You can’t group mixed frame rates. If you try to transcode 29.97 material in a 23.976 project, it will warn you that it will create 23.976 media from your 29.97 material but you will not be able to relink it via AMA or batch import it. So if you transcode it at hi res with no intention of ever relinking, you’ll be fine. A better solution would be to take your quicktime files (or I think the iPhone 4 shoots m4v) and run them through either MPEG Streamclip or Compressor. Convert the frame rate there, which will produce a 23.976 quicktime that you can import into the Avid, and can be matched back later if you need.
On Hotel Hell, we didn’t convert via compressor because our masters were shot on XDCAM, so in order to maintain matchability, we would have had to got our XDCAM disks converted via some hardware solution. Keep in mind, when you use MPEG stream clip, it will get rid of your timecode, and compressor isn’t alway totally accurate in maintaining timecode, especially when frame rates change. Fortunately, the iPhone isn’t really tracking timecode so that’s less of a worry.
Moral of the story, mixed frame rates bad. Mixed frame rates, very bad.
Richard Sanchez
Los Angeles, CA
“We are the facilitators of our own creative evolution.” – Bill Hicks