perf: reduce TEN-VAD latency from 16 ms to 10 ms, asymmetric gate ramp

- Hop size 256 → 160 samples @ 16 kHz: VAD decision every 10 ms instead
  of 16 ms (minimum supported by TEN-VAD)
- Asymmetric VAD ramp: 5 ms open (was 20 ms) to avoid masking speech onset,
  20 ms close retained for de-click on silence

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/livekit/NoiseGateProcessor.worklet.ts

@@ -182,8 +182,10 @@ class TenVADRuntime {
  * gain is instantly cut to 0 and releases over transientReleaseMs.
  *
  * TEN-VAD gate: accumulates audio with 3:1 decimation (48 kHz → 16 kHz),
- * runs the TEN-VAD model synchronously every 256 samples (16 ms), and
+ * runs the TEN-VAD model synchronously every 160 samples (10 ms), and
  * controls vadGateOpen with hysteresis. No IPC round-trip required.
+ * Asymmetric ramp: 5 ms open (minimise speech onset masking), 20 ms close
+ * (de-click on silence).
  */
 class NoiseGateProcessor extends AudioWorkletProcessor {
   // Noise gate state
@@ -207,7 +209,9 @@ class NoiseGateProcessor extends AudioWorkletProcessor {
   // VAD gate state
   private vadGateOpen = true; // starts open; TEN-VAD closes it on first silent frame
   private vadAttenuation = 1.0;
-  private readonly vadRampRate = 1.0 / (0.02 * sampleRate);
+  // Asymmetric ramp: fast open to avoid masking speech onset, slow close to de-click
+  private readonly vadOpenRampRate = 1.0 / (0.005 * sampleRate);  // 5 ms
+  private readonly vadCloseRampRate = 1.0 / (0.02 * sampleRate);  // 20 ms
 
   // TEN-VAD state
   private vadEnabled = false;
@@ -218,7 +222,8 @@ class NoiseGateProcessor extends AudioWorkletProcessor {
   private readonly decRatio = Math.max(1, Math.round(sampleRate / 16000));
   private decPhase = 0;
   private decAcc = 0;
-  private readonly vadHopBuf = new Int16Array(256);
+  // 160-sample hop = 10 ms @ 16 kHz (minimum supported by TEN-VAD)
+  private readonly vadHopBuf = new Int16Array(160);
   private vadHopCount = 0;
 
   private logCounter = 0;
@@ -234,8 +239,8 @@ class NoiseGateProcessor extends AudioWorkletProcessor {
       | undefined;
     if (tenVadModule) {
       try {
-        // hopSize = 256 samples @ 16 kHz = 16 ms; threshold = 0.5 (overridden via params)
+        // hopSize = 160 samples @ 16 kHz = 10 ms; threshold = 0.5 (overridden via params)
-        this.tenVadRuntime = new TenVADRuntime(tenVadModule, 256, 0.5);
+        this.tenVadRuntime = new TenVADRuntime(tenVadModule, 160, 0.5);
         this.port.postMessage({
           type: "log",
           msg: "[NoiseGate worklet] TEN-VAD runtime initialized, decRatio=" + this.decRatio,
@@ -382,7 +387,7 @@ class NoiseGateProcessor extends AudioWorkletProcessor {
                 : (avg * 32767 + 0.5) | 0;
           this.vadHopBuf[this.vadHopCount++] = s16;
 
-          if (this.vadHopCount >= 256) {
+          if (this.vadHopCount >= 160) {
             this.vadHopCount = 0;
             const prob = this.tenVadRuntime.process(this.vadHopBuf);
             if (!this.vadGateOpen && prob >= this.vadPositiveThreshold) {
@@ -394,17 +399,18 @@ class NoiseGateProcessor extends AudioWorkletProcessor {
         }
       }
 
-      // Ramp VAD attenuation toward target to avoid clicks
+      // Asymmetric ramp: fast open (5 ms) to minimise speech onset masking,
+      // slow close (20 ms) to de-click on silence transitions.
       const vadTarget = this.vadGateOpen ? 1.0 : 0.0;
       if (this.vadAttenuation < vadTarget) {
         this.vadAttenuation = Math.min(
           vadTarget,
-          this.vadAttenuation + this.vadRampRate,
+          this.vadAttenuation + this.vadOpenRampRate,
         );
       } else if (this.vadAttenuation > vadTarget) {
         this.vadAttenuation = Math.max(
           vadTarget,
-          this.vadAttenuation - this.vadRampRate,
+          this.vadAttenuation - this.vadCloseRampRate,
         );
       }