m4b_split.sh

#!/bin/bash
# Description: Split an m4b into its chapters. No recoding is done, just splitting
# Usage: m4b_split.sh $input_file $output_dir/
# Requires: ffmpeg, jq
# Author: Hasan Arous, Sergey Poterianski
# License: MIT


in="$1"
out="$2"
splits=""
c=0
while read -d'|' start end title; do
    let "c=c+1"
    cs=`printf %02d $c`
    splits="$splits -map 0:a -c:a libmp3lame -filter:a atempo=1.25 -ss $start -to $end $out/${cs}_${title}.mp3"
done <<<$(ffprobe -i "$in" -print_format json -show_chapters \
    | jq -r '.chapters[] | .start_time + " " + .end_time + " " + (.tags.title | gsub(" "; "_")) + "|"')
#echo $splits
ffmpeg -i "$in" $splits