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Short delay playing movie when triggering speed via midi



  • Hi, when i adjust Movie Player speed using midi in (via an Evolution X-Session midi controller) i notice the movie playing pauses briefly before playing at the new speed set. The audio of the movie also cuts out whilst the movie appears to be adjusting to the new play speed set. I'm keen to find the cause of this playback delay in the hope i can somehow tweak it out. Ideally i'd like a smooth playback, with no brief pause when adjusting the play speed.

    Perhaps the delay is due to the time taken to read the new midi in value? Or maybe because the full midi in range is only 0 to 127?

    Any assistance appreciated. Cheers, Mr J

    Am running Isadora 2.2.2 on OSX 10.10.3 and have tried a variety of movie codecs including pjpeg, mov and mp4

    Was wondering if others have noticed a short delay when triggering midi in?



  • Hello,

    Without a view of your patch, it is difficult to help…
    I try to reproduce your goal and it works perfectly, what's important:
    – choose in speed entry the proper max and min (-1 to 1 in my patch)
    – choose interactive in optimize entry
    – use limit-scale actor to optimize the few 127 steps of midi
    – use a good and efficient codec, h264 from Compressor in my case
    Here is a view of the patch

    bb1fe2-movieplayer-with-varispeed.jpg



  • Thanks Jacques, your advise has helped me a lot. Has been about a year since i last wrote a patch and i forgot to use limit-scale actor and didn't have "interactive" mode set either.... duh!!!

    Now works as desired but i'll have to stay away from using mp4's. I'm surprised you recommend using h264. It's a very efficient codec but has to read across many frames when decoding, so not a very smooth playback when adjusting speed value.

    Rgds, Mr J



  • All h264 are not equals… I use the h264 directly proposed when you choose "master" from FCPX and it's not a .mp4 but a .mov, I think it must be an I frame codec (without key-frames) and on my computers it play perfectly well with Isadora and it's very quick to output from fcpx.

    Jacques

  • Tech Staff

    @jhoepffner

    h264 is originally not an iframe codec, it seems contrary to how h264 works. But as you say you can export .h264 with iframes and will benefit of the good codec and the interactivity of iframes. Though you will have larger files. To be honest I never used it myself but will try in future to see the difference in quality, performance and size compared to ProRes 422 or PhotoJPEG.

    Best Michel



  • @michel

    Yes it seems contradictory, but as you can see in the Lumix GH4, you can choose a i-frame h264 codec to have a more fluid editing.
    At the moment it's my favorite codec, I use ProRes only for exchange between apps.
    Jacques

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