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Best video playback for OpenSesame 3.0.7 on a Mac?

edited March 2016 in OpenSesame

Hello all — I have an experiment built with two video treatments and I thought everything was A-OK until I tried watching a video to completion. The video will randomly stop playing, while the audio may or may not.

The two videos are both 7 minutes, 26MB and 28MB, in mp4 format. My backend is xpyriment and I'm using the media_player_gst plug-in. OpenSesame 3.0.7 on OSX 10.11.

I'm going to experiment with video format (a previous thread suggested avi, mpg, or mov) but in the meanwhile I wanted to see if anyone has had better success than I — or if the size of the videos is a non-starter.


  • edited March 2016

    Update: The entire videos play more smoothly with the legacy back-end but still freezes most trials.

    The only other glitch with the media_player_gst plug-in is that it is showing the videos full screen, even though I specify not to. Original size (480x360) would likely play more reliably.

    I was using xpyriment previously because the experiment includes an IAT which records reaction time.The IAT is something of an add-on — not completely essential — but I would like to retain it.

    As someone not fully comprehending the "Timing" documentation: Can legacy produce precise (but not accurate) reaction readings? My main interest is difference between treatments, so if there was some measurable effect between groups, that would be enough to warrant further investigation.

  • edited 8:44PM

    Typically, audio continues to play while the video freezes. OpenSesame immediately exits with esc+q.

  • edited 8:44PM

    Hi Zeke,

    Yes I have encountered this problem on a Mac too and I have no idea what the cause is. While creating the media_player_gst plugin I have tested it on several platforms and somehow (but as usual) this problem only occurs on a mac. Sadly, there is not much I can do about it at the moment; I think the problem lies in the GStreamer implementation for OSX. I am using a very old version of GStreamer (0.10 while 1.2 is available), so it may help to update the underlying library one day, but since there are a lot of backward incompatible changes in the newer version, it requires rewriting a lot of sections of the plugin, which will take a considerable amount of time. the only recommendation I could give you for the moment is to run your experiment on another platform than a Mac, if it is available to you.
    I'm sorry for the inconvenience

  • edited March 2016

    Hey Daniel,

    Thank you kindly for your response! I wish I could help with updating the library, but I am rather deficient in these things. My workaround for the time being has been to cut up the videos into shorter segments, and string them along in a sequence. This works flawlessly with 1 minute (<5mb) clips, except there is a white flash between each video — participants will probably think it's subliminal messaging... Today I am dividing the videos into three segments (2 minutes, <10mb apiece) to see whether it still reliably plays the entire sequence.

    My other question for you: Is there a way to get the non-fullscreen option functioning? It's a trivial matter, but if the unscaled original videos played more reliably it would be worth it.

    I'm limited to Macs, both at home and in the computer lab where participants will be surveyed.

  • edited 8:44PM

    The fullscreen/non fullscreen option used to work. I think it started to behave funky when the retina resolutions were introduced, as OSX reports lower resolutions to OpenSesame than the retina resolutions really are. You could try playing around with display scaling in the OSX settings?

    I think this can be fixed, but I don't think I can do this in the foreseeable time, at least not before you plan to run your experiments from what I make from your story, I'm sorry.

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