CN115103142A - Video switching matrix for improving quality of analog video signal - Google Patents

Abstract

The invention discloses a video switching matrix for improving the quality of analog video signals, which comprises: an analog cross-point switch for receiving RGB signals of the N-channel video signals; a video equalizer connected to the analog cross-point switch; the video delayer is connected with the video equalizer; the video acquisition device is connected with the video delayer; the first field programmable gate array is connected with the signal output end of the video collector; the output interface converter is connected with the first field programmable gate array; the second field programmable gate array is connected with the video collector; the first microprocessor is respectively connected with the first field programmable gate array and the second field programmable gate array; the second microprocessor is connected with the video collector; the data buffer is used for carrying out data interaction with the first field programmable gate array; the invention can effectively correct and compensate the time delay, interference and attenuation of the analog video signal in the video switching matrix, and improve the quality of the analog video signal in the video switching matrix.

Description

Video switching matrix for improving quality of analog video signal

Technical Field

The invention relates to the technical field of signal generator circuit design, in particular to a video switching matrix for improving the quality of an analog video signal.

Background

The video is a vivid, visual, convenient and rich-content human visual information acquisition method, and is distributed in the corners of our lives. The most common information carriers include television broadcasts, surveillance systems, video conferencing, laser projection displays, large screen tiled displays, etc. In the face of these information carriers, it is desirable to select, i.e. select and switch the video, according to interest and need. The video matrix is a device capable of meeting the requirements of video selection and switching, and the appearance of the video matrix is a great progress of video switching technology, so that video integrated switching is possible. The video matrix has the primary function of switching a video image from any input channel to any output channel so that the image can be displayed as required, and the input and the output have randomness. As a basic function of the matrix, the switching performance directly affects the quality of the image output by the display device, and also determines the grade of the matrix. The matrix is divided into three levels of civil level, professional level and broadcast level according to the grade. The civil-grade matrix allows flickering snow flakes and jitters at the switching moment, generally requires no more than one second, has stable pictures after completion, and can be applied to meeting rooms and multimedia classrooms. Professional level matrices, which allow for a slight black screen during switching, but do not flicker. The broadcast-level matrix is very strict, and switching occurs during the vertical blanking interval of the video signal, and no flicker or snow is generated during switching. With the development of microelectronics and communication technologies and the improvement of the quality of life of people, the requirements of people on visual effects have not only been satisfied with the former "visibility", but have gradually pursued high-quality enjoyment with high definition.

In the Video switching matrix, a Video Graphics Array (VGA) standard Video signal is commonly used as the analog Video signal. The VGA video signal includes red (R), green (G), blue (B) signals, and line sync (H) and field sync signals (V), etc. The RGB signals may cause a problem of signal quality degradation when transmitted by using a coaxial transmission line or a twisted pair transmission line, and particularly for high definition video signals, for example, high definition video signals with a resolution of 1920 × 108060 Hz. One is the nonlinear bandwidth limitation due to the "skin effect" of the transmission line, resulting in signal dispersion and loss of high frequency components of the signal. This reduces the sharpness of the image and produces a smearing phenomenon. On the other hand, low frequency signal attenuation due to cable impedance loss may reduce the contrast of the image. In a more serious case, the length of the transmission lines of the differential pair is different due to the inconsistency of the twist rate of the coaxial line or the twisted pair, so that the time delay of the received signals is inconsistent, and the color error of the image occurs. This causes problems such as reduced sharpness, smearing, ghosting, etc. of the analog video signal output by the video switching matrix.

Disclosure of Invention

In order to solve the above technical problems, it is an object of the present invention to provide an apparatus and method for effectively improving the quality of analog video signals in a video switching matrix, so as to improve the definition of output signals of the video switching matrix.

To achieve the above technical object, the present application provides a video switching matrix for improving quality of an analog video signal, comprising:

an analog cross-point switch for receiving RGB signals of the N paths of video signals;

the video equalizer is connected with the signal output end of the analog cross-point switch;

the video delayer is connected with the signal output end of the video equalizer;

the video acquisition device is connected with the signal output end of the video time delay device;

the first field programmable gate array is connected with the signal output end of the video collector;

the output interface converter is connected with the signal output end of the first field programmable gate array;

the second field programmable gate array is connected with the signal input end of the video collector and is used for transmitting the HV signals of the N paths of video signals to the video collector;

the first microprocessor is respectively connected with the first field programmable gate array and the second field programmable gate array and is used for acquiring RGB signals and/or HV signals according to the switching operation command;

the second microprocessor is connected with the video collector and is used for adjusting the collecting phase of the video collector,

and the data buffer performs data interaction with the first field programmable gate array and is used for storing the signal data output by the video collector.

