Playback of 3 streams not smooth - Video card issue?

  • Hi Izzy team,

    This is my first post here, but I’ve been reading this forum for a few days now.
    But I can’t find the answer to my problem…
    For our next production we need 3 projector screens + 1 control monitor on a 2009 Mac Pro 2.93 Ghz Quad-Core.
    I can’t seem to get real smooth playback with 3 streams at the same time. Although the source material is 25 fps, the playback looks like it was 15 fps or worse.
    The resolution does not have to be extremely high, 1024x768 or 720p is more than enough. I have been testing with both ProRes LT and HAP codecs, but both don’t play at the same quality like f.i. VLC player plays the source material.
    The strange thing is that the old Classic Movie Player actor does a better job than the new Isadora 2 Movie Player. As I understand Isadora 2 uses the graphics card to render video, while the classic player is CPU based.
    While playing 3 streams ProRes LT at 720p 25fps in 3 Isadora 2 Movie Players + Projectors, I get a steady 25fps and a VPO of around 2.7 in the Show Status window. The Mac activity monitor does not show extreme CPU usage. So the bottleneck has to be something different…
    Now I was thinking that maybe the two standard Nvidea GT 120 graphics cards in the Mac Pro could be the culprit. Is that possible?
    And would I get much better performance if I put a ATi Radeon HD 5870 in there?
    In that case I would have 3 outputs for the projectors on that HD 5870 and keep one of the GT 120’s for the control monitor. Will that work? Because I’m confused what the ’Shared OpenGL Resources’ setting in preferences will do in such setup.
    Has anyone a setup like this and can you confirm this works fine and you get smooth playback of 3 streams?

    Thanks a lot!