MP4 to MP3 converter

convert_mp4_to_mp3.sh

#!/bin/bash

# Quick and dirty MP4 to MP3 converter
# by Grzegorz Błaszczyk <[email protected]> 2014-2015
# License: MIT http://rem.mit-license.org/

MPLAYER=`which mplayer`
LAME=`which lame`
RM=`which rm`

EXECS=( "MPLAYER" "LAME" "RM" );

for exec in "${EXECS[@]}"; do
  if [ "x${!exec}" == "x" ]; then
    echo "Error: Executable $exec is not installed!"
    exit 1;
  fi
done

if [ "x$1" == "x" ]; then 
  echo "Syntax $0 [some MP4 file]"
  exit 1
fi

MP4_FILE=$1

if [ -e "${MP4_FILE}" ]; then
  FILENAME="${MP4_FILE%.*}"
  MP3_FILE="${FILENAME}.mp3"

  echo "Output file will be: ${MP3_FILE}"

  $MPLAYER -vc dummy -vo null -ao pcm:file=${MP4_FILE}.wav ${MP4_FILE}
  $LAME -h -b128 ${MP4_FILE}.wav ${MP3_FILE}
  $RM -v "${MP4_FILE}.wav"
else
  echo "Input file ${MP4_FILE} does not exist :("
fi