[pulseaudio-discuss] Dolby Digital / DTS s/pdif pass-through

Michał Sawicz michal at sawicz.net
Tue Dec 28 04:35:38 PST 2010

Dnia 2010-12-28, wto o godzinie 12:46 +0100, Vincent Tschanz pisze:
Can someone explain to me in broad terms how things should work through 
> Pulseaudio and Alsa?  And what I should do to get ac3/DTS decoded by
> my amp?

Pulseaudio can't currently pass AC3 or DTS through to your SPDIF output.
There are pending patches [1] for AC3 but AFAIK they're not ready yet.

You can use ALSA to pass through AC3 and DTS in mplayer by providing a
'alsa:spdif' as a default audio output (mplayer option 'ao') and
'hwac3,hwdts,' as audio codec (mplayer option 'ac', note the comma!).

With the above, mplayer will pass through AC3 and DTS through SPDIF and
also feed stereo streams as PCM. You could use Pulse for stereo streams
over SPDIF, but mplayer has no facilities to switch audio outputs
easily, you'd have to provide a '-ao pulse' option on the command line
when there's a stereo stream played.

In VLC you will also need to use ALSA:spdif output and enable pass

Michał Sawicz <michal at sawicz.net>
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