Setting up surround sound with optical out

Question

I have Centos 6.3 running on this pc. The built in sound card is detected normally and is a 7.1 card with all speakers listed. It includes a optical out as well as HDMI for the built in video. It looks like pulse audio is automagically misconfiguring the optical out, as it is listed as stereo digital out. The analog out is listed as analog stereo - analog surround 5.1. There are 4 or so different variations listed in the pulseaudio sound applet. If I select the test sound it has left and right front. I get audio through the digital connection but is only those 2 channels.

opening alsamixer it appears that the surround is activated and detected. It defaults to pulseaudio for both input and output. If I select the hardware card instead, it appears they are turned on properly.

I need a way to specify that digital audio is more than 2 channels, or create a specific profile for sound through the iec958 link with 8 channels.

Answer 1

The Finally: Digital AC-3 surround sound with pulseaudio (aka Surround Sound Awesomeness) thread (at ubuntuforums.org) presents a solution involving /etc/asound.conf.  But this post covers Ubuntu (obviously).  I found that you cannot use the asound.conf as it crashes PulseAudio.  I had used the same PulseAudio settings from Fedora, though.

For Fedora/CentOS you have to install the a52, ffmpeg and lacreate? libs.  It took a bit of digging to figure out what libs they were in now as names have changed. I had it working in fc23 with a bit of digging on what provides what.