CN101031091B - Method and device for video communication terminal to correct gamma characteristics of video stream - Google Patents

Abstract

The present invention relates to video communication technology, in particular to a method and equipment for locally correcting the gamma characteristics of video streams by video communication terminals, so as to solve the problem that the gamma characteristics of video streams cannot be locally corrected on the communication terminal side in the prior art. The method includes outputting after correcting the gamma value of the local video stream to a first target gamma value when outputting the local video stream; and/or receiving an incoming video stream whose gamma value is the first target gamma value , correct the gamma value of the incoming video stream to the reciprocal of the gamma value of the local display device and then transmit it to the local video display device; and/or when displaying the local video stream, correct the gamma value of the local video stream to the local video The reciprocal of the gamma value of the display device is transmitted to the local video display device. The device includes a module for storing gamma parameter information of a video input device and/or a video display device and a correction module. Applying the method of the invention can conveniently realize the local correction of the gamma characteristic.

Description

Method and device for video communication terminal to correct gamma characteristics of video stream

technical field

The invention relates to video communication technology, in particular to a method and equipment for locally correcting video stream gamma characteristics by a video communication terminal.

Background technique

Video communication is currently being widely used with the rapid development of broadband networks. Domestically and internationally, video conferencing and videophone services are becoming basic services on NGN (Next Generation Network, Next Generation Network). Telecom operators in various countries also attach great importance to this market opportunity. It can be expected that in the next few years, video communication services will become an important business growth point for operators. A key issue in developing this type of business is to improve the end-to-end (End-to-end) user experience (UserExperience, or Quality of Experience). In user experience, in addition to network QoS (packet loss, delay, jitter, R factor, etc.) parameters, for video, the Gamma nonlinearity caused by each link causes distortion of the brightness signal, which also affects the end user experience. important factor. However, at present, the methods and technologies for improving end-to-end user experience are mainly focused on ensuring network QoS and pre-processing (Post-processing) related to video compression coding, and lack of attention and attention to the brightness distortion problem caused by Gamma characteristics. However, the seriousness of this problem has attracted the attention of some major international telecom operators. France Telecom (FranceTelecom) recently proposed in the International Telecommunication Union ITU-T to consider the influence of Gamma characteristics on communication user experience in video communication, and suggested to solve such problems.

In the process of video communication, in a video communication terminal (hereinafter referred to as the terminal), the optical signal from the scene (person, background, file, etc.) to be transmitted enters the camera/camera, and is converted into a digital image signal by A/D. After compression and encoding, it is sent out to the other party's terminal, and then decompressed (Decompression) decodes and restores to a digital image signal, which is then displayed on a display device, and finally becomes an optical signal to be perceived by the human eye. In this process, the image luminance signal (Luminance, here is a generalized luminance signal, that is, the initial optical signal, to the electrical signal, and then to the digital image luminance/grayscale signal, the signal at each stage contains the luminance signal. information, so broadly speaking, the luminance signal has passed through multiple links) through multiple links.

As shown in Figure 1, Figure 1 is a schematic diagram of a model of the Gamma characteristic of a link. The Gamma characteristic is that the input-output relationship of a luminance signal in a link is not linear, but a nonlinear one. The influence of Gamma nonlinear link distortion is shown in Figure 2. The brightness of the upper row of gray squares increases linearly, from 0.1 to 1.0. The lower row is distorted by the Gamma nonlinear link, and the brightness increases according to the law of the power function.

In practice, Gamma nonlinearity is caused by different reasons, for example: Gamma characteristics of CRT (Cathode Ray Tube, cathode ray tube) display satisfies formula 1 under ideal conditions:

L _out =L _in ^2.2 (1)

The ideal Gamma of the corresponding camera/camera satisfies Formula 2:

L _out =L _in ^0.45 (2)

From the perspective of the origin of the Gamma problem, it originated from the CRT display, because its Gamma value is 2.2. In order to compensate for this non-linearity, a Gamma value of 0.45 is artificially introduced into the camera. If there are only two gamma links in the system: CRT display and video camera, then complete gamma correction can be achieved. It should be noted that the input and output luminance signals here are normalized (Normalized) in their respective coordinate spaces, that is, 0≤L _out ≤1, 0≤L _in ≤1. For other types of displays, such as liquid crystal displays, the Gamma function forms are either different, or although the form is also a power function, the parameters are different.

As shown in Figure 3, Figure 3 is a schematic diagram of the model of the Gamma characteristics of multiple links cascaded (Cascading or called in series). The total Gamma characteristics are equal to the composition of the Gamma functions of each link, which satisfies Formula 3:

G _CT (.)＝G ⁽¹⁾ (.)οG ⁽²⁾ (.)οG ⁽³⁾ (.)......G ^(n-1) (.)οG ⁽ⁿ⁾ (. )

l _out ＝G _CT (l _in )＝G ⁽ⁿ⁾ (G ^(n-1) (G ^(n-2) (...G ⁽²⁾ (G ⁽¹⁾ (l _in )) )))(3)

"ο" represents the compound operation of the function. CT stands for Cascaded Total, which means cascaded total Gamma.

think.

The ideal situation is that there is a linear relationship between the input light signal and the output light signal from entering the camera to finally displaying the output light signal on the display, that is: L _out = L _in , so that the scene seen by people is the same as the original Exactly the same, best user experience.

