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koel/resources/assets/js/services/audioService.ts
2024-07-06 17:44:57 +02:00

100 lines
2.8 KiB
TypeScript

import { equalizerStore } from '@/stores'
import { frequencies } from '@/config'
import { dbToGain } from '@/utils'
export interface Band {
label: string
node: BiquadFilterNode
db: number
}
export const audioService = {
unlocked: false,
context: null as unknown as AudioContext,
source: null as unknown as MediaElementAudioSourceNode,
element: null as unknown as HTMLMediaElement,
preampGainNode: null as unknown as GainNode,
analyzer: null as unknown as AnalyserNode,
bands: [] as Band[],
init (mediaElement: HTMLMediaElement) {
this.element = mediaElement
this.context = new AudioContext()
this.preampGainNode = this.context.createGain()
this.source = this.context.createMediaElementSource(this.element)
this.analyzer = this.context.createAnalyser()
this.source.connect(this.preampGainNode)
const config = equalizerStore.getConfig()
this.changePreampGain(config.preamp)
let prevFilter: BiquadFilterNode
// Create 10 bands with the frequencies similar to those of Winamp and connect them together.
frequencies.forEach((frequency, i) => {
const filter = this.context.createBiquadFilter()
if (i === 0) {
filter.type = 'lowshelf'
} else if (i === frequencies.length - 1) {
filter.type = 'highshelf'
} else {
filter.type = 'peaking'
}
filter.Q.setTargetAtTime(1, this.context.currentTime, 0.01)
filter.frequency.setTargetAtTime(frequency, this.context.currentTime, 0.01)
filter.gain.value = dbToGain(config.gains[i])
prevFilter ? prevFilter.connect(filter) : this.preampGainNode.connect(filter)
prevFilter = filter
this.bands.push({
node: filter,
label: String(frequency).replace('000', 'K'),
db: config.gains[i]
})
})
prevFilter!.connect(this.analyzer)
// connect the analyzer node last, so that changes to the equalizer affect the visualizer as well
this.analyzer.connect(this.context.destination)
this.unlockAudioContext()
},
changePreampGain (db: number) {
this.preampGainNode.gain.value = dbToGain(db)
},
changeFilterGain (node: BiquadFilterNode, db: number) {
node.gain.value = dbToGain(db)
},
/**
* Attempt to unlock the audio context on mobile devices by creating and playing a silent buffer upon the
* first user interaction.
*/
unlockAudioContext () {
['touchend', 'touchstart', 'click'].forEach(event => {
document.addEventListener(event, () => {
if (this.unlocked) return
const source = this.context.createBufferSource()
source.buffer = this.context.createBuffer(1, 1, 22050)
source.connect(this.context.destination)
source.start(0)
this.unlocked = true
}, {
once: true
})
})
}
}