CN105047140A - Self-adapting dynamic backlight control system and method based on image content - Google Patents

Abstract

The invention discloses a self-adapting dynamic backlight control system and method based on image content. According to image content, a plurality of backlight regions are control independently, therefore the effects are achieved that power consumption is lowered and frame contrast is raised. A video stream is divided into two paths: one path is used for calculating backlight brightness, and the other path carries out liquid crystal compensation. In the backlight brightness calculation path, a histogram statistic module carries out statistics of image brightness, weighted average of the maximum value and the average value of the corresponding regions is carried out and backlight brightness information of the current region is obtained. Through a set threshold determination condition, the brightness is adjusted, final brightness information is obtained, adjustment by an output control module is carried out, and output through a serial data flow is carried out. In addition, because an image content distortion phenomenon can happen after backlight modulation, compensation of the original video signal is carried out according to the obtained backlight brightness information in the liquid crystal compensation path, and screening display as a final video signal is carried out.

Description

A kind of adaptive dynamic backlight control system of image content-based and method

Technical field

The invention belongs to Digital Television and Digital Video Processing field, be specifically related to the adaptive dynamic backlight control system of a kind of image content-based and method.

Background technology

Conventional digital TV all adopts the area source of constant luminance, and power consumption is large, is energy ezpenditure the best part in digital television system, and the transmitance of liquid crystal cells is difficult to control is zero, namely there is light leakage phenomena, causes picture contrast to decline.The power consumption reducing backlight just reduces the power consumption of complete machine.This technology wherein comprises the driving circuit improving backlight, the luminescence efficiency improving LED, develops new LED kind and dynamic backlight etc.Dynamic backlight can make up the deficiency that area source causes just, be in these technology the most easily realize, the most obvious technology of effect.Especially direct-light type LED backlight system collocation dynamic backlight technology, significantly can reduce complete machine power consumption, raising display frame contrast, grey exponent number and reduce ghost etc.

In order to reduce the contrast of power consumption and raising liquid crystal display, create self-adaptation dynamic backlight technology.Dynamic backlight control technology comprises the light modulation of the zero dimension overall situation, the light modulation of one dimension subregion and two-dimentional local light modulation three kinds.The i.e. environmentally brightness regulation picture overall brightness of zero dimension overall situation light modulation, to reduction power consumption and improve viewing comfort level and have certain effect, but has little effect; Namely backlight block is divided into some pieces by level or vertical direction according to concrete scene and application by the light modulation of one dimension subregion, and zones of different independently can control backlight intensity, although it controls simple, application scenarios is extremely limited; The light modulation of two dimension local is owing to being divided into some arrays by backlight block, and control flexibly, application scenarios is extensive, strong adaptability, strengthens in static contrast have obvious advantage at reduction Overall Power Consumption.

The key problem of two dimension dynamic backlight regulable control how to determine according to each area image content the backlight illumination that each region is suitable.Modal for determining that back light source brightness method has mean value method, maximum value process and mean value and maximal value method of weighted mean at present.The determined backlight intensity of mean value method is partially dark, although effectively can reduce power consumption, picture contrast also declines to some extent simultaneously, and image fault is more serious.Although maximum value process can retain image detail largely, reducing, the effect in power consumption and minimizing light leak etc. is very little.Although mean value and the average weighted method of maximal value overcome the problem of mean value method and maximum value process individualism, do not do corresponding compensation for original video content, still do not solve the problem of picture material distortion.

Summary of the invention

The object of the invention is to overcome the problem existing for traditional monitor backlight mode, the adaptive dynamic backlight control system of a kind of image content-based and method are provided.

To achieve these goals, the present invention is achieved by the following technical solutions:

The adaptive dynamic backlight control system of a kind of image content-based, comprises the backlight computing module of the backlight brightness values for obtaining respective regions and the liquid crystal compensation module for compensating corresponding pixel brightness value; Wherein, backlight computing module comprises:

Statistics with histogram module is for the mean value of pixel that calculates each backlight block and cover and variance;

Average and value weighted mean module are for enriching according to image detail the brightness value that degree calculates current backlight block;

RAM module for reading and writing for control backlight illumination information stored in reading;

Serial data stream time-sequence control module is used for the transmission of backlight illumination information;

When vision signal inputs, video flowing is divided into two-way, one tunnel obtains the backlight brightness values of respective regions through backlight computing module, and exported by serial data stream time-sequence control module, another road, through liquid crystal compensation module, compensates and output display corresponding pixel brightness value according to backlight illumination information.

