Nintendo Ultra 64 Sound Format

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The Nintendo Ultra64 Sound Format (USF) is a file format by Adam Gashlin that contains the sound-generating code from a Nintendo 64 video game (akin to PSF for the Sony PlayStation). The basic USF file structure is a subformat of PSF.

There is no official standard for storing music in Nintendo 64 ROMs, which makes ripping significantly harder. USF files are generated by manually isolating the program code responsible for playing music, plus the stored music data. The rest of the ROM bytes are zeroed, and the resulting data is stored sparsely (zero bytes are not stored in the USF, so unspecified bytes can be assumed to be zero) but otherwise without compression. The file also contains a Project64 save state which is used to initialize emulation upon loading the USF, rather than follow the complete N64 boot process.

USF files can be played back in Winamp through the use of an appropriate plug-in, such as 64th Note. It requires two files be present in the same directory: the song file (extension ".miniusf") which is quite small (typically less than a kilobyte), and a library file specific to each game (extension ".usflib") which can be somewhat larger (up to several megabytes).