Record system output audio with FFMPEG on Ubuntu Linux

record-system-output-audio.sh

#!/usr/bin/bash
#
# Records the oudio from your browser and other applications.
#
# USAGE:
#
#     record-system-output-audio.sh DURATION
#
# Where DURATION is [<HH>:]<MM>:<SS> or <SS>[s] (read ffmpeg-utils manual)
#
# Recording advices:
# 1. Dont open more play more than one video/audio during recordings.
# 2. Dont change the system volume during recordings.
#
# Read: 
# Recording Browser Audio on Linux with ffmpeg, by Lubos Rendek
# https://linuxconfig.org/recording-browser-audio-on-linux-with-ffmpeg
#

duration="${1:-0}"

filename=`date +'%F_%T'`;
output="$filename.wav";

monitor=`pactl list sinks | grep $(pactl get-default-sink).monitor | cut -d : -f 2`;
record="ffmpeg -loglevel error -t $duration -f pulse -i $monitor $output";

if [[ -n "$monitor" ]]; then

    echo "---------------"
    echo "Recording advices:"
    echo "1. Dont play more than one video/audio during recordings."
    echo "2. Dont change the system volume during recordings."
    echo "---------------"
    
    echo $record && time $record;
    
else
    echo "Pulse monitor not found.";
    exit 1;
fi;

# Programmer notes:
# 1. dont use dots in $filename. Otherwise: "file.name.wav: Protocol not found".
# 2. dont use quotes around $monitor. Otherwise: "alsa.monitor: No such process".
# 3. dont change de wav extension. Otherwise you'll only hear noise in the output file.