[Protux-devel] available sampling rate detection

[Martin Herren]

Hej,

i'm new on this list as well as to alsa.

We need to find out the supported sampling rates (and other parameters) for the 
pcm devices of soundcards.

We used snd_pcm_hw_params_test_rate() for this, which according to the 
documentation 
(http://www.alsa-project.org/alsa-doc/alsa-lib/group___p_c_m___h_w___params.html#a53)
should return 1 if the rate is available, 0 otherwise.
The problem is that it always returned an non-null value, for any rate even if 
we knew it wasn't supported.

Then we found out that we need to call snd_pcm_hw_params_any() first, and then 
snd_pcm_hw_params_test_rate() returns 0 for supported rates, and a negativ 
value (-22) otherwise.

Is this the correct way to do the test or did we miss a point ?
If it is correct, the documentation should be updated.

An additional question, what is the correct way to find out all existing 
cards/buses on a system ? Currently we scan /proc/asound/card?/ for all 
pcmX[cp]. Is there a better way to do it ?

Thanks,

Martin

-- 
Martin Herren

Protux - A Free Professional Audio Tool for GNU/Linux:
-> http://www.nongnu.org/protux/
Open your Windows - Free your Mind - Enjoy:
->http://gnuwin.epfl.ch

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