I use my iPhone to create small music videos. Depending on the lighting the iPhone automatically records in 720p with 24 or 30 fps. So when putting together 8 clips where some have 24 fps or others 30 fps, what is the best way to handle this project to avoid any sync issues or other problems?

Should I create a 24 fps project and use the clips as is?
Should I create a 30 fps project and use the clips as is?
Should I convert the 24 fps clips to 30 fps and use for the project?
Or should I convert the 30 fps clips to 24 fps and use for the project?

Also, is the an absolute way to check the exact fps of the clips? For example when I check the info on a clip in Ubuntu Studio it says 30 fps, but if I check the same file in my MacBook it says 29.97 fps. Now, does it matter much? If so, how can I be sure what fps the file actually has?

My understanding is that MLT, the media framework kdenlive uses adjust frame rates of your source files to project frame rate. I thought iphone was variable frame rate anyway? Maybe I'm wrong there.

Mediainfo or ffplay or ffprobe should give you the info you need.

Yes, I have also read that iPhone uses variable frame rate, but so far what I have seen on my own recordings and from other comments on the net it only use the two choices, 24 (or 23.99) in bad lighting and 30 (or 29.97) in good lighting. Sadly, you can't lock the frame rate, then again it's not a professional video camera. :P

I tried the commands you suggested and interesting results:
ffplay: 23.99 fps
ffprobe: 23.99 fps

Seems I don't have mediainfo installed, I'm running Ubuntu Studio 12.10.

As for the project, I also read that different frame rates gets compensated with cutting frames or duplicating frames depending on the clip fps and the project. So I wonder what is the best thing there, to have my 30 fps clips adjusted to 24 fps? Or let my 24 fps clips adjust to 30 fps?

Doesn't Filmic Pro allow fixing of framerate? Its a great App.

I'd go for a 23.976 project personally with these files, even though if it drops frame rate in lower light your best source files will be the 30p ones I guess, so perhaps decide if the low light files are worth using and choose frame rate accordingly.

But try FilmicPro for any new recording it also allows locking white balance and exposure.

Mediainfo I get from a PPA.

Thanks for all your help!

I didn't follow the thought of "using 23.976 even though it drops frame rate in lower light". It would be the other way around? It would drop frames from the 29.97 clips?

I will need to use all clips due to the "restrictions" of the VideoSong format I'm applying.
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A VideoSong is a new medium with 2 rules:
1. What you see is what you hear (no lip-syncing for instruments or voice).
2. If you hear it, at some point you see it (no hidden sounds).
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Filmic Pro seems like a great app! I will definitely use it for my next project.

Hi, with ffmpeg you can convert them easily to anything.
I'd simply try out the different cases.