iMovie avoids unnecessary data duplication by facilitating the copy-on-write feature of APFS. Nice!

[porg]

Video files tend to be large, how is iMovie dealing with them?

• iMovie has had self-contained libraries and projects for ease-of-use and robustness since its inception in 1999.
  • On those elder iMovie versions running macOS on a HFS+ file system this often meant a huge waste of file storage when you had the file both somewhere in your folder structure and imported it into iMovie. Because this was a real copy taking up space twice.
  • Project efforts like dedup-imovie-library show this.
• As I had gained trust in apfs-clone-checker's reliability in User evaluation: apfs-clone-checker seems to work correctly on macOS 11 Big Sur #1 I now wanted to check:
  • Do contemporary versions of iMovie on macOS with APFS make good use of it's copy-on-write feature?
  • Answer: Yes! Details below:

Versions

iMovie 10.2.2
macOS 11.2.1 Big Sur
Internal SSD formatted as APFS

Investigation

# Added 1-original.mov from Finder via drag-n-drop to "iMovie Library" into event "General"
# Disk I/O shows only few KBs. Not the 72MB the file takes.
# A first good sign. Either copy-on-write or linking took place.

$ clone_checker ~/Documents/Tests/copying-on-APFS/1-original.mov \
~/Movies/iMovie\ Library.imovielibrary/General/Original\ Media/1-original.mov 
1 # Nice! 1 means it is a copy-on-write clone. Consumes no extra storage except its metadata overhead!

# Within iMovie I added a movie from "LIBRARIES > Photos"
# to "LIBRARIES > iMovie Library > "Family", a so called "event".
# Think of it like a category or folder for organizing clips.

$ clone_checker ~/Pictures/Fotos\ Library.photoslibrary/originals/C/very-long-UID.mov \
~/Movies/iMovie\ Library.imovielibrary/Family/Original\ Media/very-long-UID.mov 
1  # Nice! Again a real clone!

[porg]

Closing, as this was just meant for documentation purposes.
(May the search engines help those in need for information! 😉 )