[mythtv-users] AC3 Passthrough on SB Audigy 4

[Greg Arena]

	I apologize if this has been asked a million times
before, but I've gone through all the wiki's and howto's I can
find and I just can't get the AC3 passthrough to work with MythTV
on my setup. Either I end up with no audio or I end up with
static. I can get 2-channel stereo audio to work fine on the
SPDIF optical output with SD & HD channels, but no 5.1 audio on
the HD channels. Video works fine.
	First, here's my system info:

Pentium D @ 3.2 GHz w/2GB RAM
pcHDTV HD-5500 tuner card
Sound Blaster Audigy 4 (non-pro version) w/digital I/O module
Kenwood surround sound receiver (connected via optical cable)
PNY NVIDIA GeForce 7600GS PCI Express graphics card (if that
matters any)

Red Hat Enterprise Linux 5 (I use this for my business; thought
this would save time since I already have the discs)
Kernel version 2.6.22.9 (plain vanilla kernel downloaded from
kernel.org)
MythTV version: 0.20.1-157.el5
ALSA drivers/libraries/utilities version: 1.0.14

	I tried upgrading the ALSA drivers & libraries from the
1.0.12 version that was supplied with RHEL5, but that didn't
change anything. I went through the "Configuring Digital Sound
with AC3 and SPDIF" on the MythTV wiki (including copying &
pasting the .asoundrc file like it said), and I had no success
there, either. Anytime I try to get the AC3 passthrough to work,
I end up with silence or I get a nasty static sound. I went
through alsamixer and tried playing with all the settings (ran it
with the "-V all" option) that looked like they might affect the
SPDIF output, but again - either static or no audio.
	When I try to play a test AC3 file that I came across on
the net that was mentioned in one of the wiki's, this is what I
get:
----
[root at arenamedia ~]# aplay -D spdif test.ac3
ALSA lib confmisc.c:1105:(snd_func_refer) Unable to find
definition
'cards.Audigy2.pcm.iec958.3:CARD=0,AES0=4,AES1=130,AES2=0,AES3=2'
ALSA lib conf.c:3479:(_snd_config_evaluate) function
snd_func_refer returned error: No such file or directory
ALSA lib conf.c:3947:(snd_config_expand) Evaluate error: No such
file or directory
ALSA lib pcm.c:2143:(snd_pcm_open_noupdate) Unknown PCM spdif
aplay: main:545: audio open error: No such file or directory
---
	What does this mean? The ALSA documentation appears to be
developer-oriented, not user-oriented (at least beyond basic
setup procedures), so I have no idea what's going on here.
	The pass-through works fine running Windows XP Pro on the
same box - I tested it by playing a DVD in Windows Media Player
and the 5.1 audio was routed to my receiver without a problem.
The receiver is working fine with my stand-alone DVD player and
my HD cable box, so there's nothing wrong with the receiver or
any of my speakers. There's apparently nothing wrong with the
sound hardware in the PC, either.
	I really don't know what I'm missing here, so if somebody
can offer assistance, I'd appreciate it. Maybe someone with a
similar setup could please send me a copy of their .asoundrc file
and/or a screenshot of their "Audio" setup screen in
mythfrontend?

Thank you,
Greg A.