Comment 4 for bug 276957

It turns out that using raw mplayer works so only gmplayer that has the issue. I temporarily solved it by editing the /usr/share/application/mplayer.desktop file to add in command line option -ao oss as mentioned here:

http://linuxwindows.org/2008/05/ao_alsa-unable-to-find-simple-control-pcm0.html