screencast: A bash script to simultaneously record audio from mic and video from screen

screencast.sh

#!/bin/bash
# 
# Record screen and microphone audio
# Stefan Siegert 2020, adapted from code by Steven Gordon
#
# Example usage:
#    screencast intro-to-datacomms
# The audio and screen will be recorded. Press 'z' to stop.
# Two files will be created: intro-to-datacomms-audio.flac, intro-to-datacomms-screen.mp4

# Add a 5 second delay before starting. 
echo -n "Starting in "
for i in 5 4 3 2 1
do
  echo -n " $i"
  sleep 1
done
echo "Press z to finish..."

# Basename of file. Separate extensions for audio and screen are added
# E.g. internet-lecture
outfile=$1

# Name and default options for audio output
audioFile=${outfile}-audio.flac
audioRate=44100
audioBits=16
audioChannels=1

# options for screen output
# H.265 video codec and options for fast recording
screenFile=${outfile}-screen.mp4
screenSize=2560x1440
screenOffset=' '
screenRate=10;
screenCodec=libx265
screenOptions=" -preset ultrafast -crf 25" # higher crf worse quality

# Record the microphone audio using SoX, putting process in background,
# and get the process ID (so we can kill it later)
rec -q -r ${audioRate} -b ${audioBits} -c ${audioChannels} ${audioFile} &
audioPID=$!

# Record the screen using ffmpeg, putting the process in background,
# get the process ID (so we can kill it later)
ffmpeg -v 0 -f x11grab -r ${screenRate} -s ${screenSize} -i :0.0+0,0 -vcodec ${screenCodec} ${screenOptions} ${screenFile} &
screenPID=$!

# Enter loop reading input from terminal, stop when 'z' key pressed
op="s"
while [ ${op} != "z" ]
do
  read -n1 op
done

# Kill the SoX and ffmpeg processes, which causes them to stop recording
kill ${audioPID} ${screenPID}

exit