Full native C++ TTS validated on short + long phrases

Dynamic formula: target_len = n_tokens × 3.2 + 5 (calibrated)
- Short "Bonjour..." (18 tokens → 62 trailing): OK
- Long "Je suis Kazeia... difficiles" (30 tokens → 101 trailing): OK

RMS trim disabled (garbage is loud, can't distinguish from speech).
Length controlled purely by maxTokens = trailing count.

Pipeline: prepare_tts_native.py "any text" → adb push → run → audio

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

kazeia-android/app/src/main/java/com/kazeia/tts/Qwen3TtsEngine.kt

@@ -2606,41 +2606,9 @@ class Qwen3TtsEngine(
         return result
     }
 
-    /** Trim trailing garbage from audio by detecting RMS drop.
-     *  Scans forward, finds where RMS drops significantly → end of speech. */
-    private fun trimTrailingSilence(audio: ShortArray): ShortArray {
-        val windowSamples = SR / 10  // 100ms windows
-        if (audio.size < windowSamples * 4) return audio
-
-        // Compute RMS per window
-        val nWindows = audio.size / windowSamples
-        val rmsValues = FloatArray(nWindows)
-        for (w in 0 until nWindows) {
-            var sum = 0.0
-            for (i in 0 until windowSamples) {
-                val s = audio[w * windowSamples + i].toFloat()
-                sum += s * s
-            }
-            rmsValues[w] = Math.sqrt(sum / windowSamples).toFloat()
-        }
-
-        // Find peak RMS in first half (speech region)
-        val peakRms = rmsValues.take(nWindows / 2).maxOrNull() ?: return audio
-
-        // Scan from 60% onwards, find first window where RMS drops below 15% of peak
-        // (speech ended, garbage/silence started)
-        val threshold = peakRms * 0.15f
-        var cutWindow = nWindows
-        for (w in (nWindows * 3 / 5) until nWindows) {
-            if (rmsValues[w] < threshold) {
-                cutWindow = w + 1  // keep one more window for tail
-                break
-            }
-        }
-
-        val trimPoint = minOf(cutWindow * windowSamples, audio.size)
-        return if (trimPoint < audio.size) audio.copyOf(trimPoint) else audio
-    }
+    /** No-op trim — garbage post-text has high energy, can't distinguish from speech.
+     *  Length is controlled by maxTokens = trailing count instead. */
+    private fun trimTrailingSilence(audio: ShortArray): ShortArray = audio
 
     /** Full pipeline using Hexagon talker + Hexagon CP from pre-computed embeddings. */
     private fun generateFromEmbedsHexagon(embedsPath: String): ShortArray {

scripts/prepare_tts_native.py

@@ -54,8 +54,7 @@ eos = sp[1].astype(np.float32)
 
 # Build trailing: text[1:] + eos padding
 # Audio is ~3.5× longer than text tokens. Pad with eos to ensure full coverage.
-AUDIO_RATIO = 3.5  # audio_tokens ≈ text_tokens × 3.5 (slightly generous to avoid cut)
-target_len = max(int(len(tokens) * AUDIO_RATIO), 50)  # minimum 50 for short phrases
+target_len = max(int(len(tokens) * 3.2) + 5, 40)  # calibrated: 3.2× + 5 buffer
 
 trailing = [proj[i] for i in range(1, len(proj))]  # text[1:]
 while len(trailing) < target_len: