refactor: migrate onset hold to microseconds with 500us default

Co-authored-by: aider (openrouter/openai/gpt-5) <aider@aider.chat>

Author: DavidMenting

src/lib/components/Voice.svelte

@@ -15,7 +15,7 @@
   const ONSET_TRIGGER_OPTIONS = {
     threshold: 0.1,   // 0..1 linear
     preRollMs: 1,   // include a short lead-in
-    holdMs: 0,       // minimum ms above threshold
+    holdUs: 500,     // minimum microseconds above threshold
     timeoutMs: 10000, // abort if no trigger within 10s
     highpassHz: 80    // reduce low-frequency rumble
   };

src/lib/services/audioRecorder.ts

@@ -44,10 +44,10 @@ export interface RecordingOptions {
   preRollMs?: number;
 
   /**
-   * Minimum time in milliseconds the signal must stay above threshold to trigger.
-   * Defaults to 12ms.
+   * Minimum time in microseconds the signal must stay above threshold to trigger.
+   * Defaults to 500 microseconds.
    */
-  holdMs?: number;
+  holdUs?: number;
 
   /**
    * Timeout in milliseconds while waiting for a trigger before aborting.
@@ -119,7 +119,7 @@ export async function recordAudio(
       const { samples, sampleRate } = await captureOnset(stream, {
         threshold: options.threshold,
         preRollMs,
-        holdMs: Math.max(1, Math.floor(options.holdMs ?? 12)),
+        holdUs: Math.max(0, Math.floor(options.holdUs ?? 500)),
         timeoutMs: Math.max(1000, Math.floor(options.timeoutMs ?? 10000)),
         highpassHz: options.highpassHz ?? 80,
         captureMs

src/lib/services/onsetDetector.ts

@@ -5,7 +5,7 @@ const logger = createLogger('OnsetDetector');
 export interface OnsetConfig {
   threshold: number;
   preRollMs: number;
-  holdMs: number;
+  holdUs: number;
   timeoutMs: number;
   highpassHz?: number;
   captureMs: number; // total capture length AFTER preroll; total output = preRollMs + captureMs
@@ -32,7 +32,7 @@ export async function captureOnset(
   node.port.postMessage({
     threshold: cfg.threshold,
     preRollMs: cfg.preRollMs,
-    holdMs: cfg.holdMs,
+    holdUs: cfg.holdUs,
     captureMs: cfg.captureMs,
     highpassHz: cfg.highpassHz ?? 80
   });

src/lib/services/worklets/onset-processor.js

@@ -41,7 +41,10 @@ registerProcessor('onset-detector', class extends AudioWorkletProcessor {
       const c = e.data || {};
       this.cfg.threshold = typeof c.threshold === 'number' ? c.threshold : this.cfg.threshold;
       const pre = Math.max(0, Math.round(((c.preRollMs ?? 0) * sampleRate) / 1000));
-      const hold = Math.max(1, Math.round(((c.holdMs ?? 1) * sampleRate) / 1000));
+      const holdUs = (typeof c.holdUs === 'number')
+        ? c.holdUs
+        : (typeof c.holdMs === 'number' ? c.holdMs * 1000 : 500);
+      const hold = Math.max(1, Math.round((holdUs * sampleRate) / 1_000_000));
       const cap = Math.max(1, Math.round(((c.captureMs ?? 1000) * sampleRate) / 1000));
       const hp = typeof c.highpassHz === 'number' ? c.highpassHz : this.cfg.hpHz;