by default the @ and ! keys on the keyboard are assigned to seek_chapter functions in mplayer (see mplayer -input cmdlist for a complete listing of input functions).
When playing back a standard CDDA with "mplayer cdda://:4" the @ and ! don't work. More specifically I get a lot of errors on the console:
!!! read_filepos differs!!! report this bug...
This happens when playing back the first track and trying to seek to the next track.
According to this thread on the mplayer mailing list CDDA track seeking should work:
Attaching emerge --info output...
Created attachment 153459 [details]
emerge --info output
Chapters and precise seeking with DVD and similar stuff is currently only supported with -nocache.
Though if you want you can try the experimental patch here: http://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/2008-May/057516.html
Seems like the patch made it into upstream.
It's now in mplayer-1.0_rc2_p27120, and works for me (at least what CDDA playback is concerned).
Resolving bug to UPSTREAM
Closing since ebuild is in portage (keyworded though)