[Openal] Openal, S/PDIF and surround [SOLVED]

[Alfredo Pironti]

I DID IT!
I was able to play supertux, tremulous  and chromium (ok, I know that 
when it works, then it just works :-)) with full 5.1 (6-channels) 
surround, with no problems.

Here are some details.
I switched from OpenAL SI to OpenAL Soft. With respect to the open 
problems (crappy sound, and s/pdif device not being released), they both 
disappeared with OpenAL Soft. So the a52 plugin seems to be properly 
working, probably the OpenAL SI implementation was broken. So now I can 
play music back after I finish playing to some game, transparently.

When switching from OpenAL to OpenAL Soft, the configuration file must 
be completely changed, so my hypotheses on the OpenAL Soft configuration 
did not apply. First, the configuration file for OpenAL Soft is 
.alsoftrc, and not .openalrc. The syntax too is completely different.
You can find a sample alsoftrc file in the OpenAL Soft distribution. 
Here are the parameters I needed to customize:

format = AL_FORMAT_51CHN16 # We want 5.1 (6-channels) output

[alsa]
device = a52encode # tell to use our a52encode device, that uses the a52 
alsa plugin
mmap = false # a52 plugin does not support mmap! Do not try to enable 
it, or you'll get very crappy sound, and a lot of
"AL lib: alsa.c:218: mmap commit error: Resource temporarily 
unavailable" error messages!!!

I also completely commented out the other sections.

With respect to the .asoundrc file, I only had to switch from 4 to 6 
channels in the a52encode device, to comply with the full 5.1 audio of 
the OpenAL Soft library.

Just another note: installing OpenAL Soft on Ubuntu is not supported, 
however, a "gross library hack" is available for people that can't stand 
using the old library. It is easy to install it on 32-bit systems, 
because some packages are available. It is very tricky instead for amd64 
architectures, because packages are not available: you have to build the 
packages from sources. I managed to do it, and I will post some details 
on the Ubuntu forum (don't want to go off-topic here). For more info, 
see http://ubuntuforums.org/showthread.php?t=725727

Thank you again guys, my happy report would not be here without your 
support. I want to especially thank Chris Robinson for teaching me and 
hinting me to the right places!

Cheers!
Alfredo