Really now, just think about this for a moment. The 3DS has been out for over a decade now and people have been clamoring for a video capture solution the whole time. Do you really think if it was as simple as waving a magic wand and using the IR port that someone, somewhere wouldn't have done that already?
I very much doubt the IR port has anywhere near sufficient bandwidth for video output considering it is only just barely possible to do it over wifi.