By tianka - 3/4/2015
Hello!
I recently posted a study asking subjects to rate images of food and reactions after movies.
http://research.millisecond.com/johndovidio/moodROC.web
There are 6 videos, conditionally selected for .mp4 or .mwv format depending on Mac/Windows. I've received a number of emails saying that one of the videos (of Forrest Gump reuniting with his son) appears on the screen, then freezes, and am unsure what is wrong. There have been no complaints on the other videos. Any idea for why this might be happening?
Thanks,
Karen
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By Dave - 3/4/2015
The most plausible guess based on that description is that something about this video is different compared to the others (e.g. different encoding settings) or it has a defect (based on the codec version a given participant's machine uses and other factors beyond your control, some systems may tolerate that defect while others may not). It may also be that the particular video is very large (compared to others) or has a higher resolution, which may simply be outmaxing the performance capabilities on underpowered / memory constrained systems (looking at the video's file size, this seems unlikely to me).
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By tianka - 3/6/2015
Hi Dave--thanks for your response.
I've tried tinkering with the video, but am still having issues. The gump video plays fine on Macs, but stalls on Windows. The size is 7.93MB, which seems reasonable? Strangely, I'm able to play the video in Windows Media Player fine, but it freezes once it's run through Inquisit. I thought I perhaps coded something incorrectly, so I renamed another video gump to test, and everything ran smoothly. Even with a set timeout or trialduration, the video stays frozen on the screen past the set time. Not sure what else to try--any ideas?
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By Dave - 3/6/2015
> Strangely, I'm able to play the video in Windows Media Player fine, but it freezes once it's run through Inquisit.
This isn't necessarily strange. It's actually somewhat suggestive that indeed the encoding of that particular file is the issue. As of Windows Media Player does not use the same way to render videos that Inquisit uses. Inquisit relies on so-called DirectShow codecs, while Windows Media Player uses a different codec framework called "Media Foundation" (as of Windows Vista, if I am not mistaken). Try to identify the way the Gump video was encoded and compare it to the settings of the other (working) files. Then re-encode the Gump video accordingly. To identify the encoding details, you can use tools such as http://www.codecguide.com/download_other.htm#mediainfo .
A useful general overview re. codecs in Windows: http://windows.microsoft.com/en-us/windows/codecs-frequently-asked-questions
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