[open] Error report OpenSesame on new computer

Patrick

Hi all,

I have recently purchased a new computer and OpenSesame opens without a problem. However, if I try to open the experiment files from my old pc on my new pc, an error report pops up with the description "script error", "Failed load plugin 'media_player_vlc". I use version 0.27.1 on both pc's, but for some reason the experiment files only open on my old pc. I checked the plugins in program files on my new pc, and the media_player_vlc-plugin was present, so OpenSesame should be able to open any experiment files containing a vlc-video, right? Could the operating system be causing the problem? My old pc used Windows XP and the new one uses Windows 8. Any help would be welcome.

Regards,
Patrick

lvanderlinden

Hi Patrick,

I forwarded your question to the developer of the media player plugin.

Best,

Lotje

Daniel

Hi Patrick,

Have you installed VLC at its default location on the new machine (it needs to be in Program Files (x86)\Videolan etc.). Also, could you tell me if a traceback is printed in the debug window of OpenSesame? (probably not, but better to ask anyway). I have a hunch that you are missing a library of VLC, or that the module can't find it in Windows 8. I don't have Win8 and thus haven't had the chance to test the plugin on there yet, so have no way to dive into this myself for now.

Best,

Daniel

Patrick

Hi Daniel,

That proved to be a simple yet effective solution to the error report (I saw no traceback). However, if I want to run the experiment in full screen, I only hear sound (I don't have that problem when I run it 'in window'). Do you have any idea what's going on?

Regards,
Patrick

Daniel

Hi Patrick,

Yes, that is a problem I am still struggling with as well. What the plugin actually does is 'hijack' the window away from the OS backend that is drawing the stimuli and display the movie in the window. When the player has finished playback, it gives the window back to the backend to continue as before. The problem is that some backends do not really allow the window to be hijacked, and this differs per windows version (in Linux all backends worked fine after my latest tests). The only solution I can give at the moment for this problem is to change backends and see which one works for you. In Windows XP I had success with the expyriment backend and a black screen with the legacy backend, but on a Windows 7 machine I had exactly the opposite result.

The python support of VLC remains limited, so I don't know if I'll ever be able to solve this problem using that player. In the near future I plan to write a new plugin based on the AVBin libraries which offer much more extensive possibilities and should enable me to get things working for every backend.

Best,

Daniel

Regardless of my previous e-mail, I've looked into this matter and found a nice work-around. As you mentioned, movie playback works fine in windowed mode, which you can let mimick fullscreen mode by the following back-end tweaks.

A word of warning before I begin: only do it this way if the timing of your experiment is not critical! Displaying in windowed mode probably has worse timing characteristics than fullscreen mode. If you are doing some time-critical RT measurements somewhere in your experiment these will probably contain a lot more noise due to display timing fluctuations in windowed mode!

That being said, to mimick fullscreen mode:

1. Go to General Properties of your experiment
2. Choose the backend you want to use
3. Set the values of resolution to those of your screen
4. Click Back-end settings at the bottom-left
5. Set the value of Window position to 0,0
6. Set the value of Draw window frame to no
7. Start your experiment in windowed mode

With these settings I managed to run my experiment in fullscreen and have perfect movie playback with each backend.

Let me know if it works!

Patrick

Hi Daniel,

If I choose the Xpyriment Back-end, it does not display the options in Back-end settings you talk about. However, if I choose the Legacy backend, it displays the options you mention, and OpenSesame displays the experiment as if it were in fullscreen mode. On the side, I didn't even need to run the experiment in windowed mode, because with the Legacy Back-end I could also successfully tun the experiment in fullscreen mode.

Thanks for your help!
Patrick

froukehe

I try to run the vlc-plugin on a Linux system (Lubuntu 13). I have the latest version of VLC installed (VLC media player 2.0.8 Twoflower) in the default location and have the plugin installed in the plugin folder (updating opensesame to the latest version did not seem to add this plugin automatically; and OpenSesame tells me that there is a newer version; but that's another issue). Unfortunately I still get the following error message:

"Failed to load plugin 'media_player_vlc'
line: 45
exception message: This plug-in requires that VLC player 2.X is installed in the default location. You can download VLC player for free from http://www.videolan.org/. Error: [Errno 2] No such file or directory
exception type: Exception

Traceback (also in debug window):
  File "/usr/lib/pymodules/python2.7/libopensesame/experiment.py", line 228, in parse_definition
    string, self.item_prefix())
  File "/usr/lib/pymodules/python2.7/libopensesame/plugins.py", line 293, in load_plugin
    item_module = import_plugin(plugin)
  File "/usr/lib/pymodules/python2.7/libopensesame/plugins.py", line 267, in import_plugin
    return imp.load_source(plugin, path)
  File "/usr/share/opensesame/plugins/media_player_vlc/media_player_vlc.py", line 45, in <module>
    % e)
Exception: This plug-in requires that VLC player 2.X is installed in the default location. You can download VLC player for free from http://www.videolan.org/. Error: [Errno 2] No such file or directory"

Any idea what may be going wrong?

sebastiaan

Hi Frouke,

I'm guessing you don't have the VLC python bindings installed. You can get these from here:

• https://www.olivieraubert.net/vlc/python-ctypes/

There are multiple versions, but I think you need to pick the one that matches your version of the VLC player, which needs to be installed as well (but already is in your case).

To install the Python bindings, simply put vlc.py in any Python-path folder, or the media_player_vlc folder.

Cheers!
Sebastiaan

froukehe

I think I am one step further to solving the problem. I copied the file to every python and media_player_vlc folder I could find, but the problem persists. But then I noticed that there was also a message 'permission denied' in the debug window. So I started opensesame with sudo ('sudo opensesame'), and this time it all worked. The issue now is going to be to find out for which folder I need to set permissions to all users...

Thanks!