Fix audio clock drift and adaptive jitter buffering

clients/apple/dotnet/VoiceCat.iOS/AppModel.cs

@@ -266,6 +266,8 @@ internal sealed class AppModel
         owner.Audio.InputMode = settings.InputMode; owner.Audio.VadThreshold = settings.VadThreshold;
         owner.Audio.InputGain = settings.InputGain; owner.Audio.OutputGain = settings.OutputGain;
         owner.Audio.InputNoiseReduction = settings.InputNoiseReduction;
+        owner.Audio.DeviceBufferMilliseconds = settings.AudioBufferMilliseconds;
+        IosAudioEngine.Shared.BufferMilliseconds = settings.AudioBufferMilliseconds;
     }
 
     private void PollAudio()

clients/apple/dotnet/VoiceCat.iOS/IosAudioEngine.cs

@@ -8,7 +8,7 @@ namespace VoiceCat.iOS;
 internal sealed class IosAudioEngine
 {
     internal static IosAudioEngine Shared { get; } = new();
-    private readonly PcmRing playbackRing = new(131_072);
+    private readonly AdaptivePcmBuffer playbackRing = new(2, capacityFrames: 65_536);
     private readonly short[] renderScratch = new short[16_384];
     private AVAudioEngine? engine;
     private AVAudioSourceNode? source;
@@ -28,6 +28,7 @@ internal sealed class IosAudioEngine
     private bool inputProvided;
     private bool tapInstalled;
     internal bool IsConnected { get; private set; }
+    internal int BufferMilliseconds { get => playbackRing.BufferMilliseconds; set => playbackRing.BufferMilliseconds = value; }
 
     private IosAudioEngine() { microphoneWorker = PumpMicrophoneAsync(microphoneStop.Token); }
 

clients/apple/dotnet/VoiceCat.iOS/IosSettings.cs

@@ -17,13 +17,14 @@ internal sealed class IosSettings
     internal float EventVolume { get; set; } = 1f;
     internal bool SelfTalkSounds { get; set; }
     internal bool PushToTalkSound { get; set; }
+    internal int AudioBufferMilliseconds { get; set; } = 40;
 
     internal void Load()
     {
         NSString[] keys = [(NSString)"voice.inputMode", (NSString)"voice.vadThreshold", (NSString)"voice.inputGain",
-            (NSString)"voice.outputGain", (NSString)"feedback.sounds", (NSString)"feedback.volume"];
+            (NSString)"voice.outputGain", (NSString)"voice.audioBufferMs", (NSString)"feedback.sounds", (NSString)"feedback.volume"];
         NSObject[] defaults = [NSNumber.FromInt32((int)AudioInputMode.VoiceActivation), NSNumber.FromFloat(0.025f),
-            NSNumber.FromFloat(1f), NSNumber.FromFloat(1f), NSNumber.FromBoolean(true), NSNumber.FromFloat(1f)];
+            NSNumber.FromFloat(1f), NSNumber.FromFloat(1f), NSNumber.FromInt32(40), NSNumber.FromBoolean(true), NSNumber.FromFloat(1f)];
         values.RegisterDefaults(new NSDictionary<NSString, NSObject>(keys, defaults));
         int inputMode = checked((int)values.IntForKey("voice.inputMode"));
         InputMode = Enum.IsDefined(typeof(AudioInputMode), inputMode) ? (AudioInputMode)inputMode : AudioInputMode.VoiceActivation;
@@ -31,6 +32,7 @@ internal sealed class IosSettings
         InputGain = Math.Clamp(values.FloatForKey("voice.inputGain"), 0f, 4f);
         OutputGain = Math.Clamp(values.FloatForKey("voice.outputGain"), 0f, 1f);
         InputNoiseReduction = values.BoolForKey("voice.inputNoiseReduction");
+        int audioBuffer = checked((int)values.IntForKey("voice.audioBufferMs")); AudioBufferMilliseconds = audioBuffer is 20 or 40 or 60 ? audioBuffer : 40;
         EventSounds = values.BoolForKey("feedback.sounds");
         SpokenEvents = values.BoolForKey("feedback.speech");
         EventVolume = Math.Clamp(values.FloatForKey("feedback.volume"), 0f, 1f);
@@ -42,6 +44,7 @@ internal sealed class IosSettings
     {
         values.SetInt((int)InputMode, "voice.inputMode"); values.SetFloat(VadThreshold, "voice.vadThreshold");
         values.SetFloat(InputGain, "voice.inputGain"); values.SetFloat(OutputGain, "voice.outputGain");
+        values.SetInt(AudioBufferMilliseconds, "voice.audioBufferMs");
         values.SetBool(InputNoiseReduction, "voice.inputNoiseReduction"); values.SetBool(EventSounds, "feedback.sounds");
         values.SetBool(SpokenEvents, "feedback.speech"); values.SetFloat(EventVolume, "feedback.volume");
         values.SetBool(SelfTalkSounds, "feedback.selfTalk"); values.SetBool(PushToTalkSound, "feedback.ptt"); values.Synchronize();

