Audiobook Chapters: How to Add, Edit and Split Them

Where chapters live in each format

The MP4 registry describes both M4A and M4B as able to contain a chapter track.² ffmpeg writes both a QuickTime chapter track and Nero chapters by default.¹ MP3 chapters come from a 2005 addendum to the ID3 standard that adds “two new ID3v2 frames” for chapters and a table of contents.³ FLAC has a cuesheet block for “locations of interest”,⁴ and .cue files describe a CD’s layout with times in minutes, seconds and frames, 75 frames to a second.⁵

Which players show chapters

BookPlayer’s own tests cover M4B chapters and MP3 files with and without a table of contents.⁶ Voice reads MP4 chapters, ID3 chapter frames, Ogg chapter comments and Matroska chapters.⁷ Audiobookshelf uses the chapters embedded in the first file, or makes one chapter per file.⁸ VLC has a chapter menu under Playback,⁹ but the MP3 reader in VLC 3, the current release, has no chapter code; the VLC 4 development branch adds “Support chapters in mp3 files”.^14,15 Jellyfin’s server reads embedded chapters for items in audiobook libraries.¹⁹ Podcast apps are often better with MP3 chapters than audiobook apps: Apple Podcasts reads chapters from “the ID3 tags of an MP3 or AAC file”, Overcast “displays MP3 and M4A chapter markers”, and Pocket Casts supports MP3 chapters on Android and iOS (its Android app doesn’t read Apple’s M4A chapter format).^16,17,18 Plex users report that Plexamp plays an M4B as one long track, ignoring its chapters.¹⁰ Apple Books lets you jump between chapters, though some audiobooks call them tracks or don’t define them;¹¹ Apple doesn’t say whether it reads MP3 chapters. BookPlayer’s developers note that Apple’s audio framework only assembles MP3 chapters when the file also has a CTOC table of contents, so write one.²⁰

Add or edit chapters

Chapters are just data, so changing them doesn’t touch the audio. In our chapter editor, drop the book, add marks on the waveform (they snap to the pause before the narrator speaks), name them, and save.

With ffmpeg, export the chapters to a text file, edit it in any text editor, then put it back with -c copy so nothing is re-encoded:^1,13

ffmpeg -i book.m4b -f ffmetadata chapters.txt

;FFMETADATA1
title=My Book

[CHAPTER]
TIMEBASE=1/1000
START=0
END=754000
title=Opening Credits

[CHAPTER]
TIMEBASE=1/1000
START=754000
END=2311500
title=Chapter 1: The Storm

ffmpeg -i book.m4b -i chapters.txt -map 0:a -map_metadata 1 -map_chapters 1 -c copy edited.m4b

Split a book into chapters

• It has chapter marks: the M4B chapter splitter cuts one file per chapter, as M4B or MP3, without re-encoding when you keep M4B.
• No marks, but a spoken “Chapter One”: the auto chapter detector listens for the announcements with on-device speech recognition.
• No marks, but clear pauses: split by silence proposes breaks at the long pauses.

For ACX, every chapter must be a separate file of 120 minutes or less, with its header spoken.¹²

Share or export the chapter list

Need the list itself, for a description, a podcast feed or YouTube? The chapter list export turns an audiobook’s chapters into plain text, CUE, CSV, JSON or YouTube timestamps.