Convert M4B to 3GP — Free Online Converter

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.