DVI matrix switcher and engineering application (LCD lifter)

Source:YDIT 誉德 Release time:2019/4/17 9:32:33 Views:928

 

There are two major problems in the engineering application of DVI signals, because both the signal source and the display device already have a DVI interface, so transmission and switching become the main problem. (Paperless conference system) Now we mainly discuss the matrix switching problem of DVI. .
The DVI signal is a four-way digital signal with a maximum code stream of 1.65G (1600×1200×60 hours), and there are many problems different from the analog matrix when performing matrix switching. (Paperless conference system) If it is a general DVI switch, it can be completed by using DVI's solution/encoding chip (even with relay method, it is not desirable in actual use, because there is no drive capability, the transmission distance is too short. ). For example, decoding a DVI signal into parallel data, since the code stream is low at this time (maximum 165 MHz), it can be switched using a general-purpose digital circuit and then encoded. (Paperless conference system) However, due to the problem of the wiring structure, the switch can be formed in this way. In the range of 2, 1 and 4, it is difficult to complete when it is large, so it is used. The dedicated high-speed chip completes the matrix switching, and the (liquid crystal panel lifter) can form an 8- to 8-DVI matrix switch if the existing 3.3G switching chip is available.
In contrast, the switching chip itself is not the main problem of the matrix switcher. The main problem (liquid crystal panel lifter) lies in the technical process between them. The most typical problems are the driving capability and the routing process.
The normal transmission distance of the DVI signal is about 7 meters. As the input/output port of the matrix switcher, because it is not known how far the signal is "walking", how much drive power is left, and the switch itself has to have Connector and internal routing (the loss of the driver's drive capability is much larger than we expected), it is impossible to venture in the project (the LCD flipper) to use only the original signal drive capability, so the Repeater will be performed on the input port first. , complete the "isolation" of the switch and the distance, forming a "standard length". (LCD flip-flop) Similarly, the output port does not dare to do the drive processing, otherwise the output line may (possibly) not reach the "one standard length" (the experimental result is up to half), so the matrix The external conditions are too high and cannot be applied in the project. This "isolation" approach is equivalent to adding 16 sets of Repeater, which has a large increase in cost and brings many technical problems in the internal connection and routing. The complete isolation of the input and output ports also has the advantage of being flexible. In actual engineering, if you can consider the distance of the trace and the signal interface in advance, you can use the input and output interface board replacement methods to complete multiple function combinations. For example, the input interface board can be a simple Repeater; it can also be a fiber optic receiver to obtain DVI signals directly from the fiber; it can also be a cable equalizer to complete long-line reception; or it can be a VGA to DVI converter. A small number of VGA signals are converted to DVI signals to form an all-digital system. The interface board for digitally converting Video and Audio signals is also considered, and the functions of the multimedia digital matrix to be described below are completed. The output port is also the same, the simple Repeater completes the "one standard length" output; the fiber optic transmitter converts the DVI signal directly into an optical signal into the fiber optic transmission system; it can also convert the DVI to a VGA signal for some special applications; It can output analog or digital Video and Audio signals. The combined application is very flexible.
Currently used is a 34×34, 3.3G code stream digital switching chip, according to DVI signal 4 groups for one way calculation, can form 8 × 8 DVI matrix (actually input and output each surplus 2 channels), if DVI There are not so many signals, for example, only 5×4 DVI signals, then the input and output ports only occupy 20×16, and there is a surplus of 14×18, (electronic table cards) and these surplus channels can be completely composed, such as 8×8. Or 8 x 16 digital video, matrix of digital audio. Because the chip cares about digital streams that do not exceed 3.3G streams, there is no DVI or video or audio signal. With the development of digital applications, digital video (SDI, D1, MPEG2, MPEG4, etc.) and digital audio have many applications. After the completion and application of HDMI (1.95G) or HDCP standard in the future, this DVI matrix is ​​equipped with HDMI. The interface board is fully applicable to matrix switching with HDMI, because in fact, the matrix is ​​a high-speed digital matrix. (Electronic Table) At present, this DVI matrix can be combined with various input and output interface boards to form a multimedia digital matrix. With a flexible control interface, this matrix will be field programmable (onsite). The multi-functional media matrix that determines the number of DVI, digital video, and digital audio in/out) is self-evident.
(Micker lifter) The distance between the conference room and the machine room is about 120-200 meters. Considering the poor electromagnetic environment, the image quality must be guaranteed (maximum resolution 1280×1024). Therefore, the trunk transmission can use the optical fiber transmission system. Guarantee image quality and solve electromagnetic environment problems.
In each conference room, considering that the computer is about 20 meters away from the projector, the cable equalizer is used to ensure the transmission distance at one end (rear end) of the projector, and a DVI 2-to-1 and 1-minute 2-synthesized switcher is specially modified. Complete the switching of the local signal and the return signal, and ensure that the signal goes up. (Microphone lifter) Other local signals such as VGA signal such as notebook, (ultra-thin one lifter) use the projector's VGA channel to directly display, do not take the digital system, because the distance is short, the quality can be guaranteed, and the cost is low.
In the main control room, the optical receiver is used to demodulate the uplink signal into a DVI signal and access the matrix. The matrix output downlink DVI signal is directly downlinked through the optical fiber transmission system, and some of the signals need to be reserved, and the DVI signal can be directly sent to the media. In the memory. The video in this system uses the analog mode and does not enter the digital system.
(Ultra-thin integrated lifter) The current digital application scheme is more costly than the analog solution, mainly in matrix switching (currently, the price of dedicated chips is too high, and can only wait for its price reduction, and the cost of the interface board is also high) However, the benefit is that the quality of all projectors is the same as that of notebooks, which fully utilizes the quality of the projector and successfully solves the problems of long-distance transmission and electromagnetic environment, and has its own characteristics in terms of cost performance. Therefore, when considering the engineering scheme, the (ultra-thin integrated lifter) can consider two sets of digital and analog schemes. Party A requires high quality or other special circumstances, such as long distance or poor electromagnetic environment, and the funding is not too tight. Digital solutions can be recommended (digital, fiber-optic transmission solutions should be impeccable in terms of technology leadership, and image quality is really beautiful).
(Paperless office system) Now the projector's indicators are getting higher and higher, but in fact the quality of the signal source reaching the projector is difficult to guarantee, (paperless office system) caused high-end display equipment waste, to 1280 × 1024 × 60, for example, the pixel clock is 108MHZ. According to the Nyquist sampling principle, the analog bandwidth is about 150MHZ. If the cable is transmitted 100m, even if it is equipped with a good long-line driver, the bandwidth limit can be guaranteed at around 150MHZ. The signal bandwidth of the device side will not exceed 100MHZ (unbelievable to measure), which is a great waste for high-end display devices