feat: player: implement a basic simple 10 band music EQ

Signed-off-by: EndCredits <[email protected]>

packages/web/utils/player.ts

@@ -29,6 +29,11 @@ interface TrackListSource {
   id: number
 }
 
+interface Filter {
+  gain: GainNode;
+  filter: BiquadFilterNode;
+}
+
 export enum Mode {
   TrackList = 'trackList',
   FM = 'fm',
@@ -370,6 +375,34 @@ export class Player {
         this._howlerOnEndCallback()
       },
     })
+
+    const audioCtx: AudioContext = Howler.ctx
+
+    const filters: Filter[] = []
+
+    const bandsNum = 10;
+    const gainFrequencies = [ 30, 58, 90, 170, 200, 500, 10000, 20000, 80000, 160000]
+
+    gainFrequencies.forEach((freq, index) => {
+      const gainNode: GainNode = audioCtx.createGain()
+      gainNode.gain.value = 1
+
+      const filter: BiquadFilterNode = audioCtx.createBiquadFilter()
+      filter.type = 'peaking'
+      filter.frequency.value = freq
+      filter.Q.value = 1
+      filter.gain.value = 0;
+
+      filters.push({
+        gain: gainNode,
+        filter: filter
+      })
+
+      if (index > 0) {
+        filters[index - 1].filter.connect(filters[index].gain);
+      }
+    })
+
     _howler = howler
     ;(window as any).howler = howler
     if (autoplay) {
@@ -378,6 +411,8 @@ export class Player {
     }
     _howler.once('load', () => {
       this._cacheAudio((_howler as any)._src)
+      const source: MediaElementAudioSourceNode = Howler.ctx.createMediaElementSource((_howler as any)._sounds[0]._node)
+      source.connect(filters[0].gain)
     })
 
     if (!this._progressInterval) {