Speeding up video while maintaining frame rate in Premiere

[Ed Glaser]

Got a puzzler for you:

In a 30fps sequence, using Adobe Premiere CS5, can you speed up a 24fps video clip and *maintain* the 24fps frame rate of the clip?

It sounds goofy, I know ("why not just use a 24fps sequence?"), but I'm mixing it with 24fps video that's been converted to 30fps beyond my control. Using a 24fps sequence would make that video extra choppy. So I'm trying to effectively keep the overall appearance of 24fps throughout a 30fps sequence.

For reference, when speeding up 24p video in a 30p sequence, by default Premiere makes use of all 30 frames, resulting in video that's too smooth for what I'm looking for.

Any help would be enormously appreciated. I'm looking for something more elegant than, say, creating separate 24p sequences for each clip I want to speed up.

[John Wiley]

Ed, the question does not make sense. If you speed up a 24p clip, it will no longer play at 24fps.

If you drop 24p footage onto a 30p timeline, it will no longer play back at 24p either. It will be 30p with some of the frames either duplicated or blended.

If you speed up a 24p clip on a 30p timeline so that there are no blended or duplicated frames, the video will play back 25% faster, but the motion will be smooth.

You can choose to do one of two things: maintain speed (so one second of 24p video fills up one second on a 30p timeline, by duplicating and blending frames), or maintain motion (each frame is displayed once only and in the correct order, but at a different speed to what it was recorded as). You can't have the best of both world, unfortunately.

Depending on your final output, you might be able to put everything on a 60i timeline and add a pulldown to the 24p material - this breaks the 24p clip up into fields and alternates plays in a particular sequence to maintain both motion and speed. This is the method used to broadcast films over NTSC systems, but is not very useful if your final output has to be progressive (eg for web use).

[Ed Glaser]

Thanks for the response, John!

Apologies, I could have been more specific. You're right, while 24p video in a 30p timeline technically becomes 30p (as you say, with duplicated or blended frames), it still "feels" like 24p, which is what I'm looking for.

The reason I'd like to speed up particular clips is for a fast-motion effect rather than any kind of frame-rate correction. But I'd still like to maintain the 24p "feel", e.g. with duplicated frames. The idea is to imitate undercranked film played back at 24p. As it stands, when speeding up a 24p clip in a 30p sequence, Premiere makes use of all 30fps, which in most situations makes total sense, but sadly isn't what I want.

So far the only method I can think of, to do what I'm looking for, is to break off each sped-up clip into its own 24p sequence, then bring that [24p] sequence back into the 30p sequence. I was just hoping there was a more elegant solution.

This is what happens when you want to do something crazy. :-D