[LAD] Opening ALSA devices (hardware and PCM)

Julien Claassen julien at c-lab.de
Mon Jun 7 20:46:11 UTC 2010


Good evening everyone!
   I was wondering, is there a difference in opening a device like
plughw:0,0
   and
plug:pcm.my_own_device
   I've looked in the code of aplay, but small as this tool is, it contains 
still a good deal of functionality, so it seems. I've compared it to the other 
code in question. there are differences. So now I think it's best to ask and 
to guess, which is which and what piece of code, which function signatures are 
acutally used for which purpose.
   The application is question is chan_alsa from asterisk. So it's quite 
limited: configured for 8kHz, 16bit (either se or le) and mono. They use a 
fixed periodsize and connected buffer.
   I found, that plughw:0,0 acutally let's me here things, if not really 
capture input myself, but I'll pounce on that, when it's time.
   I want to connect a pcm-device wired to JACK to the asterisk software, yet 
it either tells me, that the argument is invalid Plug:pcm.name or plug:name) 
or it gets read/write errors or it simply crashes. :-(
   I've seen that they use nonblocking mode and interleaved data.
   So any suggestions on that?
   Warmly yours
           Julien

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