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

[Michael T. Dean]

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...

> 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.

You can also try specifying ALSA output without specifying the device 
(since you've set your default to mixed digital--i.e. "ALSA").  Don't 
know if Myth supports ALSA without an explicit device, but it's worth a try.

Good luck,
Mike