Sonic & Knuckles Collection/Technical information/Music and sound effects

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Sonic & Knuckles Collection
Sonic & Knuckles Collection Music and sound effects

Note: All data is little endian unless stated otherwise.

Music

Music playback is handled by the external DLL MIDIOUT.DLL.

DLL exports

This short section needs expansion. You can help Sonic Retro by adding to it.

Format

Music tracks are stored in the DLL as "CMP" resources. These can be converted to and from standard MIDI files using SKC-Midi.

TODO: Compression

Once decompressed, tracks are stored using the following format:

Offset	Type	Description
0	4 bytes	Time Division.
4	4 bytes	Number of events.
8	4 bytes	Unknown.
12	4 bytes	Unknown.
16	8 * (number of events) bytes	Array of MIDI events (8 bytes each) Offset Type Description 0 4 bytes Event delta time. 4 3 bytes Event data. The purpose depends on the event type. 7 1 byte Event type. Can be one of the following values: $00 MIDI Channel Event. The event data contains the numeric value and parameters. $01 Tempo Event. The event data contains the sequence tempo in terms of microseconds per quarter-note. $02 Loop Start/End. The event data is unused.

Sound effects

Sound effects are stored in the SONIC3K.DS2 file, in 8-bit unsigned Mono at 22kHz. This can be edited using SKCsnd.

The file format consists of a 32-bit integer containing the number of sound effects, followed by an array of 32-bit integers containing the length of each sound effect in bytes. After this is the sound data as raw PCM for each sound effect stored sequentially until the end of the file.