AST files are sound files used in some GameCube and Wii games such as Super Mario Galaxy, Super Mario Galaxy 2 and Mario Kart: Double Dash!!. The file contains a header followed by blocks with data.

File Format

Header

The file starts with a 0x40 bytes long header as follows:

Offset	Type	Description
0x00	Char[4]	File magic. Always STRM in ASCII.
0x04	UInt32	Size of all sound blocks in bytes.
0x08	UInt16	Audio format. 0 = AFC ADPCM, 1 = PCM16.
0x0A	UInt16	Bits per sample.
0x0C	UInt16	Number of channels.
0x0E	Int16	Loop flag. -1 if it loops, 0 if it doesn't.
0x10	UInt32	Sample rate.
0x14	UInt32	Total number of samples.
0x18	UInt32	Loop start in samples.
0x1C	UInt32	Loop end in samples.
0x20	UInt32	Seems to be the block size of the first block.
0x24	UInt32	Unknown. Only seen as 0.
0x28	Byte	Volume. Values range from 0 to 127.
0x29	Byte[3]	Padding.
0x2C	Byte[0x14]	Unknown. Only seen as 0. Probably padding.

A file contains many BLCK sections which contain sound data. Each block has the following structure:

Offset	Type	Description
0x00	Char[4]	Block magic. Always BLCK in ASCII.
0x04	UInt32	Sound data size per channel in bytes.
0x08	UInt32	Unknown, only set when audio format is ADPCM.
0x0C	UInt32	Unknown, only set when audio format is ADPCM.
0x10	Byte[0x10]	Unknown. Probably padding to align sound data.
0x20	Byte[][]	Sound data.

The following tools can handle AST files: