SGI Audio Tools: Difference between revisions
Add envelope, keymap, and sound properties.
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This article assumes you're familiar with the following terms/concepts:
* Audio samples
* ADSR and envelopes
* Sample rate
* MIDI
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==== The Instrument Bank File ====
An instrument bank file usually has the file extension of <code>.ins</code>.
* <code>envelope</code> section(s), indicating an [https://en.wikipedia.org/wiki/Envelope_(music) ADSR]
* <code>keymap</code> section(s), indicating the range of "piano keys" a sound occupies, as well as other data
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==== envelope ====
The SGI Audio Tools represent an [https://en.wikipedia.org/wiki/Envelope_(music) ADSR] with <code>envelope</code>s. Volume for each of the ADSR points ranges from <code>0</code> to <code>127</code>. Time is modelled in microseconds for each of the ADSR points.
Different samples and sounds can use the same <code>envelope</code>, but your tracks will generally sound better if you ensure that each sample has a matching envelope. If you're unsure, it doesn't
An <code>envelope</code> looks like the following:
envelope AnExampleEnvelope
{
attackTime = 10000;
attackVolume = 127;
decayTime = 500000;
decayVolume = 100;
releaseTime = 200000;
}
In the example above, the volume goes from <code>0</code> to <code>127</code> in 10000 microseconds (the attack), then decays to 100 over <code>500000</code> microseconds. When the sound using is envelope ends, the sound fades out over <code>200000</code> microseconds. This should generally match up to your sample.
For more information, review the N64 SDK Documentation at [http://n64devkit.square7.ch/pro-man/pro18/18-01.htm#02-05 18.1.2.5].
==== keymap ====
A <code>keymap</code> represents a range of "keys" for a sound to cover. The [https://www.inspiredacoustics.com/en/MIDI_note_numbers_and_center_frequencies MIDI Standard] represents each of the western music pitches from <code>0</code> to <code>127</code>. <code>60</code> can be considered middle C.
A <code>keymap</code> looks like the following:
keymap AnExampleKeymap
{
velocityMin = 0;
velocityMax = 127;
keyMin = 0;
keyMax = 127;
keyBase = 60;
detune = 0;
}
The example above maps to every available pitch as <code>keyMin</code> is <code>0</code> and <code>keyMax</code> is <code>127</code>. <code>keyBase</code> represents the "reference pitch" to scale when changing keys. In the example above, a sample with the pitch of middle C should be used. Samples at different frequencies will require a different <code>keyBase</code> value.
For more information, review the N64 SDK Documentation at [http://n64devkit.square7.ch/pro-man/pro18/18-01.htm#02-04 18.1.2.4].
==== sound ====
A <code>sound</code> combines a <code>keymap</code>, <code>envelope</code>, and an <code>aifc</code> file together into a unit. A <code>sound</code> also has properties for stereo panning and volume from <code>0</code> to <code>127</code> each.
An example might look like:
sound AnExampleSound
{
use ("your/particular/path/to/compressed_song_sample.aifc");
pan = 64;
volume = 127;
keymap = AnExampleKeymap;
envelope = AnExampleEnvelope;
}
Note how the <code>keymap</code> and <code>envelope</code> parts correspond to names of our examples above.
For more information, review the N64 SDK Documentation at [http://n64devkit.square7.ch/pro-man/pro18/18-01.htm#02-03 18.1.2.3].
==== instrument ====
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==== bank ====
TODO
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