Is the amount of information that is now on the web. What you noted is OK, well done but google this too "VideoWall" as well as "Videowall using a PC."
Plenty of content on this subject.
I am trying to make a video wall with TVs arranged in 2x2 or 3x3 fashion. For the input to the TVs, I want to use a graphic card with multiple output ports. This card will be installed in a computer's PCIe/PCI slot. Along with that, to give the input to the video wall from any external system for which I thought of installing another graphic card with an HDMI/DP input port. Both graphic card will be connected to each other via Crossfire/SLI. In this arrangement, it will be transferring the display from the HDMI/DP input port to the 4 port output and then to the video wall.
The whole point of this arrangement is to get the screen of an external computer mirrored to the video wall. I know this sounds quite long shot but if it can be done, it will be really helpful. Please share your inputs.

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