Audiobook Binder Pro / Split an Audio File into Chapters

Split an Audio File into Chapters

Every other guide here starts with a folder of files. This one starts with a single file.

A nine-hour novel that came as one MP3. A two-hour lecture you recorded in one sitting. A rip that landed as one track because the disc was mastered that way. The audio is fine. It carries no chapter marks, so a player treats it as one block of speech and a scrub bar is the only way to move around inside it.

Audiobook Binder Pro cuts that file into chapters from a list of times. You supply the list as a plain text file, a CUE sheet, or an OGM chapter list. The app reads the marks, cuts the audio at each one, and every segment becomes a chapter row you can rename before you export.

This shipped in 2.1.1, after two people asked for it separately in the same few weeks. Both had one long recording and a text file of timestamps sitting next to it. The rest of how the app changed from user requests is on its own page.

What a chapter list looks like

The simplest form is a .txt file with one line per chapter: a timestamp, then a title.

0:00 Introduction
4:32 Chapter One
41:08 Chapter Two
1:22:15 Chapter Three

Times read as m:ss or h:mm:ss. Square brackets around the time are fine. A dash, colon, or pipe between the time and the title is dropped, so 4:32 - Chapter One reads the same as the line above. Lines beginning with # or ; are treated as comments, and any line that does not open with a timestamp is ignored.

That last rule is what makes a pasted list work. Copy a chapter list out of a video description or a forum post, save it, and the prose around it falls away while the timed lines stay.

Three list formats

Plain timestamps in a .txt file, as above. This is the one most people end up writing by hand.

CUE sheets, the TRACK / TITLE / INDEX 01 layout that arrives with a disc rip or a recorded set. Times are read as mm:ss:ff at 75 frames per second, which is what a CUE sheet means by those numbers.

OGM lists, the mkvmerge style, where CHAPTER01=00:00:30.000 pairs with CHAPTER01NAME=Introduction.

The app looks at what is inside the file before it looks at the extension. A CUE sheet someone saved as .txt still reads as a CUE sheet.

Let the app find the list on its own

Name the list after the audio file, keep the two together in one folder, and the chapters are there the moment you import. For Middlemarch.mp3 the app checks these names in order:

Middlemarch.chapters.txt
Middlemarch.chapters.cue
Middlemarch.txt
Middlemarch.cue
chapters.txt
chapters.cue

The first one that parses into two or more chapters wins. If another one in the folder would also have worked, the app names it in the import summary rather than silently preferring one over the other.

Auto-detection runs only when you import exactly one audio file. A list of times describes one specific recording, so applying it to a folder of 20 tracks would be a guess. Import a folder and nothing splits by itself: if there is a readable chapter list in there, the app tells you it found one and leaves the decision to you.

Add a list after the fact

Two ways in, both after the import has already happened.

The import summary offers Add Chapter File… when you brought in one file that carries no chapters of its own. Pick a .txt or .cue, and the file expands into chapters as it comes into the project.

For anything else, right-click a chapter row (or use its … button) and choose Split into Chapters…. This works on a project you built weeks ago. No re-import, no rebuilding the book around one long track you should have cut earlier.

Nothing is cut until you confirm

Picking a file does not start the split. The app reads it and shows Review Chapter Split first: the list file it read, how many chapters it proposes, any warnings, and a table of every title and time. From there you confirm, choose a different file, or cancel.

Before the preview appears, the marks are tidied up. Anything past the end of the audio is dropped, two marks at the same time collapse into one, zero-length chapters are removed, and the rest are sorted by start time. A list has to yield at least two usable chapters. When a file yields none, the app says so and the project is left as it was.

The review step exists because a chapter list is easy to get subtly wrong. An offset of a few seconds, a stray line, a list that belongs to a different edition of the same book: all of it shows up in that table before any audio is touched.

Which files can be split

MP3, M4A, M4B, AAC, WAV, AIFF, and FLAC. Ogg, Opus, WMA, APE, WavPack, and the video containers import fine but cannot be split this way. Export one of those to M4A first, then start a project from that file.

How the cut is made depends on the source. M4A, M4B, and AAC files are cut without re-encoding, so the segments come out lossless and the split takes seconds. Some formats are re-encoded during the split. At spoken-word settings the difference is not audible.

Splitting into chapters is not splitting into parts

Three different jobs share the word “split”, and they are worth keeping apart.

Split into chapters takes one long file and gives it internal structure. One recording in, one book out, with as many chapter marks as your list has entries. That is this page.

Split into parts happens at export, when a finished book is long enough that one file is unwieldy. The app cuts by duration or by size and always lands the cut on a chapter boundary, so you end up with Part 1, Part 2, and Part 3 as separate M4B files. Each part keeps its own chapters.

Extracting chapters is the reverse of building a book: an existing M4B goes in and one M4A per chapter comes out. That one lives on the edit an M4B page.

After the split

Once the file is in pieces, it behaves like any other project. Rename chapters, drag them into a different order, run Clean Up Names over titles that came out of the list with repeated text, add a cover and metadata, then export a chaptered M4B.

If your material is a folder of separate tracks rather than one long file, you want the other direction. MP3 to M4B with chapters covers one file per chapter, the more common shape.

Frequently asked questions

Related workflows

Next step

Use this workflow when the audio arrived as one long file and you already know, or can work out, where the chapters begin. Audiobook Binder Pro is a one-time purchase, runs fully offline with no account, and requires macOS 14.0 (Sonoma) or later.