[linux-audio-dev] Linux Audio Hardware Selection
Paul Davis
paul at linuxaudiosystems.com
Fri Jan 24 08:12:01 UTC 2003
>I was looking for a good, up-to-date documentation pointer upon software featu
>res provided by alsa. But I'm new to this architecture and I might be "intoxic
>ated" by some kernel streaming architectures : is there a kind of hardware ab
>straction with ALSA, e.g. features that are managed by the software at usr or
>kernel level, in a +/-transparent way, when the HW does not provide them ?
yes, its called alsa-lib. its big, its bold, and to some people its
beautiful.
>My understanding is that Alsa does not provide multiple device open (a second
>open can be blocking, or return with an error, but won't succeed, as no sw mix
>ing is available).
that's correct right at this very moment in time. however, the
mythical "mix" ALSA PCM "plugin" provides
multi-open-without-h/w-support by streaming data to a server called
"aserver". at this time, the mix plugin is not part of the ALSA source
base. its far from clear that anyone is doing any work on it.
>is there anything that can be emulated by alsa on user request, when the hw ca
>nnot ? (for instance frequency change, frame conversion (n channels to m chan
>nels) etc...).
all of it.
the other alternative that many of us here like rather a lot is JACK
(http://jackit.sf.net/), which provides a different model: data
sharing between applications, shared access to hardware,
sample-synchronous execution of all applications, and no hardware
parameters to be configured. it sits on top of ALSA (and potentially
other similar hardware abstractions).
--p
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