Mirroring stimulus display to an iPhone

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1

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

2

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

3

Hi Chris,

Makes sense. Thanks for the explanation.

Best,
-Mehrdad