Sunday Morning idle queries ??

Tom Horsley tom.horsley at
Sun Jul 6 15:31:05 UTC 2008

On Sun, 06 Jul 2008 10:16:39 -0400
William Case <billlinux at> wrote:

> 3) My project for the next while is to work out how various multimedia
> work.

I'd tackle something simpler if I were you, like maybe quantum theory
or ending war.

All I know is that the only tool that (so far) has worked on absolutely
everything is 32 bit mplayer with every Windows codec I could find on
the web stashed in /usr/lib/codecs/ (it works on an awful lot of stuff
without the Windows codecs, but that last 10% need them).

The part that goes really haywire is interfacing to audio. You'd
think it might be simple to say "Hey, play this DVD and send the
dolby sound bitstream out the optical SP/DIF interface.", but 6 weeks
of web searches were needed for me to find the totally obvious
(that's sarcasm :-) command sequence I needed:

amixer set IEC958 unmute
amixer set 'IEC958 Playback AC97-SPSA' 0
amixer set 'IEC958 Playback Source' PCM
mplayer -ao alsa:device=hw=0.0 -ac hwdts,hwac3,

Naturally, those obvious commands only work for my specific
hardware given the specific device numbers allocated by the
kernel, etc. Naturally, fedora 9 has changed audio so much
that I haven't been able to discover how to make any of this
work there (heck, maybe it is even simpler, but the last
thing any linux developers ever do is provide documentation :-)

And, of course, that only works for something like a DVD that
has an already encoded bitstream available. To get my plain
old mp3s to play out the SP/DIF port, I'd apparently have to
become an international pirate and build my own version of alsa
with support for illegal plugins to do PCM encoding :-).

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