Fix adaptive voice information meter

lib/screens/mapflow_shell.dart

@@ -719,15 +719,17 @@ class AddExperienceFlow extends ConsumerStatefulWidget {
 }
 
 class _AddExperienceFlowState extends ConsumerState<AddExperienceFlow> {
-  static const _minimumInformationUnits = 18.0;
+  static const _minimumInformationUnits = 9.0;
   static const _nearbyPlaceRadiusMeters = 200;
 
   final _api = MapflowApi();
   final _recorder = AudioRecorder();
   final _waveSamples = List<double>.filled(160, 0.0);
+  final _visualRandom = math.Random();
 
   Future<List<PlaceRecommendation>>? _nearbyPlacesFuture;
   Timer? _timer;
+  Timer? _visualTimer;
   StreamSubscription<Uint8List>? _audioStreamSub;
   var _step = 0;
   var _seconds = 0;
@@ -735,6 +737,9 @@ class _AddExperienceFlowState extends ConsumerState<AddExperienceFlow> {
   var _recording = false;
   var _submitting = false;
   var _micAllowed = true;
+  var _ambientLevel = 0.008;
+  var _voiceCeiling = 0.045;
+  var _visualPhase = 0.0;
   DateTime? _lastAudioChunkAt;
 
   @override
@@ -745,6 +750,7 @@ class _AddExperienceFlowState extends ConsumerState<AddExperienceFlow> {
   @override
   void dispose() {
     _timer?.cancel();
+    _visualTimer?.cancel();
     _audioStreamSub?.cancel();
     _recorder.dispose();
     super.dispose();
@@ -790,6 +796,7 @@ class _AddExperienceFlowState extends ConsumerState<AddExperienceFlow> {
     );
     _audioStreamSub = stream.listen(_handleAudioChunk);
     _lastAudioChunkAt = DateTime.now();
+    _startIdleWave();
     _timer = Timer.periodic(const Duration(seconds: 1), (_) {
       if (!mounted) {
         return;
@@ -808,6 +815,7 @@ class _AddExperienceFlowState extends ConsumerState<AddExperienceFlow> {
 
   Future<void> _stopRecording() async {
     _timer?.cancel();
+    _visualTimer?.cancel();
     await _audioStreamSub?.cancel();
     _audioStreamSub = null;
     await _recorder.stop();
@@ -818,6 +826,35 @@ class _AddExperienceFlowState extends ConsumerState<AddExperienceFlow> {
     setState(() => _recording = false);
   }
 
+  void _startIdleWave() {
+    _visualTimer?.cancel();
+    _visualTimer = Timer.periodic(const Duration(milliseconds: 70), (_) {
+      if (!mounted || !_recording) {
+        return;
+      }
+
+      final lastSignalAt = _lastAudioChunkAt;
+      final hasFreshSignal =
+          lastSignalAt != null &&
+          DateTime.now().difference(lastSignalAt).inMilliseconds < 220;
+      if (hasFreshSignal) {
+        return;
+      }
+
+      _visualPhase += 0.24;
+      final idleSamples = List<double>.generate(8, (index) {
+        final wave = math.sin(_visualPhase + index * 0.72) * 0.5 + 0.5;
+        final noise = _visualRandom.nextDouble() * 0.16;
+        return (0.10 + wave * 0.18 + noise).clamp(0.0, 1.0);
+      });
+      setState(() {
+        _waveSamples
+          ..removeRange(0, idleSamples.length)
+          ..addAll(idleSamples);
+      });
+    });
+  }
+
   void _handleAudioChunk(Uint8List chunk) {
     if (chunk.length < 2) {
       return;
@@ -825,22 +862,32 @@ class _AddExperienceFlowState extends ConsumerState<AddExperienceFlow> {
 
     final bytes = ByteData.sublistView(chunk);
     final sampleCount = chunk.length ~/ 2;
-    final bucketCount = 10.clamp(1, sampleCount);
+    final bucketCount = 12.clamp(1, sampleCount);
     final bucketSize = (sampleCount / bucketCount).ceil();
     final peaks = <double>[];
+    var totalRms = 0.0;
     for (var bucket = 0; bucket < bucketCount; bucket++) {
       final startSample = bucket * bucketSize;
       final endSample = math.min(startSample + bucketSize, sampleCount);
       var peak = 0.0;
+      var sumSquares = 0.0;
+      var bucketSamples = 0;
       for (
         var sampleIndex = startSample;
         sampleIndex < endSample;
         sampleIndex++
       ) {
         final sample = bytes.getInt16(sampleIndex * 2, Endian.little) / 32768.0;
-        peak = math.max(peak, sample.abs());
+        final absoluteSample = sample.abs();
+        peak = math.max(peak, absoluteSample);
+        sumSquares += absoluteSample * absoluteSample;
+        bucketSamples += 1;
       }
-      peaks.add((peak * 3.4).clamp(0.0, 1.0));
+      final rms = bucketSamples == 0
+          ? 0.0
+          : math.sqrt(sumSquares / bucketSamples);
+      totalRms += rms;
+      peaks.add(math.max(peak, rms * 2.6));
     }
     if (peaks.isEmpty) {
       return;
@@ -851,15 +898,21 @@ class _AddExperienceFlowState extends ConsumerState<AddExperienceFlow> {
     _lastAudioChunkAt = now;
     final deltaSeconds =
         now.difference(previousChunkAt).inMilliseconds.clamp(20, 300) / 1000;
-    const noiseFloor = 0.08;
+    final currentRms = totalRms / peaks.length;
+    _ambientLevel = currentRms < _ambientLevel
+        ? (_ambientLevel * 0.86 + currentRms * 0.14)
+        : (_ambientLevel * 0.985 + currentRms * 0.015);
+    _voiceCeiling = currentRms > _voiceCeiling
+        ? (_voiceCeiling * 0.68 + currentRms * 0.32)
+        : math.max(_ambientLevel + 0.018, _voiceCeiling * 0.992);
+    final dynamicRange = math.max(0.012, _voiceCeiling - _ambientLevel);
+    final normalizedPeaks = peaks
+        .map((peak) => ((peak - _ambientLevel) / dynamicRange).clamp(0.0, 1.0))
+        .map((peak) => math.pow(peak, 0.62).toDouble())
+        .toList();
     final voicedAmount =
-        peaks
+        normalizedPeaks.fold<double>(0, (sum, value) => sum + value) /
-            .map(
+        normalizedPeaks.length;
-              (peak) =>
-                  ((peak - noiseFloor) / (1 - noiseFloor)).clamp(0.0, 1.0),
-            )
-            .fold<double>(0, (sum, value) => sum + value) /
-        peaks.length;
     final informationDelta = voicedAmount * deltaSeconds;
 
     if (!mounted) {
@@ -867,8 +920,13 @@ class _AddExperienceFlowState extends ConsumerState<AddExperienceFlow> {
     }
     setState(() {
       _waveSamples
-        ..removeRange(0, peaks.length)
+        ..removeRange(0, normalizedPeaks.length)
-        ..addAll(peaks);
+        ..addAll(
+          normalizedPeaks.map((peak) {
+            final visibleSignal = 0.12 + peak * 0.88;
+            return visibleSignal.clamp(0.0, 1.0);
+          }),
+        );
       _informationUnits = math.min(
         _minimumInformationUnits,
         _informationUnits + informationDelta,