4K Capture Recommendations

  • I've got an interesting challenge for an Isadora rig--live compositing for recording a Vive in MR mode. The Isadora output requirements are ordinary (HD 30fps), but I'd need to capture two simultaneous video feeds, one 4K (a grid of four 2K elements from from the Vive) and one HD (the live-action video feed). Once in Isadora, the five HD elements would be combined for the final composite.
    Is it reasonable to expect Isadora to handle this on one machine? What capture card/deck would you recommend? (PCI card vs. Thunderbolt box?) And would you recommend running Isadora on Mac or PC? (I imagine many more years of optimization have gone into the Mac side, but can that advantage beat, say, a 4GHz quad i7 and Geforce 1080?)
  • Tech Staff

    So you are looking at 5 capture inputs?
    If so, I think this will require more machines.... however; 
    if you can combine the grid into a single feed externally via hardware, and capture that feed, then you have 2 feeds, and a single machine may handle this I think.

    Especially if you use Black Magic capture devices (if they support the incoming resolution from the combined grid) since these are hardware accelerated and have native drivers within Isadora.
    Generally, for these BM devices you need a bus per device (at least this is true for PC)
    Also I suspect you will be down-scaling the inputs... have the hardware do this work, and Isadora + your video card will thank-you.
    With the right hardware setup, the load on Isadora can be made fairly manageable. Your video card choice will depend on what you are planning to do with the video once inside Isadora (FFGL, Crop/scale, glsl etc... these all use the gpu)

  • That's right, the Vive computer is outputting a 4K grid, so the Isadora computer "only" needs one 4K and one 2K input. All GPU-enabled Actors are a given...got any thoughts on the performance of the new GLSL Actor vs. the traditional Zoomer, Alpha Mask, etc. for splitting and compositing the 4K feed?

  • Tech Staff

    GPU and GLSL run basically the same way.

    Don't use any vid-CPU anything.
    You may want to use the 'Chop Pixels' actor to cut up your 4K grid.