test: harden Smart Speed worklet coverage

client/static/smart-speed/SilenceDetectorProcessor.js

@@ -0,0 +1,76 @@
+const SPEAKING = 0
+const SILENCE = 1
+const CANDIDATE = 2
+
+const DEBOUNCE_MS = 200
+const RMS_REPORT_INTERVAL = 10
+
+class SilenceDetectorProcessor extends AudioWorkletProcessor {
+  constructor() {
+    super()
+    this.state = SPEAKING
+    this.silenceThreshold = -40
+    this.candidateStartSample = 0
+    this.sampleRate = sampleRate
+    this.blockCount = 0
+
+    this.port.onmessage = (event) => {
+      const msg = event.data
+      if (msg.type === 'reset') {
+        this.state = SPEAKING
+        this.candidateStartSample = 0
+        return
+      }
+      if (msg.type === 'set-threshold') {
+        this.silenceThreshold = msg.value
+      }
+    }
+  }
+
+  process(inputs) {
+    const input = inputs[0]
+    if (!input || !input.length) return true
+
+    const channel = input[0]
+    if (!channel) return true
+
+    let sum = 0
+    for (let i = 0; i < channel.length; i++) {
+      sum += channel[i] * channel[i]
+    }
+    const rms = Math.sqrt(sum / channel.length)
+    const dbfs = rms === 0 ? -Infinity : 20 * Math.log10(rms)
+
+    this.blockCount++
+
+    if (dbfs < this.silenceThreshold) {
+      if (this.state === SPEAKING) {
+        this.candidateStartSample = currentFrame
+        this.state = CANDIDATE
+      } else if (this.state === CANDIDATE) {
+        const elapsedMs = ((currentFrame - this.candidateStartSample) / this.sampleRate) * 1000
+        if (elapsedMs >= DEBOUNCE_MS) {
+          this.state = SILENCE
+          const silenceStartTime = (this.candidateStartSample / this.sampleRate) * 1000
+          this.port.postMessage({ type: 'silence-start', time: silenceStartTime })
+        }
+      }
+    } else {
+      if (this.state === SILENCE) {
+        const currentTime = (currentFrame / this.sampleRate) * 1000
+        this.port.postMessage({ type: 'silence-end', time: currentTime })
+      }
+      if (this.state !== SPEAKING) {
+        this.state = SPEAKING
+      }
+    }
+
+    if (this.blockCount % RMS_REPORT_INTERVAL === 0) {
+      this.port.postMessage({ type: 'rms', value: dbfs })
+    }
+
+    return true
+  }
+}
+
+registerProcessor('silence-detector', SilenceDetectorProcessor)