Preferably, the video switching matrix further comprises a video output host connected to the signal input terminal of the analog cross-point switch for outputting N video signals.

Preferably, the video equalizer is configured to perform high frequency peak, output low pass filter cut-off frequency, and wide band flat gain adjustment on the R signal, G signal, and B signal of the RGB signals output from the analog cross-point switch, respectively, for compensating for attenuation and distortion of the RGB signals during transmission.

Preferably, the video delay is configured to perform phase delay on the compensated RGB signals, and compensate for phase differences of the R signal, the G signal, and the B signal caused by different transmission lengths during transmission.

Preferably, the second field programmable gate array is connected to a signal output terminal of the video output host for receiving an HV signal of the N-channel video signal, wherein the HV signal is indicative of the line sync and the field sync signals.

Preferably, the video collector is configured to generate an acquisition clock by performing frequency multiplication on the HV signal as a clock source, and then collect the RGB signals after the phase compensation according to the acquisition clock to generate RGB digital parallel signals.

Preferably, the first microprocessor is further configured to traverse adjustment steps of the video equalizer, compensation steps of the video delay, and acquisition phase parameters of the second microprocessor for traversing the video acquisition unit to obtain a total number of steps;

the programmable gate array is further used for generating the definition of the image through a definition evaluation function of the image based on the total step number, wherein the definition evaluation function comprises a first evaluation function based on frequency domain features, a second evaluation function based on statistical features and a third evaluation function based on space domain features.

Preferably, the second evaluation function includes a gray scale entropy function, wherein the expression of the gray scale entropy function is:

wherein A is the total number of gray levels of the image, p _i Is the probability of the occurrence of a pixel with a gray value i in the image.

The invention discloses the following technical effects:

the invention can effectively correct and compensate the time delay, interference and attenuation of the analog video signal in the video switching matrix, can improve the quality of the analog video signal in the video switching matrix, and has the advantages of intellectualization, high image definition, high reliability and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a block diagram of a video switch matrix according to the present invention; wherein 1 is an analog cross-point switch; 2 is a video equalizer, 21 is a 1 st path video equalizer, 22 is a 2 nd path video equalizer, and 2M is an M th path video equalizer; 3 is a video delayer, 31 is a video delayer of the 1 st path, 32 is a video delayer of the 2 nd path, and 3M is a video delayer of the M path; 4 is a video collector, 41 is a video collector of the 1 st path, 42 is a video collector of the 2 nd path, and 4M is a video collector of the M path; 5 is a first field programmable gate array; 6 is an output interface converter, 61 is an output interface converter of the 1 st path, 62 is an output interface converter of the 2 nd path, and 6M is an output interface converter of the M-th path; 7 is a second field programmable gate array; 8 is a first microprocessor; 9 is a second microprocessor; and 10 is a data buffer.

Fig. 2 is a data processing flow chart of the video switching matrix auto-calibration procedure according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present application without making any creative effort, shall fall within the protection scope of the present application.

As shown in fig. 1-2, the apparatus for improving quality of analog video signals in a video switching matrix for improving quality of analog video signals according to the present invention includes an analog cross point switch 1, a video equalizer 2, a video delay 3, a video collector 4, a first Field Programmable Gate Array (FPGA)5 and a second Field Programmable Gate Array (FPGA)7, a first Microprocessor (MCU)8 and a second Microprocessor (MCU)9, a data buffer 10, and an output interface converter 6. N-channel video signal output by user host

L,

The signals of RGB three channels are transmitted to the analog cross point switch 1 through the video transmission line, and the first microprocessor 8 receives the switching operation command of the user and controls the analog cross pointA switch 1 and a second field programmable gate array 7 for converting RGB signals in the analog video signal

L,

Switching to M video outputs

L,

M is less than or equal to N, and simultaneously line synchronization signals and field synchronization signals in the N paths of input video signals are transmitted through the second field programmable gate array 7

L,

Switching to M-way line-synchronous and field-synchronous outputs

L,

After switching, RGB signal

L,

The RGB signals are respectively processed in the video equalizer 2 through the video equalizer 2 and the video delayer 3 in sequence

High-frequency peak value is carried out on R signals, G signals and B signals of three channels of 1,2, L and M

Cut-off frequency of output low-pass filter

And broadband flat gain

Adjusting to compensate the attenuation and distortion of the RGB signals in the transmission process; separately for RGB signals in a video delay 3

