[pulseaudio-discuss] channel_map problems with alsa

Alex Malinovich alex at malinovich.name
Wed Feb 14 01:54:43 PST 2007

On Wed, 2007-02-14 at 08:57 +0100, Pierre Ossman wrote:
> The channel remapper is a bit stupid right now, so it won't move a two
> channel (f-r, f-l) stream to b-r, b-l. That is why you're not getting
> any audio with that channel map.

You're a genius. Or, actually, I'm stupid. See below. :)

> > If I change the rear-left or rear-right volumes for combined, nothing
> > happens. If I change front-left or front-right volumes, it changes both
> > of the speakers on that particular side. It's not a problem using things
> > like audacious, but it could be a problem once I start using things like
> > mplayer or totem to play DVD's and I suddenly get half of the audio
> > coming out of twice as many speakers. :) Any suggestions on what I can
> > try?
> I would guess that you've made a mess of your channel map. The FAQ
> contains an example of exactly this setup (#27).

Ok, so it took me quite a bit of tinkering but I finally figured out
what was going on. Your comment above is what finally did it. I was just
hoping for something that doesn't seem to be the case (but if it does,
please correct me).

I thought I had my setup "working" because I could start up audacious
and hear sound through all 4 speakers. In fact, this is "broken" since
the files I was playing were 2-channel mp3's. But my setup was set so
that the rear channels were just a copy of the front channels.

I finally got a proper 6-channel test file and played it through
mplayer, and I got independent sound from all 4 speakers. (Except that
rear left seems to be center, and rear right is subwoofer, but I'm just
attributing that to the fact that I've got a 4.1 setup and I'm using a
5.1 test file.)

So now the only remaining question is, is it still possible to get the
"broken" 4 speaker output for 2-channel files? Is it possible to somehow
set up a 2nd combined sink that duplicates the two front channels to the
two rear channels while leaving the "functional" combined sink in place?

Alex Malinovich
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Encrypted mail preferred. You can get my public key from any of the
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