What is ProjectM?
ProjectM is an open source music visualizer based on the Milkdrop plugin for Windows/Winamp. It now has a Qt GUI that can visualize your audio output through either JACK or PulseAudio, in addition to a component. This wiki currently focuses on the PulseAudio standalone GUI.
The binaries for ProjectM are not currently included in Arch. However you have two options for obtaining the packages. Either build AUR yourself or you can get them from an unofficial repository. Currently packages are being built by Luciferin and are on the compiz-fusion-git repository.AUR from
/etc/pacman.conf as root and add the following repositories to the bottom:
[compiz-fusion] Server = http://compiz.dreamz-box.de/i686
Save and Exit.
To synchronize the newly added repository and install the latest package group for PulseAudio:
# pacman -Syy projectm-pulseaudio
Once everything is install just do the following from the command line:
The first PulseAudio sound output device is used from the list shown by the command
If this is not the device you want to use, the easiest thing to do is to press 'm' to bring up the menu, then Settings > Pulse Audio Settings. Uncheck the checkbox at the bottom which says "Try first available playback monitor," then select the correct device. Most likely it is one which ends in ".monitor" (if you want the visualizer to visualize what's being output/played).
Some information on usage and configuration can be found in the ProjectM FAQ
Otherwise a good place to ask question are the projectM help forums on Sourceforge.