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

[Maarten Bosmans]

2011/1/14 Alban Browaeys <prahal at yahoo.com>:
> Le jeudi 06 janvier 2011 à 10:30 +0000, Colin Guthrie a écrit :
>> 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)
>
> Most likely yes . Acer uses fortemedia in quite many of its models (I
> have an acer ferrari one 200).
>
>> Can you explain how to use the module and what users need to do to make
>> it work?
>>
>
> Currently one have to explicitely add:
> load-module module-fmaudiosma
> to /etc/pulse/default.pa
> restart pulse. (or one could use pacmd to load the module).
>
> Then I uses gnome-control-center 3 sound panel and in input tab select
> "FMAudio SMA Source <name of input stereo>"
> Same could be achieved via pavucontrol.

So did you try loading module-alsa-source manually in default.pa and
setting device to front:0 or hw:0, or some other variation? If there
is nothing interesting (see below) pulse could do with the two
channels, it would be much nicer to get a  single mono channel from
alsa with proper audio.

> PS: any tweak to make the small array of microphones work somewhat
> applied by hand should be reverted . The most common fix used was to
> "mute" one of the channel of the stereo input. This is not critical
> though.

"small array of microphones" make it sound there are more than two
microphones. Can you confirm that? Or is it just one microphone and is
the signal somehow split in the driver? If there really is an array,
you could probably do some more interesting processing with the sound,
for example tuning the recording for the speech of the person staring
at the screen, or to record all audio in the whole room.

Maarten