[pulseaudio-discuss] pulseaudio overwrites correct channel mapping provided by alsa

[Tanu Kaskinen]

On Thu, 2016-03-24 at 14:26 +0100, Dennis Heuer wrote:
> Hello,
> 
> I already wrote to this list and provided some incorrect temporary
> information. Because nobody answered, I went to the alsa mailinglist
> and got the case corrected. Here's the new stand (also see the
> appendix):
> 
> --- cite ---
> 
> Dennis Heuer wrote:
> > 
> > Dennis Heuer <einz at verschwendbare-verweise.seinswende.de> wrote:
> > I now updated to linux 4.4.0.13.
> > 
> > > 
> > > > 
> > > > > 
> > > > > 	control.41 {
> > > > > 		iface PCM
> > > > > 		name 'Playback Channel Map'
> > > > > 		value.0 3
> > > > > 		value.1 4
> > > > > 		value.2 5
> > > > > 		value.3 6
> > > > > 		value.4 7
> > > > > 		value.5 8
> Oops, the valid values actually begin at 3.  This channel map is
> correct: 3:front left, 4:front right, 5:rear left, 6:rear right,
> 7:front center, 8:LFE
> 
> PulseAudio's map:
> > 
> > front-left,front-left-of-center,front-center,
> > front-right, front-right-of-center,rear-center
> would be the equivalent of 3,12,7,4,13,11.  This is not what the driver
> tells it; this appears to be a bug in PulseAudio.

Where is this "front-left,front-left-of-center,front-center,front-
right,front-right-of-center,rear-center" coming from? PulseAudio
doesn't use such map by default, and if I understood correctly, you are
not trying to use such map either. Where do you see this map occurring?
Does "pactl list sinks" show that, or is that visible somewhere else?

> I did put this line in default.pa, which worked but without effect:
> 
> load-module module-alsa-sink
> sink_name=alsa_output.pci-0000_00_14.2.analog-surround-51 device_id=1
> channels=6
> channel_map=front-left,front-right,rear-left,rear-right,front-center,lfe

I don't know what "device_id=1" is supposed to do when given to module-
alsa-sink. I tried to look it up in the code, but I gave up, because
the code in question was too complicated. Usually when you load module-
alsa-sink, you would use "device=surround51:1", if you're trying to use
5.1 on card 1.

In any case, this is likely to conflict with the sinks that get
automatically loaded, unless you have removed module-udev-detect from
the configuration.

-- 
Tanu