The invention also discloses the adaptive dynamic backlight control method of a kind of image content-based, comprise the following steps:

1) backlight illumination calculates:

The backlight illumination that the average brightness of the pixel SR01) covered according to the backlight block of input video is corresponding to variance yields precomputation, obtains the histogram results of area image;

SR02) after obtaining the histogram results of area image, the pixel number of statistics GTG between threshold value and maximal value;

SR03) statistics step SR02 obtained and the threshold value Y preset _gtcompare, the Rule of judgment that comparative result calculates as backlight;

SR04) backlight illumination that comparative result and step SR01 precomputation that step SR03 obtains obtain is carried out calculating obtain final backlight brightness values, and pass through the serial line interface output driving backlight array of decision programmable;

2) the original pixel brightness value that each backlight block covers is compensated:

SL01) judge according to liquid crystal compensation Rule of judgment whether carry out liquid crystal compensation; If carry out liquid crystal compensation, then perform step SL02; If do not carry out liquid crystal compensation, then video flowing directly exports;

SL02) compensate original image brightness, video flowing monochrome information is compensated, to offset the dimmed picture material distortion brought of backlight, then export the video flowing after compensating.

Further, step SR01) in, the concrete grammar of the corresponding backlight illumination of precomputation is as follows:

The backlight block of input video has been divided into M × N number of sub-block, and the pixel number that every individual sub-backlight block covers is P × Q; First vision signal carries out statistics with histogram to P × Q pixel after entry of backlight calculates passage, obtains mean value and the variance yields of current block;

Wherein following formula calculating is adopted in the calculating of variance:

$BMV=\underset{j=0}{\overset{M-1}{\Σ}}\underset{k=0}{\overset{N-1}{\Σ}}\left|F_{jk}-{\mathrm{Block}}_{meanlight}\right|$

Wherein, BMV is approximate mean square deviation; J is the line number of current backlight block place pixel; K is the columns of current backlight block place pixel; F _jkfor the brightness value of pixel; Block _meanlightfor the average brightness of current block pixel;

Variance representative image details enrich degree, the function that it is independent variable that backlight illumination is expressed as with mean value and variance:

$E_f=min\{1,\frac{{\mathrm{BMW}}_{current}}{{\mathrm{BMW}}_{\max }}\×\mathrm{\α}\}$

Block _light＝(1-E _f)×Block _meanlight+E _f×light _max

Wherein, E _fexpression formula in BMW _maxfor the maximal value of previous frame image all pieces of variances; α is predefined constant, regulates the degree of modulation of backlight; BMW _currentrepresent the approximate mean square deviation of present frame current block place pixel; Block _lightrepresent the brightness value that current block backlight is preliminary; Light _maxrepresent the maximal value of backlight Block Brightness.

Further, step SR04) in, the method obtaining final backlight brightness values is as follows:

The backlight illumination that the comparative result obtain step SR03 and step SR01 precomputation obtain calculates, if the pixel number Num of GTG between threshold value and maximal value _{(W (threshold value ~ maximal value))}be less than Y _gt, then current block backlight illumination is Block _light, otherwise be Light _max:

Wherein, light _lastrepresent the brightness value that current block is final, Y _gtrepresent the quantity of the pixel preset;

After obtaining backlight illumination information, by it stored in dual port RAM; When in RAM stored in brightness number reach predetermined value after, output control module sets high Serial_STT signal, and sends backlight illumination information by the serial line interface of decision programmable; After Serial_STT sets high, after 0.1 ~ 0.15us, Serial_CLK first rising edge arrives, and the rising edge of Serial_CLK starts to transmit data, ignores front 16bit data, and then the most significant digit of first backlight block arrives, and a secondary high position, exports successively; After DTD, Serial_STT sets low.

Further, the sequential of serial data stream receives sequential by screen and determines, and when hardware implementing, uses register each time interval of flexible configuration to make the interface sequence of its compatible different screen.

Further, step SL01) in, compensation judgment condition is:

A) whether this pixel grey decision-making exceedes the GTG threshold value that liquid crystal starts light leak;

B) whether the backlight brightness values at this pixel place is less than maximal value;

When two conditions meet simultaneously, liquid crystal compensation is carried out to this pixel, otherwise uncompensation.

Further, step SL02) in, video flowing monochrome information is compensated,

Wherein, Y represents the brightness value of the pixel after compensation; B _fullfor backlight complete bright time brightness value; B represents the brightness value of current block when carrying out dynamic backlight; λ is the gamma factor of display; Y _tfor the brightness value of target pixel points; T _valuefor constant, it is the judgment threshold whether liquid crystal compensation carries out; B in expression formula _fullfor constant 255; B ∈ (0,255) and be integer;

Look-up table is that address obtains (B with B _full/ B) ^{1/ λ}value, then through multiplication calculate with fixed point process can obtain monochrome information (B _full/ B) ^{1/ λ}× Y _tvalue.

