Add LPCNet voice mode support

lib/services/voice_codec_preferences.dart

@@ -0,0 +1,21 @@
+import 'package:shared_preferences/shared_preferences.dart';
+import '../utils/voice_message_parser.dart';
+
+class VoiceCodecPreferences {
+  static const String _codecKey = 'voice_codec';
+  static const VoiceCodecKind defaultCodec = VoiceCodecKind.codec2;
+
+  static Future<VoiceCodecKind> getCodec() async {
+    final prefs = await SharedPreferences.getInstance();
+    final raw = prefs.getString(_codecKey);
+    return VoiceCodecKind.values.firstWhere(
+      (codec) => codec.name == raw,
+      orElse: () => defaultCodec,
+    );
+  }
+
+  static Future<void> setCodec(VoiceCodecKind codec) async {
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setString(_codecKey, codec.name);
+  }
+}

lib/services/voice_codec_service_io.dart

@@ -1,20 +1,27 @@
 import 'dart:typed_data';
 import 'package:codec2_flutter/codec2_flutter.dart';
+import 'package:lpcnet_flutter/lpcnet_flutter.dart';
 import 'package:flutter/foundation.dart';
 import '../utils/voice_message_parser.dart';
 
-export 'package:codec2_flutter/codec2_flutter.dart' show Codec2Mode;
-
-/// Maps [VoicePacketMode] to the [Codec2Mode] enum from the FFI plugin.
 Codec2Mode codec2ModeFor(VoicePacketMode pktMode) {
   switch (pktMode) {
-    case VoicePacketMode.mode3200: return Codec2Mode.mode3200;
-    case VoicePacketMode.mode1600: return Codec2Mode.mode1600;
-    case VoicePacketMode.mode1400: return Codec2Mode.mode1400;
-    case VoicePacketMode.mode700c: return Codec2Mode.mode700c;
-    case VoicePacketMode.mode1200: return Codec2Mode.mode1200;
-    case VoicePacketMode.mode1300: return Codec2Mode.mode1300;
-    case VoicePacketMode.mode2400: return Codec2Mode.mode2400;
+    case VoicePacketMode.mode3200:
+      return Codec2Mode.mode3200;
+    case VoicePacketMode.mode1600:
+      return Codec2Mode.mode1600;
+    case VoicePacketMode.mode1400:
+      return Codec2Mode.mode1400;
+    case VoicePacketMode.mode700c:
+      return Codec2Mode.mode700c;
+    case VoicePacketMode.mode1200:
+      return Codec2Mode.mode1200;
+    case VoicePacketMode.mode1300:
+      return Codec2Mode.mode1300;
+    case VoicePacketMode.mode2400:
+      return Codec2Mode.mode2400;
+    case VoicePacketMode.lpcnet1600:
+      throw ArgumentError('LPCNet mode does not map to Codec2');
   }
 }
 
@@ -39,17 +46,24 @@ class VoiceCodecService {
     }
   }
 
-  /// Encode [pcm] (Int16 samples, 8000 Hz mono) with [mode].
-  /// Returns the raw Codec2-encoded bytes.
   Future<Uint8List> encode(Int16List pcm, VoicePacketMode mode) {
     _ensureCodec2Supported();
-    return Codec2.encodeInIsolate(pcm, codec2ModeFor(mode));
+    switch (mode.codec) {
+      case VoiceCodecKind.codec2:
+        return Codec2.encodeInIsolate(pcm, codec2ModeFor(mode));
+      case VoiceCodecKind.lpcnet:
+        return LpcNet.encodeInIsolate(pcm);
+    }
   }
 
-  /// Decode [codec2Bytes] back to Int16 PCM (8000 Hz mono) with [mode].
   Future<Int16List> decode(Uint8List codec2Bytes, VoicePacketMode mode) {
     _ensureCodec2Supported();
-    return Codec2.decodeInIsolate(codec2Bytes, codec2ModeFor(mode));
+    switch (mode.codec) {
+      case VoiceCodecKind.codec2:
+        return Codec2.decodeInIsolate(codec2Bytes, codec2ModeFor(mode));
+      case VoiceCodecKind.lpcnet:
+        return LpcNet.decodeInIsolate(codec2Bytes);
+    }
   }
 
