[mythtv] A weird problem with ALSA, X11, DirectFB

[Michael T. Dean]

jpahka at welho.com wrote:

>So, the thing is, I can hear the audio throuh my external amplifier when I'm
>running mythfrontend in X11 (a vnc desktop, that's why it doesn't find Xv
>support), but I get a 'Unable to set sw params for playback: Invalid argument'
>when I'm running mythfrontend with QT/E+DirectFB setup.
>  
>
...

>Mythfrontend in QT/E + DirectFB:
>  
>
...

>2005-06-08 17:31:18.224 Opening audio device 'spdif'.
>2005-06-08 17:31:18.302 Unable to set sw params for playback: Invalid argument
>2005-06-08 17:31:18.302 Unable to set ALSA parameters
>  
>
It looks like you're watching a channel on the X11 version that sends a 
48kHz PCM audio signal (or AC3) and one on the QT/E version that sends a 
44.1kHz (or 32kHz) PCM audio signal.  Nearly all sound cards require you 
to send PCM data at 48KHz to a digital audio output.  Since you're 
sending the output to the "spdif" device, you're sending it directly to 
the hardware.  Instead, you should define a device which does the 
appropriate conversions before sending the audio to the card.

Take a look at 
http://mythtv.info/moin.cgi/DigitalSoundHowTo#head-b318f22131b4a59eef5f28edfac9160204e13719 
and try using either the "ALSA:digital" or "ALSA:mixed-digital"  devices 
(and use either "default" or "ALSA:default" for the mixer device).  You 
may have to adjust the device numbers for your sound card (as described 
in the page).

HTH.

Mike