[alsa-devel] Getting pcm_usb_stream plugin to know its limits.

Michaël Cadilhac michael at cadilhac.name
Thu Dec 31 05:15:07 CET 2009

michael at cadilhac.name (Michaël Cadilhac) writes:

> Next, Audacity stopped segfaulting but still didn't work: it couldn't
> manage to configure the plugin properly.

My second idea was to allow usb_stream to fix its own rate and
period_size, as in:

pcm.!usb_stream {
	type usb_stream
	period_size 128
	rate 44100
	card "1"

This would be great because it would prevent PortAudio from doing lots
of test (which are pretty slow).  This is what I thought would work:

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Basically, I tweaked the argument parsing to accept "rate" and
"period_size", stored them in the snd_pcm_us_t, and used them in
us_set_hw_constraint.  It looks to work great with the rate, but when I
set the period_size, aplay can't find a valid configuration (indeed,
snd_pcm_hw_params_any(handle, params); returns an error).

Any help appreciated again!

Michaël `Micha' Cadilhac (LITQ, U. de Montréal) -- http://michael.cadilhac.name
	||   Free jazz is the Vegemite of the the musical world.
	||   It's an aquired taste.
	||        -- Marten, QC

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