Improved triggering with multi pass trigger point detection (#206)

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: spessasus <spesekspesek@gmail.com>

Author: 3 people

package.json

@@ -1,6 +1,6 @@
 {
     "name": "SpessaSynth",
-    "version": "4.2.0",
+    "version": "4.2.1",
     "type": "module",
     "private": true,
     "scripts": {

src/website/changelog.ts

@@ -11,5 +11,6 @@ export const WHATS_NEW: string[] = [
     `Delay effect!`,
     `Insertion effects!`,
     `Overhauled synthesizer controller!`,
+    `Better waveform stabilization! (by src3453)`,
     `Bug fixes!`
 ] as const;

src/website/js/renderer/render_waveforms.ts

@@ -73,8 +73,40 @@ export function renderSingleWaveform(
         }
         const halfLength = Math.floor(length / 2);
         triggerPoint = waveform.length - halfLength;
-        for (let i = triggerPoint; i >= 1; i--) {
-            if (waveform[i - 1] < 0 && waveform[i] >= 0) {
+        let max = -Infinity;
+        // Multi-pass trigger point detection
+        // Pass 1: find the maximum in the last part of the waveform
+        // TODO: optimize by using max function on a subarray when available
+        const searchStart = Math.max(0, triggerPoint - halfLength);
+        let bestIndex;
+        for (let i = triggerPoint; i >= searchStart; i--) {
+            const value = waveform[i];
+            if (value > max) {
+                max = value;
+                bestIndex = i;
+            }
+        }
+        // Pass 2: find the maximum within a tolerance range around the first trigger point
+        bestIndex = triggerPoint;
+        triggerPoint = waveform.length - halfLength;
+        const maximumTolerance = 0.04; // 4% tolerance for the second pass
+        for (let i = triggerPoint; i >= searchStart; i--) {
+            const value = waveform[i];
+            if (value > max * (1 - maximumTolerance)) {
+                bestIndex = i;
+                break;
+            }
+        }
+        triggerPoint = bestIndex;
+        // Pass 3: find the zero crossing after the trigger point
+        const zeroCrossEnd = Math.max(triggerPoint - Math.floor(halfLength), 0);
+        const waveformAverage =
+            waveform.reduce((sum, v) => sum + v, 0) / waveform.length;
+        // Look for the average to remove DC offset
+        for (let i = triggerPoint; i >= zeroCrossEnd; i--) {
+            // Reverse search for zero crossing
+            if (waveform[i] <= waveformAverage) {
+                // Zero crossing detected
                 triggerPoint = i;
                 break;
             }