Finished movie size gigantic

So I used iMovie to splice together 21 mp4 clips that were filmed in 1080p (with sound). Total size of the 21 clips is 8.6GB.

Nothing fancy was done in iMovie other than a few titles and just adding the 21 clips one after another. When I go to export (share) the movie as a file, iMovie estimates the mov file at 135GB. Actual size turned out to be 133GB.

What am I missing her that the size goes from 8GB to 133GB? I just would like the quality to be the same as the original.

I used "ProRes" as the quality, thinking it would keep it at what it was filmed at with no degradation. If I change it to "High", the estimate comes down to 18GB. What is "ProRes" doing that would eat up that much more space?

Thanks.

iMac (Retina 5K, 27-inch, Late 2014), macOS High Sierra (10.13.2)

Posted on Jan 25, 2018 6:27 PM

Top-ranking reply

Jim Wanamaker

Level 5

6,317 points

Posted on Jan 25, 2018 8:55 PM

ProRes 4.2.2 is an I frame encoder which means it encodes every frame of the video with high quality and so the file size is large. When you chose High Quality iMovie uses the H264 codec which uses predictive frames and not every actual frame plus a slightly lower quality encoding. This provides a very compressed file but with a quality close to ProRes. The result is a much smaller output file. I doubt you can see any appreciative difference when you play the files.

View in context

Finished movie size gigantic

Similar questions