If you compile a new mplayer release from scratch, you might find that your -ao options don't work anymore. I had been beating myself up trying to get it to work then I finally discovered they changed the format.

instead of
-ao alsa:device=hw#0,2
now use
-ao alsa:device=hw=0.2

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FRONTEND 1 - R5A16, Athlon 3000+, NVidia Motherboard, SB live, GeForce 5200, AA 9A60
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