[pulseaudio-discuss] Prologic II upmixing with the Asus Xonar DX

Colin Guthrie gmane at colin.guthr.ie
Mon Dec 20 03:06:43 PST 2010

'Twas brillig, and Dom H at 20/12/10 10:06 did gyre and gimble:
> Is this possible to use while running Pulseaudio?
> I've noticed that alsamixer has a toggle 'Stereo Upmixing' with
> options like 'Front+Surround'. I'm not sure how this will work, I have
> the 4.1 profile selected in pulse with remixing/LFE enabled so this
> probably conflicts. I'm guessing pulse would have to pass stereo
> output to the Alsa driver for this to work which I'm also guessing is
> not possible if pulse has remixing enabled.

You can kinda do things manually, but certainly not easily. PA (to the
best of my knowledge) does not handle this alsa control so it should
really just be set to Off and then let PA do things in software.

If the 4.1 profile is selected then PA will always want to pass the
device 5 channel data, whether it is upmixed or not and I'm guessing a 5
channel stream (with some channel silent) would not trigger the h/w
support. Thus you'd have to swtich to a Stereo profile to do the
upmixing (I think this is correct, but not 100% certain).

Then you get the more complex cases like when you are playing both
Stereo and 4.1 sound at the same time - e.g. watching a movie but have
an event noise due to a new email or Voip call etc. - then you'll have a
mix of different formats so would likely need a software mixer to take
care of it to provide a consistent experience.

For us it's a matter of choosing the most sensible structure that works
for most people. I guess there would be a way to make things work better
but it would be pretty complicated and it would only benefit a small
subset of users. Maybe one day.

If I'm wrong with any of the above, hopefully someone will correct me. I
don't really have access to much in the way of interesting h/w :(



Colin Guthrie

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