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

[紅 蒼穹]

>>> The easy way is to use hdajackretask your grey line out as internal 
>>> speaker, there will be headphone, 5.1 line out jacks and stereo speaker 
>> I tried that (removing the remap config), but for some reason the 
> only thing pavucontrol now sees is a single audio device that is able 
> to playback at most 5.1 channels. I can't re-route sound to anything 
> else in pavucontrol and the stereo speaker output is silent. I tried 
> both internal speaker and internal speaker (back) 
> 
> https://lists.freedesktop.org/archives/pulseaudio-discuss/2016-April/025971.html 
> 
> Try enable independent headphone and disable pulseaudio mute if you 
> want two sinks, you can configure the grey jack as second headphone 
> jack 
Thanks, I will look at that later, since the current setup mostly works.

----------------------------------------
> From: tanuk at iki.fi
> To: pulseaudio-discuss at lists.freedesktop.org
> Date: Tue, 12 Apr 2016 14:40:51 +0300
> Subject: Re: [pulseaudio-discuss] Splitting a 7.1 device into virtual 5.1 + 2.0 devices?
>
> 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?
At least I can't hear any on any non-5.1 content. It is correctly present with 5.1 content though

>> 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).
Yes, it seems the option is indeed only intended for upmixing. It doesn't make sense to lose the LFE channel when downmixing, or at least I can't think of any use beyond experimenting.

> 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.
Setting that together with "enable-lfe-remixing = yes" option seems to work better, it sounds about the same as "enable-lfe-remixing = no"

>> - 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.
Ok, I plugged out all jacks except the center/LFE one, and it is as you say. The LFE is silent in this case. Incidentally, I have a song that is available both in 2.0 and 5.1. What I think my issue is that while with the 5.1 version there are low frequencies present on all channels except the center, playing the 2.0 version with "lfe-remixing = yes" results in the front channels having their low frequencies stripped and moved to LFE. 

In addition to that, the synthesized LFE channel is very quiet, which is why I thought it wasn't there in the first place. I guess this is what the "lfe-crossover-freq = 0" "fixes", but all content is sent to LFE as a result and the music sounds rather muddy. That's the main reason why I wanted to configure it to only downmix, but never upmix.

Speaking of volumes, is there an option to somehow boost only the LFE in pulseaudio? Changing it with alsamixer gets overridden next time I use my media keys.

>> 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.
My card is set to 7.1 + stereo input at first - manually, but it's also what the card was set to the first time I installed pulseaudio, if I remember correctly. So it's manual but also the default. I plug my stereo headset to the front headphone jack (so yes, a separate one). The card switches to stereo input and mutes rear output as expected. I unplug the headphones from the front jack. The card unmutes /only the front channels/, leaving the speakers (connected to the side channels socket) muted. It also stays in stereo input instead of changing back to 7.1 + stereo input.

Regards,
Soukyuu