AST file
From WiiBrew
AST files contain PCM16 (16-bit signed) sound data. They're used in Super Mario Galaxy for musics, Legend of Zelda: Twilight Princess, and possibly in other games.
They contain a header, followed by BLCK chunks which are divided in blocks (channels).
All the data in those files are big-endian, except where mentioned.
All the offsets are absolute (from beginning of the file), except where mentioned.
All the sizes are in bytes, except where mentioned.
Contents |
AST header
The header is 64 bytes long. Here's a description of it:
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 4 | "STRM" (0x5354524D) |
| 0x0004 | 4 | Size of all the BLCK chunks (size of the file minus 64) |
| 0x0008 | 4 | Unknown (0x00010010) |
| 0x000C | 2 | Number of channels (typically 2 = stereo) |
| 0x000E | 2 | Unknown (0xFFFF) |
| 0x0010 | 4 | Sampling rate in Hz (typically 32000) |
| 0x0014 | 4 | Total number of samples |
| 0x0018 | 4 | Loopstart position in samples/bytes? |
| 0x001C | 4 | Unknown (typically same as entry 0x0014) |
| 0x0020 | 4 | Block size for the first chunk? (typically 0x2760) |
| 0x0024 | 28 | Unknown (Usually all zeros except 0x0028, which is 0x7F) |
BLCK chunks
The BLCK chunks directly follow the AST header. They contain a 32-byte header, followed by PCM16 sound data.
Here's a description of them:
| Offset
(from beginning of BLCK chunk) | Size | Description |
|---|---|---|
| 0x0000 | 4 | "BLCK" (0x424C434B) |
| 0x0004 | 4 | Block size (typically 0x2760) |
| 0x0008 | 24 | Padding (zero) |
| 0x0020 | variable | PCM16 data blocks |
The data is divided into blocks. There's one block per channel.
The length of each block is defined by entry 0x0004 in BLCK chunk header.
WARNING: The PCM16 data is stored in BIG-ENDIAN! If you aren't working on the Wii, don't forget to byteswap each sample you read or your sound will be pure junk!
Block mapping inside BLCK chunks
| Number of channels | Type | Block mapping |
|---|---|---|
| 2 | Stereo | Left; Right |
| 4 | 4.0 Surround | Left; Right; Surround left; Surround right |
Stereo is the most common type. Some music in SMG, such as the beach theme, are 4.0 Surround, though.
AST file structure
| Element | Size |
|---|---|
| AST header | 64 bytes |
| BLCK chunk header | 32 bytes |
| PCM16 block 1 | N |
| PCM16 block 2 | N |
| ... | |
| PCM16 block N' | N |
| BLCK chunk header | 32 bytes |
| PCM16 block 1 | N |
| PCM16 block 2 | N |
| ... | |
| PCM16 block N' | N |
| BLCK chunk header | 32 bytes |
| ... |
Where:
- N is the number of channels (entry 0x000C in AST header)
- N' is the block size (entry 0x0004 in BLCK chunk header)