   /// Decode and concatenate multiple [packets] into a single PCM Int16List.
@@ -59,24 +73,14 @@ class VoiceCodecService {
     VoicePacketMode mode,
   ) async {
     _ensureCodec2Supported();
-    final c2Mode = codec2ModeFor(mode);
-    final c2 = Codec2.create(c2Mode);
-    final spf = c2.samplesPerFrame;
-    c2.destroy();
-
-    // Estimate total samples (use actual data or silence per missing packet)
     final all = <Int16List>[];
     for (final pkt in packets) {
       if (pkt == null || pkt.codec2Data.isEmpty) {
-        // Silence for missing packet — duration approximated by mode
-        final silenceSamples = (codec2ModeFor(mode).framesPerSecond) * spf;
-        all.add(Int16List(silenceSamples));
+        all.add(Int16List(mode.samplesPerPacket));
       } else {
-        final decoded = await Codec2.decodeInIsolate(pkt.codec2Data, c2Mode);
-        all.add(decoded);
+        all.add(await decode(pkt.codec2Data, mode));
       }
     }
-
     final total = all.fold<int>(0, (sum, l) => sum + l.length);
     final result = Int16List(total);
     var offset = 0;

lib/services/voice_codec_service_stub.dart

@@ -1,7 +1,6 @@
 import 'dart:typed_data';
 import '../utils/voice_message_parser.dart';
 
-/// Web/unsupported platform stub — Codec2 FFI is not available.
 enum Codec2Mode {
   mode3200(0),
   mode2400(1),
@@ -19,13 +18,20 @@ enum Codec2Mode {
 
   int get bytesPerSecond {
     switch (this) {
-      case mode3200: return 400;
-      case mode700c: return 100;
-      case mode1200: return 150;
-      case mode1300: return 175;
-      case mode1400: return 175;
-      case mode1600: return 200;
-      case mode2400: return 300;
+      case mode3200:
+        return 400;
+      case mode700c:
+        return 100;
+      case mode1200:
+        return 150;
+      case mode1300:
+        return 175;
+      case mode1400:
+        return 175;
+      case mode1600:
+        return 200;
+      case mode2400:
+        return 300;
     }
   }
 
@@ -40,13 +46,22 @@ enum Codec2Mode {
 
 Codec2Mode codec2ModeFor(VoicePacketMode pktMode) {
   switch (pktMode) {
-    case VoicePacketMode.mode3200: return Codec2Mode.mode3200;
-    case VoicePacketMode.mode1600: return Codec2Mode.mode1600;
-    case VoicePacketMode.mode1400: return Codec2Mode.mode1400;
-    case VoicePacketMode.mode700c: return Codec2Mode.mode700c;
-    case VoicePacketMode.mode1200: return Codec2Mode.mode1200;
-    case VoicePacketMode.mode1300: return Codec2Mode.mode1300;
-    case VoicePacketMode.mode2400: return Codec2Mode.mode2400;
+    case VoicePacketMode.mode3200:
+      return Codec2Mode.mode3200;
+    case VoicePacketMode.mode1600:
+      return Codec2Mode.mode1600;
+    case VoicePacketMode.mode1400:
+      return Codec2Mode.mode1400;
+    case VoicePacketMode.mode700c:
+      return Codec2Mode.mode700c;
+    case VoicePacketMode.mode1200:
+      return Codec2Mode.mode1200;
+    case VoicePacketMode.mode1300:
+      return Codec2Mode.mode1300;
+    case VoicePacketMode.mode2400:
+      return Codec2Mode.mode2400;
+    case VoicePacketMode.lpcnet1600:
+      throw ArgumentError('LPCNet mode does not map to Codec2');
   }
 }
 
@@ -66,6 +81,5 @@ class VoiceCodecService {
   Future<Int16List> decodePackets(
     List<VoicePacket?> packets,
     VoicePacketMode mode,
-  ) =>
-      Future.error(UnsupportedError('Voice not supported on web'));
+  ) => Future.error(UnsupportedError('Voice not supported on web'));
 }

lib/services/voice_player_service.dart

@@ -5,7 +5,7 @@ import 'package:audioplayers/audioplayers.dart';
 import 'package:flutter/foundation.dart';
 import 'package:path_provider/path_provider.dart';
 
