RAS (File Format)

RAS (RetroStudios Audio Stream?) is a streamable audio file format used in Donkey Kong Country Returns.

File Format

Header

The file starts with the following header:

Offset	Type	Description
0x00	Char[4]	File magic. Always RAS_ (0x5241535F) in ASCII.
0x04	UInt32	Version number. Always 2 in Donkey Kong Country Returns.
0x08	UInt32	Number of channels.
0x0C	UInt32	Unknown. Seems to be some size related to the last block.
0x10	UInt32	Number of unknowns.
0x14	UInt32	Sample rate in Hz.
0x18	UInt32	Sound data offset.
0x1C	UInt32	Sound data size in bytes.
0x20	UInt32	Block size in bytes.
0x24	UInt32	Number of blocks per channel.
0x28	UInt32	Unknown, seems to be some sort of size in bytes or samples.
0x2C	UInt32	Number of samples in the last block per channel.
0x30	UInt32	Loop start block index.
0x34	UInt32	Loop start sample into the loop start block specified above.
0x38	UInt32	Loop end block index.
0x3C	UInt32	Loop end sample into the loop end block specified above.

The file has looping defined if loop end block index or loop end smaple is not zero.

DSP ADPCM Channel Info

After the header there is a DSP ADPCM channel info data structure, one per channel. It has the following structure:

Offset	Type	Description
0x00	Int16[8][2]	16-bit Coefficients.
0x20	UInt16	Gain.
0x22	Int16	Pred scale.
0x24	Int16	Yn 1.
0x26	Int16	Yn 2.
0x28	UInt16	Loop pred scale.
0x2A	Int16	Loop Yn 1.
0x2C	Int16	Loop Yn 2.
0x2E	byte[2]	Padding.

Unknown

After channel infos, there is an unknown structure with the following layout:

Offset	Type	Description
0x00	Float	Unknown.
0x04	UInt32	Unknown.
0x08	UInt16	Unknown.
0x0A	Byte[2]	Unknown.
0x0C	UInt32	Unknown.

Sound Data

The sound data is stored in DSP ADPCM format. The header may allow specifying other formats, but it is currently unknown if that is the case.

Tools

The following tools can handle RAS files:

• vgmstream