Converts all mp4 files in a folder tree to another folder tree

convertall.sh

#!/bin/bash

# loop & print a folder recusively,
recurse() {
echo $1 $2 $3
    for i in "$1"/*;do
        if [ -d "$i" ];then
            outputdir=`echo $i | sed "s/$2/$3/g"`
            echo "outputdir: $outputdir"
            mkdir -p "$outputdir"
            recurse "$i" "$2" "$3"
        elif [ -f "$i" ]; then
            outputfile=`echo $i | sed "s/$2/$3/g"`
            outputfile=`echo $outputfile | sed "s/mp4/mp3/g"`
            convert "$i" "$outputfile"
        fi
    done
}

convert() {

    input=$1
    output=$2

    ffmpeg -i "$input" -vn -ab 256 "$output"
}

echo "convert from path: $1 to $2"
mkdir -p "$2"
recurse "$1" "$1" "$2"