[modfodder]

Current playback technologies only playback one frame rate. yes you can mix frame rates in an edit, but they will be converted to the master frame rate of the timeline (so that 24fps footage would be converted to playback at 48fps, not it's native frame rate). Sometimes this looks fine, other times this can cause image problems.

And it's only recently that mixing frame rates in the same timeline has worked well. 5-10 yrs ago, we would have to convert the footage, typically using hardware specifically built for conversion (Teranex or Alchemist). Then came along desktop software that could do decent jobs converting. Now, if i'm cutting in Premiere or FCPX, I can just drop the footage in and the software will take care of it, usually without issue (Avid still has problems with non-native frame rates and it's recommended to convert before importing the media).

And it's been this way since playback frame rates were standardized (and automated). Projectors had no way of changing playback speed on the fly depending on what frames were projected. Television was locked into one broadcast frame rate spec (29.97 in N. America, 25 in Europe) and TVs were locked into one of those specs. Tapes and disc playback was typically locked into one in the early days, although DVD eventually allowed for multiple playback options, as does Bluray, but the hardware typically converted them for playback on 29.97 screens (pre-HD). We're still limited to what the screen can playback to some extent, the broadcast specs of 23.976, 24, 25, 29.97, 30, 50, 59.94 and 60.

With computers and monitors we have the capability to playback multiple frame rates, if the software allows it, and that is where the current issue is. I can playback different frame rate QTs on the same screen, at the same time without issue. But there is no software (that I know of) to create or playback videos consisting of multiple frame rate videos. Game engines might be able to change playback on the fly, but I have zero knowledge of that tech.

And it would be advantageous to have tech that allowed switch on the fly playback. I'm currently consulting on a documentary that uses source footage from at least 3 frame rates (24, 25 and 29.97). And the editor is cutting in Avid, so we have to convert before import, which slows down the creative process and adds complications to the finishing process.