Phase of R, G and B signals of three channels of 1,2, L and M

And

delaying to compensate the phase difference of the R signal, the G signal and the B signal caused by different transmission lengths in the transmission process; then, the RGB signals and the line synchronization and field synchronization signals are inputted to the video grabber 4, respectively, and the video grabber 4 inputs the line synchronization and field signals with the inputted line synchronization and field signals

i-1, 2, L, M is used as clock source to carry out frequency multiplication to generate collecting clock, and respectively collect three channel signals of RGB, and at the same time, the second microprocessor 9 controls and adjusts the collecting phase phi of the video collector 4 _s (ii) a After passing through the video collector 4, the RGB signals are converted from analog signals into digital parallel signals

L,

Buffering to the data buffer 10 via the first field programmable gate array 5; finally, under the control of the first FPGA 5, the RGB signal data in the data buffer 10 is output via the output interface converter 6 to Video _OUT1 ,Video _OUT2 ,L,Video _OUTM 。

An auto-calibration procedure is run in the video switching matrix. After a user deploys the video output host, the video switching matrix and the video output display device, an automatic correction program of the video switching matrix can be started, the user host outputs a test image to the video switching matrix, and the test image can be respectively adjusted under a controller of a microprocessor 8 in the video switching matrix: (1) the high-frequency peak value, the cut-off frequency and the broadband flat gain of an output low-pass filter of three channels of RGB signals in the video equalizer; (2) the signal phase of the RGB three channels in the video delayer is delayed. The second microprocessor 9 adjusts the acquisition phase of the video acquirer. The first microprocessor 8 calculates the value of the definition evaluation function of the image acquired by the video switching matrix when the user host outputs the test image under the current parameter setting in the programmable gate array by adjusting the acquisition phase parameters of the video equalizer, the video delayer and the second microprocessor 9 video acquirer each time. When the first microprocessor 8 finishes traversing the video equalizer, the video delayer and the second microprocessor 9 finishes traversing the acquisition phase parameters of the video acquisition device, the numerical values of the definition evaluation functions of a group of images can be obtained. And selecting the acquisition phase parameters of the group of video equalizer, video delayer and video collector with the maximum value of the image definition evaluation function as the optimal setting parameters. The specific implementation operation is as follows: for the case that the nth video signal of the user host is switched to the mth video signal for outputting, N is more than or equal to 1 and less than or equal to N, M is more than or equal to 1 and less than or equal to M, considering the case of R signal in RGB signal, as shown in FIG. 2, recording the high frequency peak value

The number of the adjusting steps is P, and the cut-off frequency of the output low-pass filter

The adjustment step number is Q, and the broadband flat gain

Adjusting step number to be U, phase delay in video delayer

Adjusting the step number to be V, and the acquisition phase of the video acquisition device

When the adjustment step number is W, the total step number required when the first microprocessor 8 finishes traversing the video equalizer, the video delay unit, and the second microprocessor 9 finishes traversing the acquisition phase parameters of the video acquisition unit is L × P × Q × U × V × W, and for each step k of adjusting the above parameters, k is 1,2, L, the programmable gate array all calculates the value D of the sharpness evaluation function of the image _Rk . Through traversal search, the acquisition phase parameters of the video equalizer, the video delayer and the video acquisition device of the group which enable the value of the definition evaluation function of the image to be maximum can be obtained

That is to say that the first and second electrodes,

the optimal parameters of the G signal and the B signal in the RGB signals for maximizing the value of the sharpness evaluation function of the image can be obtained in the same way,

because the video delayer is used for delaying the RGB signals in the video transmission process, the acquisition phase parameters of the RGB signal video acquisition device

And

should be consistent or close.

By using the same method, the optimal parameter which can switch the N paths of videos output by the user host to the M paths of videos to output and enables the value of the image definition evaluation function to be maximum can be obtained. When a user executes a video switching command, the corresponding setting parameters are used to set a video equalizer, a video delayer and a video collector, for example, the nth video signal of a user host is switched to the mth video output, N is more than or equal to 1 and less than or equal to N, M is more than or equal to 1 and less than or equal to M, and the first microprocessor 8 and the second microprocessor 9 respectively switch the nth video signal to the mth video output

And

and setting parameters are respectively written into the video equalizer, the video delayer and the video collector which respectively correspond to the RGB signals. This ensures that the video switching matrix has the best video quality when switching analog video signals.

In calculating the sharpness evaluation function of the image, evaluation functions that can be used include an evaluation function based on frequency domain features, an evaluation function based on statistical features, and an evaluation function based on spatial domain features. Taking an evaluation function based on statistical characteristics as an example, a commonly used function is a gray scale entropy function. The entropy value of the image is an important index for measuring the richness of the image information, and according to the Shannon information theory, the information quantity is the largest when the entropy is the largest, and the image is the clearest. As can be seen from the information theory, H is,

wherein A is the total number of gray levels of the image, p _i Is the probability of the occurrence of a pixel with a gray value i in the image.

