[pulseaudio-discuss] Mixing midi output and microphone to conferencing app

guest271314 guest271314 at gmail.com
Sat Jan 16 18:51:21 UTC 2021

One approach would be to create the virtual device for the MIDI output
alone. Then capture both MIDI output and headset microphone tracks
individually using exact constraints at getUserMedia(), then connect each
individual MediaStreamTrack to a Web Audio API
MediaStreamAudioDestinationNode where both tracks will be playing in that
stream, for example, see https://stackoverflow.com/a/40571531.

On Sat, Jan 16, 2021 at 9:55 AM Jan De Luyck <ml+pulseaudio at kcore.org>

> Hi folks,
> I'm trying to send the output of an usb-connected plantronics headset and
> my digital piano (using midi + fluidsynth) over google meet/zoom/jitsi/..
> to the other side. I also  need to hear my piano in the headset (it has no
> speakers)
> I've based myself off of
> https://unix.stackexchange.com/questions/576785/redirecting-pulseaudio-sink-to-a-virtual-source
> and been testing all kinds of combinations, but I'm hitting a roadblock.
> The commands I'm using at the moment are:
> HEADSET="alsa_output.usb-Plantronics_Plantronics_Blackwire_3225_Series_1129BBD004004FF4BD2E6F2248C0D73E-00.analog-stereo"
> MIC="alsa_input.usb-Plantronics_Plantronics_Blackwire_3225_Series_1129BBD004004FF4BD2E6F2248C0D73E-00.analog-stereo"
> pacmd load-module module-null-sink sink_name=mix-for-virtual-mic
> sink_properties=device.description=Mix-for-Virtual-Microphone
> pacmd load-module module-combine-sink
> sink_name=virtual-microphone-and-speakers
> slaves=mix-for-virtual-mic,$HEADSET
> pacmd load-module module-loopback latency_msec=20
> sink=virtual-microphone-and-speakers source=$MIC
> pacmd load-module module-null-sink sink_name=silence
> sink_properties=device.description=silent-sink-for-echo-cancel
> pacmd load-module module-echo-cancel sink_name=virtual-microphone
> source_name=virtual-microphone source_master=mix-for-virtual-mic.monitor
> sink_master=silence aec_method=null
> source_properties=device.description=Virtual-Microphone
> sink_properties=device.description=Virtual-Microphone
> The effect is that I can perfectly pick the microphone "Virtual
> Microphone" in the conferencing apps, but only my keyboard is sounding
> through. My voice / mic never gets picked up.
> I've tried recording using
> parecord --channels=2 -d mix-for-virtual-mic.monitor /tmp/x.wav
> but same story, only the piano is being picked up.
> What did I miss? In all logic, this should work?
> Kind regards,
> Jan
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