Convert MPEG-4 Audiobook (.m4b) to Matroska Video (.mkv) 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 .mkv file when it's ready.
MKV (Matroska Video) is an open container that supports virtually every codec, including AAC audio from M4B. Converting M4B to MKV packages audiobook content in Matroska's versatile container, which natively supports chapter markers — a feature that aligns perfectly with M4B's audiobook chapters. Unlike converting to M4A or MP3, an MKV conversion can preserve the audiobook's chapter structure in Matroska's chapter specification.
MKV is one of the few formats besides M4B that supports rich chapter metadata. Media servers like Plex and Jellyfin display MKV chapters in their player UI. If you want to move audiobooks out of Apple's ecosystem while preserving chapter navigation, MKV is an excellent target. MKV also supports multiple audio tracks, external subtitle files, and embedded cover art — useful for enhanced audiobook experiences.
FFmpeg copies the AAC audio from M4B into an MKV container (stream copy, zero quality loss). M4B chapters can be mapped to Matroska chapter metadata during the mux operation. Matroska chapters support titles, timestamps, nested chapters, and language tags — actually richer than M4B's chapter format. The operation is near-instant since no transcoding occurs.
Zero quality change with stream copy. The AAC audio data is transferred bit-for-bit from the M4B container to the MKV container.
| Device | M4B | MKV |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Partial | Partial |
| 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 MKV is uniquely advantageous because MKV can preserve chapter structure. It is the best open-format target for audiobooks that need to maintain navigability.
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| No |
| Tính năng | M4B | MKV |
|---|---|---|
| Tên đầy đủ | MPEG-4 Audiobook | Matroska Video |
| Phần mở rộng | .m4b | .mkv |
| Phù hợp nhất cho | Chapter support | Multiple audio tracks |