Extract audio from any media file ffmpeg can play into a new one (without converting or reencoding!)

extract-audio.sh

#!/bin/sh
#
# Author: Riyad Preukschas <riyad@informatik.uni-bremen.de>
# License: Mozilla Public License 2.0
#
# Extract audio from any file ffmpeg can play (without converting or reencoding!).


if [[ $# -ne 3 ]]; then
  echo "Error: wrong number of arguments"
  echo "Usage: $0 -f <format> <input_file>"
  echo "       will extract (without converting or reencoding!) the audio from"
  echo "       <input_file> to a new file in the specified <format>."
  echo ""
  echo "OPTIONS"
  echo " -f <format>"
  echo "       specify the format of the output file (e.g. mp3, ogg, opus, m4a)."
  echo "       NOTE: not all input and output formats are compatible."
  exit 1
fi

if [[ "$1" == "-f" ]]; then
  # $@ == -f format input_file
  readonly format="$2"
  readonly input_file="$3"
else
  # $@ == input_file -f format
  readonly format="$3"
  readonly input_file="$1"
fi
readonly output_file="${input_file}.${format}"

# if the input file doesn't exists ffmpeg will complain anyway

# if the output file exists ffmpeg will ask whether it should be overwritten

ffmpeg -i "${input_file}" -vn -c:a copy "${output_file}"