sound-redirect.sh

#!/usr/bin/env bash

###
### Inspired by https://newbedev.com/redirecting-pulseaudio-sink-to-a-virtual-source
### with help from https://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/User/Modules
###

MODULE_REGISTRY="modules.txt"

function load_module() {
        echo "loading: $@"
        pactl load-module "$@" >> $MODULE_REGISTRY
}

function unload_modules() {
        for module_idx in $(tac $MODULE_REGISTRY); do
                echo "unloading $module_idx"
                pactl unload-module "$module_idx"
        done
        : > $MODULE_REGISTRY
}

function device_description() {
        echo -n "device.description=$1"
}

###########################################
set -e
##########################################

mixer_name="$1"           # some name which identifies input and output that mixer combines
original_output_name="$2" # pactl list sinks
original_input_name="$3"  # pactl list sources

mixer_output_name="${mixer_name}-combiner"
mixer_input_name="${mixer_name}-virtual-mic"
mixer_silence_sink="${mixer_name}-silence"

unload_modules

load_module module-null-sink sink_name="$mixer_name" sink_properties=$(device_description "$mixer_name")

load_module module-combine-sink sink_name="$mixer_output_name" slaves="$mixer_name,$original_output_name" sink_properties=$(device_description "$mixer_output_name")

load_module module-loopback source="$original_input_name" sink="$mixer_name" latency_msec=20

load_module module-null-sink sink_name="$mixer_silence_sink" sink_properties=$(device_description "$mixer_silence_sink") rate=44100

load_module module-echo-cancel \
                source_name="$mixer_input_name" source_properties=$(device_description "$mixer_input_name") source_master="${mixer_name}.monitor" \
                sink_name="$mixer_silence_sink" sink_properties=$(device_description "$mixer_silence_sink") sink_master="$mixer_silence_sink" aec_method=null

echo "new output(headphones) name: $mixer_output_name"
echo "new input(mic) name: $mixer_input_name"