Previous 1 2 Next 17 Replies Latest reply: Jan 25, 2016 10:31 AM by johns3112
lichtpausen Level 1 Level 1



I am using iMovie 10.0 on OS X 10.9 Mavericks build 13A603. The computer is a "late 2012" type iMac (2.7 GHz i5, 8 GB RAM).


Even when I close all other tasks, iMovie runs so slowly as to be unusable. Specifically, it seems that every time I run iMovie, it starts some mysterious background tasks that don't show up anywhere (no progress bar, no messages) and slow down the computer to almost a standstill. This happens even when I'm running a very small project in iMovie. When I try to close the program, it asks me: "Are you sure you want to close iMovie library? Tasks that are currently in progress will not be completed."


Please help me get rid of these mystery tasks so that I can finally get my work done. Thanks...

iMac (21.5-inch, Late 2012), OS X Mavericks (10.9)
  • Afterimages Level 1 Level 1

    It's probably rendering stuff to Theater and/or uploading to icloud. These will complete eventually. Just leave it run.

  • Smokie Level 1 Level 1

    Is there a way to view these tasks?  I attempting to share video to a file and there is no progress bar.  I am assuming this it the task that is running, but am unsure.

  • lichtpausen Level 1 Level 1

    No, I didn't set iMovie to save any projects to Theater or iCloud. It would only do so if I clicked the Share button.


    Anyhow, it never completes. I left it running for three days straight and it's still behaving that way. Totally messed-up.

  • lichtpausen Level 1 Level 1

    Well, it looks like the Apple guys are stumped on this one.

  • Lu Ko Level 1 Level 1

    I'm having exactly the same issue. iMovie is taking all the CPU power making the entire system performing very slow. Im my case iMovie is rendering a movie in the background altough it was already properly rendered. The process resposible for this task seems to ProTranscoderTool_sb. I tryed to force quit it and got message in the notification center that the "Shared failed; The share operation  "movie" has failed". I had to force quit the process 3 times because iMove tried to render the same clip again. It solved the performance problem for now. But I am wondering why is the same movie being shared all over again.


  • GeeD Level 5 Level 5

    I found this at first.  If you update a lot of projects from iMovie 9 to iMovie 10 is has to reconvert all the clips into the new intermediate codec using the ProTranscoderTool before they can be shared.  Even worse, if you had shake stabililzation active in many clips it will automatically re-analyze each clip and this is a very CPU - intensive task.  Its just a matter of letting it get on with it.   I think background tasks only start operating on the currently active project but if you load a different one it will start up  on that  as well as continuing with the ongoing ones.


    Unlike FCP 10.1 which can display what background tasks are running 1Movie 10 deos not have this capability - only the Activity Monitor app can show you.



  • Bengt Wärleby Level 6 Level 6

    My penny to this



    • Minimum of 25Gb free space on Start-Up hard disk

    • No other programs running in BackGround e.g. Energy-Saver

    • Don’t let HD spin down or be turned off (in Energy-Save)

    • Move hard disks that are not to be used to Trash - To be disconnected/turned off

    • Goto Spotlight and set the rest of them under Integrity (not to be scanned)

    • Set screen-saver to a folder without any photo - then make an active corner (up right for me) and set pointer to this - turns on screen saver - to show that it has nothing to show

    • No File Vault on - Important

    • NO - TimeMachine - during iMovie/iDVD work either ! IMPORTANT

    Lot's of icons on DeskTop/Finder also slows down the Mac noticeably

    Start a new User-Account and log into this and iMovie get's faster too - if a project is in a hurry

    • And let Mac run on Mains - not just on battery


    Yours Bengt W

  • plant_geek Level 1 Level 1

    Thanks for these small fixes.  Yes, I'm having the exact same problems.  This issue actually caused my macbook air to crash.  I thought 10GB free on my hard drive was enough to do some editing.  I did a bunch of dumb things at onces, like having Time Machine running, having a portable drive connected with other libraries.  Having a couple other programs open didn't help either.  Since then, I freed up 60 GB on my hard drive and it's still having the same issues.  If I let iMovie run a while, it will use around 40GB of virtual memory.  Now I keep Activity Monitor open and just close and re-open iMovie occasionally.  It's barely useable.  I'm not using stabilization on any clips again until the very end of editing.  Apple better get on this if they want people to use the program.

  • twirl2 Level 1 Level 1

    I'm also having this issue, and it just got worse when I updated it recently. Apple, come on!

  • NickRedwoodCity Level 1 Level 1

    I've run into this problem as well. Uncheck the "add to theater" box when sharing a file and in iMove preferences, uncheck "automatically upload content to iCloud". This supposedly only happens when items are added to the theater, but I wouldn't be surprised if something is going on anyway. I also went ahead and removed old projects so that I only have a few videos in the library. I have 23GB free on a 2013, Haswell Macbook Air, i7, 8gb.

  • ABusLux Level 1 Level 1

    At first I was also going nuts with the "iMovie must complete other tasks before performing this operation" message. There is a blue circle on the right side of the toolbar. If you click on it you will see which tasks are running as well as the estimated remaining running time.

  • NickRedwoodCity Level 1 Level 1

    I've had the message pop up without any obvious tasks running (no blue circle). Apparently other things are going on.

  • Bengt Wärleby Level 6 Level 6

    Reg Conspiratory Theory !


    May be it is a strategy to force You to buy a new Mac.


    To rule this out - DO


    - Secure lot's of free Space on Start-Up Macintosh HD (25Gb or much more)

    - Create a New User Account

    - Log into this


    Now try and see if Your Mac got into better pace - If not - Do as I - keep the old one with OS X.6 and don't up-date till it fall's into pieces.


    Yours (open for realistic and mysterious ways to keep it up and running) Bengt W

  • lbay Level 1 Level 1

    I found that when I have a lot of old events in my library, iMovie is very slow, as if it is opening all those events in the background in case I want to use clips from them.  When I moved all those events into a separate library, and then closed that separate library, iMovie seems to run like new again.  (Of course, since I did that last, I've added 71 new events to my library, and iMovie has slowed to a crawl the number of events does seem to be related)

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