[pulseaudio-discuss] Weak bass in stereo mode – possibility of virtual 2.1 sound profiles

[Karl Ove Hufthammer]

Alexander E. Patrakov skreiv 05.10.2018 14:41:
> пт, 5 окт. 2018 г. в 12:36, Karl Ove Hufthammer <karl at huftis.org 
> <mailto:karl at huftis.org>>:
>
>     I use my NVIDIA graphics card as a combined graphics and sound card,
>     connected to my 5.1 home theatre system via an HDMI cable (something
>     which works surprisingly well). […]
>
>
> Hello!
>
> I think you forgot to specify the version of PulseAudio...

Yes, sorry. I use PulseAudio 12.2 (on openSUSE Tumbleweed).

>
>     The 5.1 profile (‘hdmi-surround-extra1’) also work fine for *some*
>     stereo material, mainly music. But for *most* stereo material, the
>     upmixing makes everything sound too echoey (this is typically a
>     problem
>     for movies with just stereo sound and for vocal-heavy music), so I
>     usually just use the stereo profile (‘hdmi-stereo-extra1’) for stereo
>     material.
>
>
> There is a setting that prohibits upmixing (i.e. filling the rear 
> channels with a copy of front). It is 
> called remixing-use-all-sink-channels=false. But it is a relatively 
> recent addition. It does exist in Ubuntu 18.04.

Thank you! That almost did the trick! With

   remixing-use-all-sink-channels = no

and the ‘Digital Surround 5.1’ profile, stereo material now sound much 
richer, i.e. with proper bass effects, and without any echo effect. The 
audio is coming from just my front left/right speakers and subwoofer. 
Perfect!

But, strangely, real 5.1 material are now somewhat messed up. I use the 
wonderful

   hd_dts_hd_master_audio_sound_check_5_1_lossless.m2ts

video file (available several places on the Web – I’m not sure what its 
original Web site is) as a test file. The front left/right/centre sounds 
are OK. But when the rear right sound is played, the sound is mainly 
coming from my *front* right speaker (though *some* sound is also coming 
from my rear right speaker). And the sound volume is much when playing 
the sound is much lower than for the front left/right/centre sounds. For 
the rear left sound, a similar thing happens; i.e. the sound is mainly 
coming from my *front* left speaker.

I don’t understand why this is happening. Shouldn’t 
‘remixing-use-all-sink-channels = no’ just affect *upmixing* of sound, 
and leave 5.1 material alone?

(When I use ‘remixing-use-all-sink-channels = yes’, the 5.1 sound is 
correct, i.e. all the sounds come from the speakers they are supposed to.)

>
>     But I have noticed than when playing music or videos using the stereo
>     profile, the sound is missing quite some oomph, i.e. the bass is
>     *much*
>     weaker (compared to the same material played using the 5.1 profile).
>
>     I guess the reason is that PulseAudio outputs a pure stereo sound,
>     and
>     my home theatre system doesn’t redirect enough of the low-frequency
>     sound to my subwoofer. And unfortunately, my (not too expensive) home
>     theatre system doesn’t have any options for increasing this (for HDMI
>     audio).
>
>
> Are you sure that the subwoofer gets anything at all in this mode?

Yes, it gets *some* sound. But I guess that’s just my home theatre 
system redistributing some of the 2.0 sound.

-- Karl Ove Hufthammer