I have a few ideas about syncing audio to video for my 50D. Please tell me if it is possible to EITHER:
Fire the flash at intervals during video recording
OR
Record the Shutter Release status with every frame during video recording. Data could go in exif/separate file/audio track.
I know ML doesn't offer this now, but are the capabilities there in the API? I have some coding experience.
The first one needs reverse engineering (figuring out how Canon does it; most likely by talking to the MPU, or by triggering some property).
The second one... 50D is the only camera that, to my knowledge, crashes if you take a picture while recording (also with Canon firmware). If you find out why, the rest is easy. Sure, the method is a bit clunky; the flash one sounds more interesting to me, but definitely harder to figure out.