ARVideoCapture

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ARVideoCapture

How to install, setup and use the ARVideo video capture engine.

Overview and Introduction:

The ARVideo video capture engine is one of multiple video capture engines
supported by Psychtoolbox's Screen() command. This engine internally uses
the video capture library implemented by the free software "ARToolkit", a
free toolkit for augmented reality applications, licensed under GPL v2
license and included in Psychtoolbox.

The ARVideo engine has the engineId 2. On MS-Windows operating systems,
this is the default engine used for video capture if no other engine is
explicitely selected. You can change the global default selection of a
videocapture engine via the command

Screen('Preference', 'DefaultVideoCaptureEngine', engineId);

anywhere in your scripts. The setting will affect the next
Screen('OpenVideoCapture',...); command and override the built-in default
engine selection for your operating system.

You can also select the engine on a case by case basis by passing the
optional 'engineId' parameter to the Screen('OpenVideoCapture',..., engineId);
command when opening a video device.

ARVideo uses different capture engines under the hood, depending on the
operating system you're running:

On GNU/Linux, it uses the open source GStreamer multi-media framework to
access almost any kind of video source supported on the Linux OS. You'll
need to have GStreamer installed on your Linux system for this to work.

On Mac OS/X, it uses the Quicktime Sequencegrabber engine, just as the
default Quicktime engine (engineId 0) does on OS/X, so most of the time
you will want to use the OS/X default engine instead.

On MS-Windows, where ARVideo is the default engine, it uses the Microsoft
Windows DirectShow multi-media framework. As pretty much all video
capture devices for Windows come with DirectShow drivers, this should
allow to access almost any video capture device that is supported on the
Windows platform.

Installation on MS-Windows:

On MS-Windows, you'll need to install a few special runtime DLL libraries
before you can use the video capture engine (or other parts of ARToolkit,
e.g., the ones supported by PsychCV()). For that you need to open the
Psychtoolbox subfolder Psychtoolbox/PsychContributed/ARToolkitStuff/ ,
e.g., via the Windows explorer. Then you'll need to copy a few of the
.dll files inside that folder into one of the following locations in your
system: Either the Matlab DLL installation directory - that is the
directory inside your Matlab folder which also contains the Matlab main
executable "Matlab.exe" and a host of other libraries (files ending with
the extension .dll or .DLL). Another option is to copy these files into
the main system library folder, e.g., C:\Windows\system32\ on most XP or
Vista systems, or C:\WINNT\system32\ on older Windows 2000 systems.
You will likely need administrator privileges to copy the DLL files
there.

On some systems, it is sufficient to copy the files libARvideo.dll and
DSVL.dll to one of the target folders. If the video capture engine
doesn't work and aborts with some error message about failing to load
DLL's, you'll also need to copy the Microsoft Visual C runtime libraries
msvcp71.dll and msvcr71.dll as well.

Another prerequisite is that you have the Microsoft DirectShow runtime
and proper drivers for your video capture device installed, but this can
be almost taken for granted on any Windows 2000 system or later.