What is the MMF file format?
.mmf is the file extension for Synthetic Music Mobile Application Format (SMAF), a binary audio container developed by Yamaha Corporation. It was the standard ringtone and background-music delivery format for Japanese carrier feature phones in the early 2000s, used on i-mode, EZweb, and related platforms.
MMF is an old format. Modern audio software no longer supports .mmf playback natively, but users can use Awave Studio or online converters to convert such files into MP3 or WAV for playback on current devices.
Inside each .mmf file, a root MMMD chunk (magic bytes 4D 4D 4D 44) wraps sub-chunks carrying content metadata (CNTI), FM-synthesis or PCM instrument data (MTR, ATR), and optional platform data (OPDA). Three instrument modes are supported: FM synthesis, PCM sample playback, and Stream PCM for longer clips. Yamaha defined successive chip generations - MA-1 through MA-7 - each expanding synthesis capability; the SMAF for Flash variant targeted Java ME phones.
A typical .mmf ringtone is 5-200 KB, storing instrument parameters internally in a manner similar to module audio formats.
Note that older documentation sometimes lists .mmf as a Microsoft Mail Message File - an entirely separate, unrelated database format from Microsoft NT Mail. The two formats share only the extension and have no structural or functional relationship.
Security & safety
RISK: LOWPure audio container; no executable content. Historical format - unlikely to be weaponized.
Format details
in a nutshell- Microsoft Mail Message File - Legacy Microsoft Mail/Exchange offline message store - unrelated binary format, same extension.
Programs that open MMF files
Windows2 apps
VLC media player
Open-source Drag and drop the MMF file onto VLC. Playback may be partial depending on codec support. 
Technical details
deep spec| Magic bytes | `4D 4D 4D 44` (`MMMD`) at offset 0; followed by 4-byte big-endian file size |
| Byte order | Big-endian |
| Container | SMAF chunk-based (`MMMD` root wrapping `CNTI`, `OPDA`, `MTR`, `ATR`, and other sub-chunks) |
| MIME type | audio/x-mmf (also audio/mmf, application/vnd.smaf) |
| Instrument types | FM synthesis, PCM sample playback, Stream PCM (for longer audio clips) |
| Chip generations | MA-1 through MA-7; each generation expanded FM and PCM synthesis capability |
| PCM sample rate | Up to 8,000 Hz for voice PCM; synthesis rate is chip-dependent |
| Typical file size | 5 KB - 200 KB (ringtones); up to ~500 KB with Stream PCM |
| Chunk framing | 4-byte size field per chunk for chunk-level data integrity |
| Platform origin | Japanese carrier networks (i-mode, EZweb); Symbian and J2ME feature phones |
| Variant | SMAF for Flash targeted Java ME mobile browsers |
| Obsolescence | Superseded by MP3/AAC; format frozen ~2008, commercially obsolete since ~2010 |
| Released | 1999 (with Yamaha MA-1 sound chip) |
| Latest version | SMAF for Flash (MA-7 era); format frozen ~2008 |
MMF conversions
Community Q&A
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