To obtain a linear relationship, Gamma Correction (Gamma Correction) must be performed on links with nonlinear Gamma characteristics. As shown in Figure 4, for a link, if its Gamma characteristic is given, then another correction link can be used to cascade with it, so that the total Gamma characteristic after cascading is called a true linear relationship, thus achieving For the purpose of compensating the nonlinearity of a given link, the model of the correction link is the inverse model of the equivalent model of Gamma characteristics. If the equivalent model can be expressed by a functional relational expression, then the functional relational expression of the inverse model is its inverse function. Obviously, G _g (.) and G _c (.) are inverse functions of each other. In general, for a function, there may not necessarily be a solution to obtain its inverse function (or even if the solution exists, it cannot be obtained by calculation).

More situations in practical applications are shown in Figure 5. The correction link needs to be inserted between the two given links before and after. At this time, the situation of G _c (.) is more complicated, and G _c (.) and G _a (.) or G _p (.) is no longer a simple inverse functional relationship.

In video communication, there are multiple links inside the terminal, each link has its own gamma characteristics, and they are cascaded. In video communication, the main gamma links involved in video on a terminal include:

1. Camera/camera Gamma, expressed as G _Cam (.);

General cameras have Gamma characteristics. In addition to the nonlinearity of imaging devices such as CCD itself, the camera introduces artificial nonlinearity. The purpose is to make the Gamma characteristics of the camera just compensate for the Gamma characteristics of the display, so that the total Gamma characteristics are linear. . If the ideal Gamma of the display is: L _out =L _in ^2.2 ; then the ideal Gamma of the camera is: L _out =L _in ^0.45 .

Therefore, in theory, the Gamma characteristics of the camera are determined by the Gamma characteristics of the display. However, due to the increasing complexity of the terminal system, there are multiple links between the camera and the display, the number of which is uncertain, and their respective Gamma characteristics are also unknown, so that even if the Gamma of the camera and the display match exactly, they can compensate each other, but because of the existence of intermediate links, this compensation Generally invalid. And there are many types of displays, such as: CRT and liquid crystal, plasma and other displays, their Gamma characteristics are quite different, and the Gamma characteristics of cheap cameras often seriously deviate from their ideal Gamma.

2. Display the look-up table Gamma, expressed as G _LUT (.);

Some display devices, in order to compensate for the non-linearity of the display, artificially introduce Gamma, which is represented as a LUT (Look-Up Table), and the brightness data read from the frame memory must be converted by the LUT to drive the display.

3. Display Gamma, expressed as G _Disp (.).

There are mainly two methods for implementing Gamma correction in the prior art:

Existing technology 1: rely entirely on the Gamma characteristics of the camera/camera or display LUT to correct the Gamma characteristics of the display, assuming that in an ideal state:

G _Cam (.): L _out = L _in ^0.45 ; G _LUT (.): L _out = L _in ^0.45 ; G _Disp (.): L _out = L _in ^2.2 ;

Then: G _Cam οG _Disp (.) becomes: L _out =L _in , forming a standard linear relationship; G _LUT οG _Disp (.) becomes: L _out =L _in , forming a standard linear relationship.

But there is following deficiency in above-mentioned technology:

The ideal state is difficult to obtain, and there is no guarantee that the Gamma of the camera/camera and LUT will exactly match the Gamma of the monitor. And there are many types of displays, and the Gamma of cheap cameras is definitely not ideal;

There are two typical situations for the application of two-party video communication: A. mobile phone video communication, and B. communication based on PC or videophone terminal. These problems are very serious. In the above two cases, there are many brands and models of terminals, and the conditions of the terminals are very different. It is likely that the video input devices and display screens of the two communication parties are completely different. One side uses a professional Sony/Panasonic camera, and the other uses a cheap camera worth tens of yuan; one side uses an ordinary CRT monitor, and the other side uses an LCD or even a plasma monitor. The huge contrast makes the video/image that cannot get gamma correction well locally sent to the other terminal, and the difference is even greater.

Prior art two:

Between some links, such as after the camera link or before the display frame storage link, a Gamma correction link is inserted to perform Gamma correction. In addition, a more accurate model may be used in terms of the Gamma characteristic model of the display, such as formula 4:

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 0.45</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}& \mathrm{<span\; class="notranslate">\; if</span>}\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 0.081</span>}\\ \frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 1.099</span>}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 0.099</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2.2</span>}}& \mathrm{<span\; class="notranslate">\; if</span>}\mathrm{<span\; class="notranslate">\; 0.081</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Correspondingly, the Gamma of the camera is considered to exactly match the Gamma of the display, such as formula 5:

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 0.45</span>}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}& \mathrm{<span\; class="notranslate">\; if</span>}\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 0.081</span>}\\ \mathrm{<span\; class="notranslate">\; 1.099</span>}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}}^{\mathrm{<span\; class="notranslate">\; 0.45</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.099</span>}& \mathrm{<span\; class="notranslate">\; if</span>}\mathrm{<span\; class="notranslate">\; 0.081</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

This method still cannot avoid the problem of over-correction or under-correction because of the inability to match accurately.

To sum up, there is currently no general method to realize the Gamma correction method from the light signal entering the camera/camera to the image displayed on the display. Therefore, there is no general solution to the degradation of video quality caused by the Gamma problem.

The present invention provides a method and device for video communication terminals to correct the gamma characteristics of video streams, so as to solve the problem in the prior art that the gamma characteristics of video streams cannot be corrected locally on the communication terminal side.

