[alsa-devel] snd-hda-intel, AD 1988b: SPDIF output not working correctly, volume low for analog output

[Takashi Iwai]

At Tue, 24 Jul 2007 17:58:12 +0200,
Matthias Dahl wrote:
> 
> > So, the culprit looks like the analog loopback.
> > Could you try the patch below, and make sure that you set "PCM" as the
> > "IEC958 Playback Source"?
> 
> I can confirm this definitely solves the volume problem for me. I can increase 
> the pcm and spdif volume to 100% and no clipping or distortions whatsoever 
> happen on the spdif output. Works like a charm.

Great, thanks for confirmation.

> So far the other distortions I wrote about are now only hearable when I turn 
> up the volume of my headphone to nearly its maximum. If it stays that way, I 
> can live with it... reminds me, before the problem was fixed, I had my 
> headphone at almost 100% most of the time, so that could be the reason why 
> those distortions where so visible in the first place. I'll have an eye on 
> it...

I'm not sure whether it's a driver problem or a hardware problem.
Is the dB above 0 in the maximum level?

> I am curious, will that patch make it into the offical mercurial repository 
> and what was the problem exactly with the analog loopback?

Yes, the patch will be merged soon.  Hopefully we can put it to 2.6.23
tree, too.

The problem was that the analog loopback is routed wrongly to the
SPDIF output unconditionally, and no way to cut it out.
The patch fixes the implementation of "IEC958 playback source" mixer
element to handle correctly it.


Takashi