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

[Alfredo Pironti]

Chris Robinson wrote:
> Hi Alfredo.
> 
> After some quick searching around, it seems ALSA has an a52 plugin that can 
> encode a surround sound stream to pass-through an S/PDIF output.
> 
> http://alsa-project.org/main/index.php/A52_plugin
> 
> As far as I can understand, when you have ALSA built with A52 support, you'd 
> tell OpenAL to use the 'plug:a52' device, with 6 channel output.

Thank you very very much for this hint! It helped in solving the 
configuration problem! I can now play games with 4 channel surround 
sound! (See below)

> 
> However, at that last point, I should ask what version of OpenAL are you 
> using? OpenAL SI (v0.0.8, used by default in most package managers) does not 
> do 5.1 output. If you're using that, you may have to create a plugin with 
> ~/.asoundrc that maps a 4 channel device onto a 6 channel slave, however, it 
> would be better to use the newer OpenAL Soft, which does natively support 5.1 
> output.

Unfortunately, I'm using 0.0.8 version (btw, does SI stand for Software 
Implementation?). However, 4 channels for a game are enough (at least 
for me). As far as I can understand, OpenAL Soft is a software 
implementation of the OpenAL API. So, in case I wanted 5.1 audio, should 
I have replaced the OpenAL library that came installed with my 
distribution, with the OpenAL Soft one? Is this enough?

Note that there is no need to map 4 channels into 6. The a52 plugin has 
an option to accept exactly 2, 4 or 6 input channels (see doc/a52.txt).

I documented in a text file the steps I performed in order to have my 
setup working. Nothing extremely difficult, but at least a couple of 
tricks that is worth documenting about. Shall I post documentation on 
this mailing list, or there is a better place where to put documentation?

Thank you very much for the support!

Cheers,
Alfredo