[mythtv-users] SPDIF working, but AC3 passthrough is (mostly) broke

[Matt]

Hi everyone... I'll give you the quick summary:

1) I've used Alsa for two years without issues
2) I've been able to pass through analog audio over the SPDIF
connector (PCM) without issue for a long time
3) I can not successfully passthrough any AC3/Digital audio to my
receiver.  HOWEVER, sometimes I can get certain channels to appear.

For example - I can get background music tracks, but no voices - etc.
It's like a signal is being sent, but it's not completely compliant.
When I pass AC3 audio to the receiver via my standalone DVD player,
it'll show that it's digital (DTS, dolby, etc) and a blue light will
appear.  When I pass AC3 audio from the mythbox, nothing shows up and
the blue light stays off.  It's like the signal itself is incomplete
or something

So - I know the receiver can receive AC3 content just fine, but not
from myth.  Any ideas?  This has been driving me nuts for months -
especially since I'm going to start migrating to more digital content
and movies soon.

Thanks!
Matt