clients/apple/dotnet/VoiceCat.iOS/SettingsController.cs

@@ -14,23 +14,23 @@ internal sealed class SettingsController : UITableViewController
     public override void ViewDidLoad() { base.ViewDidLoad(); TableView.RegisterClassForCellReuse(typeof(UITableViewCell), "setting"); }
     private void Reload() => TableView.ReloadData();
     public override nint NumberOfSections(UITableView tableView) => 5;
-    public override nint RowsInSection(UITableView tableView, nint section) => section switch { 0 => 4, 1 => 4, 2 => 5, 3 => model.Client?.Permissions is { } p && (p.IsAdmin || p.CanAdminAccounts) ? 1 : 0, _ => 2 };
+    public override nint RowsInSection(UITableView tableView, nint section) => section switch { 0 => 5, 1 => 4, 2 => 5, 3 => model.Client?.Permissions is { } p && (p.IsAdmin || p.CanAdminAccounts) ? 1 : 0, _ => 2 };
     public override string? TitleForHeader(UITableView tableView, nint section) => section switch { 0 => "Audio", 1 => "Voice", 2 => "Notifications", 3 => "Administration", _ => "Server" };
     public override UITableViewCell GetCell(UITableView tableView, NSIndexPath path)
     {
         UITableViewCell cell = tableView.DequeueReusableCell("setting", path); cell.AccessoryView = null; cell.Accessory = UITableViewCellAccessory.None;
         string title = path.Section switch
         {
-            0 => path.Row switch { 0 => "Audio preset", 1 => "Speaker output", 2 => "Advanced audio", _ => model.ScreenSharing ? "Stop sharing screen audio" : "Share screen audio" },
+            0 => path.Row switch { 0 => "Audio preset", 1 => "Speaker output", 2 => "Advanced audio", 3 => "Audio buffering", _ => model.ScreenSharing ? "Stop sharing screen audio" : "Share screen audio" },
             1 => path.Row switch { 0 => "Input mode", 1 => $"VAD threshold: {model.Settings.VadThreshold:0.000}", 2 => $"Microphone volume: {model.Settings.InputGain:P0}", _ => "Microphone noise reduction" },
             2 => path.Row switch { 0 => "Event sounds", 1 => $"Sound volume: {model.Settings.EventVolume:P0}", 2 => "Speak events", 3 => "Own voice activity sounds", _ => "Push-to-talk cue" },
             3 => "Manage accounts", _ => path.Row == 0 ? "Disconnect" : "VoiceCat 0.0.1"
         };
-        var content = cell.DefaultContentConfiguration; content.Text = title; content.SecondaryText = path.Section == 0 && path.Row == 0 ? IosAudioRouter.Shared.Preset.ToString() : path.Section == 1 && path.Row == 0 ? model.Settings.InputMode.ToString() : path.Section == 0 && path.Row == 3 && model.ScreenSharing ? "Sharing" : null; cell.ContentConfiguration = content; cell.AccessibilityLabel = title;
+        var content = cell.DefaultContentConfiguration; content.Text = title; content.SecondaryText = path.Section == 0 && path.Row == 0 ? IosAudioRouter.Shared.Preset.ToString() : path.Section == 1 && path.Row == 0 ? model.Settings.InputMode.ToString() : path.Section == 0 && path.Row == 3 ? $"{model.Settings.AudioBufferMilliseconds} ms" : path.Section == 0 && path.Row == 4 && model.ScreenSharing ? "Sharing" : null; cell.ContentConfiguration = content; cell.AccessibilityLabel = title + (content.SecondaryText is null ? "" : ", " + content.SecondaryText);