-/// Plays decoded 8000 Hz / 16-bit mono PCM samples by writing a WAV file
+/// Plays decoded mono PCM samples by writing a WAV file
 /// to the system temp directory and using [AudioPlayer].
 class VoicePlayerService {
   final AudioPlayer _player = AudioPlayer();
@@ -49,16 +49,17 @@ class VoicePlayerService {
     });
   }
 
-  /// Play [pcmSamples] (Int16, 8000 Hz, mono).
-  Future<void> play(Int16List pcmSamples) async {
+  Future<void> play(Int16List pcmSamples, {required int sampleRateHz}) async {
     debugPrint('🔊 [VoicePlayer] play() called, ${pcmSamples.length} samples');
     if (_isPlaying) await stop();
     _position = Duration.zero;
-    _duration = Duration(milliseconds: (pcmSamples.length * 1000) ~/ 8000);
+    _duration = Duration(
+      milliseconds: (pcmSamples.length * 1000) ~/ sampleRateHz,
+    );
     _playbackStartedAt = DateTime.now();
     _events.add(null);
 
-    final wavBytes = _buildWav(pcmSamples, sampleRate: 8000);
+    final wavBytes = _buildWav(pcmSamples, sampleRate: sampleRateHz);
     final tmpDir = await getTemporaryDirectory();
     final file = File('${tmpDir.path}/vc_voice.wav');
     await file.writeAsBytes(wavBytes);

lib/services/voice_recorder_service.dart

@@ -4,7 +4,7 @@ import 'dart:typed_data';
 import 'package:flutter/foundation.dart';
 import 'package:record/record.dart';
 
-/// Captures raw PCM audio at 8000 Hz, 16-bit mono.
+/// Captures raw PCM audio at a codec-selected sample rate, 16-bit mono.
 ///
 /// [startCapture] returns a [Stream<Int16List>] that emits chunks of PCM
 /// samples every [chunkDuration].  Call [stopCapture] to end recording.
@@ -27,9 +27,10 @@ class VoiceRecorderService {
   /// [enableBandPassFilter] applies voice-tuned band-pass filtering when true.
   /// [enableCompressor] normalizes speech dynamics before encoding.
   /// [enableLimiter] protects against clipping peaks before encoding.
-  /// The returned stream emits [Int16List] chunks that are ready for Codec2 encoding.
+  /// The returned stream emits [Int16List] chunks that are ready for voice encoding.
   Stream<Int16List> startCapture({
     Duration chunkDuration = const Duration(seconds: 1),
+    int sampleRateHz = 8000,
     bool enableBandPassFilter = true,
     bool enableCompressor = true,
     bool enableLimiter = true,
@@ -43,6 +44,7 @@ class VoiceRecorderService {
 
     _startRecording(
       chunkDuration,
+      sampleRateHz: sampleRateHz,
       enableBandPassFilter: enableBandPassFilter,
       enableCompressor: enableCompressor,
       enableLimiter: enableLimiter,
@@ -52,13 +54,14 @@ class VoiceRecorderService {
 
   Future<void> _startRecording(
     Duration chunkDuration, {
+    required int sampleRateHz,
     required bool enableBandPassFilter,
     required bool enableCompressor,
     required bool enableLimiter,
   }) async {
-    final config = const RecordConfig(
+    final config = RecordConfig(
       encoder: AudioEncoder.pcm16bits,
-      sampleRate: 8000,
+      sampleRate: sampleRateHz,
       numChannels: 1,
       bitRate: 128000, // ignored for PCM, but required by API
     );
@@ -66,16 +69,17 @@ class VoiceRecorderService {
     try {
       final stream = await _recorder.startStream(config);
       final voiceFilter = _VoiceBandPassFilter(
-        sampleRate: 8000,
+        sampleRate: sampleRateHz,
         lowCutHz: 250.0,
         highCutHz: 3400.0,
       );
       final dynamics = _VoiceDynamicsProcessor(
-        sampleRate: 8000,
+        sampleRate: sampleRateHz,
         enableCompressor: enableCompressor,
         enableLimiter: enableLimiter,
       );
-      final chunkBytes = 8000 * 2 * chunkDuration.inMilliseconds ~/ 1000;
+      final chunkBytes =
+          sampleRateHz * 2 * chunkDuration.inMilliseconds ~/ 1000;
       final buffer = <int>[];
 
       _sub = stream.listen(