What is an M4B file?
Discover the power of the M4B audiobook format, a specialized file type recognized by its .m4b extension and celebrated for its advanced features. While it shares a foundation with the standard M4A format, M4B is distinctly engineered for audiobooks, offering crucial functionalities like chapter breaks and digital bookmarking to enhance your listening experience. At its core, the audio within an M4B file is encoded using high-efficiency AAC compression within an MPEG-4 container, ensuring excellent sound quality. A key characteristic of M4B files is their availability in two distinct types: DRM-protected and DRM-free versions. Encrypted, DRM-enabled M4B files are typically paid audiobooks distributed through platforms like the Apple Books and iTunes Store.
M4B File Format
The audiobook files containing metadata, images, bookmarks and hyperlinks can be saved with .m4a extension but generally .m4b extension is used while saving, just to specify that the file has an audiobook file format. Fairplay DRM (Digital Rights Management) is used by apply to protect their M4B files. So the files downloaded from iTunes can be played only on authorized devices or computers.
Key Characteristics of M4B Files
| Characteristic | Description |
|---|---|
| File Extension | .m4b |
| Format Type | Audio Container Format |
| Core Codec | Advanced Audio Coding (AAC) |
| Key Feature | Chapter Markers & Resume Playback |
| Primary Use Case | Audiobooks, Podcast Series |
| DRM Capable | Yes (Commonly used by Audible/Apple) |
| Platform | Native on Apple Devices (iOS, macOS); requires specific apps on |
M4B vs MP3
Both M4B and MP3 are audio-only file formats.
M4B: Wins when compared to MP3 in terms of quality if encode both at the same bit rate. The M4B is an audiobook file which is compressed using AAC encoding. It is basically associated with “MPEG-4 Audio Layer”, files with .m4b extension are the audio layer of MPEG-4 movies but with extra audiobook related features. Its goal is to overtake MP3 and become the new standard in audio compression. It is very close to MP3 in many ways but developed to have a better quality in a same or even smaller file size. The M4B format was first introduced by Apple. The format type is also realized as the Apple lossless Encoder (ALE).
Therefore, currently the M4B couldn’t get the MP3’s mainstream success because the audio format is not commonly playable yet.
Mp3: A digital audio format which is well familiar to everyone. A very first compression format on the scene and became very famous among music listeners. Its mainstream success is so rapid that the file type is being able to be played universally and compatible with almost anything, hardware or software. In a general sense, the M4A will produce better sound quality, but many would argue that, whether it’s true or not, the sound difference is not comparable, and it would be a waste of time trying to convert MP3 files into M4A files. Finally, the conversion will just make you lose the original sound quality.
M4B file format specification
Similar to M4A, the M4B files also consist of consecutive chunks. Each chunk has 8 byte header and sub-divided as:
- 4-byte chunk size (big-endian, high byte first)
- 4-byte chunk type - one of pre-defined signatures: “ftyp”, “mdat”, “moov”, “pnot”, “moof”, “udta”, “uuid”, “free”, “ctab”, “skip”, “jP2 “, “wide”, “load”, “imap”, “matt”, “chap”, “kmat”, “clip”, “crgn”, “sync”, “tmcd”, “PICT”, “scpt”, “ssrc”.
Similar to M4A the First chunk in M4B will be of type “ftype” and has a sub-type at offset 8. The M4B defined by sub-type which must be “M4B_”.
Iterating chunks, until chunk of unknown type is detected, It will compose M4B (MPEG-4 Audio) file.
FAQ
Q1: Can I play M4B files on my Android device?
A: Yes, you can use third-party audiobook player apps like “Smart Audiobook Player” or “Voice Audiobook Player” which fully support M4B features.
Q2: How can I convert an M4B file to MP3?
A: You can use free audio conversion software like Audacity (with the FFmpeg library) or Any Audio Converter to change M4B to MP3, though you will lose chapter markers and resume functionality.
Q3: Are all M4B files protected by DRM?
A: No, only M4B files from specific vendors like Audible have DRM; many M4B files from other sources or created by users are DRM-free.
Q4: What is the main difference between M4A and M4B?
A: The primary difference is that M4B supports bookmarking and chapter metadata for audiobooks, while M4A is generally used for music and does not.
Q5: Can I listen to M4B files on a Windows PC?
A: Absolutely, you can use media players like VLC Media Player, iTunes, or Windows Media Player (with the correct codecs installed) to play M4B files on Windows.
