automation-events

A module which provides an implementation of an automation event list.

This module provides an implementation of an automation event list to manage the internal state of an AudioParam as defined by the Web Audio API.

Usage

The automation-events module is available on npm and can be installed as usual.

npm install automation-events

AutomationEventList

It exports an AutomationEventList class which can be imported and used like this:

import { AutomationEventList } from 'automation-events';

const automationEventList = new AutomationEventList(1);

automationEventList.add({ startTime: 10, type: 'setValue', value: 0 });

// It will return 1 for a time >= 0 and <10.
console.log(automationEventList.getValue(5));

// It will return 0 for a time >= 10.
console.log(automationEventList.getValue(10));

add(automationEvent)

This function can be used to add an automation event to the list. All automation events can also be created with utility functions as described below.

getValue(time)

This function returns the value at the given time.

flush(time)

This function will remove all events from the AutomationEventList which are unnecessary to compute values at a time which is greater or equal to the given time.

utility functions

The automation-events package also exports utility functions to create all events that can be scheduled on an AudioParam.

createCancelAndHoldAutomationEvent()

import { createCancelAndHoldAutomationEvent } from 'automation-events';

createCancelAndHoldAutomationEvent(10);
// { cancelTime: 10, type: 'cancelAndHold' }

createCancelScheduledValuesAutomationEvent()

import { createCancelScheduledValuesAutomationEvent } from 'automation-events';

createCancelScheduledValuesAutomationEvent(5);
// { cancelTime: 5, type: 'cancelScheduledValues' }

createExponentialRampToValueAutomationEvent()

import { createExponentialRampToValueAutomationEvent } from 'automation-events';

createExponentialRampToValueAutomationEvent(2, 10);
// { endTime: 10, type: 'exponentialRampToValue', value: 2 }

createLinearRampToValueAutomationEvent()

import { createLinearRampToValueAutomationEvent } from 'automation-events';

createLinearRampToValueAutomationEvent(-1, 4);
// { endTime: 4, type: 'linearRampToValue', value: -1 };

createSetTargetAutomationEvent()

import { createSetTargetAutomationEvent } from 'automation-events';

createSetTargetAutomationEvent(0.5, 1, 0.1);
// { startTime: 1, target: 0.5, timeConstant: 0.1, type: 'setTarget' }

createSetValueAutomationEvent()

import { createSetValueAutomationEvent } from 'automation-events';

createSetValueAutomationEvent(1, 8);
// { startTime: 8, type: 'setValue', value: 1 }

createSetValueCurveAutomationEvent()

import { createSetValueCurveAutomationEvent } from 'automation-events';

const values = new Float32Array([1, 0, -1]);

createSetValueCurveAutomationEvent(values, 0, 5);
// { duration: 5, startTime: 0, type: 'setValueCurve', values }