[pulseaudio-discuss] Cannot have iec958:0 and a52:0 simultaneously?

Tanu Kaskinen tanuk at iki.fi
Thu Jul 15 02:27:37 PDT 2010

On Thu, 2010-07-15 at 08:04 +0000, Michael Rans wrote:
> Ok. But my question then is why does the A52 profile not appear in
> Sound Preferences when I put card $CARD, but it does appear if I put
> card 0 or "card { @func iadd integers [ $CARD -2 ] }" (to map a52:2 to
> card 0)?

I think you don't quite understand what "profile" means in pulseaudio
context (which isn't really your fault at all). I believe what you
called "A52 profile" that is (or isn't) visible in "Sound Preferences"
is really "A52 sink". Card profiles are a different thing than sinks.
The active profile determines what sinks and sources exist at any given
time for a sound card. When you change the active profile of a card, all
existing sinks and sources of that card are removed and new sinks and
sources are created.

Now the answer to your question: if you replace $CARD with 0, then what
happens is that when scanning for available profiles for each card, it
seems to pulseaudio that the profile is available for each of your three
cards (main card, webcam's mic and graphics card's hdmi output), because
a52:0, a52:1 and a52:2 actually all use the main card's spdif output.
The reason why the A52 sink isn't loaded for the main card by default is
that there are other profiles with higher priority. Since the webcam
only has the microphone, the A52 profile becomes the top priority
profile for output, and the A52 sink is created by default.

If you use "$CARD -2", then scanning for the A52 profile for the main
card and the webcam probably fails completely due to the negative card
index. For the graphics card the scanning succeeds. In this case the A52
profile is activated by default because the only other output profile is
hdmi, which has lower priority than a52.

I'm not sure what you mean by "Sound Preferences", but it's probably
gnome-volume-control, and AFAIK you should be able to switch the card
profile with that. I don't know how, though. Debian doesn't enable
pulseaudio by default, which is probably why my version of
gnome-volume-control doesn't contain any pulseaudio stuff. In
pavucontrol the card profile can be changed from the Configuration tab.

Tanu Kaskinen

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