Compared with prior art, the present invention has following beneficial outcomes:

1) the present invention obtains suitable backlight illumination by effectively utilizing mean picture brightness information and variance covariance information, and by corresponding liquid crystal compensation measure, solve the leakage problem of liquid crystal display in dark scape, improve the static contrast of picture, reduce the power consumption of complete machine, especially Be very effective in large-sized monitor simultaneously.

2) the present invention is by the pixel intensity mean value in the method zoning of statistics with histogram and variance, can realize instant computing and significantly reduce the consumption of hardware resource.

3) the present invention can pass through register configuration, quantity M × the N of backlight block in flexible adaptation panel, and pixel number P × Q that corresponding backlight block covers, and can register amendment serial line interface sequential, make the compatibility of the present invention to display stronger.

4) the present invention can control the brightness value of each sub-block backlight flexibly, therefore can realize backlight scanning easily, switches the crosstalk caused about effectively reducing active-shutter 3D rendering.

Accompanying drawing explanation

Fig. 1 is process flow diagram of the present invention;

Fig. 2 is the structured flowchart of backlight computing module;

Fig. 3 is the structured flowchart of liquid crystal compensation module;

Fig. 4 is the sequential chart of backlight brightness data stream.

Embodiment

Below in conjunction with accompanying drawing, the present invention will be further described in detail.

See Fig. 1 to Fig. 4, present system is divided into two large modules, and backlight illumination calculates and original image content compensates.Video flowing is divided into two-way after the system of entering: a road is for calculating backlight illumination; Liquid crystal compensation is carried out on another road.Backlight computing module obtains the backlight value of current block, is exported, and provide the Rule of judgment whether compensated to liquid crystal compensation module by the serial line interface of decision programmable; Export after the Rule of judgment that liquid crystal compensation module provides according to backlight computing module and the Rule of judgment self generated compensate pixel.

Realization flow of the present invention as shown in Figure 1, elaborates to each step in flow process below:

1, backlight brightness values is calculated.

1) step SR01: backlight illumination precomputation.The backlight illumination corresponding to variance yields precomputation according to the average brightness of the pixel of backlight block covering.System backlight module has been divided into M × N number of sub-block, and the pixel number that every individual sub-backlight block covers is P × Q.As shown in Fig. 2 statistics with histogram module, first vision signal carries out statistics with histogram to P × Q pixel after entry of backlight calculates passage, obtains mean value and the variance yields of current block.

Wherein the calculating of variance adopts one to be easy to hardware implementing approximate treatment, and the details that image has been reacted in this calculating to a great extent enriches degree, significantly reduces again the consumption of hardware resource simultaneously.

$BMV=\underset{j=0}{\overset{M-1}{\Σ}}\underset{k=0}{\overset{N-1}{\Σ}}\left|F_{jk}-{\mathrm{Block}}_{meanlight}\right|$

Variance representative image details enrich degree.Due in backlight modulation process, there is comparatively dark but picture detail degree is the very abundant again simultaneously scene of some overall picture, so the backlight of these scenes needs by taking variance as coefficient adjustment, as Fig. 2, the function that it is independent variable that backlight illumination can be expressed as with mean value and variance:

$E_f=min\{1,\frac{{\mathrm{BMW}}_{current}}{{\mathrm{BMW}}_{max}}\×\mathrm{\α}\}$

Block _light＝(1-E _f)×Block _meanlight+E _f×light _max

Above-mentioned E _fexpression formula in BMW _maxfor the maximal value of previous frame image all pieces of variances.Because the correlation degree of video flowing in a certain scene between each two field picture is very high, the maximal value of therefore using a two field picture variance can't affect the accuracy of obtained backlight illumination, can ensure that again monochrome information calculates acquisition in present frame, and export with present frame audio video synchronization.α is predefined constant, regulates the degree of modulation of backlight.

2) step SR02: after obtaining the histogram results of area image, the pixel number of statistics GTG between threshold value and maximal value.

3) step SR03: the statistics that step SR02 is obtained and the threshold value Y preset _gtcompare, the Rule of judgment that comparative result calculates as backlight;

4) step SR04: obtain final backlight illumination information, and export driving backlight array by the serial line interface of decision programmable.As shown in Fig. 2 backlight computing module, the comparative result that step SR03 obtains and the backlight illumination that obtains of step SR01 precomputation carry out calculating and obtain final backlight brightness values: if the pixel number Num of GTG between threshold value and maximal value _{(W (threshold value ~ maximal value))}be less than Y _gt, then current block backlight illumination is Block _light, otherwise be Light _max.

