; If be little scene change, then execution in step f; And the scene variable condition of preserving nearest n two field picture; Wherein scene variable condition determination methods is as follows: when D＞T1, be quick scene change; When T2＜D≤T1, be scene change at a slow speed; When D≤T2, be little scene change; Wherein D is the diversity factor of present frame figure grey level histogram and former frame image grey level histogram, and T1, T2 are threshold value, 16≤n≤32 and be integer;

D. in the n-1 frame whether quick scene change is arranged before judging, if having, then the duty ratio PWM value with target is set at default value, and backlight adjusting speed is set at fast, execution in step g; If no, then the average brightness value according to present frame obtains target duty than the PWM value, and backlight adjusting speed is set at fast, execution in step g;

E. in the n-1 frame whether quick scene change is arranged before judging,, then backlight adjusting speed is set at fast if having, according to the average brightness value calculating target duty of present frame than PWM value, execution in step g; If no, then backlight adjusting speed is set at a slow speed, calculate target duty than PWM value, execution in step g according to the average brightness value of present frame;

F. backlight the regulating the speed of once setting before keeping and the desired value of duty ratio PWM finished;

G. according to backlight regulate the speed and target duty big or small than PWM value, set the step-length of the duty ratio PWM value of adjustment at every turn, the certain hour adjustment of every interval once, up to adjusting to target duty than the PWM value.

Further, in the described step g, the adjustment step-length is S, and computational methods are as follows:

S＝|PWM _cur-PWM _obj|/V _obj，

Wherein, S is for adjusting step-length, PWM _CurBe current dutyfactor value, PWM _ObjBe target duty ratio, V _ObjBacklight regulating the speed.

In the described step g, certain hour is 50 milliseconds at interval.

The invention has the beneficial effects as follows: reduce the scintillation in the liquid crystal TV set automatic backlight is adjusted, the figure image quality is better.

Description of drawings

Fig. 1 is an implementation method flow chart of the present invention.

Embodiment

The invention will be further described below in conjunction with accompanying drawing.

The present invention proposes a kind of control method of liquid crystal display television automatic backlight adjusting speed, solves conventional art in the liquid crystal TV set automatic backlight is adjusted, and picture is the problem of flicker easily, and as shown in Figure 1, its implementation is as follows:

1. obtain the grey level histogram of present frame grey level histogram and former frame image, and the average brightness value of current frame image;

2. calculate the diversity factor between above-mentioned two grey level histograms; Computational methods are as follows:

$D={\left(\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{|H_i\left(j\right)-H_{i+1}\left(j\right)|}^2\right)}^{\frac{1}{2}}$

Wherein D represents two two field picture diversity factoies, H _i(j) and H _I+1(j) be i, the value of the histogram of i+1 frame on gray scale j;

3. judge the scene variable condition of current frame image, if current frame image is quick scene change, then execution in step 4; If current frame image is scene change at a slow speed, then execution in step 5; If be little scene change, then execution in step 6; And the scene variable condition of preserving nearest n two field picture; Wherein scene variable condition determination methods is as follows: when D＞T1, be quick scene change; When T2＜D≤T1, be scene change at a slow speed; When D≤T2, be little scene change; Wherein D is the diversity factor of present frame figure grey level histogram and former frame image grey level histogram, and T1, T2 are threshold value, T1=100 for example, T2=20;

4. the scene state according to the previous frame image of the average brightness value of current frame image and preservation determines backlight adjusting speed jointly.In the n-1 frame whether quick scene change is arranged before judging, if have, think that so this section video belongs in the quick change procedure, PWM (duty ratio) value of obtaining target by the average brightness value of present frame has little significance, therefore controlling PWM value backlight should be set at default value, backlight adjusting speed is set at fast (referring to finish variation in the time of 16 two field pictures the control rate V=16 of i.e. adjustment backlight), execution in step 7; If no, then the average brightness value according to present frame obtains target P WM value, and backlight adjusting speed is set at fast, execution in step 7, and target P WM value calculating method is as follows: if APL＞M1, then desired value PWM gets PWM1; If M2＜APL≤M1, then desired value PWM gets PWM2; If APL＜M2 then desired value PWM gets PWM3; Here, APL is the average brightness value of current frame image, and M1, M2 are threshold value, and PWM1, PWM2, PWM3 are control PWM value backlight corresponding under the different frame mean picture brightness, PWM1=100% here, PWM2=80%, PWM3=60%;

