[alsa-devel] Verifying mixer dB data/Invalid dB data from USB cards, especially Aureon 5.1 MkII

Lennart Poettering mznyfn at 0pointer.de
Sun Feb 21 20:39:33 CET 2010

On Sun, 21.02.10 11:49, Raymond Yau (superquad.vortex2 at gmail.com) wrote:

> The most common onboard audio is HDA so this is not any exceptional cases
> Those HDA multi streaming  feature are most users wanted in desktop
> enviornment, are pulseaudio really designed for deskop or just only for
> notebook and mobile ?
> The front panel green/pink jack can be used by one application while the
> rear panel audio jacks can be used to another application for surround or
> mic for karaoke

I am not entirely convinced that this is really a common case. 

But anyway, there is nothing in PA that would limit it to not use
multiple parallel devices of a sound card at the same time, with the
exception that ALSA currently has no enumeration API which could
inform us which uses of the card are exclusive each other and which
ones are not. PA currently tries to open the sound card in all
combinations possible, assuming that EBUSY means it found an invalid
combination. If one day ALSA gains an API that allows figuring out
which combinations of streams are possible and which ones are not, I
am happy to reinvestigate the whole issue.

>  Send a game's sound through 5.1 speakers while the Internet chatting audio
> is sent through your headset.

More often than not you'd probably use two seperate cards for that. 

> Send a DVD movie with 5.1 audio to a surround sound system in the living
> room, while you listen to digital music and surf the Web on the PC.

I somehow doubt that this is the most common of use cases we need to
care about.

> THe point is that PA release/close the device (suspend on idle) , if another
> application using the subdevice 0 before PA resume/reopen, PA will open
> subdevice 1 and cannot find the correct capture volume control and user will
> complain they cannot record
> Since PA did not check the subdevice number to find the correct mixer
> control

I'd certainly check the subdevice id if the smixer API would supply me
with it.


Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4

More information about the Alsa-devel mailing list