Messages in this thread | | | Date | Wed, 22 Oct 2014 15:45:42 -0400 | Subject | Re: [alsa-devel] [PATCH v2 5/6] sound/usb: pcm changes to use media token api | From | Devin Heitmueller <> |
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> this seems like a feature, not a bug. PulseAudio starts streaming before > clients push any data and likewise keeps sources active even after for some > time after clients stop recording. Closing VLC in your example doesn't > immediately close the ALSA device. look for module-suspend-on-idle in your > default.pa config file.
The ALSA userland emulation in PulseAudio is supposed to faithfully emulate the behavior of the ALSA kernel ABI... except when it doesn't, then it's not a bug but rather a feature. :-)
> I also agree that the open/close of the alsa device is the only way to > control exclusion.
I was also a proponent that we should have fairly coarse locking done at open/close for the various device nodes (ALSA/V4L/DVB). The challenge here is that we have a large installed based of existing applications that rely on kernel behavior that isn't formally specified in any specification. Hence we're forced to try to come up with a solution that minimizes the risk of ABI breakage.
If we were doing this from scratch then we could lay down some hard/fast rules about things apps aren't supposed to do and how apps are supposed to respond to those exception cases. Unfortunately we don't have that luxury here.
Devin
-- Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com
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