Jerky video playback scrubbing backwards

  • I've noticed since committing myself to version 1.3 (I've been using 1.2 for ages) that video scrubbing is very jerky when moving backwards. This happens even with very small videos ("small" in resolution as well as file size).
    Is there any way round this as that's what I mainly use Isadora for. Version 1.2 was perfectly smooth.
    I haven't updated Quicktime since and am still using the same files (.mov, H264)

  • Tech Staff

    H264 isn't a very good codec really. Try Photo - JPEG at 70%+ 

    _edited: I keep typing MJPEG instead of P(hoto)JPEG - I do it every time! Sorry!_

  • Dear Nic + Everyone,

    Newer versions of Isadora have been updated to stay in line with the more modern programming interface of QuickTime. This may be a reason that the performance is different since 1.2.
    But the most important thing to do is to convert the movie to Photo JPEG. H264 is not designed to play backwards -- to jump back a frame, it has to jump back to the last _keyframe_ and then decode forward until it finds the frame you want.
    Here's a screen shot that shows the CPU usage in QuickTime player when playing an H264 movie forwards and backwards. Isadora performs similarly.
    With the Photo JPEG and DV an other codecs, each frame is compressed individually. Therefore, they play backwards equally well as forwards.
    For other "best practices" check out the "Optimizing for Speed" section of the manual as well as online [here](
    Best Wishes,

  • I have the same problem.

    video scrubbing won't go backwards using Photo-JPEG codec.
    video scrubbing ok using DV-PAL codec.
    Isadora v.1.3.0f24 on a new MacBook Pro Retina Display.
    any advice?
  • Tech Staff


    Please try the newest pre-release HERE. Does this solve your problem?


  • Dear Claudio,

    And what version of Mac OS?
    Best Wishes,

  • @mark


  • @Michel

    downloading 1.3.1f02 now.
    will test and let you know.

  • Hey all, I've just revisited this post and I've no idea what you did Mark but 1.3.1f02 solves the jerky scrubbing issue. This has been a real problem for ages but now it's working fabulously!

  • Dear Nic,

    Glad to hear. But, when you have an opportunity, move to 1.3.1f06 to make sure you're with the latest, and that it's still working well for you.
    Best Wishes,