Re: pa echo-cancel module and alsa

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So it appears my alsa configuration was messing things up a bit I think, and as I have only one app using audio, there is only little interest in not using the default pulse config...
A parallel thread regarding AEC points out to time scheduling issues on raspberry pi.

So I could make AEC work by: 
- removing my alsa config and just keeping the default pulse device
- loading module-alsa-sink with tsched=off
- defining my echo-cancel sink and source as default

Now the autoload creates an additional sink for the alsa device
alsa_output.platform-bcm2835_audio.stereo-fallback and sets it by as the default sink, overwritting the default sink i defined in the configuration.

How can i force pulse autoload to either not add that input device, or not set it as default sink?


On Tue, 2020-05-19 at 13:00 +0200, Monkey Bizness wrote:

I'm hoping someone here can help me figure out how to setup my configuration properly.

I'm trying to output sound through the echo-cancel module but by going through the alsa device. Unfortunately, the application doesn't support pulseaudio for the playback.

raspberry pi 4
ubuntu 20.04
ffmpeg : 4.2.2-1ubuntu1
pulseaudio : 13.99.1-1ubuntu3.2

In order to do that, i've defined the echo-cancel configuration in /etc/pulse/ module-echo-cancel use_master_format=1 aec_method=webrtc aec_args="analog_gain_control=0\ digital_gain_control=1" source_name="echoCancel_source" sink_name="echoCancel_sink"

It works. I can test it with :
ffmpeg -i recording.wav -f pulse -device echoCancel_sink test

Now in order to playback through alsa, i've defined a pcm device:
cat /etc/alsa/conf.d/90-echocancel.conf  
pcm.pulse-echo-cancel {
       type pulse
       device "echoCancel_sink"

ctl.pulse-echo-cancel {
       type pulse
       sink "echoCancel_sink"

When I try this configuration with:
ffmpeg -i recording.wav -f alsa pulse-echo-cancel

Sound is scrambled and super slow.

Does anyone know how to make this configuration work?
Any pointer would be appreciated.

I feel I got the correct overall approach but i am missing something about the rate convertion or specification.

Best regards

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