[pulseaudio-discuss] {PATCH][RFC] AC3 passthrough support

Michael Rans mcarans at yahoo.co.uk
Sun Jul 11 02:26:04 PDT 2010

That's the the problem - as you put it "both sinks (spdif/stereo and spdif/a52) 
can't exist at the same time".

If A52 encoding occurred in Pulseaudio, there would only be one sink, hence the 
switch between stereo and A52 would be transparent and could occur even while 
the music is playing (with a small interruption).

Is the A52 profile in Ubuntu Lucid 10.04LTS?


From: Tanu Kaskinen <tanuk at iki.fi>
To: pulseaudio-discuss at mail.0pointer.de
Sent: Sun, 11 July, 2010 10:15:12
Subject: Re: [pulseaudio-discuss] {PATCH][RFC] AC3 passthrough support

On Sun, 2010-07-11 at 08:43 +0000, Michael Rans wrote:
> At the moment I can switch between A52 and stereo SPDIF but it
> requires file editing and restarting Pulseaudio. 
> 1. I haven't tried the new profiles yet - does this mean with the
> profiles in a GUI, I would be able to switch from A52 to stereo SPDIF
> output without editing any files or restarting Pulseaudio? 

Yes. And the A52 profile is not new, it's at least a year old now. The
profile that I mean should show up as "Digital Surround 5.1 (IEC958/AC3)
Output" in the card profile list, while the stereo profile is "Digital
Stereo (IEC958) Output" or "Digital Stereo Duplex (IEC958)" (the latter
actually means that only output is enabled, no input at all - that's a

> 2. Would I be able to switch while music is playing between stereo and
> A52 and back (as is currently possible between my SPDIF and HDMI on
> different soundcards)?

The switching requires changing the card profile, because both sinks
(spdif/stereo and spdif/a52) can't exist at the same time. So, just
select the card profile and you're done. Except I think it's possible
that your music gets routed to some wrong sink, so you may need to also
move the music stream after switching the card profile.

Tanu Kaskinen

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