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

Michael T. Dean mtdean at thirdcontact.com
Fri Jun 10 15:16:08 UTC 2005

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 
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).



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