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

Dominique Dumont domi.dumont at free.fr
Fri Mar 23 20:29:12 CET 2007

Dag Lem <dag at nimrod.no> writes:

> Both mythtv and mplayer seem to disable the audio flag correctly.
> AC3/DTS passthrough works beautifully, as long as the S/PDIF is not
> "locked up" :-/


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...

> If you wanted to play back AC3/DTS from software which is not aware of
> the audio flag, I suppose you could try the following:
> iecset audio off

I've tried that to no avail

> No noise as far as I'm concerned, I hope I'm not too noisy myself :-)


> As far as I can tell the format value 0x4011 translates to PCM,
> 44.1kHz, rate multiplier 1, rate divisor 1, 16 bits, 2 channels - all
> by the book. And NID 0x6 corresponds to S/PDIF out according to the
> Realtek documentation.


> If so, there is probably some quirk that must be used for the Realtek
> chips to control the S/PDIF frame rate. Someone at Realtek should have
> an idea on what is going on here...

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


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