A method for correcting video stream gamma characteristics by a video communication terminal, comprising the steps of:

A. When outputting the local video stream, the gamma value of the local video stream is corrected to the first target gamma value and then output;

B. When receiving an incoming video stream whose gamma value is the first target gamma value, first determine whether the gamma value of the local video display device is the second target gamma value, and the second target gamma value is the same as the first target gamma value The product of a target gamma value is 1 or the difference with 1 is within the set range, if so, the incoming video stream is directly transmitted to the local video display device, otherwise the gamma value of the incoming video stream is corrected to the local The reciprocal of the gamma value of the display device is transmitted to the local video display device.

Further includes:

C. When displaying the local video stream, the gamma value of the local video stream is corrected to the inverse of the gamma value of the local video display device and then transmitted to the local video display device.

According to the method of the present invention,

The step A also includes: firstly judging whether the gamma value of the local video input device is the first target gamma value, if so, outputting the local video stream directly, otherwise performing correction before outputting.

The step C also includes: firstly judging whether the product of the gamma value of the local video input device and the local video display device is 1, if so, directly transmitting the local video stream to the local video display device; otherwise, performing correction before transmitting.

Wherein, when correcting the output local video stream, in step A, the first corrected gamma value for correcting the local video stream is divided by the first gamma value divided by the gamma value of the local video input device ;

When correcting the incoming video stream, in step B, the second correction gamma value used to correct the incoming video stream is the quotient of dividing the second target gamma value by the local video display device gamma value .

When correcting the displayed local video stream, in the step C, sequentially use the first corrected gamma value and the second corrected gamma value to correct the gamma value of the local video stream hierarchically and then transmit it to the local video stream display screen. Or, when correcting the displayed local video stream, in the step C, the third correction gamma value used to correct the local video stream is the product of the local video input device gamma value and the local video display device gamma value reciprocal.

In the method, the first target gamma value is 0.45; the second target gamma value is 2.2.

The gamma value of the local video input device and/or video display device is determined according to the factory data of the device, or determined according to the actual detection result.

A video gamma characteristic correction device based on the same technical idea, including:

Gamma information saving module, used for saving the gamma parameter information of video input device and/or video display device;

A correction module, connected to the gamma parameter information storage module, for correcting the gamma value of the video stream according to the gamma parameter information and/or the target gamma parameter;

The gamma information setting module is connected to the gamma parameter information saving module, and is used to save the initial gamma parameter information input from the external video input device and/or video display device to the gamma parameter information saving module;

The control coordination module is used to control and coordinate the working status of each module.

The correction module further includes:

The outbound video stream correction sub-module is used to correct and output the gamma value of the outbound video stream collected by the video input device;

The incoming video stream correction sub-module is used to correct the gamma value of the incoming video stream from the outside and output it to the video display device for local display; and

The local display video stream correction sub-module is used to correct the gamma value of the local video stream and output it to the video display device for local display.

The correction module further includes:

The outbound video stream correction sub-module is used to correct and output the gamma value of the outbound video stream collected by the video input device;

The incoming video stream correction sub-module is used to correct the gamma value of the incoming video stream from the outside and output it to the video display device for local display; or re-correct the video stream corrected by the outgoing video stream correction sub-module and output it Give the video display device to display locally.

The correction sub-module further includes: a judgment unit and a correction execution unit, the judgment unit judges whether the received video stream needs to be corrected according to the gamma parameter information of the video input device and/or video display device, and if so, the input correction execution sub-module performs Output after correction, otherwise output directly.

The calibration device also includes:

The gamma parameter measurement module is connected to the gamma parameter information storage module, and is used to detect the gamma parameter of the video input device and/or video display device and save it to the gamma parameter information storage module.

The gamma parameter measurement module further includes: a video input device gamma parameter measurement submodule and a video display device gamma parameter measurement submodule.

The beneficial effects of the present invention are as follows:

The present invention provides a general video terminal method for correcting the gamma characteristics of the video code stream, which can realize the complete correction of the local video display video stream, and when the sending ends of the communication parties use the method of the present invention to output the gamma of the video stream When the gamma value is corrected to the set target value, the receiving end can completely correct the incoming video stream without exchanging the gamma characteristic information of both parties, which reduces the amount of data transmission in video communication and improves the quality and quality of video communication. user experience;

The present invention also provides a correction device for a video communication terminal, which can realize gamma characteristic correction of local video display video stream, outgoing video stream and incoming video stream according to the correction method of the present invention.

Description of drawings

Figure 1 is a general model of the Gamma characteristic of a link;

Fig. 2 is a schematic diagram of brightness signal distortion caused by link Gamma characteristics;

Figure 3 is a general model of multi-link cascaded Gamma characteristics;

Figure 4 is a schematic diagram of the Gamma characteristic of a single link of correction;

Fig. 5 is a schematic diagram of the Gamma characteristic of correcting multiple given links;

Fig. 6 is a schematic diagram of the correction principle of the method of the present invention;

FIG. 7 is a schematic structural diagram of the calibration device described in Embodiment 2 of the present invention;

FIG. 8 is a schematic structural diagram of the calibration device described in Embodiment 3 of the present invention;

FIG. 9 is a schematic structural diagram of a syndrome submodule.

Detailed ways

Because multi-party video communication is based on two-party video communication, essentially, one N-party communication can be decomposed into at most N(N-1)/2 two-party communications. On the issue of local Gamma correction, if each terminal has completed the Gamma correction of the output video stream of the terminal, in essence, the situation under two-party communication and multi-party communication is exactly the same. For the convenience of description, the following discussion takes two-party communication as the background of the problem.