5. in the n-1 frame whether quick scene change is arranged before judging,, then backlight adjusting speed is set at fast, according to the average brightness value calculating target P WM value of present frame, execution in step 7 if having; If no, then backlight adjusting speed is set at a slow speed (referring to finish variation the control rate V=64 of i.e. adjustment backlight), according to the average brightness value calculating target P WM value of present frame, execution in step 7 in the time of 64 two field pictures;

6. backlight the regulating the speed of once setting before keeping and the desired value of PWM;

7. regulate the speed and target P WM value size according to backlight, set the step-length of each PWM value of adjusting, the certain hour adjustment of every interval once, up to adjusting to target P WM value, such as: every the 50ms adjustment once, the adjustment step-length is S, and computational methods are as follows: S=|PWM _Cur-PWM _Obj|/V _Obj, wherein, S adjusts step-length, PWM _CurBe current dutyfactor value, PWM _ObjBe target duty ratio, V _ObjBacklight regulating the speed.

Claims (3)

1. the control method of liquid crystal display television automatic backlight adjusting speed is characterized in that: may further comprise the steps:

A. obtain the grey level histogram of present frame grey level histogram and former frame image, and the average brightness value of current frame image;

B. calculate the diversity factor between above-mentioned two grey level histograms;

C. judge the scene variable condition of current frame image, if current frame image is quick scene change, execution in step d then; If current frame image is scene change, then execution in step e at a slow speed; If be little scene change, then execution in step f; And the scene variable condition of preserving nearest n two field picture; Wherein scene variable condition determination methods is as follows: when D＞T1, be quick scene change; When T2＜D≤T1, be scene change at a slow speed; When D≤T2, be little scene change; Wherein D is the diversity factor of present frame figure grey level histogram and former frame image grey level histogram, and T1, T2 are threshold value, 16≤n≤32 and be integer;

D. in the n-1 frame whether quick scene change is arranged before judging, if having, then the duty ratio PWM value with target is set at default value, and backlight adjusting speed is set at fast, execution in step g; If no, then the average brightness value according to present frame obtains target duty than the PWM value, and backlight adjusting speed is set at fast, execution in step g;

E. in the n-1 frame whether quick scene change is arranged before judging,, then backlight adjusting speed is set at fast if having, according to the average brightness value calculating target duty of present frame than PWM value, execution in step g; If no, then backlight adjusting speed is set at a slow speed, calculate target duty than PWM value, execution in step g according to the average brightness value of present frame;

F. backlight the regulating the speed of once setting before keeping and the desired value of duty ratio PWM finished;

G. according to backlight regulate the speed and target duty big or small than PWM value, set the step-length of the duty ratio PWM value of adjustment at every turn, the certain hour adjustment of every interval once, up to adjusting to target duty than the PWM value.

2. the control method of liquid crystal display television automatic backlight adjusting speed as claimed in claim 1, it is characterized in that: in the described step g, the adjustment step-length is S, and computational methods are as follows:

S＝|PWM _cur-PWM _obj|/V _obj，

Wherein, S is for adjusting step-length, PWM _CurBe current dutyfactor value, PWM _ObjBe target duty ratio, V _ObjBacklight regulating the speed.

3. the control method of liquid crystal display television automatic backlight adjusting speed as claimed in claim 1 or 2 is characterized in that: in the described step g, certain hour is 50 milliseconds at interval.

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