MikeCaracalas
Level 1 (4 points)
iLife

Q: Why does a 500MB MP4 clip turn into a massive file on Sharing?

I have an MP4 (generated by Zoom.us) that is 500MB on disk.  I want to delete 3 minutes of footage, so I open it in iMovie, snip the 3 minutes, then try to save.  First of all, I can't just do a Save As, I need to Share, but ok... if I share to Quicktime it's about 53GB.  Sharing to most of the other services it's about 10GB.  Why does the size expand so much from the original clip, and why can't I just save in the same format as the clip, minus the 3 minutes I snipped out?

MacBook Pro with Retina display, iOS 10.0.2

Posted on Oct 15, 2016 1:26 PM

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MikeCaracalas

Q: Why does a 500MB MP4 clip turn into a massive file on Sharing?

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  • by Jim Wanamaker,

    Jim Wanamaker Jim Wanamaker Oct 15, 2016 8:38 PM in response to MikeCaracalas
    Level 4 (3,919 points)
    iLife
    Oct 15, 2016 8:38 PM in response to MikeCaracalas

    If you are using iMovie 10.1.2 when you select file in the share menu the output file size is determined by the quality setting. Selecting High Quality will give you an MP4 file.

  • by Rich839,

    Rich839 Rich839 Oct 16, 2016 8:17 AM in response to MikeCaracalas
    Level 4 (3,839 points)
    iLife
    Oct 16, 2016 8:17 AM in response to MikeCaracalas

    Further to what Jim said, if you share out at Best Quality (pro res) you will get a .mov file with much larger file size because of the higher bit rate.

     

    Possibly you are sharing out your vid at a much higher bit rate than it was when you put it in to iMovie.  If you have the free download MPEG Streamclip on your computer, try opening the imported-in and shared-out vids in Streamclip, and clicking on File/Show Stream Info in the Streamclip menu.  You can compare bit rates with the info that comes up.  If the bit rate is considerably higher on the shared vid, then, as Jim said, you can chose to export at a lower quality.