[mythtv-users] Via VT8233 and SPDIF TOSLINK output

Robert Tsai rtsai1111 at comcast.net
Wed Mar 2 04:38:08 UTC 2005


On Tue, Mar 01, 2005 at 07:50:27PM -0700, Shawn Willden wrote:
> I have a Shuttle FX43G mainboard with builtin Via VT8233 audio.  It
> has TOSLINK input and output, and I have the output connected to my
> Yamaha 5.1 receiver, but I'm unable to get any audio out of it.
> 
> If I run "aplay -D spdif <any wav>", I hear a click when aplay opens
> the audio device and another when it closes the audio device, but
> nothing in between.  That also gives an error about rates (22050Hz
> requestion got 32000Hz), and suggests "-Dplug:spdif".  That gives no
> error, but the behavior doesn't change.
> 
> I've also tried with mplayer, using "mplayer -vo null -ao
> alsa:device=spdif dvd://".  I'm testing using a DVD that only has
> 2-channel audio; don't know if that might cause problems.  I'll try
> one with 5.1 in a few minutes, after I install libdvdcss (I'm using
> the one I am because it's not encrypted).  The behavior with mplayer
> is identical:  I hear a click when mplayer opens the audio device
> and another when it closes the device.  In this case there are no
> errors about rate mismatches; it says it's doing 48000 Hz.
> 
> I have played with the settings in alsamixer, turning the iec958
> output on and off and setting the "IEC958 Playback AC97-SPSA" to
> various volume levels, including 0 (I saw some previous posts that
> said that was necessary for some reason).  The behavior doesn't
> change -- click on open, click on close.
> 
> Has anyone made this work?

I had the same symptoms.

Have you first tried the normal analog audio ports to make sound is
working at all? If the analog audio isn't working, then maybe you have
a deeper problem. (I encountered a Dell motherboard where the normal
audio port in Linux was actually the *surround* port in Windows.)

Assuming that that much is working, try the following two commands in
sequence:

	amixer set 'IEC958 Playback AC97-SPSA' 3
	amixer set 'IEC958 Playback AC97-SPSA' 0

The last one (setting to "0") is the important one, which you've
alluded to. It's supposed to be idempotent (e.g., just establishing
some configuration), but I consistently have to *change* the value to
zero to get SPDIF audio working properly, so I've just placed these
two commands into my myth user's .login

I haven't used aplay because I don't have any WAV files; I was using
mpg321 with some mp3s as my test program for playing music.

Anyway, you've already mentioned that you've fiddled with the above
alsamixer settings, so maybe you have something else going wrong, but
the above two amixer commands do the trick for me.

FWIW, I have a Soltek SL-K8TPro-939 motherboard (same VIA VT8233 audio
chip).

HTH,
--Rob


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