Multiple frame rates 23.976, 29.97 and 25

Edited a project in 23.976, all the footage was shot at that frame rate. Now we are talking about purchasing some stock footage to use in that project as well.

The stock footage has different frame rates (most clips are either 29.97 and 25 FPS).

I'm assuming I'll need to convert these clips to 23.976 using Compressor or another program.
Will the clips look ok or will the motion look weird due to the conversion?

Any help/workflow tips for a smooth conversion would be greatly appreciated.

Thanks

The pal stuff you have will have a slight difference but it will mostly come from the frame rate and will not be all that noticeable.

As a general loose rule, when you have mixed frame rates you should tally up the frame rates to see which fps has the greatest number of clips or hours and then convert every thing else to that codec or frame rate.

""" What you do with what you have, is more important than what you could do, with what you don't have."

> > > Knowledge + Action = Wisdom - J. Corbett 1992 """"

Hey J,

Yes, the 23.976 stuff is 98% of the project.

What is the best method to convert the other frame rates?

29.97p or 59.94i or some of each? 25p or 50i or some of each?

Dennis Couzin
Berlin, Germany

It's actually 30p and 25p.

Try Compressor.

The sensible way to transform 25p to 23.976p is to use Compressor's "make source frames play at 23.98 fps". This leaves the original frames all intact, like a conform does. The video becomes about 4% longer so the action is about 4% slower which few people can notice. Unlike a conform, Compressor up-pitches the sound by about 4% before stretching it to the elongated video. So there is no pitch change (which most people would notice) from the original.

You can transform 30p to 23.976p using "Rate Conversion: Fast (Nearest frame)". This essentially drops one frame in every group of five. This can make unpleasant hiccups in some motions. I believe that the hiccup can be mitigated by a tad of randomization (in the choice of which frame to drop) but I haven't seen software that does this.

Another way to transform 30p to 23.976p is by Optical Flow. It essentially keeps the 1st, 5th, 10th, etc. frames intact and constructs two new frames to replace the three original frames between each of these. Compressor's Optical Flow is accessed as "Rate Conversion: Best (High quality motion compensated)". It sometimes does it nicely, and sometimes doesn't. All the Optical Flow software can run into trouble and produce absurdities from natural footage. Andreas Kiel, writing in this forum, has found no Optical Flow software better than Twixtor.

30p to 23.976p is tough. If your 30 fps material had been 60i you could have double deinterlaced and then applied Nearest Frame with better results.

Dennis Couzin
Berlin, Germany

Is there some step by step guide or tutorial on the best and simplest method? I checked out one by Larry Jordan and he doesn't even mention selecting "make source frames play at 23.98 fps".

So when using Compressor do I need to adjust the framerate in the video settings to 23.98 as well or just click "make source frames play at 23.98 fps" ?

I'm hoping to find the definitive method, if it's using compressor so be it but here is what I did:

For 25 and 29.97, I converted to Pro Res using mpeg streamclip, then conformed to 23.98 in Cinema tools. For most of the clips this delivered great results and was much quicker than using Compressor. However, this doesn't seem to be the preffered method?

One of the clips, ended up jerky, so for that one, I used compressor, changed video settings to 23.98 and selected "make source frames play at 23.98 fps". That delivered a satisfying result.

Lastly, I have one clip that was 59.96, neither of the above methods delivered a good result, it still appeared to be interlaced (showing lines when paused), even though I selected "Better" under the deinterlace option in compressor.

I haven't tried the double deinterlacing method on it and I'm hoping I don't have to. What actually gave me the best result so far with the 59.96 clip, was converting it in Adobe Media Encoder to 23.98 (No lines when paused).

Quote
Joe Riggs
So when using Compressor do I need to adjust the framerate in the video settings to 23.98 as well or just click "make source frames play at 23.98 fps" ?

The former. If you don't, you won't be given the option "make source frames play at 23.98 fps".

Quote
Joe Riggs
Lastly, I have one clip that was 59.96, neither of the above methods delivered a good result, it still appeared to be interlaced (showing lines when paused), even though I selected "Better" under the deinterlace option in compressor.

In round numbers, 30p to 24p is a rough conversion, 60p to 24p a smoother conversion. So starting with 60i and wishing 24p, deinterlacing to 30p is a worse first step than double deinterlacing to 60p. That said, when you ask Compressor to do the whole job, it will first deinterlace the 59.94i to 29.97p, and then convert the 29.97p to 23.976p, each according to your choices in Frame Controls. How could it screw this up? Are there rescalings involved that you haven't mentioned?

In general, when a user understands the logical order of steps of a complex job, but is unsure Compressor does, the user can break the job down step-by-step. Compressor can output just the first step. That output can be fed back into Compressor for the second step. Etc. (Since this involves re-compressions, it should be done uncompressed or through a nearly lossless codec like ProRes HQ.) Recognizing that the user might need to control the order of steps, Compressor even provided a convenient way to do this: see "About Chaining Jobs" in the User Manual.

Dennis Couzin
Berlin, Germany

An interesting topic came up recently between a friend of mine.

He's working on a 23.98p project, but they will be shooting some it with a camcorder for a different look. That camera only shoots 30p (or it could be 60i). There will also be dialogue during these moments, so audio speed needs to be preserved.

Now, someone suggested the sound mixer record dialogue for those scenes at 30fps.
Is this a good or bad idea? Because when going from 30 to 24, the audio will be slowed down. Wouldn't it best to record audio at 23.98, then match the it using this method [philipbloom.net]?

Joe,
It makes no difference whether the sound is recorded onto a 30 fps video or a 24 fps video, since sound recording is time-based, not frame-based.

Are you confusing rate change with conforming? When 30 fps material is rate changed to 24 fps, the duration is unchanged and the sound is also unchanged. But when a 30 fps file is conformed to 24 fps, the duration is increased by 25% for both picture and sound. Conforming is just a header change; it does not create new sound samples. So the 48 KHz sampling becomes 38.4 KHz, and pitches are reduced accordingly. The pitch change can be avoided by using Compressor's "make source frames play at ..." instead of conforming.

Dennis Couzin
Berlin, Germany

[Note added 22 Sept: Frame rate change can introduce a tiny duration change due to rounding. For 30-to-24 this is at most 1/60 second.]