Class Adsr

ADSR (Attack Decay Sustain Release) envelope. An envelope is a value that changes over time, usually in response to an intial trigger.

See the ixfx Guide on Envelopes.

Example: Setup

import { Envelopes } from 'https://unpkg.com/ixfx/dist/modulation.js'
const env = new Envelopes.Adsr({
 attackDuration: 1000,
 decayDuration: 200,
 sustainDuration: 100
});
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Options for envelope are as follows:

initialLevel?: number
attackBend: number
attackDuration: number
decayBend: number
decayDuration:number
sustainLevel: number
releaseBend: number
releaseDuration: number
releaseLevel?: number
peakLevel: number
retrigger?: boolean
shouldLoop: boolean
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If retrigger is false (default), a re-triggered envelope continues at current value rather than resetting to initialLevel.

If shouldLoop is true, envelope loops until release() is called.

Example: Using

env.trigger(); // Start envelope
...
// Get current value of envelope
const [state, scaled, raw] = env.compute();
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• state is a string, one of the following: 'attack', 'decay', 'sustain', 'release', 'complete'
• scaled is a value scaled according to the stage's levels
• raw is the progress from 0 to 1 within a stage. ie. 0.5 means we're halfway through a stage.

Instead of compute(), most usage of the envelope is just fetching the value property, which returns the same scaled value of compute():

const value = env.value; // Get scaled number
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Example: Hold & release

env.trigger(true);   // Pass in true to hold
...envelope will stop at sustain stage...
env.release();      // Release into decay
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Check if it's done:

env.isDone; // True if envelope is completed
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Envelope has events to track activity: 'change' and 'complete':

env.addEventListener(`change`, ev => {
 console.log(`Old: ${evt.oldState} new: ${ev.newState}`);
})
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It's also possible to iterate over the values of the envelope:

const env = new Envelopes.Adsr();
for await (const v of env) {
 // v is the numeric value
 await Flow.sleep(100); // Want to pause a little to give envelope time to run
}
// Envelope has finished
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