CN100479494C - Adjusting method for the image quality - Google Patents

Abstract

The present invention is an adjustment method for image quality, which detects and calculates the accumulated brightness values of all effective pixels on the functional hardware platform for detecting the overall brightness of the image, and calculates the overall brightness of the image signal according to the accumulated brightness values , determine the target brightness value to be adjusted, and then adjust the brightness value, and at the same time compensate the contrast of the picture. The method can adjust the brightness in real time according to the dynamic change of the brightness of the display screen, and at the same time adjust the contrast of the screen accordingly, so as to enrich the gray level and color level performance, so that the display screen has a clear contrast between light and dark.

Description

A method for adjusting image quality

technical field

The invention relates to an image picture quality adjustment technology of a video device, in particular to a dynamic real-time tracking adjustment technology for realizing the image brightness and contrast of a TV dynamic picture.

Background technique

With the rapid development of TV technology, various technologies for image quality processing are also emerging, such as conventional black level extension, blue level extension, SVM processing, and for TVs that use digital processing chips, there are more image noise processing technologies. Noise reduction processing, skin tone correction for color improvement, and more. These processing methods have played a great role in improving and enhancing the picture quality, providing users with better picture effects. However, there are still some unsatisfactory aspects when using the above-mentioned image quality processing method to adjust the picture. For example, for those pictures that are generally bright or white and have unclear layers, the existing technology only adjusts the brightness and then appears. The phenomenon that the overall picture level is not clear, that is, the gray level performance and color level performance of the image are not ideal. In addition, once this is set, all displayed images will be processed in the same way. It is not once and for all.

In order to solve the above problems, the patent document published on November 9, 2005, with the application number CN200510020238.1 and titled "Method for Improving the Dynamic Depth of Field of Television Images", discloses a method of dynamic adjustment, so that the TV picture always has a good depth of field performance. However, the implementation process of this method needs to "statistically calculate the brightness information of each pixel in the input picture within a certain range, and the brightness information includes the number of pixels and the average brightness of each brightness signal value", which requires supported hardware It has relatively powerful functions, and the amount of statistical information is huge. To realize the statistics of the number of pixels of each luminance signal value for TV, it is necessary to add a special-purpose computing chip (such as some special-purpose picture quality enhancement chip), which will increase the cost of TV relatively greatly. In addition, to add its function to the existing model, the hardware circuit needs to be changed again, the cycle is longer, and the increase of additional cost is brought at the same time. To sum up, this is a function realized by adding a dedicated additional processing chip. The implementation is a hardware way. It has brought about a significant increase in cost, and it is also difficult to popularize on existing models. .

Contents of the invention

The purpose of the present invention is to provide a TV image quality adjustment method based on the existing hardware platform through software, aiming at the overall brighter and very bright picture, by dynamically reducing the brightness setting value to different degrees, and correspondingly adjusting the contrast ratio. Compensation and extension, so that the picture quality has a good expressiveness at any time.

Another object of the present invention is to provide a method for adjusting the picture quality of a TV, by dynamically reducing the overall brighter picture accordingly, and at the same time compensating and extending the contrast, but not adjusting the darker picture, so that the difference The adjustment method is more scientific and reasonable, and it is convenient to realize and low in cost.

Another object of the present invention is to provide a method for adjusting the picture quality of a TV, which can realize dynamic improvement by gradually improving the brightness and contrast of the picture, thereby avoiding the visual impact on the audience caused by the sudden change of the picture quality. Impact can also enable users to form a good visual effect during use, and can choose the most suitable adjustment effect for them.

The basic idea of the present invention is: for an overall bright or white picture, appropriately reduce the brightness of the image to different degrees and correspondingly increase the contrast, so as to obtain a picture effect with clear layers and clear contrast between light and dark. The above-mentioned appropriate reduction of brightness for this kind of picture is only equivalent to subtracting the DC component in the brightness, so the details of the darker part will basically not be lost, even if there is some loss, because the human eye is mainly focused on the brighter part , also has little effect. In addition, for an overall dark picture, the brightness of the image cannot be reduced at all, otherwise a lot of details in the dark part will be lost.

In order to achieve the above object, the method of the present invention is based on the existing functional hardware platform with the overall brightness of the detection image, and its implementation steps are:

(1) Calculate the overall brightness value Yi of the image signal;

(2) Determine the target brightness value Bi to be adjusted according to the above-mentioned overall brightness value Yi;

(3) Adjust the brightness value and compensate the contrast of the picture at the same time.

(4) Return to step (1) cycle, so as to realize real-time dynamic adjustment frame by frame.

In step (2), if the overall brightness value Yi<=starting value Y_start, the brightness of the image will not be adjusted, and the starting value Y_start can be determined by the engineer according to the actual situation.

