ubuntu-audio-dev team mailing list archive

[David Henningsson <david.henningsson@xxxxxxxxxxxxx>]

(Adding ubuntu-audio-dev to CC)

On 2011-05-11 09:13, James Hunt wrote:
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>
> Hi David,
>
> There is already a bug on this issue:
>
> 	https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/433055/
>
> The crucial comment is:
>
> https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/433055/comments/21
>
> Which is equivalent to my notes:
>
> - - in Skype, ensure everything is set to "pulse audio"
> - - ensure the check-box to allow Skype to manage sound is *UNCHECKED*.
> - - run "pavucontrol"
> - - select "input devices"
> - - click padlock icon to *UNLOCK* left and right channels.
> - - set one channel (I chose the right channel) to *ZERO*.
> - - et voila!

Ok, thanks. So there are in principle two different ways of working 
around this problem 1) silencing one channel or 2) inverting one 
channel. Inverting one channel would seem to be the "right" way about 
this as it would, at least theoretically give better quality.

Thinking about this, the problem is to autodetect *when* to apply it. 
There could be other stereo inputs where you do not want to apply it 
(and when applying it would cancel out things in the way the int mic is 
doing by default).

You can invert one channel through an alsa ttable plugin. You can 
silence one channel through either an alsa ttable plugin, or by 
modifying volume controls. I've been looking at the PulseAudio source 
code and as of current there does not seem to be a way for it (through 
just modifying profile path config files) to have it modify one channel 
and mute the other. It does not seem terribly difficult to write a 
PulseAudio patch to make it do that, however.

Secondly, having pulseaudio use a ttable plugin needs the person to 
switch profile manually. At least for now - that might change for Ubuntu 
11.10 as the jack detection patches are coming in. But  according to 
comment 
https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/433055/comments/29 
an almost identical solution already works.

Any thoughts from the collective mind of ubuntu-audio-dev? :-)

--
David Henningsson
http://launchpad.net/~diwic