BRSTM file

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BRSTM files contain ADPCM sound data. They are used for music in some games, such as Super Smash Bros. Brawl and Mario Kart Wii.

They contain an header, followed by a HEAD chunk, a ADPC chunk and a DATA chunk.
All the data in those files are big-endian, except where mentioned.
All the offsets are absolute (from begining of file), except where mentioned.
All the sizes are in bytes, except where mentioned.

BRSTM header

The header is 64 bytes long.

Offset Size Description
0x0000 4 "RSTM" (0x5253544D)
0x0004 4 Magic (0xFEFF0100)
0x0008 4 Size of the whole file
0x000C 4 Unknown
0x0010 4 Offset to HEAD chunk
0x0014 4 Size of HEAD chunk
0x0018 4 Offset to ADPC chunk
0x001C 4 Size of ADPC chunk
0x0020 4 Offset to DATA chunk
0x0024 4 Size of DATA chunk
0x0028 24 Unknown/Padding (zero)

HEAD chunk

The head chunk is typically 256 bytes long.
It contains what looks like the ADPCM table and YN1/YN2, twice, probably once for the first part and once for the last (looping) part.
It also contains some other unknown stuff.

ADPC chunk

The ADPC chunk is typically 1216 bytes long. It seems to contain some other ADPCM table.

DATA chunk

The DATA chunk contains ADPCM sound data.