[alsa-devel] SPDIF/IEC958 sample rate on HDA/ALC882

Dag Lem dag at nimrod.no
Sat Mar 24 00:00:00 CET 2007

Dominique Dumont <domi.dumont at free.fr> writes:

> What I see on my side:
> - CPM 48Khz works flawlessly
> - CPM 44KHz sounds horrible
> - AC3 does not work (requires non-audio flag)
> - DTS does not work (does not require non-audio flag tx to
>   compatibility with DTS CD)
> - With DTS and AC3, my amp does not show the frame rate
> My best guess is that I've also some trouble with the frame rate also.
> At some point it did work, but I don't remember how. Probably when I
> first loaded manually the driver. I'll try in this area. May be I'll
> get a real lead...

I have the exact same experiences as you, except that even 48kHz audio
playback can get severely messed up... I have problems with the ALC882
not sending correct AC3/DTS all the time. I haven't found any reliable
pattern to it, but try the following:

1. Turn off IEC958 (e.g. in alsamixer).
2. Start playing a 44.1kHz sound file with aplay (no sound is output,
   of course).
3. Interrupt aplay.
4. Turn on IEC958.
5. Play an AC3/DTS file from DVD (mplayer dvd:// -ao alsa -ac hwdts,hwac3,)

If it still doesn't work, repeat all the steps again...
When you finally do get it to work, you're good until you reboot.

It's not really usable right now, unfortunately :-(

> I've downloaded Realtek's version of alsa driver. I'll compare their
> code to vanilla alsa.

I came across this link while googling today:


It seems it is not possible to get anything but 48kHz over S/PDIF in
Windows either, except with an old driver (WDM_R131.exe).

Do you have a Windows setup on your machine so that you can try this
driver? You'll find it by googling for the file name. I would be
extremely interested in knowing whether it is at all actually possible
to get 44.1kHz over S/PDIF with these chips. If this driver does work,
I suppose it should be possible to sniff out how the S/PDIF frame rate
is actually controlled.

I also sent an email to Realtek technical support today, in the hope
that they can offer information that can help us.

Best regards,

Dag Lem

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