mirror of
https://github.com/coop-deluxe/sm64coopdx.git
synced 2024-11-25 05:25:14 +00:00
47 lines
2.8 KiB
Markdown
47 lines
2.8 KiB
Markdown
Sound in SM64 consists of three parts: samples, sound banks, and sequences.
|
|
|
|
Samples represent raw sound data, given as AIFF files with a custom ADPCM-based
|
|
compression format that reduces file sizes by ~70% compared to uncompressed
|
|
AIFF (with 16-bit samples). The build system automatically converts
|
|
uncompressed AIFF files into this format.
|
|
|
|
Samples are collected into banks, given by directories. The order in which each
|
|
bank's samples end up in the final binary is determined by their file names.
|
|
Thus, to keep the ROM OK, sample files should be prefixed by a number to
|
|
maintain sort order. (Bank directories are ordered by their usages in way
|
|
that automatically makes the ROM match.)
|
|
|
|
Samples cannot be referred to directly from sequence files. Instead, there is
|
|
an indirect step in the form of sound banks. Each sound bank refers to a single
|
|
sample bank, and amends it with extra information in the form of a JSON file.
|
|
This JSON file contains a set of "instruments", which describe how note values
|
|
(pitches) map to samples, which pitch corrections to perform, and what ADSR
|
|
envelopes to use. The `instrument_list` key maps indices to instruments; these
|
|
indices are what sequence files can refer to. A special instrument `percussion`
|
|
is also supported, as an array with (usually) 64 different entries, covering
|
|
note values 0..63. It is referred to as instrument ID 0x7f.
|
|
|
|
C-style comments are supported in the JSON. Similar to samples, the sound banks
|
|
come in alphabetical order in the ROM, so they should be prefixed to maintain
|
|
sort order.
|
|
|
|
Sequence files are what actually controls the audio. The are in .m64 format,
|
|
which is similar to MIDI, but Turing complete. An .m64 file has a sequence
|
|
script that can spawn channels, which have channel scripts that can spawn
|
|
layers, which have layer scripts that can play notes. Each note is performed
|
|
using an instrument from a sound bank. A sequence file can use multiple banks;
|
|
`sequences.json` describes the mapping from sequences to sound banks. Channels
|
|
can switch between banks using a command. However, in practice most sequences
|
|
limit themselves to a single sound bank. The main exception is sequence 0,
|
|
which is responsible for sound effects.
|
|
|
|
Like samples and sound banks, sequence files are included in the ROM in
|
|
alphabetical file name order. They can be located in either `sound/sequences/`
|
|
or `sound/sequences/<version>/`, and can optionally be given in disassembled
|
|
form -- see `include/seq_macros.inc` for more details on the format.
|
|
|
|
The repo gitignores .m64 and .aiff files by default, unless they include
|
|
"custom" somewhere in the name (including in a directory name). Thus, for new
|
|
custom-made samples and sequences it is advisable to include that substring
|
|
in the file name (this also helps distinguish custom sounds from ones from
|
|
the game). `git add -f` also works for adding edited existing files to git.
|