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Revision as of 20:13, 20 June 2016

330 bytes added ,  20 June 2016
Multi-track SNG clarifications
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imported>Jackoalan
imported>Jackoalan
(Multi-track SNG clarifications)
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The '''CSNG format''' contains MIDI data. It appears in Metroid Prime 1 and 2.  It is essentially MusyX's SON music format, with a custom header.  
The '''CSNG format''' contains MIDI data. It appears in Metroid Prime 1 and 2.  It is essentially MusyX's GameCube SNG music format, with a custom header.  


__TOC__
__TOC__
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All offsets are relative to the start of the main header (after the custom header).  
All offsets are relative to the start of the main header (after the custom header).  


Timings are represented in ''ticks'', like MIDI. Unlike MIDI, the tick-resolution is fixed at 384
Overall, SNG functions similar to a Type-1 (multi-track) MIDI file, with (up to) 64 tracks
merging their events into 16 General-MIDI sequencer channels. In addition to the multi-track
structure, SNG supports storing MIDI regions as indexed ''patterns'', so songs with repetitive
refrains can save on memory by referencing patterns more than once.
 
Timings are represented in ''ticks''. Unlike MIDI, the tick-resolution is fixed at 384
ticks per beat (e.g. 120 beats-per-minute works out to <code>384 * 120 / 60 = 768</code> ticks-per-second).
ticks per beat (e.g. 120 beats-per-minute works out to <code>384 * 120 / 60 = 768</code> ticks-per-second).


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| 0x10
| 0x10
| 4
| 4
| '''SON File Length'''
| '''SNG File Length'''
|-
|-
| 0x14
| 0x14
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| 0x0
| 0x0
| 4
| 4
| '''Version'''; always 0x18
| '''Track Index Offset'''; usually 0x18 for GCN games
|-
|-
| 0x4
| 0x4
| 4
| 4
| '''Track Data Offset'''; (absolute SON-offset)
| '''Region Data Index Offset'''
|-
|-
| 0x8
| 0x8
| 4
| 4
| '''Channel Map Offset'''; (absolute SON-offset)
| '''Channel Map Offset'''
|-
|-
| 0xC
| 0xC
| 4
| 4
| '''Tempo Table Offset'''; (absolute SON-offset) 0x0 if tempo doesn't change
| '''Tempo Table Offset'''; 0x0 if tempo doesn't change
|-
|-
| 0x10
| 0x10
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|-
|-
| 0x18
| 0x18
| 256
| '''Track Header Offsets'''; (absolute SON-offsets) 64 elements, 0x0 if track not present
|-
| 0x118
| colspan=2 {{unknown|End of header}}
| colspan=2 {{unknown|End of header}}
|}
|}


===Track Header===
===Region Info===


This is a variable-length table of headers for each track
The ''track index'' has offsets relating the first '''region info''' for each track.
 
There is a sequence of at least 2 region info structures populating each track, last one acting as terminator:


{| class="wikitable"
{| class="wikitable"
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| 0x0
| 0x0
| 4
| 4
| '''Start Tick'''; time-point to begin executing track data  
| '''Start Tick'''; time-point to begin executing region data  
|-
|-
| 0x4
| 0x4
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| 0x8
| 0x8
| 2
| 2
| '''Track Data Index'''
| '''Region Data Index'''; used to select region data via the ''region data index''; value is negative on a dummy ''region info'' to terminate track regions
|-
|-
| 0xA
| 0xA
| 2
| 2
| '''Padding'''
| {{unknown|'''Unknown'''}}
|-
|-
| 0xC
| 0xC
| 4
| colspan=2 {{unknown|End of region info}}
| '''Start Tick'''; copy of start tick
|-
| 0x10
| 4
| {{unknown|'''Unknown'''}}; commonly 0xffff0000
|-
| 0x14
| 4
| {{unknown|'''Unknown'''}}; commonly 0xffff0000
|-
| 0x18
| colspan=2 {{unknown|End of header}}
|}
|}


===Track Data===
===Region Data===


Here begins a free-form blob of indexed track data. It starts with a variable-length  
Here begins a free-form blob of indexed region data. It starts with a variable-length  
'''u32 array''' of SON offsets for each track, then the track data itself.
'''u32 array''' of SNG offsets for each region, then the region data itself.


====Track Data Header====
====Region Data Header====


{| class="wikitable"
{| class="wikitable"
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| 0x0
| 0x0
| 4
| 4
| '''Track Data Header Size'''; size of the header ''after'' this field (always 0x8)
| '''Region Data Header Size'''; size of the header ''after'' this field (always 0x8)
|-
|-
| 0x4
| 0x4
| 4
| 4
| '''Pitch Wheel Data Offset'''; (absolute SON-offset) 0x0 if no pitch-wheel messages on track
| '''Pitch Wheel Data Offset'''; (absolute SNG-offset) 0x0 if no pitch-wheel messages in region
|-
|-
| 0x8
| 0x8
| 4
| 4
| '''Mod Wheel Data Offset'''; (absolute SON-offset) 0x0 if no mod-wheel messages on track
| '''Mod Wheel Data Offset'''; (absolute SNG-offset) 0x0 if no mod-wheel messages in region
|-
|-
| 0xC
| 0xC
| colspan=2 {{unknown|End of header}}
| colspan=2 {{unknown|End of region data}}
|}
|}


====Track Commands====
====Region Commands====


After the track data header, the actual playback commands begin. There are only 2 types of commands
After the region data header, the actual playback commands begin. There are only 2 types of commands
in SON: ''note'' and ''control change''.
in SNG: ''note'' and ''control change''.


=====Delta Time RLE=====
=====Delta Time RLE=====
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this is a '''note command'''.  
this is a '''note command'''.  


Unlike MIDI, which has separate commands for note-on/note-off, SON attaches a ''note length'' value
Unlike MIDI, which has separate commands for note-on/note-off, SNG attaches a ''note length'' value
to a note-on command, which is then able to track its own lifetime.
to a note-on command, which is then able to track its own lifetime.


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|}
|}


=====End Of Track=====
=====End Of Region=====


When the two bytes following the delta-time == 0xffff, this track has no more commands.
When the two bytes following the delta-time == 0xffff, this region has no more commands.


====Continuous Pitch / Modulation Data====
====Continuous Pitch / Modulation Data====


If the pitch or mod offsets in a track are non-zero, they point to a buffer of RLE-compressed
If the pitch or mod offsets in a region are non-zero, they point to a buffer of RLE-compressed
(delta-tick, delta-value) pairs, decoding to signed 16-bit precision. The decoder must track
(delta-tick, delta-value) pairs, decoding to signed 16-bit precision. The decoder must track
the absolute time and value, summing each consecutive update for the current time/values.
the absolute time and value, summing each consecutive update for the current time/values.
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===Channel Map===
===Channel Map===


This is a simple '''u8 table''' mapping 64 SON tracks to 16 MIDI channels for instrument selection via the [[AGSC (File Format)#MIDI Setup Entry|SongGroup MIDI-Setup]].
This is a simple '''u8 table''' mapping 64 SNG tracks to 16 MIDI channels for instrument selection via the [[AGSC (File Format)#MIDI Setup Entry|SongGroup MIDI-Setup]].


===Tempo Table===
===Tempo Table===


When the SON has a non-zero tempo table offset, this song features tempo changes.  
When the SNG has a non-zero tempo table offset, this song features tempo changes.  
The change events are simple absolute-tick / BPM pairs.
The change events are simple absolute-tick / BPM pairs.


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