Referring to Figure 6, taking the video communication between terminal A and terminal B as an example, the terminals respectively include video input devices, video display devices, video codecs, and network interfaces connected to the communication network, and the gamma link involved in the video stream mainly includes :

1. Video input device Gamma, that is, camera/camera Gamma, expressed as G _Cam (.);

General cameras have Gamma characteristics. In addition to the nonlinearity of imaging devices such as CCD itself, the camera introduces artificial nonlinearity. The purpose is to make the Gamma characteristics of the camera just compensate for the Gamma characteristics of the display, so that the total Gamma characteristics are linear. . If the ideal Gamma of the display is: L _out =L _in ^2.2 ; then the ideal Gamma of the camera is: L _out =L _in ^0.45 .

2. Display frame memory Gamma, expressed as G _FBuf (.);

Because the color depth of the display storage in the early display is not enough, for example, it can only support 4-bit, 8-bit, and 16-bit color depth, instead of the ideal 24-bit true color, which is equivalent to compressing the dynamic range of the input brightness signal, so Gamma is also introduced. characteristic. In addition, because in the non-true color mode, the used palette (Palette) color mapping technology or dithering (Dither) technology will introduce non-linear Gamma.

3. Display the look-up table Gamma, expressed as G _LUT (.);

Some display devices, in order to compensate for the non-linearity of the display, artificially introduce Gamma, which is represented as a LUT (Look-Up Table), and the brightness data read from the frame memory must be converted by the LUT to drive the display.

4. Display Gamma, expressed as G _Disp (.);

5. Encoder Gamma, expressed as G _Enc (.);

Gamma caused by DCT (Discrete Cosine Transform) transformation and quantization in compression.

6. Decoder Gamma, expressed as G _Dec (.).

Gamma caused by DCT inverse transformation and inverse quantization in decompression.

Among the above-mentioned links, the two links that have the greatest impact on the video are the video input device and the video display device. Compared with them, the influence of other links is very small, so as long as the Gamma characteristics of the video input device and video display device are corrected, the video It can fully meet the viewing effect requirements of most non-professional grades (professional grades refer to TV stations, film studios and other commercial media production entities, etc.) in various scenarios. Based on the above considerations, when the video input device and the video display device have ideal Gamma values and ignore the influence of the Gamma characteristics of other links, the local correction of the Gamma characteristics of the video stream can be fully or partially realized.

It should be noted that the video described in this paper not only includes a motion picture sequence (Motion Picture Sequence, the narrow definition of video), but also includes still images, computer graphics, animations (such as Flash animations, GIF animations, etc.) and the like.

Still referring to Figure 6, in order to achieve local correction, a Gamma correction device needs to be cascaded behind the video input device of the terminal, and the locally collected video stream is corrected to the ideal target Gamma characteristics by the Gamma correction device, and then output to the local video display respectively equipment, or coded by a video codec and then output to a receiving terminal through a communication network, or the video stream received through a communication network is corrected by a correction device and then output to a local video display device for display. The following is a specific embodiment combined with the accompanying drawings Describe the technical solution of the present invention in detail.

Embodiment 1. Method for Correcting the Gamma Characteristics of a Video Stream by a Video Communication Terminal

The correction of video stream Gamma characteristics includes three situations:

1. Gamma correction for outgoing video streams

The outgoing video stream is output from the local terminal, through the network to the central communication node such as the multi-point control unit, or the video code stream to other video communication terminals. The requirement is that the Gamma value of the outgoing video stream should be corrected to 0.45. That is to say, the achieved effect is equivalent to that the video code stream comes from a video input device with an ideal Gamma value. So if the video input device is ideal, ie has a Gamma of 0.45, then no correction is required. If not, use γ _Cam to represent the Gamma value of the video input device, then the Gamma value γ _Cor of the Gamma correction module to the video stream should satisfy Formula 6:

γ _Cam γ _Cor = 0.45 (6)

2. Gamma correction of incoming video stream

The incoming video stream is the video stream entering the local terminal from the network, which may come from a central communication node such as a multipoint control unit, or a video code stream from other video communication terminals. The incoming video stream comes from other terminals (even if it comes from the multi-point control unit, in the final analysis, it still comes from other terminals, because the video stream of the multi-point control unit is also from the terminal.), according to the previous requirements, it already has an ideal Gamma Value 0.45. If the video display device of the local terminal is ideal, that is, has an ideal Gamma value of 2.2, then no Gamma correction is required for the incoming video stream. If not, Gamma correction needs to be performed locally on the incoming video stream, so that the Gamma value of the corrected video stream is equal to 1/γ _Disp , where γ _Disp represents the Gamma value of the video display device. Then the Gamma value γ _Cor of the Gamma correction module entering the video stream should satisfy Formula 7:

γ _Disp γ _Cor = 2.2(1/0.45) (7)

3. Gamma correction of local display video stream

A local display video stream refers to a video stream that comes from a local video input device and is directly displayed on a local video display device. If both the video input device and the video display device are ideal, that is, Equation 8 is satisfied:

γ _Cam = 0.45, γ _Disp = 2.2 (8)

or satisfy formula 9

γ _Cam · γ _Disp = 1 (9)

It should be noted that 8 is a special case of 9. What needs to be further explained in formula 9 is: in general, the specific value of γ _Cam or γ _Disp is a rounded divisor, so the product γ _Cam · γ _Disp is close to 1, as long as the product If the difference with 1 is within the set range, it can be considered that Formula 9 is established.

