Audibook convert m4b to mp3. This will split into chaptered mp3 files and automatically reconfigure proper ID3v2 tags.

convert_m4b.sh

#!/bin/bash
#
# sudo apt-get install id3v2 ffmpeg
#
# USAGE: 
# cd /book title/
# bash ~/this_script_path.sh
# rm *.m4b (you need to manually remove the original in case something goes wrong)
#
#
# EXAMPLE:
#
#   $ ls
#   The Wheel of Time - Book 11 - Knife of Dreams, Part 1.m4b  The Wheel of Time - Book 11 - Knife of Dreams, Part 2.m4b
#   $ ~/convert_m4b.sh
#   .....
# 
#   [OUTPUT]:
#
#   File: Knife of Dreams - Chapter 18 - News for the Dragon.mp3
#   Metadata: ID3v2.3
#   Title: Chapter 18 - News for the Dragon
#   Artist: Robert Jordan
#   Album: Knife of Dreams
#   Track: 23
#   Genre: Audiobooks

#initial track number
track=1

#assumes ( if there are multiple files Part 01/Part 02) that they are in alphabetical order
for i in *.m4b;
do
    name=`echo $i | cut -d'.' -f1`;
    echo $name;
    ffmpeg -i "$i" -acodec libmp3lame -ar 22050 -ab 64k "$name.mp3"
    full_file_path="$name.mp3"

    #split chapters
    title=$(pwd | sed 's,^\(.*/\)\?\([^/]*\),\2,' | cut -d , -f 1)

    ffmpeg -i "$full_file_path" 2> tmp.txt

    while read -r first _ _ start _ end; do
        if [[ "${first}" = "Chapter" ]]
        then
            read  # discard line with Metadata:
            read _ _ chapter
            chapter=$(sed -re ":r;s/\b[0-9]{1,$((1))}\b/0&/g;tr" <<<$chapter)
            chapter_file="${title} - ${chapter}.mp3"
            echo "processing $chapter"
            </dev/null ffmpeg -loglevel error -stats -i "${full_file_path}" -ss "${start%?}" -to "${end}" -codec:a copy -metadata track="${chapter}" "${chapter_file}"
            id3v2 --song "$chapter" "$chapter_file"
            id3v2 --album "$title" "$chapter_file"
            id3v2 --track "$track" "$chapter_file"
            echo "$title - $chapter"
            track=$((track+1))
        fi
    done <tmp.txt

    rm tmp.txt
    rm "$full_file_path"

done;

Wonderful. Cheers

awesome!!!

Thank you, amazing script!
But it seems due to bug in ffmpeg if m4b file contains mjpeg picture it recognizes it as video stream and output a error.
So in line 36 you can add "-vn" flag to ignore all video streams, the final command will be:
ffmpeg -i "$i" -vn -acodec libmp3lame -ar 22050 -ab 64k "$name.mp3"

and at line 50 you probably want to add $name in the resulting filename otherwise several m4b files with same chapter names, e.g. "Chapter 1, Chapter 2, ... Chapter N" will produce wrong results, so probably it should be:
chapter_file="$name - ${title} - ${chapter}.mp3"

Thanks for this! Only thing it is missing for me personally would be keeping the artist/reader if it is there, but that is a minor tweak I can do manually when needed :)

Works flawlessly!

Fantastic, just what I nedded before a 10,000km road trip.
added variable track_string and added it to the mp3 filename ahead of the chapter.
This means that all mp3 files are in the sequence they are in the m4b file when played by an mp3 player.

        printf -v track_string "%03d" "$(($track))"
        chapter_file="${title} - ${track_string} - ${chapter}.mp3"

example:
bookname - 001 - Opening Credits.mp3
bookname - 002 - Prologue.mp3
bookname - 003 - Chapter One
.....

how do i use this on mac?

how do i use this on mac?
If you can't install id3v2 and ffmpeg on a mac, you could use UTM to install Debian minimal, then install id3v2 and ffmpeg in the Linux VM, then it should run

how do i use this on mac?

Thanks.

Thanks!