Alexander E. Patrakov skreiv 07.10.2018 09:44:
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?
This is a known bug that appears because there are two 5.1 standards:
proper 5.1 and 5.1 Side. The video player (I guess you use mpv) says:
the extra two channels have to come from the side.
Looks like you’re right. If I run ‘ffprobe’ on my 5.1 test file, it returns:
Stream #0:1[0x1100]: Audio: dts (DTS-HD MA) ([134][0][0][0] /
0x0086), 48000 Hz, 5.1(side), s32p (24 bit)
So the video file (and mpv) seems to use the ‘5.1(side)’ standard.
(Which is a bit strange, since this is supposed to be a video file to
test a normal 5.1 setup, AFAICS.)
But your system does not have speakers there, it has them on the rear.
So PulseAudio attempts to remix. In fact, sound both with and without
remixing-use-all-sink-channels is wrong.
What’s wrong about the remixing when one uses
‘remixing-use-all-sink-channels = yes’?
Solutions: either upgrade to a 7.1 system or use a different player
that doesn't care about Side and Rear. Totem or anything other
GStreamer-based should work fine.
I found another solution. In ‘.config/mpv/mpv.conf’, add the following:
audio-channels=5.1,stereo
Now both 5.1 and stereo material use the correct channel mapping (if I
use ‘remixing-use-all-sink-channels = no’ and the 5.1 ouput profile in
pavucontrol).
With VLC, I had the same channel mapping problem as in mpv. In the
preferences dialogue, there is an ‘Advanced | Audio | Filters | Remap’
setting where I can remap the side audio to the rear speakers. But
unfortunately, it doesn’t seem to have any effect (I *have* enabled the
‘remap’ filer in ‘Advanced | Audio | Filters’, and even restarted VLC).
But no worries; I prefer mpv anyway, and with the additional config
option, everything seems to work fine.
For anyone else who has a similar system (computer connected to a 5.1
receiver / home theatre system using HDMI), here’s all the config file
changes I have made to get both stereo and 5.1 sound working perfectly
(with PulseAudio 12.2):
In /etc/pulse/daemon.conf, change the default options to
remixing-use-all-sink-channels = no
enable-lfe-remixing = yes
default-sample-channels = 6
default-channel-map =
front-left,front-right,rear-left,rear-right,front-center,lfe
In /etc/pulse/default.pa and /etc/pulse/system.pa, comment out the line
(e.g. prefix it with a #)
load-module module-suspend-on-idle
In .config/mpv/mpv.conf, add
audio-channels=5.1,stereo
But in reality this should be fixed in PulseAudio code. Maybe I will
work on it next week.
That would be great. More stuff *automatically* working correctly is
always a good thing! :)
--
Karl Ove Hufthammer
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