custom recording waveform

app/components/CustomRecordPlugin.js

@@ -10,6 +10,83 @@ class CustomRecordPlugin extends RecordPlugin {
   static create(options) {
     return new CustomRecordPlugin(options || {})
   }
+  render(stream) {
+    if (!this.wavesurfer) return () => undefined
+
+    const container = this.wavesurfer.getWrapper()
+    const canvas = document.createElement('canvas')
+    canvas.width = container.clientWidth
+    canvas.height = container.clientHeight
+    canvas.style.zIndex = '10'
+    container.appendChild(canvas)
+
+    const canvasCtx = canvas.getContext('2d')
+    const audioContext = new AudioContext()
+    const source = audioContext.createMediaStreamSource(stream)
+    const analyser = audioContext.createAnalyser()
+    analyser.fftSize = 2 ** 5
+    source.connect(analyser)
+    const bufferLength = analyser.frequencyBinCount
+    const dataArray = new Uint8Array(bufferLength)
+
+    let animationId, previousTimeStamp;
+    const BUFFER_SIZE = 2 ** 8
+    const dataBuffer = new Array(BUFFER_SIZE).fill(canvas.height)
+
+    const drawWaveform = (timeStamp) => {
+      if (!canvasCtx) return
+
+      analyser.getByteTimeDomainData(dataArray)
+      canvasCtx.clearRect(0, 0, canvas.width, canvas.height)
+      canvasCtx.fillStyle = 'black'
+
+      if (previousTimeStamp === undefined) {
+        previousTimeStamp = timeStamp
+        dataBuffer.push(Math.min(...dataArray))
+        dataBuffer.splice(0, 1)
+      }
+      const elapsed = timeStamp - previousTimeStamp;
+      if (elapsed > 10) {
+        previousTimeStamp = timeStamp
+        dataBuffer.push(Math.min(...dataArray))
+        dataBuffer.splice(0, 1)
+      }
+
+      // Drawing
+      const sliceWidth = canvas.width / dataBuffer.length
+      let x = 0
+
+      for (let i = 0; i < dataBuffer.length; i++) {
+        const valueNormalized = dataBuffer[i] / canvas.height
+        const y = valueNormalized * canvas.height / 2
+        const sliceHeight = canvas.height + 1 - y * 2
+
+        canvasCtx.fillRect(x, y, sliceWidth * 2 / 3, sliceHeight)
+        x += sliceWidth
+      }
+
+      animationId = requestAnimationFrame(drawWaveform)
+    }
+
+    drawWaveform()
+
+    return () => {
+      if (animationId) {
+        cancelAnimationFrame(animationId)
+      }
+
+      if (source) {
+        source.disconnect()
+        source.mediaStream.getTracks().forEach((track) => track.stop())
+      }
+
+      if (audioContext) {
+        audioContext.close()
+      }
+
+      canvas?.remove()
+    }
+  }
   startRecording(stream) {
     this.preventInteraction()
     this.cleanUp()