.mp4 files won't playproperly in iMovie

Discussion in 'Digital Video' started by pmcgeary1104, Oct 1, 2009.

  1. pmcgeary1104 macrumors newbie

    Oct 1, 2009
    I recently got a Vado HD mini video cam. It natively stores files in .avi format. Vado recently came out with a Mac app that exports the clips to iMovie in .mp4 format. The clips import into iMovie OK, but when I try to play them they are very herky-jerky. The only way to get smooth playback is to "convert" the images to .mov format. I thought that iMovie could play .mp4 natively but I can't seem to get them to work properly. Any help appreciated.
  2. MisterMe macrumors G4


    Jul 17, 2002
    Once again, iMovie is an editor, not a player. iMovie's display is intended to facilitate the editing process. Depending on the specific video format, rendering a smooth display may consume valuable clock cycles making editing more difficult. If you want to watch your video, then use the QuickTime Player, QuickTime X, or one of the other video players. If you want edit your video, then use iMovie. Don't use a hammer when a saw is required.
  3. pmcgeary1104 thread starter macrumors newbie

    Oct 1, 2009
    Thanks, but...

    Thanks, I take your point, but I'm a bit anal about the editing process. It seems to me that in earlier versions of iMovie, I could run the clip frame by frame so that I could decide where to cut, for example. With the herky-jerky playback, where one frame will freeze on the screen for a while, so you only see the clip in fits and starts, it's hard to decide where to make the cuts.
    Am I missing something?
  4. uuaschbaer macrumors regular


    Aug 31, 2009
    Perhaps the specifications of your hardware could shed light on the cause of your problem.
  5. pmcgeary1104 thread starter macrumors newbie

    Oct 1, 2009
    Specs for iMac

    I'm running OSX 10.5.8 (Leopard)

    Here are the specs for the computer and storage:

    Model Name: iMac
    Model Identifier: iMac4,1
    Processor Name: Intel Core Duo
    Processor Speed: 1.83 GHz
    Number Of Processors: 1
    Total Number Of Cores: 2
    L2 Cache: 2 MB
    Memory: 2 GB
    Bus Speed: 667 MHz
    Boot ROM Version: IM41.0055.B08
    SMC Version (system): 1.1f5

    Macintosh HD:
    Capacity: 148.73 GB
    Available: 21.44 GB
    Writable: Yes
    File System: Journaled HFS+
    BSD Name: disk0s2
    Mount Point: /
  6. uuaschbaer macrumors regular


    Aug 31, 2009
    If I'm not mistaken the playing back of video is done by the CPU unless the graphics card has some kind of smooth playback functionality. I believe that your computer uses an ATI Radeon X1600 which supports such functionality indeed, but please correct me if I'm wrong.
    Could it be the case that iMove fails to use this functionality? I don't know, but what MisterMe said before seems to apply either way. Your hardware may be lacking in power to play back HD video and run iMove simultaneously, but what is most interesting is that you say it is capable of that when the video is contained in a .mov format. Whether a movie is contained in a .mov of .mp4 format should not matter much since they're mere containers. What uses the CPU or GPU to a great extend is decoding the video file. It could be the case that when you convert the .mp4 file to a .mov file you inadvertently change the codec used. Could it be that one codec is more complicated than the other, or that one codec is supported by your graphics card's smooth playback functionality while the other is not?
    I do apologise for the woolly writing and ill-formulated sentences, I'm a bit sleepy.
  7. pmcgeary1104 thread starter macrumors newbie

    Oct 1, 2009
    codec and iMovie playback

    That's interesting. In some of my earlier research, codecs were mentioned as a possible suspect, but the specific one that was mentioned (Divx) wasn't where it was said to be in the /library/applications support/imovie. I did find some in the QuickTime folder, but when I removed them it had no effect on playback.
    Any place else I might look?

  8. MacForMeOneDay macrumors member

    Jun 16, 2007
    I have the same jerky video, and now that I've installed the VadoCentral to convert new clips some of my old clips have lost their audio (not sure if they are related but I'm bummed about the Vado more and more)

    My specs are more robust, so I don't think its a system power issue in this case:
    Model Identifier: iMac7,1
    Processor Name: Intel Core 2 Duo
    Processor Speed: 2.8 GHz
    Number Of Processors: 1
    Total Number Of Cores: 2
    L2 Cache: 4 MB
    Memory: 4 GB
    Bus Speed: 800 MHz
    ATI Radeon HD 2600 Pro:

    Chipset Model: ATI,RadeonHD2600
    Type: Display
    Bus: PCIe
    PCIe Lane Width: x16
    VRAM (Total): 256 MB
  9. pmcgeary1104 thread starter macrumors newbie

    Oct 1, 2009
    Maybe just impatience?

    I'm finding that if I wait long enough, the jerkiness goes away. (Longer waits if it's a longer clip.) I recall that in the older versions of iMovie, there was a wait while iMovie "rendered" the clip or transition or whatever. I wonder if that has been moved to the background--that it's still happening, but it doesn't take over the foreground processes. That would explain why clips play smoothly if I wait long enough. (When I first did this, I imported over 3GB worth of clips all at once. I suspect the rendering took quite a bit of time. Later, I imported a short--30-second--clip and it played back smoothly almost immediately.) I'll keep experimenting and post the results.
  10. uuaschbaer macrumors regular


    Aug 31, 2009
    That sounds a bit like the complications that could occur if you don't have enough RAM. Don't take my word for it, though.

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