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

Matthias Dahl ml_alsa at mortal-soul.de
Tue Jul 24 17:58:12 CEST 2007

On Tuesday 24 July 2007 12:47:59 Takashi Iwai wrote:

> Maybe some apps change the IEC958 status bits and doesn't restore the
> original value at close.  (Or interrupting via ctrl-C may cause it.)
> You can see the meaning of these bits via iecset utility included in
> alsa-utils package.

Thanks. I'll keep that in mind and check things when it happens again.

> 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.

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 

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

Thanks for taking the time!

Best regards,
Matthias Dahl

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