SGI Audio Tools: Difference between revisions

* ADSR and envelopes

An instrument bank file usually has the file extension of <code>.ins</code>. Inside it contains one or more of each of the following:

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].

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].

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].

=== A very simple example ===