In step (3), the adjustment of the brightness is adjusted in the way of step-by-step traction tracking, and only one step is adjusted in one cycle.

The contrast compensation is carried out by calculating the formula C=C0+C_compensate*Ba, where C0: the contrast value before dynamic adjustment; C_compensate: the contrast compensation factor constant, Ba: the actual adjusted brightness.

In practice, the more specific implementation steps are as follows:

(1) Initialization: S=0, Ba=0, wherein S: a memory variable related to the adjustment speed; Ba: the actual reduction of the brightness value of the image state;

(2) Calculate Yi: the overall brightness of the image signal output by the front-end Video Decoder or ADC module, calculated by the formula Yi=Yd/d;

Yd: It is the accumulated value of the luminance values of all effective pixels of the input image signal (that is, from the Video Decoder or ADC module) by the Scaler module. The accumulated value is 32 bits in total, and the upper 8 bits are actually assigned to Yd.

d: Resolution conversion factor. For standard definition signal d=1; for high definition signal d=total pixels of high definition format/720*480, such as 720P signal, d=1280*720/720*480=2.67

(3) Calculate Bi: the target value of brightness reduction;

① If Yi<=Y_start, then Bi=0; wherein, Y_start is the starting brightness constant.

Setting the starting brightness mainly considers that for the darker picture when Yi<=Y_start, the system will not adjust the brightness value of the image state, so that the dark level can be guaranteed to be normal.

② If Yi>Y_start, then Bi=A_strong*(Yi-Y_start); wherein, A_strong is the adjustment strength constant.

③ If Bi>Bmax, then Bi=Bmax, Bmax: adjust upper limit constant.

(4) Change the applied value of brightness adjustment to make it close to Bi by 1 step.

(5) Return to the cycle of step (2), so as to realize the real-time dynamic adjustment of the cycle.

In practical application, it can be adjusted step by step to achieve effective contrast of image brightness and the best visual effect.

By adopting the image quality adjustment method of the present invention, the brightness can be adjusted in real time according to the dynamic change of the brightness of the display screen, and at the same time, the contrast of the screen can also be adjusted accordingly, thereby enriching the expression of gray levels and color levels, so that the display screen has light and dark contrast clear effect. This method can be completely realized by using software on the basis of the existing TV hardware, and will not bring about an increase in cost. This function can be realized by upgrading the software on the existing TV models, which is simple and easy.

Description of drawings

Fig. 1 is a system architecture diagram implemented by the present invention,

Fig. 2 is a control flow diagram of the implementation of the present invention.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in further detail:

As shown in Figure 1, the system architecture supporting the image quality adjustment method of the present invention includes the following functional modules: VideoDecoder module or ADC module, Deinterlace & Scaler module, brightness/contrast control module and display. CVBS, Y, Yb, Yr image signals are decoded and the digital video signals generated are transmitted to the Deinterlace & Scaler module for progressive and scaling processing. At the same time, the Deinterlace & Scaler module will also perform brightness detection and calculation on the above-mentioned digital video signals. Realize dynamic adjustment processing, and then the brightness/contrast control module dynamically adjusts the brightness and contrast according to the detection and calculation results, and finally outputs to the display for final display.

The above is one of the dynamic image processing methods. In the other dynamic processing method, the brightness detection and calculation links are realized in the front-end Video Decoder or ADC module. When this method is adopted, the system needs to compensate the dynamic adjustment amount accordingly. For details, please refer to the description of the second embodiment below.

The method for adjusting the television image quality of the present invention will be further described by enumerating two specific implementations below.

Specific embodiment one: for the system architecture shown in Figure 1, the steps of the TV image quality adjustment of the present invention are as follows:

(1) Initialization: S=0, Ba=0, wherein, S: a memory variable related to the adjustment speed; Ba: the actual reduction of the brightness value of the image state.

(2) Calculate Yi: the overall brightness of the image signal output by the front-end Video Decoder or ADC module, calculated by the formula Yi=Yd/d.

Yd: is the accumulated value of the luminance values of all effective pixels of the input image signal (that is, from the Video Decoder or ADC module) by the Scaler module. The accumulated value has a total of 32 bits, and the upper 8 bits are actually assigned to Yd.

d: Resolution conversion factor. For standard definition signal d=1; for high definition signal d=total pixels of high definition format/720*480, such as 720P signal, d=1280*720/720*480=2.67

(3) Calculation of Bi: target value of luminance reduction amount.

① If Yi<=Y_start, then Bi=0; wherein, Y_start is the starting brightness constant.

Setting the starting brightness mainly considers that for the darker picture when Yi<=Y_start, the system will not adjust the brightness value of the image state, so that the dark level can be guaranteed to be normal.

② If Yi>Y_start, then Bi=A_strong*(Yi-Y_start); wherein, A_strong is the adjustment strength constant.

