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6 channels of synchronised HD video from 1 machine



  • I know this has been discussed somewhere and Mark seemed to indicate that it would be a bad idea... but want to explore a bit. I am considering a way of putting together a synchronised 6-channel projection for a museum / gallery video artwork, running from a single foolproof black box. The work is not technically 6 x 1080p, as one projection is just a line of text and can be rendered as 1920 x 200. If the whole thing caves in because of the 1080p I could possibly go with 720p, but 1080 is the target.

    I would be building a system from scratch, with i7, 3 x SSD's on 3 x SATAIII, and 3 x dual head DVI graphics cards on 3 x PCI-E.
    Will also experiment with low-CPU compression and will be using methods described by Michel [here](http://forum.troikatronix.com/cgi-bin/forum/gforum.cgi?post=539#539) to maintain sync.
    The only potential bottleneck I can see is the processor, but there does not seem a lot of processing needed besides monitoring and tweaking the playback speeds of the "slave" channels.
    If I am missing something crucial here please let me know, it is a potentially costly experiment but I do like to try things (which I am sure will be my downfall one day!)
    I know there are some quite robust networkable players out there that can maintain sync, but my experience is that having 6 x boxes invites 6 x problems...
    Anyway, keen to hear input
    take care
    m


  • Hi Mockej

    I think your setup works. I allready played 6 x 1080p files on a pc.
    You have to choose well your codec ( native .avi playback under windows). 
    I am only afraid of your 3 x GPU setup.
    I had bad perf. issues with isadora on pc when multiplying stages.
    I would try to make a setup with only one stage.
    Maybe a good GPU with 2 TripleHeads2Go. If you have the same resolution you can make a "span mode" ( Nvidia ) or "Eyefinity Group" (ATI).
    Then this will appear as a 11520x1080 pixels stage on isadora, and you can place a projector on each screen using the projector inputs.
    Best
    Mehdi


  • Thanks Mehdi... interesting. Even with 3 x GPU, it should be possible to span and make 1 stage. Then 6 x movie players with 6 x izzy projectors all placing the movies in different horizontal positions on the same stage... Will have to research if one expensive card + 2 x THTG will be better than 3 x not-so-expensive cards.

    m


  • Hi Mockej.

    I had a few years ago a machine with 2 GPUs for isadora, and I had quite strong perf. issues.
    It was a few yeras ago... Maybe good to give it a new try.
    This is why I was suggesting 2 THTG.
    I don't have two GPUs here to try...
    Mehdi


  • cool... if I can borrow components to do some test it will be interesting... will post results as soon as I can get my hands on the hardware



  • Is the new mac pro an option for you?

    fubbi


  • @Fubbi Hahahaaa I wish! No, I need to squeeze all the hardware (everything up to AV cables and repeaters) into a budget of R24,000 (about $2200). Of course those shiny, expensive capsules are tempting... but would then still have to shell out a bit more (as you have pointed out) to get it all running.



  • **6 x 720p synchronised...**

    OK I have started testing after finally getting most components in... Getting decent constant sync playback for 6 x 720p @ 25fps. (1080 def not cracking it with my set-up... but most of the projectors are 1280 x 800 so why bother). I was considering using the 2 x Matrox Triple Head method as advised but budget was short and I wanted as few as possible external parts as the idea is to have a completely foolproof plug-and-play "black box".

    **Solution was this:**
    PC with 3 x 64GB SSD, Win7 Pro, Izzy 1.3f24
    2 x GeForce 640 (each with 2 x DVI and 1 x HDMI)
    All test movies rendered to 1280 x 720 Quicktime Prores 422 LT (about 40Mbps or 5MBps)
    6 x stages, 6 x Movie Player Direct per scene playing out one to each stage
    All monitors and Isadora settings at 1280 x 720
    Master player is the only one really playing, all other players' speed set to "0" and "position" out of master player plugged into "position" in of slaves.
    That last trick was what saved it... having all players actively playing was making everything a bit sluggish, with no chance of introducing a sync method without making it worse. Using the master player to "drag" the others along does the trick, and ensures sync with the sound (fortunately just one stereo track from the master). (doing this without setting the slaves' speed to "0" did not deliver good results)
    Performance sits at around 22fps clocked by Isadora, and setting the master player's speed to 1.02 seems to give correct 25fps playback - if frames are dropped it is unnoticeable.
    Tried a lot of formats before settling on Quicktime Prores 422 LT... nothing seems to play out better than that one, even on PC! ... and I think it plays nice with the sync.
    Thanks for all the advice, has been an interesting experiment so far... still to be completed.
    m

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