[mythtv] Fw: [mythtv-users] Myth is locking soundcardandpreventing fullduplex operation

Edward Wildgoose edward.wildgoose at frmhedge.com
Thu Apr 17 00:45:08 EDT 2003

Thanks for your help - I'm really not sure of my way around this, and it's
very much appreciated.  See inline for results of tests

> Maybe your soundcard can't do simultaneous stereo capture and playback?
> Try:
> sox -t ossdsp -r 44100 -w -c 2 /dev/dsp -t ossdsp -r 44100 -w -c 2
> /dev/dsp
> (you may have to install sox first)
> or even perhaps:

This comes back with an error message
sox: Unable to set sample size to 16.  I think I read somewhere that the
RME/alsa driver only takes a small range of buffer sizes like 64 bytes or
somesuch.  It appears that the correct param is "-b", however, sticking that
after the first -r 44100 seems to interpret the number following it as a

I need to go to bed now (UK time it's late), but I will have a fiddle
properly tomorrow

> arecord -f S16_LE -c2 -r44100 | aplay -f S16_LE -c2 -r44100

This works fine, and in fact I was basically using this originally to test
that full duplex was in fact possible and working, however, I used a temp
file in the middle.  However, isn't this going to use ALSA hence not a
conclusive test?  However, the previous suggestion of "cat /dev/dsp >
/dev/dsp" also seemed to work fine...

> That should set most of the options Myth is using. 2 Channels,
> 44100kHz, 16bit samples. If your sample rate is different in myth for
> record or playback you should change it on that command line too.
> If *that* works even, my next guess is that perhaps you can't do
> something while the mixer device is open.

That sounds like a possibility.  There is no mixer on the RME card, and so I
don't know what purpose the mixer device serves in this case?  Any ideas on
how to simulate what myth is doing at this point?


More information about the mythtv-dev mailing list