If Equation 8 or 9 holds true, no correction of the locally displayed video stream is required. If not, a correction is required. If correction is required, then the Gamma value γ _Cor of the local display video stream Gamma correction module should satisfy the following relationship formula 10:

γ _Cam γ _Cor γ _Disp = 1 (10)

According to the previous analysis, to judge whether the video display device and video input device are in an ideal state, and to realize Gamma correction in a non-ideal state, first of all, we must know the parameters of the Gamma link, that is, the Gamma parameters of the video display device and video input device. If these parameters have been provided along with the technical information of the factory manual of the equipment, they can be obtained directly. If there is no such technical data, or the technical data does not provide the Gamma parameter, you can use the measurement method to obtain the Gamma parameter. Moreover, it is more reliable to obtain Gamma parameters through measurement, because sometimes the technical data is not necessarily correct.

As the basis of the present invention's implementation, here at first introduce a kind of detection method that determines each Gamma characteristic link equivalent model and its parameter here, comprises the steps:

First, a set of general equivalent models of the single-link Gamma properties are chosen, for example:

The first type of Gamma model satisfies Equation 11:

L _out ＝pL _in ^α +(1-p) 0<p≤1, α≥1 (11)

Wherein: the definition domain of the function shown in Formula 11 (ie, the value range of the independent variable) is the interval [0, 1], and the value range (the value range of the function value) is the interval [(1-p), 1].

The second type of Gamma model satisfies Equation 12:

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}^{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; \&Greater\; Equal;</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; \&Greater\; Equal;</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

Wherein: the definition domain of the function shown in formula 12 (that is, the value range of the independent variable) is the interval [1-1/q, 1], and the value domain (the value range of the function value) is the interval [(0, 1].

Then use one of them as the model to be tested and perform the following steps:

1. Select evenly spaced N sampling points on the interval [0, 1] of the input brightness signal L _in : L _in (0), L _in (1), L _in (2)...L _in (i)...L _in (N-2), Lin _in (N-1);

2. Input the N sampling values of the luminance signal into the link respectively, and measure the corresponding values of the actual N output luminance signals: L ^P _out (0), L ^P _out (1), L ^P _out (2).... ..L ^P _out (i)...L ^P _out (N-2), L ^P _out (N-1);

3. Construct the fitted objective function, the difference between the objective function and the actual detected output luminance signal and the theoretical output luminance signal determined by the Gamma characteristic model, and the smaller the difference, the better the equivalent effect of the model close to reality.

There are many ways to construct the objective function, and the more commonly used ones are the following formula 13 or formula 14:

$f_{T1}(p,\mathrm{\&alpha;})=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{(L_{\mathrm{out}}^P\left(i\right)-{\mathrm{PL}}_{\mathrm{in}}{\left(i\right)}^{\mathrm{\&alpha;}}-(1-p))}^2---\left(13\right)$ or,

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}^{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; QUR</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}^{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

4. Set the threshold T of the objective function value and the maximum number of iterations M, and use the mathematical optimization method to find the most suitable parameter group;

First, for the cost function of the first category $f_{T1}(p,\mathrm{\&alpha;})=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{(L_{\mathrm{out}}^P\left(i\right)-p{L}_{\mathrm{in}}{\left(i\right)}^{\mathrm{\&alpha;}}-(1-p))}^2,$ Use some mathematical optimization technique, such as: hill climbing method, 0.618 method (Hua Luogeng optimization method), steepest descent method or conjugate gradient method to find its minimum value;

This process is actually an iterative process. In this process, the parameters p and α are constantly adjusted, and the function value F is continuously decreasing. When the function value decreases to less than the given threshold T, it is considered that the minimum point has been found. At this time, the corresponding parameters p and α are considered to be the real parameters of the application environment model.

if for $f_{T1}(p,\mathrm{\&alpha;})=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{(L_{\mathrm{out}}^P\left(i\right)-p{L}_{\mathrm{in}}{\left(i\right)}^{\mathrm{\&alpha;}}-(1-p))}^2$ After M iterations, if the function cannot drop below the threshold T, it is considered that the model selection is incorrect. The second type of model should be chosen, so for $f_{T2}(q,\mathrm{\&beta;})=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{(L_{\mathrm{out}}^P\left(i\right)-{(q{L}_{\mathrm{in}}\left(i\right)+(1-q))}^{\frac{1}{\mathrm{\&beta;}}})}^2$ Repeat the above step 4 to obtain the corresponding model parameters q and β. It should be noted that the value ranges of the parameters q and β are: q≥1 and β≥1, respectively.

If you want to get more accurate parameters, you can iterate a few more times after the objective function value F drops below the threshold T. If the objective function value F continues to decline, or rises after falling, or directly rises, regardless of the objective function value F is what kind of change, then choosing the parameter corresponding to the minimum value as the measurement result will improve the accuracy of parameter measurement to a certain extent.

It can be seen that the determination of the model type and the measurement of parameters are carried out at the same time. In practice, the types of equivalent models are not limited to these two forms. Through the above method, the most suitable method can be found in all relevant equivalent models by measuring parameters. one of.

The above detection method is a general detection method, and the present invention mainly selects a power function model for detection.

