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iMovie '11 hogs CPU and freezes

1279 Views 5 Replies Latest reply: Dec 20, 2012 4:14 AM by William Gee RSS
Anniedan Calculating status...
Currently Being Moderated
Mar 12, 2012 6:43 AM

I've been importing a few video files in iMovie (from local hard disk, not HD) and it has been taking over 1hr each time... for about 1hr movies.

During each, activity monitor will show that iMovie is taking about 150% of CPU usage... never less than 95%, and I even saw a peak at over 200% (how can something go over 100% is already beyong me, mathematically... but 200%?!)


I should be glad that iMovie is using all the power possible, but I don't get the results. It's incredibly slow, and everything else is freezing. I have trouble using the computer. Even typing in an email or switching between screens is slow... when it happens. I may not be using the most powerful machine there is, but I doubt it's normal behavior.


I have a 3.2GHz processor and 4G of RAM.

I tried closing all other programs (even though activity monitor showed they were not using much CPU), but it didn't change anything.


I noticed today that this huge CPU usage and the worst freeze happens for over 40min while the progression bar of the import barely changed and stuck at about 2-3%... and then the iMovie icon starts jumping and from that point the computer goes back to acting normal and the import finishes in less than 5min.

It's like there is a bug with the process at the beginning of the import... not the import process itself.


Anyone has any idea of what's happening?




(When I export small projects -just movie cuts with no effects- it uses a lot of CPU too and slows down the whole computer... but not in as bad a way, and the process clearly goes on normally... and working in iMovie to create projects is usually OK.)

iMovie '11
  • AppleMan1958 Level 7 Level 7 (27,335 points)
    Currently Being Moderated
    Mar 12, 2012 7:29 AM (in response to Anniedan)

    Think of it this way. 100% is the maximum for a processor chip. However, modern Macs have multiple processors, called cores. So if your Mac has an Intel Core 2 Duo chip, it has 2 cores, and can go up to 200%.

    If you have an Intel I5 chip, it has 4 cores, so you can go up to 400%. If you have an Intel I7 chip, it also has 4 cores, but they can be used as 8 virtual cores, so you can go to 800%.


    iMovie, as far as I know, is only designed to take advantage of 2 cores, so you could be using 200% for iMovie at a peak, and other cores for other apps or for OSX.


    Final Cut Pro can use all your cores, and frequently does.


    If your import finished, it is probably OK. If it crashes or hangs, then you have a problem. You can find iMovie in the Activity Monitor and click on the Inspector. If you see recent hangs, there may be a problem. If not, it is probably OK.


    If you have analysis for image stabilization turned on, it could act like you are describing. It would have an active phase where it is importing the video. Then there would be a long phase of doing the analysis.

  • Bojan Landekic Level 1 Level 1 (0 points)
    Currently Being Moderated
    Dec 11, 2012 10:05 AM (in response to AppleMan1958)

    That is utter nonsense about 200% explanation!  Tools such as TOP in the CLI are unix based tools, and were originally designed for computers that had 1 CPU.  The world has evolved A LOT since 1970s.  Unfortunately a lot of the geeks who grew up with that technology are as thick headed as religious nuts who opressed women in Saudi Arabia and won't even let them drive!  They insist that things should function ONLY THEIR WAY and anything else is nonsense.  It is absolutely ridiculous for top to report more than 100% for the CPU utilization even on multi-core machines!  When it says 200% CPU Utilization it means that the operating system is over utilizing the CPU, which is impossible, mathematicaly and realistically.  The solution is really simple.  A few code changes to TOP and it can report 100% for any number of cores or CPUs.  But the unix zealots that are responsible for coding things don't want to make these changes, they are stuck in 1970s and refuse to move.  We need coders who are not afraid to step up and make the real changes needed.


    Try this.  Open up iMovie, close any open projects, unhighlight any events that might be highlighted so no clips are shown in the clip viewer nor the preview box.  Technically speaking iMovie is doing nothing and shouldn't take up more than 1% of the CPU.  Now if you run TOP, it will show iMovie using around 90% of the CPU.  How the heck is that good design?  It uses 100% of the CPU when it's doing nothing!!!  Imagine if iTunes used 100% CPU when it was paused?!?!!?  But iTunes is good, it uses only 1% of the CPU while in pause (which I think is still far too much CPU usage since it's doing absolutely nothing, too!).. iMovie is terribly programmed and has serious user interface issues.  Like for example.  The buttons in the middle for making a clip a favourite, or a star, etc... those buttons are huge and are ALWAYS there.. Even when a clip is not highlighted and when you are editing the project timeline and the buttons are not needed.  So much iMovie 11 functionality is ********!!  I am shocked that a company as creative as Apple can put out such a bad product!!!  But it's the best proudct of it's kind, so we should be thankful!


    Here look at this screenshot.. iMovie taking up 100% of the CPU while doing absolutely nothing!

    Screen Shot 2012-12-11 at 12.55.15 PM.png

  • Bojan Landekic Level 1 Level 1 (0 points)
    Currently Being Moderated
    Dec 11, 2012 10:09 AM (in response to Anniedan)

    The same happens to everyone.  The only way to use iMovie is to import clips at night when you're asleep.  And when you're done working with a project, you have to quit iMovie, because even when it's idle and all projects closed, it still uses up 100% CPU for no reason!  iMovie is TERRIBLE coded and has absolutely terrible design!


    And Apple claims that Mac OS X is pre-emptive multitasking????  How is it if iMovie renders your computer absolutely useless, we can't even read email properly when iMovie is open!

  • William Gee Calculating status...
    Currently Being Moderated
    Dec 20, 2012 4:14 AM (in response to Anniedan)

    Thanks for these informative (if over technical!) responses.  I shall follow the advice and import while I am away at lunch!


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