According to the calculation formula, it is shown that the brighter the picture, the greater the adjustment amount of the brightness value of the image state.

③ If Bi>Bmax, then Bi=Bmax, Bmax: adjust upper limit constant.

In practical application, it can be divided into multi-stage processing according to actual needs.

(4) Change the applied value of brightness adjustment to make it close to Bi until it is equal.

S=S+1,

ifS<A_speed directly return to step (2)

ifS=A_speed,

then: S=0,

if Ba<Bi, Ba=Ba+1;

if Ba>Bi, Ba=Ba-1

Among them, A_speed is the adjustment speed constant. The larger the value, the slower the adjustment. Using this cycle can control the adjustment range and avoid jumping changes in the adjustment process.

(5) Use Ba to actually adjust brightness and perform corresponding contrast compensation.

Brightness adjustment: B=B0-Ba; B0: the brightness value before dynamic adjustment, such as 50 or the user-set value in the standard state.

Contrast compensation: C=C0+C_compensate*Ba; wherein, C0: contrast value before dynamic adjustment; C_compensate: contrast compensation factor constant.

(6) Return to step (2) for loop real-time detection and adjustment.

The aforementioned one cycle period is approximately 10 ms.

Specific embodiment two: if the dynamic regulation of brightness is realized in front-end video decoder or ADC module, can affect the real Yd value of image, in this case, need to adjust Yi when using the method of the present invention to adjust television image quality To compensate, the compensation formula is:

Yi=(Yd+y*Ba)/d y: Compensation factor, determined by actual measurement.

If you do not want to perform compensation calculation or the compensation is inaccurate, you do not need to perform compensation, but you must

if Ba<Bi, Ba=Ba+1;

if Ba>Bi, Ba=Ba-1

changed to

if Ba<Bi-2, Ba=Ba+1;

if Ba>Bi, Ba=Ba-1

The purpose of such modification is to prevent self-excitation, and at the same time ensure that when Bi is 0, Ba must be able to return to zero, so as to ensure that the level of the dark picture is not lost. Specific processing steps may be performed with reference to the operations described in the first specific embodiment above.

In the above two specific implementation manners, the appropriate values of the involved constants need to be measured and determined in specific applications. For those skilled in the art, the selection and determination of these constant parameters is relatively easy to implement. In our PDP42U2A products, the values of the constants are as follows: brightness starting value Y_start=6; adjustment strength A_strong=1.5; adjustment speed A_speed=1; adjustment upper limit Bmax=30; contrast compensation factor C_compensate=0.6.

Claims (4)

1, a kind of method of adjustment that is used for image quality is characterized in that the performing step of this method is:

(1) the overall brightness value Yi of computed image signal;

A, the decrease of the relevant memory variable of governing speed, image brightness value is carried out initialization, S=0 during initialization, Ba=0, wherein S: the memory variable relevant with governing speed; Ba: the decrease of image brightness value;

B, by formula Yi=Yd/d, calculate the overall brightness Yi of the picture signal of front end image decoder or analog to digital converter output, wherein, Yd is the accumulated value of brightness value of the effective pixel points of institute's received image signal, d is the resolution reduced factor, for SD signal d=1; For the total pixel/720*480 of high-definition signal d=high-definition format;

(2) determine the target brightness value Bi of required adjusting according to above-mentioned overall brightness value Yi;

(3) regulate brightness value, and simultaneously the contrast of picture is compensated;

(4) turn back to the circulation of (1) step, thereby realize circulating frame by frame real-time dynamic adjustments.

2, the method for adjustment that is used for image quality as claimed in claim 1, it is characterized in that in step (2), if overall brightness value Yi rises smaller or equal to brightness and transfers normal value Y_start, then the brightness of image is not adjusted, adjust big or small related with overall brightness value Yi.

3, the method for adjustment that is used for image quality as claimed in claim 1, the compensation that it is characterized in that contrast is undertaken by computing formula C=C0+C_compensate*Ba, wherein, C0 is the contrast value before the dynamic adjustments, C_compensate is a contrast compensation factor constant, and Ba is the decrease of the image brightness value of practical adjustments.

4, the method for adjustment that is used for image quality as claimed in claim 1 is characterized in that the target brightness value Bi of step (2), and concrete condition has:

If 1. Yi＜=Y_start, then Bi=0;

Brightness is set works secretly picture when transferring normal value Y_start mainly to consider for Yi＜=Y_start, system does not adjust the brightness value of image state, so just can guarantee that dark rank are normal;

If 2. Yi＞Y_start, then Bi=A_strong* (Yi-Y_start); Wherein, A_strong is for regulating the intensity constant.

If 3. Bi＞Bmax, Bi=Bmax then, Bmax: regulate upper limit constant.

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