Simple MIDI file reader

#!/bin/bash

# Hacky script to create a JSON file listing only the notes from the

# given input MIDI file. Does not take into account tempo changes and

# uses a fixed timebase.

# Set this to the number of MIDI ticks per second.

# This assumes MIDI timebase = 480ppq and tempo = 120bpm.

divisor=960

set -e

if [ -z "$1" -o -n "$2" ]; then

    echo "Usage: miditojson.sh <midifile.mid>" 1>&2

    exit 2

fi

infile="$1"

set -u

mydir="$(dirname $0)"

echo '[';

"$mydir"/midifile "$infile" |

    grep 'Note:' |

    awk -F: '{ print $1/'"$divisor"'.0,$3 } ' |

    awk '{ print $1,$2,$3,$4,$5/'"$divisor"'.0,$6,$7,$8,$9 }' |

    sed -e 's/channel [0-9] //' \

        -e 's/^/{ "time": /' \

        -e 's/ pitch /, "pitch": /' \

        -e 's/ duration /, "duration": /' \

        -e 's/ velocity /, "velocity": /' \

        -e 's/$/ },/' |

    sed '$s/,$//'

echo ']'