[mythtv-users] ALSA and SPDIF Out For nForce2 Motherboards

[KianTeck]

Michael T. Dean wrote:

> KianTeck wrote:
>
>> No joy again.
>>
>> I changed the "Audio Output device" in mythtv to "ALSA:mixed-digital" 
>> and tried to watch live TV again.  This is what the mythfrontend says:
>> ------------------ <snip>----------------------
>> Opening ALSA audio device 'mixed-digital'.
>> Unable to set hw params for playback: Invalid argument
>> Error setting audio params: Invalid argument
>> ------------------ <snip>----------------------
>>
>> I get the same deal too, as above, if I change the "Audio output 
>> device" in mythtv to "ALSA:default".  Anyway, I do not get the 
>> "Device or Resource busy" message in both the above settings now.
>
>
> Are you certain your MythTV was compiled with native ALSA support?  
> There's a section in mythtv's settings.pro:
>
> # Native ALSA support
> #CONFIG += using_alsa
> #ALSA_LIBS = -lasound
>
> Uncomment the CONFIG and ALSA_LIBS lines when building mythtv and see 
> if that helps (unless you're positive it's been compiled that way).  
> May not help, but...


I installed my MythTV using "apt-get install mythtv-suite" as detailed 
in Jarod's guide.  So, I cannot be certain if it was compiled with 
native ALSA support.  How can I confirm it?

>
>> Setting .asoundrc in mixed digital, while live TV is running, and 
>> issuing "aplay /usr/share/sounds/KDE_Startup.wav" (via ssh) run 
>> immediately without any queuing.
>>
>> I also noticed TWO other settings in mythtv audio setting (Setup | 
>> General | Audio) "Mixer Device = /dev/mixer" and "Mixer Controls = 
>> PCM".  Do I  need to change any of one of these 2 values?
>
>
> Shouldn't be necessary.  AFAIK, S/PDIF output is line-level output 
> that requires a decoder and an amplifier, so you can only adjust 
> volume externally (on the receiver you're using as a decoder).  
> However, the .asoundrc has defined control devices even for the 
> digital and mixed-digital devices, so if your software tries to use 
> it, it's available (just probably doesn't do anything).
>
> Since you previously said aplay outputs through S/PDIF, your ALSA 
> setup is correct.  (At the time, you were using unmixed digital output 
> as the default, but the only change we've made since then makes mixed 
> digital the default.  You might want to verify that aplay still works 
> with S/PDIF, though.  Use "aplay" and "aplay -D mixed-digital" to 
> test.)  Therefore, it's probably either the way your MythTV was 
> compiled or an error (i.e. typo or something) in your Myth database.

------------------ <snip>----------------------
pcm.!default {
  type plug
## Uncomment the following to use mixed analog by default
#  slave.pcm "dmix-analog"
## Uncomment the following to use unmixed digital by default
#  slave.pcm "digital-hw"
## Uncomment the following to use mixed digital by default
  slave.pcm "dmix-digital"
}
------------------ <snip>----------------------

ok, so with mixed-digital still at my default in .asoundrc, I tried both 
the "aplay -D mixed-digital"  and "aplay", I can get sound through the 
SPDIF.  But still not able to get sound through SPDIF in MythTV.

However, reviewing through this thread (way back to the Apr 10), I did 
noticed a reply by Chris.  After following his instructions in adding 
the "options snd-pcm-oss adsp_map=2" to /etc/modules.conf and changing 
MythTV to use /dev/adsp, I can get sound through SPDIF.  I am I right in 
saying this is using the oss emulation?

KianTeck
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