Before each correction, it is necessary to judge whether the gamma value of the video input device or the video display device is the ideal target gamma value. If so, no correction is required, otherwise, the correction is performed. The basis for judgment is:

1. For the output local video stream:

If the Gamma value of the video input device γ _Cam = 0.45, then the Gamma value of the corresponding local video stream is an ideal target Gamma value of 0.45, which does not need to be corrected, and is directly output through the communication network; otherwise, the Gamma value of the local video stream is corrected to 0.45 post output;

2. For incoming video streams from the network or other terminals:

Since the Gamma value of the incoming video stream has been the ideal target Gamma value of 0.45, if the Gamma value γ Disp of the video display device is γ _Disp = 2.2, complete correction can be achieved, and the incoming video stream is directly transmitted to the video display device for display, otherwise , it is necessary to correct the Gamma value of the incoming video stream to 1/γ _Disp to achieve complete correction;

3. Display video stream locally:

If the Gamma value of the video display device automatically compensates the Gamma value introduced by the video input device, that is, the equation (8) or (9) is established, of course (8) is a special case of (9), and there is no need for local display The local video stream has been corrected, otherwise, it needs to be corrected. In fact, the step of judging can be omitted. If the Gamma value of the video display device and the Gamma value of the video input device are automatically compensated, the calculated corrected Gamma value is actually 1, so for an ideal video display device and video input device Said, the transmission speed of the video stream is reduced, so the correction method with judgment first is preferred.

The above method is a general method for video terminals to correct the gamma characteristics of the video code stream, which can realize the complete correction of the local video display video stream, and when the sending ends of the communication parties use the method of the present invention to output the gamma of the video stream Value correction When setting the target value, the receiving end can realize the complete correction of the incoming video stream without exchanging the gamma characteristic information of both parties, which reduces the amount of data transmission in video communication and improves the quality of video communication and user experience and the method of the present invention is not limited to the application scenarios where the standard Gamma values of existing video input devices and display devices are 0.45 and 2.2, and the target Gamma value can be adjusted accordingly according to the development of video technology to achieve an ideal correction effect .

Embodiment 2. A structure of Gamma correction equipment

In summary, a structure of a calibration device for implementing the calibration method of the present invention is shown in Figure 7, including, wherein the calibration module includes the following three sub-modules:

1. Outgoing video stream Gamma correction sub-module

It is connected between the video input device and the video codec to perform Gamma correction on the outgoing video stream;

This module first judges whether γ _Cam =0.45 is set up, if so, then directly transmits the local video stream to the video codec, otherwise corrects;

This module has a corrected Gamma value γ _Cor = 0.45/γ _Cam , on the basis of obtaining γ _Cam , calculate γ _Cor , and then use hardware circuit or software to realize the correction, wherein: the standard power can be realized by using the hardware circuit method Function input and output characteristics, there are quite a lot of such methods, which are mature technologies, so I won’t repeat them here. The software implementation includes the following:

Direct calculation method: generate standard power function input and output characteristics by program method, such as using function call or subroutine method;

Table look-up method: For enough points calculated on the value interval of the input brightness signal, the correction result is calculated according to γ _Cor and the standard power function, and saved as a look-up table. Then, when performing correction, for the input signal value to be corrected, the correction result is obtained by looking up the table. The more table entries, that is, the denser the sample collection, the more accurate the table lookup effect.

It should be noted that the significance of distinguishing between hardware and software methods here is that the hardware is completely realized by means of circuits and cannot contain any microprocessors and memories. Software includes the use of DSP and memory, because in this case, it is also the program software that works.

2. Incoming video stream Gamma correction sub-module

It is connected between the video codec and the video display device, and is responsible for performing Gamma correction on the incoming video stream;

This module first judges whether γ _Disp =2.2 holds true, if yes, then can automatically compensate the Gamma characteristic of incoming video stream, otherwise, need to correct;

This module has a corrected Gamma value γ _Cor =2.2/γ _Disp . On the basis of obtaining γ _Disp , calculate γ _Cor , and then use hardware circuit or software to realize correction, among them: the method of using hardware circuit can realize the standard power function input and output characteristics, there are quite a lot of such methods, which belong to mature technology , which will not be repeated here. The software implementation includes the following:

Direct calculation method: generate standard power function input and output characteristics by program method, such as using function call or subroutine method;

Table look-up method: For enough points calculated on the value interval of the input brightness signal, the correction result is calculated according to γ _Cor and the standard power function, and saved as a look-up table. Then, when performing correction, for the input signal value to be corrected, the correction result is obtained by looking up the table. The more table entries, that is, the denser the sample collection, the more accurate the table lookup effect.

It should be noted that the significance of distinguishing between hardware and software methods here is that the hardware is completely realized by means of circuits and cannot contain any microprocessors and memories. Software includes the use of DSP and memory, because in this case, it is also the program software that works.

3. Local display video stream Gamma correction sub-module

It is connected between the video input device and the video display device, and is responsible for performing Gamma correction on the local display video stream.

This module has a Gamma value γ _Cor =1/γ _Cam ·γ _Disp . On the basis of obtaining _γCam and _γDisp , calculate _γCor , and then use hardware circuit or software to realize correction, among which: the method of using hardware circuit can realize the standard power function input and output characteristics, there are quite a lot of such methods, It is a mature technology and will not be repeated here. The software implementation includes the following:

Direct calculation method: generate standard power function input and output characteristics by program method, such as using function call or subroutine method;

Table look-up method: For enough points calculated on the value interval of the input brightness signal, the correction result is calculated according to γ _Cor and the standard power function, and saved as a look-up table. Then, when performing correction, for the input signal value to be corrected, the correction result is obtained by looking up the table. The more table entries, that is, the denser the sample collection, the more accurate the table lookup effect.