After obtaining backlight illumination information, by it stored in dual port RAM.When in RAM stored in brightness number reach predetermined value after, output control module sets high Serial_STT signal, and sends backlight illumination information by the serial line interface of decision programmable.Concrete sequential as shown in Figure 4, after Serial_STT sets high, after 0.1 ~ 0.15us, Serial_CLK first rising edge arrives, the rising edge of Serial_CLK starts to transmit data, ignore front 16bit data (adjustable), then the most significant digit of first backlight block arrives, a secondary high position ..., after DTD, Serial_STT sets low.This sequential needs to determine when being received by screen, and when hardware implementing, each time interval of register flexible configuration can be used to make the interface sequence of its compatible different screen.

2, the original pixel brightness value that each backlight block covers is compensated.

1) step SL01: generate liquid crystal compensation Rule of judgment.Whether carry out the generation of liquid crystal compensation Rule of judgment.As shown in Figure 3, whether liquid crystal compensation is carried out to some pixels and has established two Rule of judgment, a GTG threshold value being this pixel grey decision-making and whether exceeding that liquid crystal starts light leak, another is whether the backlight brightness values at this pixel place is less than maximal value, when two conditions meet simultaneously, liquid crystal compensation is carried out to this pixel, otherwise uncompensation.

2) step SL02: carry out liquid crystal compensation.Compensate original image brightness, to offset the dimmed picture material distortion brought of backlight.If step SL01 judged result is not for need to carry out liquid crystal compensation, then video flowing directly exports, and as needs carry out liquid crystal compensation, then compensates video flowing monochrome information.

Wherein B _fullfor backlight complete bright time brightness value, B represents the brightness value of current block when carrying out dynamic backlight, and λ is the gamma factor of display, Y _tfor the brightness value of target pixel points, T _valuefor constant, it is the judgment threshold whether liquid crystal compensation carries out; B in expression formula _fullfor constant 255,1/ λ is constant, B ∈ (0,255) and be integer, and therefore expression formula result is by programmable look-up tables'implementation.Look-up table is that address obtains (B with B _full/ B) ^{1/ λ}value, then through multiplication calculate with fixed point process can obtain monochrome information (B _full/ B) ^{1/ λ}× Y _tvalue.

The present invention also proposes a kind of device realizing said method: specifically comprise statistics with histogram module, mean value computation module, variance computing module, average be worth most weighted mean module, RAM module for reading and writing, serial data stream time-sequence control module, liquid crystal compensation module; When vision signal inputs, video flowing is divided into two-way, one tunnel obtains the backlight brightness values of respective regions through backlight computing module, and exported by serial data stream time-sequence control module, another road, through liquid crystal compensation module, compensates and output display corresponding pixel brightness value according to backlight illumination information.

Above content is only and technological thought of the present invention is described; protection scope of the present invention can not be limited with this; every technological thought proposed according to the present invention, any change that technical scheme basis is done, within the protection domain all falling into claims of the present invention.

Claims (7)

1. the adaptive dynamic backlight control system of image content-based, is characterized in that: comprise the backlight computing module of the backlight brightness values for obtaining respective regions and the liquid crystal compensation module for compensating corresponding pixel brightness value; Wherein, backlight computing module comprises:

Statistics with histogram module is for the mean value of pixel that calculates each backlight block and cover and variance;

Average and value weighted mean module are for enriching according to image detail the brightness value that degree calculates current backlight block;

RAM module for reading and writing for control backlight illumination information stored in reading;

Serial data stream time-sequence control module is used for the transmission of backlight illumination information;

When vision signal inputs, video flowing is divided into two-way, one tunnel obtains the backlight brightness values of respective regions through backlight computing module, and exported by serial data stream time-sequence control module, another road, through liquid crystal compensation module, compensates and output display corresponding pixel brightness value according to backlight illumination information.

2. adopt the adaptive dynamic backlight control method of the image content-based of system described in claim 1, it is characterized in that, comprise the following steps:

1) backlight illumination calculates:

The backlight illumination that the average brightness of the pixel SR01) covered according to the backlight block of input video is corresponding to variance yields precomputation, obtains the histogram results of area image;

SR02) after obtaining the histogram results of area image, the pixel number of statistics GTG between threshold value and maximal value;

SR03) statistics step SR02 obtained and the threshold value Y preset _gtcompare, the Rule of judgment that comparative result calculates as backlight;

SR04) backlight illumination that comparative result and step SR01 precomputation that step SR03 obtains obtain is carried out calculating obtain final backlight brightness values, and pass through the serial line interface output driving backlight array of decision programmable;

2) the original pixel brightness value that each backlight block covers is compensated:

SL01) judge according to liquid crystal compensation Rule of judgment whether carry out liquid crystal compensation; If carry out liquid crystal compensation, then perform step SL02; If do not carry out liquid crystal compensation, then video flowing directly exports;

SL02) compensate original image brightness, video flowing monochrome information is compensated, to offset the dimmed picture material distortion brought of backlight, then export the video flowing after compensating.

