[mythtv-users] ALSA Digital output

Peter Osterberg peter at supergirl.se
Wed Aug 24 11:54:10 UTC 2005

Don't know for sure if this question can be posted here, please ignore if 
you feel it could not.

I want to use digital output on my soundcard. The card have both an optical 
and coax connection the card is a Intel 80801EB/ER ICH5 AC97.

So this is what I've done so far. Checked out alsamixer and found settings 
that seem interesting IEC958 and IEC958 Playback. IEC958 can't be changed 
in any way neither can the level be changed nor can it be muted. IEC958 
Playback level can be changed at 4 specific positions 0, 33, 66 and 100%. 
This all I can find in alsamixer that has to do with digital output. I've 
connected both the optical and the coax outputs to the corresponing inputs 
on my amplifier and it detects NO digital signal. So I downloaded a lot of 
different mixer to see if anything made me lucky. In a mixer called opmixer 
there is a setting called dig1, if I unmute this on I get PCM 48kHz 
detected on my amplifier but it doesn't seem stable since my amp loses it 
for short moments every now and then.

After digging thru some material I found that sound have to be directed 
directly for digital output via a specific hardware option in i.e. mplayer.

mplayer -ao alsa:device=hw=0.0 is the correct setting for analog output
mplayer -ao alsa:device=hw=0.3 should be the correct setting for digital output

Well I get no sound what so ever when using the digital output options in 
mplayer even though me amp has detected a digital signal.

Does anyone know? And an upcoming question will be how I change whether to 
use optical or coax, for now I only get signal detected when using coax.


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