Mirroring stimulus display to an iPhone

Mehrdad Jazayeri's Avatar

Mehrdad Jazayeri

12 Jun, 2014 07:31 PM

Hi Chris,

Is it technically feasible to run a light version of the client simply showing a low-res (and, if needed, a few seconds delayed) copy of the stimulus window on an iPhone? This may seem like a frivolous feature but we actually will have use for it.

Thanks,
-Mehrdad

  1. Support Staff 1 Posted by Christopher Sta... on 13 Jun, 2014 02:09 PM

    Christopher Stawarz's Avatar

    Hi Mehrdad,

    This is technically possible, but I suspect it would work poorly in practice.

    The scenario you describe entails three basic tasks, all of which must execute on the Mac running MWServer:

    1. Capturing frames from the graphics hardware driving the stimulus display
    2. Encoding those frames, in real time, into H.264 video
    3. Broadcasting those frames over the network

    Task #1 requires copying the contents of the frame buffer from VRAM to main memory, which is a time-consuming operation that will degrade (possibly severely) MWorks' display-update performance. Task #2 is going to be CPU and/or GPU intensive, again impacting MWorks' performance. Task #3 probably won't be too detrimental to system performance, but getting it working would take significant development effort (though perhaps some existing third-party software could do the job).

    I think a better approach would be to handle this not in software but with dedicated hardware (something like this, perhaps). That said, I believe Evan mentioned that you had tried something similar and hadn't been happy with the results. Do you recall the specific problems you had?

    Chris

  2. 2 Posted by Mehrdad Jazayer... on 13 Jun, 2014 04:15 PM

    Mehrdad Jazayeri's Avatar

    Hi Chris,

    Makes sense. Thanks for the explanation.

    Best,
    -Mehrdad

  3. Christopher Stawarz closed this discussion on 30 Jun, 2014 07:59 PM.

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