How does Premiere handle off frame rates? at DVinfo.net

Adrian Tan · May 1st, 2015, 01:53 PM

So, this mystifies me. I've done a few tests, but I'm still not sure what's going on and was wondering if someone actually knew. I'm having trouble finding info online.

Say I create a 25fps timeline. I drop 25fps clips on it, all well and good.

Now I drop a 24fps or 30fps clip on it. Somehow, Premiere automatically processes the clip to maintain duration. So, if the 24fps clip is exactly 1 second long, it'll still be exactly 1 second long in the 25fps timeline. Ditto with the 30fps clip.

So what exactly is it doing? Anyone know?

It seems to me what it could be doing is: speed change, interpolating frames, dropping frames, doubling frames, or some mix of the above. With the 24fps clip I tested, just clicking forward frame by frame, it seemed the first frame of each second got doubled. With a 10fps clip, it looked like some frames got doubled and some got tripled, but perhaps this was a speed change. With a 30fps clip, I'm assuming interpolation is involved on every third pair of frames or something like that, rather than speed change or dropped frames.

Gary Huff · May 1st, 2015, 10:04 PM

Yes, it duplicates (or subtracts) frames to maintain duration within different timebases.

May 1st, 2015, 01:53 PM	#1
Adrian Tan Trustee Join Date: Oct 2012 Location: Sydney, Australia Posts: 1,149	How does Premiere handle off frame rates? So, this mystifies me. I've done a few tests, but I'm still not sure what's going on and was wondering if someone actually knew. I'm having trouble finding info online. Say I create a 25fps timeline. I drop 25fps clips on it, all well and good. Now I drop a 24fps or 30fps clip on it. Somehow, Premiere automatically processes the clip to maintain duration. So, if the 24fps clip is exactly 1 second long, it'll still be exactly 1 second long in the 25fps timeline. Ditto with the 30fps clip. So what exactly is it doing? Anyone know? It seems to me what it could be doing is: speed change, interpolating frames, dropping frames, doubling frames, or some mix of the above. With the 24fps clip I tested, just clicking forward frame by frame, it seemed the first frame of each second got doubled. With a 10fps clip, it looked like some frames got doubled and some got tripled, but perhaps this was a speed change. With a 30fps clip, I'm assuming interpolation is involved on every third pair of frames or something like that, rather than speed change or dropped frames.

May 1st, 2015, 10:04 PM	#2
Gary Huff Inner Circle Join Date: Jan 2013 Location: Austin, Texas Posts: 2,006	Re: How does Premiere handle off frame rates? Yes, it duplicates (or subtracts) frames to maintain duration within different timebases.