Wechselspieler is an interactive tool to transform movement information coming from a file or camera based video stream into sound in realtime using the MIDI protocol. It features an easy to use GUI for defining and editing the image region to MIDI mappings.

The original idea behind it was to let people on a dance floor influence the music they are dancing to. The German name Wechselspieler, which could be translated to Interplayer, was chosen to express this idea.

The software is "free" under the terms of the GNU general public license Version 2.

Currently wechselspieler does not implement all of the features listed below which are planned for the 1.0 release.

• Runs on GNU/Linux.
• Video image binarisation with color thresholds and difference images.
• Multi object video tracking.
• Video input from S-Video, Composite, TV, local and remote file streams.
• MIDI protocol output via "Note On/Off" and "Controller Change" events. All MIDI parameters can be customized.
• Control of all parameters for trigger regions and image binarisation while program is active.
• Flexible image processing customizing through the GStreamer media processing framework.
• Session management support. On start up the program automatically restores the state before you last quitted it.
• Graphical user interface compliant to the GNOME user interface guidelines.
• Binary packages for Debian GNU/Linux 3.1 distribution.
• OSC protocol support for integration with PD, SuperCollider 3, Max/MSP and others.

Although there are definitly places for improvements (better region editing, selectable ALSA input, changeable video size, to name a few) the software does what is it supposed to do: grabbing images from video, analysing it in realtime for changes and sending MIDI events if a change occured in a certain place in the image. What it needs most is testing by other users on different hardware and different Linux distributions.