problems with consistent video duration

Mon Aug 12 16:24:50 UTC 2013

Hi,

I am experiencing the same problem, and would appreciate any advice.

I have 8 videos in my study, which is running in E-Prime 2. Each video is 
approximately 3 minutes long and in avi (MPEG4 [Xvid] and MPEG4 [FMP4]) 
format, with MPEG-1 Layer 3 (MP3) stereo sound. There is a gap ranging 
between 30 seconds to 2 minutes in between the different videos. The 
e-prime file executes just fine, and runs to the end. The videos play, but 
then randomly cut off somewhere through the video. The experiment then just 
goes on the next stimulus. They videos do not always stop at the same 
point, and it does not matter whether they are displayed early on or later 
into the experiment. The videos do lag, however, and the sound and image 
may go out of sync before the movie ends. All the videos play correctly on 
the computer outside of e-prime (on VLC and Windows Media Player).

It is not just the case that the larger video file is the more likely it is 
to stop, but what I have noticed is that the videos that I resized 
beforehand using Avidemux never play to the end. The videos that were in 
the correct resolution (1024 x 1028) to start with do not give the same 
problems. However, I would like all of the videos in the experiment to be 
the same resolution (or at least same length, without needing to stretch 
them), so I have no option but to resize the videos.

I have tried converting the videos to a different format (mpeg1) as 
suggested elsewhere (
https://groups.google.com/forum/#!msg/e-prime/ENSVeWNy6p0/RyME4_tKof4J), 
but that only made it worse. I have also tried to increase the pre-release 
time, set the MovieDisplay to show the movie for a fixed amount of time, 
and simplifying the script to the very basics; all to no effect. Even the 
simplest possible experiment with only one movie in it fails to display the 
movie to the end.  I have installed the latest Combined Community Codec 
Pack (2013-08-01; http://www.cccp-project.net/wiki/index.php?title=Main_Page), 
but it has not made a difference.

The experimental computer is an Intel i3 530 at 2.93 GHz machine with 1.86 GB 
Ram and an Intel H55 Express chipset, running a 1280 x 1024 16bit desktop 
display. I suspect that the computer is underpowered. I have run the 
experiment on my laptop and the videos ran smoothly (I can't use my laptop 
for the final presentation as I need to use the lab computer that is 
connected to the eye tracking equipment).

Another possibility would be the interaction of the codecs with e-prime. I 
ran the e-prime codec config tool, and it renders all the files correctly. 
However, they still perform as described above when running the actual 
experiment. Everything in the e-prime codec config is currently set to the 
default values. Is there perhaps something within this tool that I could 
change to give a better result?

I don't know whether the recoding with Avidemux caused the problem (has 
anyone else used it successfully/unsuccessfully with e-prime?), or whether 
just resizing the videos was problematic in general.

Any suggestions on how to get the movies to display correctly? Your help 
would be greatly appreciated.

Thank you,
Michelle

On Monday, 27 February 2012 12:33:14 UTC+2, Vinson, David: UCL wrote:
>
> Hi Lindsay,
>
> Unfortunately it can be a lot of work to get videos to display 
> correctly, and it looks like you've gone through a sensible process so 
> far.   We experienced something similar, and suspected it could be 
> related to the time it takes to load the video files from the hard drive 
> and get them displayed in time.  We might not be correct but we managed 
> to eliminate these problems (or at least sufficiently reduce them) by a 
> combination of a few factors:
>
> 1. pre-load the video (e.g. MovieDisplay1.Load in an inline object) well 
> before the movie is due to start playing
> 2. include a fairly high % of breaks between trials if possible, which 
> may help resolve the buildup of lag
> 3. if you are using an older/slower machine it may be useful to have 
> video files on a different hard drive than the one being used for 
> virtual memory
>
> And 4. a bit more "trial and error" with video formats.  Keep in mind 
> that just converting from one video format to another may not be 
> sufficient - it may be necessary to re-compress with a different codec.
>
> In troubleshooting these matters it may also be helpful to set up the 
> simplest possible miniature version of your experiment (e.g. just one or 
> two videos) repeated many times in the simplest possible trial sequence, 
> and see if your problem reproduces under those conditions.
>
> OR.... am I missing something here - if one of your videos is 13 sec and 
> you only display it for 7 seconds, this would cut it off about halfway 
> through.  But surely it's not as simple as this.
>
> good luck, and please report back to the list if you figure it out.
> -dv
>
> On 25/02/2012 20:06, Lindsay wrote:
> > I am setting up an experiment with videos and am playing around with
> > displaying the videos to make sure it will work for our study. The
> > videos will play, but they will not play for the whole length every
> > time. I am using two practice videos, one 13 seconds and one 6 seconds
> > long, and have the program set up to randomly pull them from a list
> > and play them after a blank screen. I have tried pre-release, changing
> > the run time of the videos, and various video formats, but have not
> > had much success. When I increase the number of cycles, some of the
> > presentations will run the whole time and some will cut off half-way
> > through. The timing of the presentation of stimuli is not necessarily
> > important, but we need each video to run for the set length of time
> > (about 7 seconds).
> >
> > We are expanding upon a study that used still images, so we are not as
> > familiar with the various video formats, compressions, etc. I would
> > appreciate any help!
> >
> > Lindsay
> >
>
> -- 
> David Vinson, Ph.D.
> Senior Postdoctoral Researcher
> Cognitive, Perceptual and Brain Sciences Research Department
> University College London
> 26 Bedford Way, London WC1H 0AP
> Tel +44 (0)20 7679 5311  (UCL internal ext. 25311)
>
>
>

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