Difference between revisions of "AGSC (File Format)"

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'''AGSC''' is the sound effect format for Metroid Prime and Metroid Prime 2: Echoes. Each AGSC file contains a group of sound effects. According to the debug maps in Metroid Prime, there are references to various "classes", with one of them controlling audio in the map, known as AudioGroupSet.  So presumably, AGSC is an abbreviation for '''Audio Group Set Class'''.   
 
'''AGSC''' is the sound effect format for Metroid Prime and Metroid Prime 2: Echoes. Each AGSC file contains a group of sound effects. According to the debug maps in Metroid Prime, there are references to various "classes", with one of them controlling audio in the map, known as AudioGroupSet.  So presumably, AGSC is an abbreviation for '''Audio Group Set Class'''.   
  
−
The audio codec used im AGSC is the standard GameCube DSP ADPCM codec, as described in the GameCube SDK.   
+
The audio codec used in AGSC is the standard GameCube DSP ADPCM codec, as described in the GameCube SDK.   
  
 
__TOC__
 
__TOC__
Line 7: Line 7:
 
== Format ==
 
== Format ==
  
−
The AGSC format is split up into four distinct data chunks; two unknown chunks, one for sound metadata, and one for actual sound data. The format is very similar between Metroid Prime 1 and 2; the main difference is the header, and some slight changes in the way the four chunks are organized. In Metroid Prime, each chunk begins with its own size value; in Metroid Prime 2, every chunk instead has its size listed at the beginning of the file, at the end of the header. In addition, in Metroid Prime, the third chunk is sound data, and the fourth is sound metadata; in Metroid Prime 2, it's the other way around.
+
The AGSC format is split up into four distinct data chunks; two unknown chunks, one for sound metadata, and one for actual ADPCM sound data. The format is very similar between Metroid Prime 1 and 2; the main difference is the header, and some slight changes in the way the four chunks are organized. In Metroid Prime, each chunk begins with its own size value; in Metroid Prime 2, every chunk instead has its size listed at the beginning of the file, at the end of the header. In addition, in Metroid Prime, the third chunk is sound data, and the fourth is sound metadata; in Metroid Prime 2, it's the other way around.
  
 
=== Header ===
 
=== Header ===
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| 0x0
 
| 0x0
 
| 4
 
| 4
−
| Unknown; always 1.
+
| Unknown; always 1
 
|-
 
|-
 
| 0x4
 
| 0x4
Line 47: Line 47:
 
| 0x4 + D
 
| 0x4 + D
 
| 4
 
| 4
−
| '''Chunk 1 size'''.
+
| '''Chunk 1 size'''
 
|-
 
|-
 
| 0x8 + D
 
| 0x8 + D
 
| 4
 
| 4
−
| '''Chunk 2 size'''.
+
| '''Chunk 2 size'''
 
|-
 
|-
 
| 0xC + D
 
| 0xC + D
 
| 4
 
| 4
−
| '''Sound metadata chunk size'''.
+
| '''Sound metadata chunk size'''
 
|-
 
|-
 
| 0x10 + D
 
| 0x10 + D
 
| 4
 
| 4
−
| '''Sound data chunk size'''.
+
| '''ADPCM chunk size'''
 +
|}
 +
 
 +
=== Sound Metadata ===
 +
 
 +
The sound metadata chunk (chunk 4 in Metroid Prime, chunk 3 in Metroid Prime 2) is made up of two sets of tables. The structure of both these tables is identical between both games.
 +
 
 +
==== Table A ====
 +
 
 +
The first metadata table has one entry per sound, and is terminated with 0xFFFFFFFF; since there's no known sound count anywhere in the file, the only way to read this correctly is to read until you reach the terminator value. Each entry is 0x20 bytes long.
 +
 
 +
{|class="wikitable"
 +
! Offset
 +
! Size
 +
! Description
 +
|-
 +
| 0x0
 +
| 2
 +
| '''Sound ID''' (note: not 100% confirmed)
 +
|-
 +
| 0x2
 +
| 2
 +
| Padding.
 +
|-
 +
| 0x4
 +
| 4
 +
| '''Sound start offset''', relative to the start of the ADPCM chunk
 +
|-
 +
| 0x8
 +
| 4
 +
| Unknown
 +
|-
 +
| 0xC
 +
| 2
 +
| Unknown; appears to always be 0x3C00
 +
|-
 +
| 0xE
 +
| 2
 +
| '''Sample rate'''
 +
|-
 +
| 0x10
 +
| 4
 +
| '''Number of samples'''
 +
|-
 +
| 0x14
 +
| 4
 +
| '''Loop start sample'''
 +
|-
 +
| 0x18
 +
| 4
 +
| '''Loop length''', in samples. To get the loop end sample, add this to the start sample and subtract 1.
 +
|-
 +
| 0x1C
 +
| 4
 +
| '''Table B entry offset''', relative to the start of the sound metadata chunk
 +
|-
 +
| 0x20
 +
| colspan=2 | End of entry
 +
|}
 +
 
