BAS (File Format)

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BAS stands for (presumably) Binary Audio Sequence. It is used in several JSystem games, including Super Mario Galaxy and Super Mario Galaxy 2.

Header

Every BAS starts with this header. It is 0x8 in size.

Offset	Type	Description
0x00	UInt16	Entry Count
0x02	UInt16	Unused
0x04	UInt32 *	Pointer (in memory) to a class that implements virtual methods for: void doNothing(); // you can put anything here, just make sure one virtual function comes first. u32 *getSound(JAUSoundAnimation *); u32 getNumSounds(JAUSoundAnimation *); in that order. Put 0 for default behavior. Always 0 in SMG/SMG2.

It is then followed by an array of sound entries:

Offset	Type	Description
0x08	SoundEntry[Entry Count]	Array of sound entries.

Sound Entry

0x20 in size, including padding.

Offset	Type	Description
0x00	UInt32	Sound ID
0x04	Single	Start Frame
0x08	Single	End Frame
0x0C	Single	Pitch
0x10	UInt32	Flags: bool useEndFrame(?) = (flags >> 6) & 0x01 (Still unknown/unused but set: 32, 16, 4)
0x14	UInt8	Volume
0x15	UInt8	Pitch Factor
0x16	UInt8	Loop Count
0x17	UInt8	Panning
0x18	UInt8	Volume Factor
0x19	UInt8[7]	Padding

(References: Hack.io.BAS, bastool, pyjaubas)