It should be noted that the significance of distinguishing between hardware and software methods here is that the hardware is completely realized by means of circuits and cannot contain any microprocessors and memories. Software includes the use of DSP and memory, because in this case, it is also the program software that works.

Still referring to Figure 7, in order to complete the parameter detection function, the Gamma correction equipment should also include:

4. Gamma parameter measurement module, which can be divided into the following two sub-modules:

Video input device Gamma parameter measurement sub-module: If the Gamma parameter of the video input device is not provided (for example, the factory manual or Data Sheet is not listed), then this module can be used for measurement.

The specific measurement method is as described above. In Fig. 7, the first measurement excitation signal is input to the video input device, and then the first measurement response signal for the excitation signal is collected from the video input device. According to the excitation signal and the response signal, Ready to take measurements.

Video display device Gamma parameter measurement sub-module: If the Gamma parameter of the video display device is not provided (for example, the factory manual or Data Sheet is not listed), then this module can be used for measurement.

The two Gamma parameter measurement sub-modules can be set independently or combined.

Still referring to FIG. 7 , the second excitation measurement signal is input to the video display device, and then the second measurement response signal to the excitation signal is collected from the video display device, and the measurement can be performed according to the excitation signal and the response signal.

5. Gamma information setting module

For the Gamma parameter information that can be obtained through the product manual, set it through the man-machine interface provided by the subsystem. Then it is saved in the Gamma information saving module, and the saved Gamma parameter information can also be called out for editing and modification before being saved back, and the information can also be deleted.

6. Gamma information storage module

Save the Gamma parameter information set by the Gamma information setting subsystem, and also save the Gamma parameter information measured by the Gamma parameter measurement module of the video input device and the Gamma parameter measurement module of the video display device.

7. Control and coordination module: control and coordinate other modules, and play the role of master control.

Embodiment 3: Another structure of Gamma correction equipment

It can be found that its embedded video stream gamma correction module can also be used for local display video stream gamma correction. However, in this case, the input video stream is not from the video input device, but from the outgoing video stream Gamma correction module. After the locally collected video stream is corrected by the outgoing video stream Gamma correction module, the Gamma value of the video stream is 0.45, which has the same Gamma value as the incoming video stream from the video codec. At this time, if the Gamma value of the video display device is not the ideal 2.2, it needs to be corrected by the incoming video stream Gamma correction module. Because the two video streams have the same Gamma value, and the corrected destinations are both video display devices, the same correction module can be used for correction. However, since two or more video streams need to be corrected at the same time (because there may be more than one video stream for incoming and local display), multi-channel simultaneous correction capability is required.

Therefore, as shown in Figure 8, for another structure of the calibration device, the calibration module includes the following two sub-modules:

1. Outgoing video stream Gamma correction sub-module: connected between the video input device and the video codec, and performs Gamma correction on the outgoing video stream;

This module has a Gamma value γ _Cor = 0.45/γ _Cam , on the basis of obtaining γ _Cam , calculate γ _Cor , and then use hardware circuit or software to realize the correction, wherein: the standard power function can be realized by using the hardware circuit method There are quite a lot of such methods for input and output characteristics, which are mature technologies and will not be described here. The software implementation includes the following:

Direct calculation method: generate standard power function input and output characteristics by program method, such as using function call or subroutine method;

Table look-up method: For enough points calculated on the value interval of the input brightness signal, the correction result is calculated according to γ _Cor and the standard power function, and saved as a look-up table. Then, when performing correction, for the input signal value to be corrected, the correction result is obtained by looking up the table. The more table entries, that is, the denser the sample collection, the more accurate the table lookup effect.

It should be noted that the significance of distinguishing between hardware and software methods here is that the hardware is completely realized by means of circuits and cannot contain any microprocessors and memories. Software includes the use of DSP and memory, because in this case, it is also the program software that works.

2. Incoming video stream Gamma correction sub-module: It is connected between the video codec and the video display device, and is responsible for performing Gamma correction on the incoming video stream and the locally displayed video stream, and because it is necessary to correct two or even two More than one video stream (because there may be more than one incoming and local display video stream), so multiple simultaneous correction capabilities are required.

In this way, the locally displayed video stream is firstly corrected by the outgoing video stream Gamma correction module, and then the corrected output video stream is input to the incoming video stream Gamma correction module for a second correction and then output to the local video display device. At the same time, the video encoding and decrypting device outputs the decoded incoming video stream to the incoming video stream Gamma correction module for correction, and then outputs it to the local video display device for display.

This module has a Gamma value γ _Cor =2.2/γ _Disp . On the basis of obtaining γ _Disp , calculate γ _Cor , and then use hardware circuit or software to realize correction, among them: the method of using hardware circuit can realize the standard power function input and output characteristics, there are quite a lot of such methods, which belong to mature technology , which will not be repeated here. The software implementation includes the following:

Direct calculation method: generate standard power function input and output characteristics by program method, such as using function call or subroutine method;

Table look-up method: For enough points calculated on the value interval of the input brightness signal, the correction result is calculated according to γ _Cor and the standard power function, and saved as a look-up table. Then, when performing correction, for the input signal value to be corrected, the correction result is obtained by looking up the table. The more table entries, that is, the denser the sample collection, the more accurate the table lookup effect.

It should be noted that the significance of distinguishing between hardware and software methods here is that the hardware is completely realized by means of circuits and cannot contain any microprocessors and memories. Software includes the use of DSP and memory, because in this case, it is also the program software that works.

The structure and connection relationship of other modules are the same as those in Fig. 7, and will not be repeated here.

When it is necessary to judge first, as shown in Figure 9, the structure of each correction sub-module in Figure 7 and Figure 8 can further include: a judgment unit and a correction execution unit, the judgment unit is connected to the Gamma information storage module, for The Gamma parameter of the display device or the input device stored in the saving module judges whether correction is needed, if so, then the received video is input to the correction execution unit, and the correction execution unit performs correction according to the correction Gamma value given in Embodiment 1 before outputting , otherwise output directly.

The correction devices shown in FIG. 7 and FIG. 8 can be applied to any video communication terminal, and after assembly as shown in FIG. 6 , correction of the Gamma characteristic of the video stream can be realized.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (16)

1. A method for correcting gamma characteristics of a video stream by a video communication terminal, comprising the steps of:

A. when outputting the local video stream, correcting the gamma value of the local video stream into a first target gamma value and then outputting the first target gamma value;

B. when receiving an incoming video stream with a gamma value of the first target gamma value, judging whether the gamma value of the local video display equipment is a second target gamma value or not, wherein the product of the second target gamma value and the first target gamma value is 1 or the difference value of the second target gamma value and 1 is in a set range, if so, directly transmitting the incoming video stream to the local video display equipment, otherwise, correcting the gamma value of the incoming video stream to the reciprocal of the gamma value of the local display equipment and then transmitting the corrected incoming video stream to the local video display equipment.

2. The method of claim 1, further comprising the steps of:

C. and when the local video stream is displayed, correcting the gamma value of the local video stream into the reciprocal of the gamma value of the local video display equipment, and transmitting the corrected gamma value to the local video display equipment.

3. The method of claim 1, wherein step a further comprises:

firstly, judging whether the gamma value of the local video input equipment is a first target gamma value, if so, directly outputting the local video stream, otherwise, correcting and then outputting the local video stream.

4. The method of claim 2, wherein step C further comprises:

firstly, judging whether the product of the gamma values of the local video input equipment and the local video display equipment is 1 or the difference value between the product and 1 is in a set range, and if so, directly transmitting the local video stream to the local video display equipment; otherwise, the correction is carried out and then the transmission is carried out.

5. The method of claim 1 or 3, wherein when correcting the output local video stream, the first correction gamma value used to correct the local video stream in step A is the first target gamma value divided by the gamma value of the local video input device.

6. The method of claim 5, wherein, when correcting the incoming video stream, the second correction gamma value used to correct the incoming video stream in step B is the second target gamma value divided by the local video display device gamma value.

7. The method of claim 6, wherein when correcting the displayed local video stream, the step C comprises correcting the local video stream with the first correction gamma value, and then correcting the local video stream with the second correction gamma value before transmitting the corrected local video stream to the local video display device.

8. The method of claim 2 or 4, wherein when correcting the displayed local video stream, the third correction gamma value used to correct the local video stream in step C is the inverse of the product of the local video input device gamma value and the local video display device gamma value.

9. The method of claim 1 or 6, wherein the first target gamma value is 0.45; the second target gamma value is 2.2.

10. The method of claim 4, wherein the local video input device and/or video display device gamma value is determined from factory data of the device or from actual detection results.

11. A video gamma characteristic correction apparatus comprising:

the gamma information storage module is used for storing gamma parameter information of the video input equipment and/or the video display equipment;

the correction module is connected with the gamma parameter information storage module and is used for correcting the gamma value of the video stream according to the gamma parameter information and/or the target gamma parameter;

the gamma information setting module is connected with the gamma parameter information storage module and is used for storing the initial gamma parameter information of the external input video input equipment and/or the video display equipment into the gamma parameter information storage module;

and the control coordination module is used for controlling and coordinating the working state of each module.

12. The correction device of claim 11, wherein the correction module further comprises:

the outgoing video stream correction submodule is used for correcting and outputting a gamma value of an outgoing video stream acquired by the video input equipment;

the incoming video stream correction submodule is used for correcting the gamma value of the incoming video stream from the outside and outputting the gamma value to the video display equipment for local display; and

and the local display video stream correction submodule is used for correcting the gamma value of the local video stream and outputting the gamma value to the video display equipment to be displayed locally.

13. The correction device of claim 11, wherein the correction module further comprises:

the outgoing video stream correction submodule is used for correcting and outputting a gamma value of an outgoing video stream acquired by the video input equipment;

the incoming video stream correction submodule is used for correcting the gamma value of the incoming video stream from the outside and outputting the gamma value to the video display equipment for local display; or the video stream corrected by the outgoing video stream correction submodule is corrected again and then output to the video display equipment for local display.

14. The correction device of claim 12 or 13, wherein the syndrome module further comprises: the judgment unit judges whether the received video stream needs to be corrected or not according to the gamma parameter information of the video input equipment or the video display equipment, if so, the judgment unit inputs the correction execution unit to output the corrected video stream, and otherwise, the judgment unit directly outputs the corrected video stream.

15. The correction device of claim 11, further comprising:

and the gamma parameter measuring module is connected with the gamma parameter information storage module and is used for detecting the gamma parameters of the video input equipment and/or the video display equipment and storing the gamma parameters into the gamma parameter information storage module.

16. The calibration device of claim 11, wherein the gamma parameter measurement module further comprises: the video input device gamma parameter measuring submodule and the video display device gamma parameter measuring submodule.

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