The invention uses the technical route of independently switching the RGB signals in the analog video signals, the line synchronizing signals and the field synchronizing signals respectively in the video switching matrix, and carries out independent correction and compensation on three signal channels in the RGB signals in the analog video signals by respectively carrying out high-frequency peak value adjustment, cut-off frequency adjustment of an output low-pass filter, broadband flat gain adjustment, signal phase delay, acquisition phase adjustment of a video acquisition device and other technical methods on the RGB signals in the analog video signals based on the problems that the video signals can generate definition reduction, tailing, ghosting and the like caused by the inevitable delay, interference and attenuation of the analog video signals in different degrees in the transmission process (including transmission lines, connectors, transmission lines on circuit boards, transmission in components and the like). After the video output host, the video switching matrix and the video output display equipment are deployed by a user, the automatic correction program of the video switching matrix is started, so that the video signal channel output by each user can be corrected and compensated respectively, and the quality of an analog video signal in the video switching matrix is improved.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

In the description of the present invention, it is to be understood that the terms "first", "second" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (8)

1. A video switching matrix for improving the quality of an analog video signal, comprising:

an analog cross-point switch (1) for receiving RGB signals of N video signals;

a video equalizer (2) connected to a signal output terminal of the analog cross-point switch (1);

the video delayer (3) is connected with the signal output end of the video equalizer (2);

the video collector (4) is connected with the signal output end of the video delayer (3);

the first field programmable gate array (5) is connected with the signal output end of the video collector (4);

the output interface converter (6) is connected with the signal output end of the first field programmable gate array (5);

the second field programmable gate array (7) is connected with the signal input end of the video collector (4) and is used for transmitting HV signals of the N paths of video signals to the video collector (4);

the first microprocessor (8) is respectively connected with the first field programmable gate array (5) and the second field programmable gate array (7) and is used for acquiring the RGB signals and/or the HV signals according to a switching operation command;

the second microprocessor (9) is connected with the video collector (4) and is used for adjusting the collection phase of the video collector (4),

and the data buffer (10) is in data interaction with the first field programmable gate array (5) and is used for storing the signal data output by the video collector (4).

2. A video switching matrix for improving the quality of an analog video signal as defined in claim 1, wherein:

the video switching matrix further comprises a video output host connected with the signal input end of the analog cross point switch (1) and used for outputting N paths of video signals.

3. A video switching matrix for improving the quality of an analog video signal as defined in claim 2, wherein:

the video equalizer (2) is used for respectively carrying out high-frequency peak value, cut-off frequency of an output low-pass filter and broadband flat gain adjustment on the R signal, the G signal and the B signal of the RGB signals output by the analog cross-point switch (1) and compensating attenuation and distortion of the RGB signals in the transmission process.

4. A video switching matrix for improving the quality of an analog video signal as defined in claim 3, wherein:

the video delayer (3) is used for carrying out phase delay on the compensated RGB signals and compensating phase difference caused by different transmission lengths of the R signal, the G signal and the B signal in the transmission process.

5. A video switching matrix for improving the quality of an analog video signal as defined in claim 4, wherein:

the second field programmable gate array (7) is connected with a signal output end of the video output host and is used for receiving the HV signal of the N paths of video signals, wherein the HV signal is used for representing line synchronization and field synchronization signals.

6. A video switching matrix for improving the quality of an analog video signal as defined in claim 5, wherein:

and the video collector (4) is used for carrying out frequency multiplication by taking the HV signal as a clock source to generate a collection clock, and then collecting the RGB signals after phase compensation according to the collection clock to generate RGB digital parallel signals.

7. A video switching matrix for improving the quality of an analog video signal as defined in claim 6, wherein:

the first microprocessor (8) is also used for traversing the adjustment steps of the video equalizer, the compensation steps of the video delayer and the acquisition phase parameters of the second microprocessor (9) for traversing the video acquisition device to obtain the total steps;

the programmable gate array is further used for generating the definition of the image through a definition evaluation function of the image based on the total steps, wherein the definition evaluation function comprises a first evaluation function based on frequency domain features, a second evaluation function based on statistical features and a third evaluation function based on space domain features.

8. A video switching matrix for improving the quality of an analog video signal as claimed in claim 7, wherein:

the second evaluation function comprises a gray level entropy function, wherein the expression of the gray level entropy function is as follows:

wherein A is the total number of gray levels of the image, p _i Is the probability of the occurrence of a pixel with a gray value i in the image.

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