[pulseaudio-discuss] Protecting system wide settings

Colin Guthrie gmane at colin.guthr.ie
Sat Sep 4 02:37:25 PDT 2010

'Twas brillig, and john owen-jones at 04/09/10 08:45 did gyre and gimble:
> let me give you my situation,
> I have an aspire one netbook and the internal mic is stereo but the 2
> channels are combined 180 degrees out of phase so if left and right
> channels are set to similar levels there is no sound recorded.

Ahhh, that explains a problem reported to me the other day:


> The solution is to open pulse audio volume control and set one channel
> to zero and the other to an appropriate level.
> A well behaved program such as skype has the option to adjust audio
> settings automatically or not. (naturally not is appropriate)
> google voice and video plugin doesn't have this option and sets both
> audio input channels to the same level resulting in silence.

Really the applications should be setting the levels of their own
*stream*, not the device itself.

This approach would solve the problem, but sadly we do not currently
support per-stream volumes on the recording side of things, only playback.

This is an asymetrical problem of PA. Really we need to resolve that. It
also simplifies the client-side API too to be more symmetrical. I
discussed this a while back with Lennart while helping out the Skype
guys and I think he was in favour of implementing this now that flat
volumes is in the system.

I guess we just need someone to feel inspired and do the work :)

That said doing this is just a work around for an underlying problem. If
the mic is broken like this, then I guess it should be fixed at the alsa
level. May be worth testing with PA suspended and recording from the mic
directly. Also try to see if using the front: device vs. the hw: device
actually makes any difference (I know that we use front: but this is
generally discouraged for recording IIRC).

If you still have problems at the alsa level, please raise this issue on
the alsa-devel mailing list (I'll keep my eye out for it, but posting a
reference to the alsa-devel list archive here would be nice :))



Colin Guthrie

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