Convert MPEG-4 Audiobook (.m4b) to 3GPP Multimedia (.3gp) online for free. Fast, secure audio conversion with no watermarks or registration.
Upload your .m4b file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .3gp file when it's ready.
M4B is the audiobook variant of MPEG-4 Audio, distinguished from M4A by its support for chapter markers and bookmarking (remembering playback position). Converting M4B to 3GP strips away these audiobook-specific features and compresses the audio into AMR-NB or low-bitrate AAC inside a 3GPP container. This extreme conversion targets legacy feature phones and telephony systems where audiobook content needs to be delivered in the most basic mobile format available.
Some educational audio distribution in developing markets still relies on 3GP-compatible feature phones as the primary delivery platform. Converting audiobook chapters to individual 3GP files allows distribution through MMS or Bluetooth to devices that have no audiobook app or M4B support. Telephony-based educational systems may also use 3GP for lesson delivery over IVR.
FFmpeg decodes the M4B's AAC audio (typically 32-64 kbps for spoken word) and re-encodes to AMR-NB (8 kHz mono, up to 12.2 kbps) or AAC-LC at low bitrate inside a 3GP container. Chapter markers from the M4B are lost — 3GP does not support chapters. Bookmarking is also lost. For multi-chapter audiobooks, each chapter should be extracted separately before conversion.
M4B audiobooks are typically encoded at 32-64 kbps AAC, already optimized for spoken word. AMR-NB at 12.2 kbps produces telephone-quality speech — clearly intelligible but with audible compression. If the 3GP uses AAC at 32-64 kbps, quality matches the M4B source since spoken word does not need high bitrates.
| Device | M4B | 3GP |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Partial | Native |
| Linux | Partial | Partial |
| Web Browser | No |
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Resolution: N/A
Bitrate: 256 kbps
AAC format required
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
M4B to 3GP conversion serves educational and telephony distribution of spoken content on legacy mobile infrastructure. Extract chapters individually for the best results.
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| No |
| Funktion | M4B | 3GP |
|---|---|---|
| Fullstandigt namn | MPEG-4 Audiobook | 3GPP Multimedia |
| Filandelse | .m4b | .3gp |
| Bast for | Chapter support | Mobile optimized |