[alsa-devel] ALSA, GStreamer and surround

[Christian F.K. Schaller]

Hi Takashi,
Thanks for trying to help us with trying to resolve
http://bugzilla.gnome.org/show_bug.cgi?id=410403. 

I tested a bit with a 6-channel .wav file and aplay. It seems it shows
the same issues that we are seeing in GStreamer. Namely that if I try:

aplay -D front dust51.wav 
Playing WAVE 'dust51.wav' : Signed 16 bit Little Endian, Rate 48000 Hz,
Channels 6
aplay: set_params:905: Channels count non available

It correctly tells me that it doesn't support outputting this many
channels. This is fine for GStreamer as it allows our negotiation to
plug in a downmixing element.

However if I do:
 aplay -D default dust51.wav 
Playing WAVE 'dust51.wav' : Signed 16 bit Little Endian, Rate 48000 Hz,
Channels 6

It plays out the 'front' channels, but the remainders just get lost. So
when outputting to default neither do alsa downmix by itself or fail
telling you that you don't have the needed 6 channels available.

Since Jan brought up the issue of behaviour differences between
plug:surround51 ad surround51 I thought I give you the output of that
too.

aplay -D surround51:0 dust51.wav 
Playing WAVE 'dust51.wav' : Signed 16 bit Little Endian, Rate 48000 Hz,
Channels 6
aplay: set_params:878: Broken configuration for this PCM: no
configurations available

aplay -D plug:surround51:0 dust51.wav 
Playing WAVE 'dust51.wav' : Signed 16 bit Little Endian, Rate 48000 Hz,
Channels 6
ALSA lib pcm_params.c:2152:(snd_pcm_hw_refine_slave) Slave PCM not
usable
aplay: set_params:878: Broken configuration for this PCM: no
configurations available

Christian

On Thu, 2007-03-29 at 12:52 +0200, Takashi Iwai wrote:
> At Wed, 28 Mar 2007 17:52:21 +0200,
> Christian F.K. Schaller wrote:
> > 
> > Hi,
> > We are still having issues resolving how to deal with Surround sound and
> > ALSA in GStreamer. If anyone knowledgeable about ALSA would be willing
> > to comment on this bug:
> > http://bugzilla.gnome.org/show_bug.cgi?id=410403
> > 
> > We would much appreciate it.
> 
> Not sure what actually the code is doing, but does simply aplay work
> on that system?
> 
> 	% aplay -D surround51:0 foo.wav
> 
> or
> 
> 	% aplay -D plug:surround51:0 foo.wav
> 
> The 5.1 output is sensible to devices, so it's helpful to know what
> hardware is used, too.
> 
> 
> Takashi