[Pkg-alsa-devel] Bug#503839: Bug#503839: /usr/lib/alsa-lib/libasound_module_pcm_vdownmix.so: vdownmix from 5.1 does not incorporate LFE channel

[Josh Triplett]

On Mon, Sep 07, 2009 at 06:44:48PM +0200, Apelete Seketeli wrote:
> On Sat, Sep 5, 2009 at 16:45, Josh Triplett<josh at joshtriplett.org> wrote:
> > With the lines you suggested added to the stanza I mentioned in the
> > original report:
> >
> > ~$ speaker-test -c 6 -t wav
> >
> > speaker-test 1.0.20
> >
> > Playback device is default
> > Stream parameters are 48000Hz, S16_LE, 6 channels
> > WAV file(s)
> > Segmentation fault
> 
> This is to be expected. You can only use one of the setup
> instructions, not both.

"not working" seems to be expected; a segfault seems like a bug
regardless. :)

> The following lines does not enable surround
> sound on my side, it simply doesn't work:
> 
> pcm.!surround51 {
> 	type vdownmix
> 	slave.pcm "default"
> }

Those almost work for me.  When I do
speaker-test -D surround51 -c 6 -t wav
I get (spatially correct) sound for 5 channels, but no sound for the .1
(LFE).

> > If you had something different in mind than either of the two
> > alternatives I tried, please tell me what full .asoundrc to try and I'll
> > try it.
> 
> Vdownmix setup seems to be device dependant, according to what you say.
> On a Thinkpad X60 with Intel HDA sound card I'm able to play 5.1 video
> files just fine (through stereo headphones), using only these lines in
> my ~/.asoundrc:
> 
> pcm.!downmix51 {
>  type vdownmix
>  slave.pcm "surround51"
> }
> 
> pcm.!default "plug:downmix51"

With your setup, does "speaker-test -c 6 -t wav" generate sound for all
six channels?

ThinkPad X200 with Intel HDA (snd-hda-intel) here.  With that exact
setup in ~/.asoundrc:

~$ speaker-test -c 6 -t wav

speaker-test 1.0.20

Playback device is default
Stream parameters are 48000Hz, S16_LE, 6 channels
WAV file(s)
Playback open error: -16,Device or resource busy
Playback open error: -16,Device or resource busy
Playback open error: -16,Device or resource busy
Playback open error: -16,Device or resource busy
Playback open error: -16,Device or resource busy
Playback open error: -16,Device or resource busy
Playback open error: -16,Device or resource busy
Playback open error: -16,Device or resource busy
[...]

> If it really doesn't work then there's something 'wrong' with vdownmix.
> Maybe vdownmix setup depends on the sound card ? I know that it took
> me a few trials before getting 5.1 to play on my computer, and yet it
> doesn't work like I would like it to (sound mixing is disabled when
> vdownmix is enabled, for instance)...

It certainly *shouldn't* depend on the sound card.  Mixing 5.1 to 2.0 in
software should work anywhere, and I have working 2.0.  Of course, that
doesn't mean it *doesn't* depend on the sound card, just that it
*shouldn't*. :)

Happy to try any further suggestions or provide additional information,
if that helps debug this issue.

- Josh Triplett