[pulseaudio-discuss] Splitting a 7.1 device into virtual 5.1 + 2.0 devices?

[Tanu Kaskinen]

On Sat, 2016-04-09 at 16:22 +0200, 紅 蒼穹 wrote:
> > > - for the Stereo sink, I want the LFE to be mixed into the stereo 
> > > channels when downmixing, but left untouched for stereo content (just 
> > > like it did with PA6.0). Same for rear and center channels. 
> >  
> > This does not require any changes to anything. As long as remixing is 
> > enabled in daemon.conf (like it is by default), playback streams with 
> > LFE will be downmixed to have LFE in the left and right channels, and 
> > if the playback stream doesn't have an LFE channel, then there's 
> > nothing to do (leaving LFE "untouched for stereo content" doesn't make 
> > sense to me, because there's nothing to leave untouched). 
> 
> That's not what seems to be happening here, though.
> 
> When I have lfe remixing = yes (default):
> - LFE is mixed to stereo output when downmixing from 5.1
> - there are no low frequencies present at all in 5.1 output when
> playing a stereo track.

LFE remixing is supposed to move low frequencies from all other
channels to the LFE channel by default. Are you saying that the LFE
channel doesn't get low frequencies either?

If you'd prefer not to have the low frequencies moved from the other
channels to the LFE channel, you can set "lfe-crossover-freq = 0" in
daemon.conf.

> When I have lfe remixing = no:
> - LFE is mixed to stereo output when downmixing from 5.1

That's against the documentation in the daemon.conf man page, but I
think this actually makes sense. "enable-lfe-remixing = no" is really
just meant to prevent us from synthesizing the LFE channel content,
since some LFE speakers might not like high frequencies (the option
used to be disabled by default before the LFE crossover filtering was
added).

> - LFE (or rather, bass) is present in 5.1 output when playing stereo

In which channels? When LFE remixing is disabled, bass should be
preserved in all channels, but the LFE channel should be silent.

> So to me, it seems the behavior is exactly inverse to what the
> description of the option says.
> 
> Btw, the current setup triggers that bug I reported [1] in a slightly
> different way: connecting the headphones switches the device to 2.0
> mode, unplugging even without restarting leaves the device in 2.0
> mode. This mutes the remapped stereo output.

I've forgot, do you have a separate headphone connector in addition to
the 7.1 connectors? And do you mean here that using the separate
headphone connector switches to 2.0 mode? That would be expected,
because plugging in headphones makes other outputs unavailable. When
you unplug the headphones, however, the card should switch back to 7.1
mode if you had manually selected that profile previously. If you
haven't selected it manually previously, then leaving the profile at
2.0 is also expected.

-- 
Tanu