Fix audio clock drift and adaptive jitter buffering

clients/windows/VoiceCat.App/Forms/AudioSettingsForm.cs

@@ -34,6 +34,7 @@ public sealed class AudioSettingsForm : Form
     private readonly bool _origAuxEnabled;
     private readonly string? _origAuxDeviceId;
     private readonly int _origAuxGain;
+    private readonly int _origAudioBufferMilliseconds;
 
     private readonly ComboBox _cboDevice;
     private readonly Button _btnRefresh;
@@ -54,6 +55,7 @@ public sealed class AudioSettingsForm : Form
     private readonly Button _btnAuxRefresh;
     private readonly Label _lblAuxGain;
     private readonly TrackBar _trkAuxGain;
+    private readonly ComboBox _cboBuffer;
 
     private Keys _pttKey;
 
@@ -80,6 +82,7 @@ public sealed class AudioSettingsForm : Form
         _origAuxEnabled = settings.AuxEnabled;
         _origAuxDeviceId = settings.AuxDeviceId;
         _origAuxGain = settings.AuxGain;
+        _origAudioBufferMilliseconds = settings.AudioBufferMilliseconds;
 
         Text = "Audio settings";
         FormBorderStyle = FormBorderStyle.FixedDialog;
@@ -87,7 +90,7 @@ public sealed class AudioSettingsForm : Form
         MinimizeBox = false;
         StartPosition = FormStartPosition.CenterParent;
         AutoScaleMode = AutoScaleMode.Font;
-        ClientSize = new Size(420, 639);
+        ClientSize = new Size(420, 690);
 
         // ── Device row ────────────────────────────────────────────────────────
         var lblDevice = new Label
@@ -319,19 +322,34 @@ public sealed class AudioSettingsForm : Form
             "Volume of the aux input stream. 100 is unity gain; range 0–400 percent.";
         _trkAuxGain.Scroll += TrkAuxGain_Scroll;
 
+        var lblBuffer = new Label { Text = "Audio &buffering:", Location = new Point(12, 590), AutoSize = true };
+        _cboBuffer = new ComboBox
+        {
+            Location = new Point(130, 586), Width = 190, DropDownStyle = ComboBoxStyle.DropDownList,
+            AccessibleName = "Audio buffering",
+            AccessibleDescription = "Local capture and playback buffering. Lower values reduce latency; higher values tolerate more scheduling jitter."
+        };
+        _cboBuffer.Items.AddRange(["Low latency (20 ms)", "Balanced (40 ms)", "Stable (60 ms)"]);
+        _cboBuffer.SelectedIndex = settings.AudioBufferMilliseconds switch { 20 => 0, 60 => 2, _ => 1 };
+        _cboBuffer.SelectedIndexChanged += (_, _) =>
+        {
+            _settings.AudioBufferMilliseconds = _cboBuffer.SelectedIndex switch { 0 => 20, 2 => 60, _ => 40 };
+            _client.SetAudioBufferMilliseconds(_settings.AudioBufferMilliseconds);
+        };
+
         // ── OK / Cancel ───────────────────────────────────────────────────────
         var btnOk = new Button
         {
             Text = "&OK",
             DialogResult = DialogResult.OK,
-            Location = new Point(228, 600),
+            Location = new Point(228, 642),
             Size = new Size(80, 27),
         };
         var btnCancel = new Button
         {
             Text = "&Cancel",
             DialogResult = DialogResult.Cancel,
-            Location = new Point(316, 600),
+            Location = new Point(316, 642),
             Size = new Size(80, 27),
         };
 
@@ -350,6 +368,7 @@ public sealed class AudioSettingsForm : Form
             _radioPtt, _lblPttKey, _btnChangePtt, _chkSystemWidePtt, _radioAlwaysOn,
             lblGain, _trkGain, _chkNoiseReduction, _chkStereoMic,
             _chkAux, _lblAuxDevice, _cboAuxDevice, _btnAuxRefresh, _lblAuxGain, _trkAuxGain,
+            lblBuffer, _cboBuffer,
             btnOk, btnCancel,
         ]);
 
@@ -534,6 +553,8 @@ public sealed class AudioSettingsForm : Form
         _settings.StereoMic = _origStereoMic;
         _settings.PttKey = (int)_origPttKey;
         _settings.SystemWidePtt = _origSystemWidePtt;
+        _settings.AudioBufferMilliseconds = _origAudioBufferMilliseconds;
+        _client.SetAudioBufferMilliseconds(_origAudioBufferMilliseconds);
 
         if (_micStreamId != 0)
         {

clients/windows/VoiceCat.App/Forms/MainForm.cs

@@ -109,8 +109,11 @@ public partial class MainForm : Form
         BootstrapFromServer();
     }
 
-    private void ApplyPersistedVoiceSettings() =>
+    private void ApplyPersistedVoiceSettings()
+    {
         _pttKey = (Keys)_voiceSettings.PttKey;
+        _client.SetAudioBufferMilliseconds(_voiceSettings.AudioBufferMilliseconds);
+    }
 
     // ── Startup ──────────────────────────────────────────────────────────────