         if (path.Section == 0 && path.Row == 1) cell.AccessoryView = Toggle(IosAudioRouter.Shared.ForceSpeaker, "Speaker output", (_, _) => IosAudioRouter.Shared.SetForceSpeaker(((UISwitch)cell.AccessoryView!).On));
         else if (path.Section == 1 && path.Row == 3) cell.AccessoryView = Toggle(model.Settings.InputNoiseReduction, title, (_, _) => { model.Settings.InputNoiseReduction = ((UISwitch)cell.AccessoryView!).On; model.ApplyVoiceSettings(); });
         else if (path.Section == 2 && path.Row is 0 or 2 or 3 or 4) { bool value = path.Row switch { 0 => model.Settings.EventSounds, 2 => model.Settings.SpokenEvents, 3 => model.Settings.SelfTalkSounds, _ => model.Settings.PushToTalkSound }; int row = path.Row; cell.AccessoryView = Toggle(value, title, (_, _) => { bool on = ((UISwitch)cell.AccessoryView!).On; if (row == 0) model.Settings.EventSounds = on; else if (row == 2) model.Settings.SpokenEvents = on; else if (row == 3) model.Settings.SelfTalkSounds = on; else model.Settings.PushToTalkSound = on; model.Save(); }); }
-        else if (path.Section == 0 && path.Row == 2 || path.Section == 3) cell.Accessory = UITableViewCellAccessory.DisclosureIndicator;
+        else if (path.Section == 0 && path.Row is 2 or 3 || path.Section == 3) cell.Accessory = UITableViewCellAccessory.DisclosureIndicator;
         return cell;
     }
     public override async void RowSelected(UITableView tableView, NSIndexPath path)
@@ -39,7 +39,8 @@ internal sealed class SettingsController : UITableViewController
         {
             if (path.Section == 0 && path.Row == 0) Choice("Audio preset", Enum.GetValues<IosAudioPreset>().Select(value => value.ToString()).ToArray(), index => IosAudioRouter.Shared.SelectPreset(Enum.GetValues<IosAudioPreset>()[index]));
             else if (path.Section == 0 && path.Row == 2) NavigationController?.PushViewController(new AdvancedAudioController(), true);
-            else if (path.Section == 0 && path.Row == 3) ShowScreenSharing();
+            else if (path.Section == 0 && path.Row == 3) Choice("Audio buffering", ["Low latency (20 ms)", "Balanced (40 ms)", "Stable (60 ms)"], index => { model.Settings.AudioBufferMilliseconds = index switch { 0 => 20, 2 => 60, _ => 40 }; model.ApplyVoiceSettings(); });
+            else if (path.Section == 0 && path.Row == 4) ShowScreenSharing();
             else if (path.Section == 1 && path.Row == 0) Choice("Input mode", ["Voice activation", "Push to talk", "Always on"], index => { model.Settings.InputMode = (AudioInputMode)index; model.ApplyVoiceSettings(); });
             else if (path.Section == 1 && path.Row == 1) Slider("Voice activation threshold", 0.001f, 0.1f, model.Settings.VadThreshold, value => { model.Settings.VadThreshold = value; model.ApplyVoiceSettings(); });
             else if (path.Section == 1 && path.Row == 2) Slider("Microphone volume", 0, 4, model.Settings.InputGain, value => { model.Settings.InputGain = value; model.ApplyVoiceSettings(); });