high-rez NTSC out on Teensy 3.1

[quarterturn]

Now that we have 64 KB RAM with the teesy 3.1, has anyone considered doing a high-rez tvout library? 640 x 240 is doable where overscan is limited and provides an 8x10 character cell, enough for lowercase with descenders. This requires 19200 bytes at 1 bbp.

I've found something close for the atmega1284:
https://sites.google.com/site/guenterbartsch/home/atmega1284p-composite-video

I'm guessing conceptually it's the same but setting up the timers and interrupts will be different.