[pulseaudio-discuss] Testing echo cancellation on an armhf OMAP phone

Neil Jerram neil at ossau.homelinux.net
Tue Dec 18 23:41:21 PST 2012

Arun Raghavan <arun.raghavan at collabora.co.uk> writes:

> On Mon, 2012-12-17 at 21:49 +0000, Neil Jerram wrote:
> [...]
>> - load module-echo-cancel
>> - do "paplay -d
>>   alsa_output.platform-soc-audio.0.analog-stereo.echo-cancel
>>   /media/card/Documents/audio/ogg/Do\ They\ Know\ It\'s\ Christmas.ogg"
>>   in one terminal
>> - do "parecord -d
>>   alsa_input.platform-soc-audio.0.analog-stereo.echo-cancel
>>   --file-format=wav > record1.wav" in another terminal
>> - speak into the microphone.
> In general, to start with, you should pick a recording of voice rather
> than music since that's the sort of echo that is designed to be
> cancelled. I've noticed varying degrees of success for music with speex
> and much better success with the webrtc canceller, but starting with the
> basics is better.

Good point, thanks, I'll do that.  Also I realise now that I really want
the entire process of in-call audio routing to be running at 8000 only -
because that's all I need for voice, and because I presume that should
take less power than involving higher rates.

Overall, for this phone, I have two audio scenarios.

-  In-call audio, which can/should all be handled at 8000.

-  Media playback outside calls, which I think should be at 44.1 kHz for
   best quality.

Is it possible for a single instance of PulseAudio to switch between
those scenarios.  If not, I think I can pretty easily stop and restart
PulseAudio when the scenario changes.  (I'm guessing from your and
Tanu's other replies to me that I might need to restart with different
default-sample-rate settings, to get the best outcome and performance
for my two scenarios.)


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