MMF (Mobile Music File) is the default file extension for files belonging to the SMAF specification. SMAF stands for Synthetic-music Mobile Application Format.
The SMAF format was developed by Yamaha and introduced with the production of their MA-1, MA-2, MA-3, MA-5 and MA-7 LSI sound chips (respectively capable of 4-, 16-, 40-, 64- and 128-polyphony), which all found broad use in mobile phones placed on the East Asian market around the early 2000s.
Internationally, the MMF format was most endorsed by Samsung, being used as the default polyphonic ringtone format on a wide range of their mobile devices. With the increasing popularity of modern smartphones, the MMF format became less relevant to the mobile industry. However, certain lower end phones not capable of WAV or MP3 playback etc., are still and may continue using the MMF format to store their ringtones.
In structure, MMF/SMAF files highly resemble a MIDI file. However, what makes them different from MIDI, is that MMF files may also encapsulate descriptive metadata (such as artist, song title, genre), graphics and/or raw PCM audio data. PCM audio data may be there, because except through FM synthesis (like in MIDI files), playback may be also produced via PCM wavetable synthesis (similar to module files like MOD, XM, IT or S3M to name a few), in which case there are PCM audio tracks that serve as a sound source and define the timbre of the instruments. The PCM method allowed the ringtones to sound the same regardless of the sound chip that provides their playback.
To popularize the format, Yamaha published a number of tools at the official Yamaha SMAF website, which allowed users to easily play MMF files on their desktop computers and convert them from and to widely popular formats like WAV and MID. It's interesting that compared to MIDI, regular MMF/SMAF files (using only FM synthesis to produce feedback) are only two-thirds of the size, which still makes them a good choice for sharing and distributing this type of audio content.
Other .MMF file extensions
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