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LPC: Linux audio: it's a messLPC: Linux audio: it's a messPosted Sep 19, 2008 18:51 UTC (Fri) by dmarti (subscriber, #11625)In reply to: LPC: Linux audio: it's a mess by drag Parent article: LPC: Linux audio: it's a mess sitting at Plumbers Conference right now listening to Lennart Poettering summarizing the audio track. Problem is: "OSS is not virtualizable." Write to the OSS API and you can't feed it to a sound server -- it has to be on the hardware.
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LPC: Linux audio: it's a mess Posted Sep 20, 2008 13:12 UTC (Sat) by cortana (subscriber, #24596) [Link]
Isn't that the case for ALSA too if you directly fool about with the nodes in /dev/snd?
The virtualisability of ALSA comes from the alsa-lib library that all applications use. But that could, presumably, fire off data destined for the sound card to /dev/dsp instead of /dev/snd/pcmC0D0p...
Yes Posted Sep 21, 2008 3:43 UTC (Sun) by dmarti (subscriber, #11625) [Link] Yes, as Lennart pointed out, only 70% of ALSA apps use it in a way that will work with a sound server -- the other 30% only work if they can get access to the hardware.
LPC: Linux audio: it's a mess Posted Sep 21, 2008 22:39 UTC (Sun) by mezcalero (subscriber, #45103) [Link]
OSS is practically impossible to virtualize. There are hacks like LD_PRELOAD and stuff like CUSE. But they will never be able to fully provide virtualization. Stuff like mmap audio access (which is used by far too many applications unfortunately) cannot be emulated completely. Also, the timing model in OSS is too simple to really fit on a sound server backend.
OSS as a software is dead on Linux. I really hope OSS as an API will die, too. (as soon as libsydney is more than just vaporware)
ALSA can be virtualized much better than OSS, since it has better semantics and is a shared library which supports plugins and stuff. But in the end it's an API desgined for hardware devices, and the devil lies in the details: 100% ALSA compat in PA will stay a dream.
Lennart
LSB Posted Sep 21, 2008 23:29 UTC (Sun) by dmarti (subscriber, #11625) [Link] But it sounds like ALSA in some form is on track to make it into LSB -- and once it's there, apps and distributions will depend on it and continue to support it for a long time. Possible to make sure that the subset of ALSA that's in LSB is PA-safe?
LSB Posted Sep 22, 2008 0:21 UTC (Mon) by mezcalero (subscriber, #45103) [Link]
Yes, of course. Applications that use only a "safe" subset of the ALSA API should work fine with PA. That's what I'd call 70% compat.
Lennart
ALSA safe subset Posted Sep 23, 2008 8:57 UTC (Tue) by sdalley (subscriber, #18550) [Link]
Is this safe subset of ALSA documented as such anywhere? If so, we need as many people as possible to BANG A REALLY BIG DRUM about it/write a beautiful Programmers Guide about it/write love songs in it, so that Linux sound applications everywhere can start getting things right now and not break/have to be ported again when libsydney comes along.
ALSA safe subset Posted Jun 29, 2009 16:23 UTC (Mon) by pharm (guest, #22305) [Link]
Just in case this pops up in Google searches:
ALSA safe subset documentation, amongst other things:
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