 +
==== Table B ====
 +
 
 +
These are accessed through the offsets in table A's entries; note that it might not match the sound count, because the same entry in this table can be used with multiple sounds. Each entry is 0x28 bytes long.
 +
 
 +
{|class="wikitable"
 +
! Offset
 +
! Size
 +
! Description
 +
|-
 +
| 0x0
 +
| 2
 +
| Unknown
 +
|-
 +
| 0x2
 +
| 2
 +
| Unknown
 +
|-
 +
| 0x4
 +
| 4
 +
| Unknown
 +
|-
 +
| 0x8
 +
| 2 × 16
 +
| '''Coefficient table'''
 +
|-
 +
| 0x28
 +
| colspan=2 | End of entry
 
|}
 
|}
  
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[[Category:Audio]]
 
[[Category:Audio]]
 
[[Category:Metroid Prime]]
 
[[Category:Metroid Prime]]
−
[[Category:Metroid Prime 2 Echoes]]
+
[[Category:Metroid Prime 2: Echoes]]

Revision as of 06:50, 23 January 2015

AGSC is the sound effect format for Metroid Prime and Metroid Prime 2: Echoes. Each AGSC file contains a group of sound effects. According to the debug maps in Metroid Prime, there are references to various "classes", with one of them controlling audio in the map, known as AudioGroupSet. So presumably, AGSC is an abbreviation for Audio Group Set Class.

The audio codec used in AGSC is the standard GameCube DSP ADPCM codec, as described in the GameCube SDK.

Format

The AGSC format is split up into four distinct data chunks; two unknown chunks, one for sound metadata, and one for actual ADPCM sound data. The format is very similar between Metroid Prime 1 and 2; the main difference is the header, and some slight changes in the way the four chunks are organized. In Metroid Prime, each chunk begins with its own size value; in Metroid Prime 2, every chunk instead has its size listed at the beginning of the file, at the end of the header. In addition, in Metroid Prime, the third chunk is sound data, and the fourth is sound metadata; in Metroid Prime 2, it's the other way around.

Header

Metroid Prime

Offset Size Description
0x0 D Audio Directory. Always "Audio/." Zero-terminated.
0x0 + D N Audio Group Name. Zero-terminated.
0x0 + D + N End of header

Metroid Prime 2

Offset Size Description
0x0 4 Unknown; always 1
0x4 D Audio Group Name. This typically describes what sounds are in the file (for example, "Metroid" or "Weapons"). Zero-terminated.
0x4 + D 4 Chunk 1 size
0x8 + D 4 Chunk 2 size
0xC + D 4 Sound metadata chunk size
0x10 + D 4 ADPCM chunk size

Sound Metadata

The sound metadata chunk (chunk 4 in Metroid Prime, chunk 3 in Metroid Prime 2) is made up of two sets of tables. The structure of both these tables is identical between both games.

Table A

The first metadata table has one entry per sound, and is terminated with 0xFFFFFFFF; since there's no known sound count anywhere in the file, the only way to read this correctly is to read until you reach the terminator value. Each entry is 0x20 bytes long.

Offset Size Description
0x0 2 Sound ID (note: not 100% confirmed)
0x2 2 Padding.
0x4 4 Sound start offset, relative to the start of the ADPCM chunk
0x8 4 Unknown
0xC 2 Unknown; appears to always be 0x3C00
0xE 2 Sample rate
0x10 4 Number of samples
0x14 4 Loop start sample
0x18 4 Loop length, in samples. To get the loop end sample, add this to the start sample and subtract 1.
0x1C 4 Table B entry offset, relative to the start of the sound metadata chunk
0x20 End of entry

Table B

These are accessed through the offsets in table A's entries; note that it might not match the sound count, because the same entry in this table can be used with multiple sounds. Each entry is 0x28 bytes long.

Offset Size Description
0x0 2 Unknown
0x2 2 Unknown
0x4 4 Unknown
0x8 2 × 16 Coefficient table
0x28 End of entry
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