dot-audio/src/nodes/components/FilterEnvelope.js

A simple web audio library for making synthesizers

import Envelope from 'nodes/components/Envelope'
import Filter from 'nodes/core/Filter'

const defaultProps = {
    frequency: 2000,
    q: 0,
    detune: 0,
    gain: 0,
    type: 'lowpass',
}

/**
 * An envelope connected to a filter node.
 * Can be used to modulate the sound and tone of the incoming signal over time.
 *
 * @example
 * const filterEnv = new Dot.FilterEnv(AC, { frequency, 0, decay: 0.4, sustain: 0, modifier: 1000 })
 * const osc = new Dot.Osc(AC, { waveform: 'sawtooth' })
 *
 * Dot.chain(osc, filterEnv, AC.destination)
 *
 * filterEnv.triggerAttack()
 *
 * @extends Envelope
 * @param {AudioContext} AC - Audio context
 * @param {Object} opts - Initialization options
 * @param {Number} opts.frequency - Frequency of the filter in Hz (default: 2000)
 * @param {Number} opts.q - Q factor of the filter (default: 0)
 * @param {Number} opts.detune - Detune value of the filter (default: 0)
 * @param {Number} opts.gain - Gain value of the filter (default: 0)
 * @param {Number} opts.type - Fitler type of the filter (default: 'lowpass')
 * @params
 * frequency - Frequency of the filter node
 * q - Q factor of the filter node
 * detune - Detune of the filter node
 * gain - Gain of the filter node
 * @returns {FilterEnvelope} FilterEnvelope Node
 */
class FilterEnvelope extends Envelope {
    constructor(AC, opts = {}) {
        super(AC, opts)
        this.name = 'FilterEnvelope'
        this.filter = new Filter(this.AC)

        this.params = {
            frequency: this.filter.getParam('frequency'),
            detune: this.filter.getParam('detune'),
            q: this.filter.getParam('q'),
            gain: this.filter.getParam('gain'),
        }
        this.inputs = [this.filter]
        this.outputs = [this.filter]

        // Initialize
        const initProps = { ...defaultProps, ...opts }

        this.setFrequency(initProps.frequency)
        this.setQ(initProps.q)
        this.setDetune(initProps.detune)
        this.setGain(initProps.gain)
        this.setType(initProps.type)

        // Connections
        this.source.connect(this.filter.getParam('frequency'))

        return this
    }

    // - Getters -
    /**
     * Get the cutoff frequency of the filter node.
     * @returns {Number} Frequency value
     */
    getFrequency = () => this.params.frequency.value

    /**
     * Get the q factor of the filter node.
     * @returns {Number} Q factor value
     */
    getQ = () => this.params.q.value

    /**
     * Get the detune value of the filter node.
     * @returns {Number} Detune value
     */
    getDetune = () => this.params.detune.value

    /**
     * Get the gain value of the filter node.
     * @returns {Number} Gain value
     */
    getGain = () => this.params.gain.value

    /**
     * Get the filter node's type.
     * @returns {String} Filter tpye
     */
    getType = () => this.filter.getType()

    // - Setters -
    /**
     * Set the cutoff frequency of the filter node.
     * Calls the setFrequency method on the filter.
     * @param {Number} val - frequency value
     * @param {Number} [time] - update time in seconds (optional)
     */
    setFrequency = (val, time) => this.filter.setFrequency(val, time)

    /**
     * Set the q factor value of the filter node.
     * Calls the setQ method on the filter.
     * @param {Number} val - q factor value
     * @param {Number} [time] - update time in seconds (optional)
     */
    setQ = (val, time) => this.filter.setQ(val, time)

    /**
     * Set the detune value of the filter node.
     * Calls the setDetune method on the filter.
     * @param {Number} val - detune value
     * @param {Number} [time] - update time in seconds (optional)
     */
    setDetune = (val, time) => this.filter.setDetune(val, time)

    /**
     * Set the gain value of the filter node.
     * Calls the setGain method on the filter.
     * @param {Number} val - gain value
     * @param {Number} [time] - update time in seconds (optional)
     */
    setGain = (val, time) => this.filter.setGain(val, time)

    /**
     * Set the filter node's type.
     * @param {String} val - filter type
     */
    setType = (val) => this.filter.setType(val)
}

export default FilterEnvelope