[pulseaudio-discuss] Pulseaudio and S/PDIF

[Alexander E. Patrakov]

On Fri, Mar 24, 2023 at 2:32 AM Jerry Geis <jerry.geis at gmail.com> wrote:
>
> >Don't bother. This is an issue common to 99% of USB webcams. Namely,
> >those not listed explicitly in /usr/share/alsa/cards/USB-Audio.conf.
>
> >Both the analog and the fake S/PDIF microphones ultimately point to
> >exactly the same ALSA hardware device.
>
> Alexandar - thanks
>
> But it seems if I dont "mute" the S/PDIF microphone - it get feedback ???
> If I mute it from the GUI and use the webcam all is fine.
> If I unmute it back I get feedback.

What do you mean by "feedback"? Are you saying that it somehow plays
to your speakers, or that your words are captured twice, or that the
other party complains during calls?

As I said, these "analog" and "S/PDIF" microphones are in fact the
same thing (both are mapped to hw:2), and, due to the mechanisms of
profiles, only one can be active at a time, so it doesn't matter which
one you use.

To select the analog profile (which is mutually exclusive with the
fake S/PDIF), run this command:

pactl set-card-profile 2 input:analog-stereo

But I am 100% sure that it won't help.

To completely turn the webcam microphone off, run this command:

pactl set-card-profile 2 off

To filter out the sound of your speakers from the signal captured by
the webcam, run this command:

pactl load-module module-echo-cancel sink_master=alsa_output.pci-0000_00_1b.0.
hdmi-stereo source_master=alsa_input.usb-046d_Logitech_Webcam_C930e_8E44BAAE-02.iec958-stereo
channels=2 rate=48000 use_master_format=true

(or source_master=alsa_input.usb-046d_Logitech_Webcam_C930e_8E44BAAE-02.analog-stereo
if you switched the webcam to analog, but, again, this is meaningless)

This will create a new sink and a new source that have "echo
cancelled" in their names. Set them as default and move all
applications to them.

-- 
Alexander E. Patrakov