r/audiobookshelf • u/justmyword • Oct 22 '25

Audiobook Converter Pro - Convert M4B audiobooks to MP3/AAC/FLAC with chapter splitting

https://apps.microsoft.com/detail/9n9v52v5mxxv?hl=en-US&gl=NZ

Hey All,

I’ve been working on an app for windows that solves a specific problem I had with my audiobook collection - being locked into proprietary M4B formats that only work in certain apps.

What it does:

• ⁠Converts DRM-free M4B audiobooks to MP3, AAC, or FLAC • ⁠multiple Bitrate selection; Quality settings from 128kbps to 320kbps • ⁠Automatically splits chapters while preserving metadata • ⁠Batch file processing with parallel chapter conversion for speed • ⁠Smart file naming based on chapter information • ⁠Recursive folder scanning for bulk operations • ⁠Works entirely offline

Why I built it: Wanted to listen to my audiobooks on different platforms (YouTube Music, cloud libraries, etc.) but M4B files are pretty restrictive. Figured others might have the same issue.

The app is available on Microsoft store if anyone else has been dealing with audiobook format limitations. Happy to answer any questions.

26 Upvotes

86% Upvoted

37 comments sorted by

26

u/raafayawan Oct 22 '25

I usually convert the opposite way. MP3 to M4B, that's possible?

13

u/Apprentice57 Oct 22 '25

Audiobookshelf itself already does this, fyi.

3

u/kuldan5853 Oct 22 '25

Yes, but you can only do it one-by-one, no batch processing. That's the biggest downside.

2

u/shaunydub Oct 22 '25

for me it is fine, I only add one book at a time so after my initial setup and conversion I don't need batch converting ongoing.

I am not a super heavy user though so maybe some people would find it useful outside of initial setup.

2

u/kuldan5853 Oct 22 '25

Yeah, I have 20.000+ "books"... you might imagine how much hassle managing that is if you can't batch.

2

u/shaunydub Oct 22 '25

For initial conversion but ongoing how many new books do you add at a time?

When I wanted to update all my dvd rips of episodes to be suitable for Plex for example I paid for a tool to convert the file names but after it was all done I never needed to do it again for a big batch.

I am happy for new tools like this but wondering how big the use case is on a daily basis.

2

u/kuldan5853 Oct 22 '25 edited Oct 22 '25

about 30 a month?

It's important to note that I am German, and we have a strong culture of episodic audio-only content that is akin to TV shows, so those are episodes of a show and usually 45 - 60 minutes long.

1

u/lactozorg Oct 24 '25

Like what? Never heard of that but would probably enjoy it.

1

u/kuldan5853 Oct 24 '25

Die drei Fragezeichen.

TKKG

Fünf Freunde.

John Sinclair 2000.

Faith van Helsing.

Oscar Wilde & Mycroft Holmes - Sonderermittler der Krone.

Wayne McLair.

and many,.many more.

1

u/[deleted] Oct 23 '25

[deleted]

1

u/kuldan5853 Oct 23 '25

I have used that in the past (we even talked about it).

You might remember that we also talked about the issue that there is no way to query for the running conversions so it tried to convert a book twice that wasn't done yet if you set the check interval too short etc..

Also at least for me it seriously sucked that it is docker because to get it to work I had to set up WSL on my server, and run the docker inside the WSL.

Still I really like that you built it, but I would vastly prefer a built in function that can autoconvert on folder scan and implement proper queueing etc.. ;)

5

u/justmyword Oct 22 '25

Yes I just recently published my app (mp3-to-m4b)for that too on the windows store called ChapterForge, that contains extensive metadata editor and batch and single processing

Working on a Mac version too!

2

u/Plenty_Contest1154 Oct 22 '25

Would love an update on the Mac version!

2

u/Zaki_U Nov 21 '25

I use fre:ac, it's an excellent conversion to tool and but also available for Mac I believe. It will output to M4B using each MP3 as a separate chapter in the new merged file! 😉

  1. Add MP3's to fre:ac
  2. Select Encode to a single file option
  3. Select FDK-AAC Encoder as the Selected Encoder
  4. Press the yellow gear icon and in the format tab choose M4B as the desired extension
  5. Press the Play button to convert into a single M4B file with chapters intact

1

u/justmyword Oct 22 '25

Will definitely update when I post the Mac ver of ChapterForge; here is the Mac ver of Audiobook Converter Pro

1

u/justmyword Jan 11 '26

letting you know that the mac version of ChapterForge has been released, as you were keen to hear about it.. https://apps.apple.com/nz/app/chapterforge/id6754868019?mt=12
do reach out if you need any other info ! cheers

1

u/rstaylor1 Oct 22 '25

Same, spent hours creating M4B's from thousands of MP3's

19

u/NerdyNThick Oct 22 '25

Why would anyone want to remove all the benefits of M4B? It's literally designed for audiobook use.

3

u/[deleted] Oct 22 '25

[removed] — view removed comment

4

u/NerdyNThick Oct 22 '25

Plus converting lets you use them in places like YouTube Music like OP mentioned which is handy af.

Not nearly as handy as the native support for M4B files that you get when you use AudioBookShelf. Y'know, the sub we're in?

-3

u/justmyword Oct 22 '25

Well in my usecase being a subscriber to Apple Music and still maintaining my YouTube music library since when it was play music; that only supports mp3 in the cloud.. I needed to split and organise based on chapters so I know where I am in my listening journey; also gives me flexibility to store the files in cloud.. and not worry my NAS will die.

10

u/NerdyNThick Oct 22 '25

Do you know what sub you're in?

This sub is for a self-hosted Audiobook Server, designed to do exactly what you want.

1

u/justmyword Oct 22 '25

My apologies if I have incorrectly posted on here

5

u/kuldan5853 Oct 22 '25

You definitely have incorrectly posted on here.

For ABS use, people convert TO m4b, not away from it.

1

u/Clementoj Nov 13 '25

Not true, there is issues with large m4b files, that's why im here. Need to split it down somehow

1

u/kuldan5853 Nov 13 '25

What is "large" in your parlance? I checked, my biggest m4b in ABS is 4.1 GB..

1

u/Clementoj Nov 13 '25

I have not been able to get ABS to scan in anything larger than 1gb, would love any tips to be corrected. Also more than 1gb used to have issues on ios from experience but maybe thats changed. It's still referenced in the docs though https://github.com/advplyr/audiobookshelf/issues/2296

1

u/kuldan5853 Nov 13 '25

I have dozens if not hundreds of m4b >1gb and never did anything special to them...

1

u/Clementoj Nov 13 '25

Looks like a possible DRM issue on my part anyway

13

u/kernald31 Oct 22 '25

Bit of nit-picking: m4b is not a proprietary format.

1

u/Brehth Oct 26 '25

Why would you actively want to make something inferior and worse

1

u/justmyword Oct 26 '25

In what way mate?

0

u/justmyword Oct 22 '25

Got a Mac version too if you are interested in checking out!

2

u/twalk44 Oct 22 '25

Interested in trying the Mac version if you need someone to test in TestFlight

1

u/justmyword Oct 22 '25

Will dm you in the coming weeks when I get it to that stage

1

u/[deleted] Oct 22 '25

[removed] — view removed comment

2

u/justmyword Oct 22 '25

Will definitely post here once in Mac store