[alsa-devel] Bug in setting channels, related to recent ELD/EDID changes?

[VDR User]

On Tue, Jan 11, 2011 at 12:47 PM, Anssi Hannula <anssi.hannula at iki.fi> wrote:
>> First, THANK YOU for addressing this!  However, I have a couple
>> questions.  Which solution was implemented; a true/false switch
>> controlling the behavior between the old _working_ method, or the new
>> ELD restricted one?  Or, this module parameter thing that was
>> mentioned?
>>
>> As a user having to deal with the frustration of this problem, I
>> absolutely think the true/false switch is the best solution as it's
>> set-and-forget.  Set it one time, get the behavior you _want_, and not
>> have to bother with it again.  With the module parameter thing, it
>> sounds like you have to change module parameters according to what you
>> want at the moment.  Or is it that the true/false switch is controlled
>> by a module param?  Maybe I've misinterpreted it but it's not very
>> clear.
>
> Yes, it is a true/false switch controlled by a module parameter.
>
>> So I grab alsa git, but how do I use the fix to restore the old behavior?
>
> Set the module parameter static_hdmi_pcm of snd-hda-codec-hdmi to 1.
>
> For example, by adding this into /etc/modprobe.conf:
> options snd-hda-codec-hdmi static_hdmi_pcm=1
>
> For the record, this is the commit:
> http://git.kernel.org/?p=linux/kernel/git/tiwai/sound-2.6.git;a=commitdiff;h=5eedd1422c2fc79c2f9ed8b71056b97570f95572

This appears to not be working properly.  Here are the test results:

cold boot pc, kernel 2.6.34.7, alsa kernel drivers, receiver off
eld shows 2 channel stereo (from tv) available
vdr tuned to hdtv with 5.1 surround audio: no errors from alsa,
surround channels missing
vdr tuned to hdtv with 5.1 surround audio, receiver turned on: no
errors from alsa, surround channels working

cold boot pc, kernel 2.6.37, alsa snapshot drivers jan.22,2010, receiver off
eld shows 2 channel stereo (from tv) available
options snd-hda-codec-hdmi static_hdmi_pcm=1
vdr tuned to hdtv with 5.1 surround audio: no errors from alsa, some
surround channels missing
vdr tuned to hdtv with 5.1 surround audio, receiver turned on: no
errors from alsa, some surround channels missing

cold boot pc, kernel 2.6.37, alsa snapshot drivers jan.22,2010, receiver on
eld shows 8 channels (7.1) available
vdr tuned to hdtv with 5.1 surround audio: no errors from alsa, some
surround channels missing
vdr tuned to hdtv with 5.1 surround audio, receiver turned on: no
errors from alsa, some surround channels missing

The HD content I was using was the movie Watchmen.  In all cases where
"some surround channels missing", it was at a minimum whatever
channel(s) carry the main audio for the talking/spoken dialog.  All
(as far as I know, but could be wrong) the background audio seemed to
be present.

Could someone please take a look at the workaround patch.  The new
"static_hdmi_pcm" parameter when set to 1 is supposed to mimic the
original alsa behavior prior to this eld restriction stuff being added
but the patch appears to somehow have broken surround sound as
described above.

Thanks for your help resolving this very frustrating problem!
Derek