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Note: there's sound data for one channel only. Stereo mixing is performed by the Wii's DSP.+
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+
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AST files contain PCM16 (16-bit signed) sound data. They're used in Super Mario Galaxy for musics, and possibly in other games.
AST files contain PCM16 (16-bit signed) sound data. They're used in Super Mario Galaxy for musics, and possibly in other games.
−They contain an header, followed by BLCK chunks which are divided in blocks.<br>
+They contain an header, followed by BLCK chunks which are divided in blocks (channels).<br>
All the data in those files are big-endian, except where mentioned.<br>
All the data in those files are big-endian, except where mentioned.<br>
All the offsets are absolute (from begining of file), except where mentioned.<br>
All the offsets are absolute (from begining of file), except where mentioned.<br>
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| 0x000C
| 0x000C
| 2
| 2
−| Number of blocks per BLCK chunk
+| Number of channels (typically 2 = stereo)
|-
|-
| 0x000E
| 0x000E
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| 0x0010
| 0x0010
| 4
| 4
−| Sampling rate in Hz (typically 0x7D00 = 32000 Hz)
+| Sampling rate in Hz (typically 32000)
|-
|-
| 0x0014
| 0x0014
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| 0x0018
| 0x0018
| 4
| 4
−| Loopstart position in samples, from beginning of BLCK chunk
+| Loopstart position in samples/bytes?
|-
|-
| 0x001C
| 0x001C
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|}
|}
−The data is divided into blocks. The number of blocks is defined by entry 0x000C in AST header.<br>
+The data is divided into blocks. There's one block per channel.<br>
The length of each block is defined by entry 0x0004 in BLCK chunk header.<br>
The length of each block is defined by entry 0x0004 in BLCK chunk header.<br>
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!<br>
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!<br>
−=== Block mapping inside BLCK chunks ===
+{| class="wikitable"
+|-
+! 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 musics in SMG, such as the beach theme, are 4.0 Surround, though.
=== AST file structure ===
=== AST file structure ===
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Where:<br>
Where:<br>
−- N is the number of blocks per BLCK chunk (entry 0x000C in AST header)<br>
+- N is the number of channels (entry 0x000C in AST header)<br>
- N' is the block size (entry 0x0004 in BLCK chunk header)<br>
- N' is the block size (entry 0x0004 in BLCK chunk header)<br>