[pulseaudio-discuss] [PATCH] Implement Fortemedia SMA processing.

[David Henningsson]

On 2011-01-06 11:30, Colin Guthrie wrote:
> Hi Alban,
>
> 'Twas brillig, and Alban Browaeys at 06/01/11 00:32 did gyre and gimble:
>>  From 853a4d96bf2624ef30f86cf4819382949d039c87 Mon Sep 17 00:00:00 2001
>> From: Alban Browaeys<prahal at yahoo.com>
>> Date: Wed, 5 Jan 2011 17:13:04 +0100
>> Subject: [PATCH] Implement Fortemedia SMA processing.
>>
>> Those small array microphones returns two channels of opposite
>> phase thus the default remap in pulseaudio doing the sum output
>> silence.
>
>
> Many thanks for this patch, it's very interesting, especially as I've
> been helping a couple folk with mics that appear to be 180 deg OOP
> recently (although this could be an unrelated issue, see:
> https://qa.mandriva.com/show_bug.cgi?id=55930 and
> http://blog.moncef-mechri.com/?p=124 to see if you think this is a
> similar issue)
>
> Can you explain how to use the module and what users need to do to make
> it work?
>
> Many thanks.
>
> Col
>

FWIW, I think you can solve this on the ALSA level using something like:

pcm.micphasefixed { # or your favourite name
     type         route
     slave.pcm    "cards.pcm.default" # might have to change this as well
     ttable.0.0   1
     ttable.1.1   -1
}

That's for your .asoundrc. Then we have to route that into pulseaudio 
somehow as well, preferably in a way that just works for the affected 
units, via udev/alsa rules or something...don't know the details right 
now, but I might figure them out some day. (I e these units are not that 
common, so it might be quite far down on my TODO list - it'll go faster 
if someone else helps out.)

-- 
David Henningsson, Canonical Ltd.
http://launchpad.net/~diwic