[alsa-devel] [PATCH 0/30] ALSA: HDA VIA: patch series

[Robert Hancock]

On Tue, Oct 13, 2009 at 3:40 AM,  <LoganLi at viatech.com.cn> wrote:
>> >> > What is the problem, specifically?
>> >>
>> >> With the latest patch I do get the optical output lighting
>> up and the
>> >> receiver detects a PCM signal, but it seems to be just
>> silence coming
>> >> through. (In previous iterations the SPDIF digital converter wasn't
>> >> being enabled automatically so it didn't get even that far.)
>> >
>> > You can fiddle with hda-verb to issue digital-converter verbs.
>> > Possibly you need to flip the digital-enable bit to send
>> the values...
>>
>> Well, I think I tried all combinations of the flags on the digital
>> converter in hda_analyzer without any luck. I'm assuming it's
>> something else (presumably codec-specific) that hda_analyzer doesn't
>> know about..
>>
>
> Hi, Robert
>  We cannot duplicate bug of SPDIF Out cannot work on VT1828S board.
>  You said it's fine in Windows, right?

Ahh, I see the problem. I think it's related to what we were talking
about with the second SPDIF output: If I play back on subdevice 1 I
don't get any output. But if I force playing on substream 1 instead of
the default 0 (i.e. hw:0,1,1) then I get audio. I'm assuming that
substream 0 is the codec's HDMI output (which actually doesn't exist
on this motherboard).

It appears whether or not the "iec958" alias that PulseAudio uses when
selecting "Output Digital Stereo" profile actually ends up using
substream 1 instead of 0 is based on luck. as it sometimes works and
sometimes doesn't. Having different substreams go different places is
pretty non-intuitive and it seems software doesn't expect this
behavior. I think that the SPDIF and HDMI outputs really should be
separate subdevices (i.e. hw:0,1 and hw:0,2 or something) instead,
unless something makes this impossible. If the aliases for iec958 and
hdmi were set up to point to the correct subdevice then everything
would work as it should..