I've started looking into building an HDMI lag tester similar to this:

My initial plan was to build it out of a beaglebone black, using svgalib and a reasonably fast photodiode. Before I go too far down that path, I was curious if anyone had tinkered with driving HDMI from a teensy. Don't need much complexity; e.g. I dont need a 1920x1080 framebuffer [which wouldn't fit in teensy memory anyway], just the ability to draw black or white over portions of the display and know (within ~5ms) when the display was synced to whatever had been drawn.

Any thoughts?