Audio/Video sync; calc for qt playback rate, and sync to either beat or bar.

Hi, trying to figure out the calcs for an audio-video sync patch based on the global transport and total frames. I've included some details in the patch, but here's what I wrote:

"My goal in this patch:
Take a normal QT video input, probably a short clip but theoretically something larger. From this, have it replay with its start and end times synced to either a bar, a beat if too small, or multiple bars if overly large, BUT I want it to be as close to its actual FPS/playback rate as possible."

Anyway, here's my muddling sofar, but not quite sure of the next step... If anyone can advise, I'd appreciate it.