3. the adaptive dynamic backlight control method of image content-based according to claim 2, is characterized in that: described step SR01) in, the concrete grammar of the corresponding backlight illumination of precomputation is as follows:

The backlight block of input video has been divided into M × N number of sub-block, and the pixel number that every individual sub-backlight block covers is P × Q; First vision signal carries out statistics with histogram to P × Q pixel after entry of backlight calculates passage, obtains mean value and the variance yields of current block;

Wherein following formula calculating is adopted in the calculating of variance:

$BMV=\underset{j=0}{\overset{M-1}{\Σ}}\underset{k=0}{\overset{N-1}{\Σ}}\left|F_{jk}-{\mathrm{Block}}_{meanlight}\right|$

Wherein, BMV is approximate mean square deviation; J is the line number of current backlight block place pixel; K is the columns of current backlight block place pixel; F _jkfor the brightness value of pixel; Block _meanlightfor the average brightness of current block pixel;

Variance representative image details enrich degree, the function that it is independent variable that backlight illumination is expressed as with mean value and variance:

$E_f=min\{1,\frac{{\mathrm{BMW}}_{current}}{{\mathrm{BMW}}_{\max }}\×\mathrm{\α}\}$

Block _light＝(1-E _f)×Block _meanlight+E _f×light _max

Wherein, E _fexpression formula in BMW _maxfor the maximal value of previous frame image all pieces of variances; α is predefined constant, regulates the degree of modulation of backlight; BMW _currentrepresent the approximate mean square deviation of present frame current block place pixel; Block _lightrepresent the brightness value that current block backlight is preliminary; Light _maxrepresent the maximal value of backlight Block Brightness.

4. the adaptive dynamic backlight control method of image content-based according to claim 2, is characterized in that: described step SR04) in, the method obtaining final backlight brightness values is as follows:

The backlight illumination that the comparative result obtain step SR03 and step SR01 precomputation obtain calculates, if the pixel number Num of GTG between threshold value and maximal value _{(W (threshold value ~ maximal value))}be less than Y _gt, then current block backlight illumination is Block _light, otherwise be Light _max:

Wherein, light _lastrepresent the brightness value that current block is final, Y _gtrepresent the quantity of the pixel preset;

After obtaining backlight illumination information, by it stored in dual port RAM; When in RAM stored in brightness number reach predetermined value after, output control module sets high Serial_STT signal, and sends backlight illumination information by the serial line interface of decision programmable; After Serial_STT sets high, after 0.1 ~ 0.15us, Serial_CLK first rising edge arrives, and the rising edge of Serial_CLK starts to transmit data, ignores front 16bit data, and then the most significant digit of first backlight block arrives, and a secondary high position, exports successively; After DTD, Serial_STT sets low.

5. the adaptive dynamic backlight control method of image content-based according to claim 4, it is characterized in that: the sequential of serial data stream receives sequential by screen and determines, and when hardware implementing, use register each time interval of flexible configuration to make the interface sequence of its compatible different screen.

6. the adaptive dynamic backlight control method of image content-based according to claim 2, is characterized in that: described step SL01) in, compensation judgment condition is:

A) whether this pixel grey decision-making exceedes the GTG threshold value that liquid crystal starts light leak;

B) whether the backlight brightness values at this pixel place is less than maximal value;

When two conditions meet simultaneously, liquid crystal compensation is carried out to this pixel, otherwise uncompensation.

7. the adaptive dynamic backlight control method of the image content-based according to claim 2 or 6, is characterized in that: described step SL02) in, video flowing monochrome information is compensated,

Wherein, Y represents the brightness value of the pixel after compensation; B _fullfor backlight complete bright time brightness value; B represents the brightness value of current block when carrying out dynamic backlight; λ is the gamma factor of display; Y _tfor the brightness value of target pixel points; T _valuefor constant, it is the judgment threshold whether liquid crystal compensation carries out; B in expression formula _fullfor constant 255; B ∈ (0,255) and be integer;

Look-up table is that address obtains (B with B _full/ B) ^{1/ λ}value, then through multiplication calculate with fixed point process can obtain monochrome information (B _full/ B) ^{1/ λ}× Y _tvalue.