FCPX re-wraps Sony (M4ROOT) mp4 into .mov automatically

This is a common question. During import, FCP re-wraps and copies to the library tree-oriented media such as Sony MP4. This isn't new or a bug -- it's been this way for over 10 years. There are technical reasons why it's designed that way. I'll try to post more details tomorrow.

If the .mp4 video files are copied out of the folder structure to a separate disk location, FCP will then allow importing them using "leave files in place."

Another way to consistently achieve imports with "leave files in place" is to rewrap those with a tool like EditReady externally.

If instead of doing those steps, you import using "copy to library," the media files are placed inside the library, put in a different folder structure, rewrapped to a QuickTime container, and using a .mov file extension, and sometimes renamed by adding a (fcp1), (fcp2), etc. suffix. Once that is done, if you edit a timeline with those, it is almost impossible to batch relink those to the original media. So it definitely makes sense to maintain awareness of this behavior and use one of the above methods if the goal is to reliably import with "leave files in place."

If you know the above info, it's generally possible to avoid accidentally importing .mp4 media files to the library and having them re-wrapped. However if that happens and you then edit a timeline, there is a procedure to batch relink all of the rewrapped .mov clips to the original .mp4 clips on disk. This requires the following steps:

• Use Finder to batch rename the original .mp4 clips to .mov. Reason: for batch relink, file extensions must match.
• Use the third-party utility QtChange to rewrite the timecode in the renamed clips to allow FCP to read clip timecode. Reason: timecode is not standardized for the .mp4 container, and FCP normally reads that as 00:00-based, which will cause a timecode mismatch to the rewrapped .mov clips. This utility by default will do that change on a batch of clips. I've never seen it fail, but it's a good idea to have a backup of the media before trying this.
• Do batch relink as normal. The in-library clips should relink to the original external clips, and all edits in any timelines should be preserved.

Other suggestions about media handling:

• Always ensure that all clips are globally unique. That means unique across the current production and across time. IOW there should be no filename conflicts between past and future productions. Reason:
• That can be achieved by either in-camera settings or by renaming the clips. One approach is to append a 5-digit incrementing numeric suffix to the filenames. Finder can do that by batch rename using the "Format" option. However you'd have to make note of the "high water mark" of the largest number used for each batch rename operation, then start the next one at +1 that number.

Why filenames should always be globally unique:

• It's generally a good practice, regardless of camera and NLE
• It avoids relink issues on FCP and other NLEs
• It avoids certain problems when drag/dropping projects, multicam and sync clips between libraries.

I don't know if this also works for Sony MP4 media, but we shoot MXF and to prevent FCP from copying and rewrapping even with Leave files in place set, we drag the media parent folder from the Finder into the event. FCP will complain about XML files it doesn't know what to do with but all media will come in and be referenced properly.