Fix iOS voice capture and screen sharing

tests/VoiceCat.Tests/AudioEngineTests.cs

@@ -7,6 +7,27 @@ namespace VoiceCat.Tests;
 
 public class AudioEngineTests
 {
+    [Fact]
+    public void ManagedAudioWorkerUsesDeadlineSchedulingAtRealtimePriority()
+    {
+        string source = File.ReadAllText(Path.Combine(FindRoot(), "src", "VoiceCat.Audio", "AudioEngine.cs"));
+
+        Assert.Contains("Priority = ThreadPriority.Highest", source);
+        Assert.Contains("WaitUntil(deadline);", source);
+        Assert.DoesNotContain("Thread.Sleep((int)Math.Ceiling(remaining))", source);
+    }
+
+    [Fact]
+    public void MediaSenderDoesNotDependOnCoalescedAsyncTimers()
+    {
+        string source = File.ReadAllText(Path.Combine(FindRoot(), "src", "VoiceCat.Core", "ClientMediaTransport.cs"));
+
+        Assert.Contains("new Thread(Send)", source);
+        Assert.Contains("socket.Send(packet.AsSpan(0, size)", source);
+        Assert.DoesNotContain("Task.Delay(5", source);
+        Assert.DoesNotContain("SendAsync(packet.AsMemory", source);
+    }
+
     [Theory]
     [InlineData(-1000)]
     [InlineData(1000)]
@@ -29,6 +50,58 @@ public class AudioEngineTests
         Assert.Equal(0, GC.GetAllocatedBytesForCurrentThread() - before);
     }
 
+    [Fact]
+    public void AdaptivePcmBufferPreservesPartialFrameAcrossCaptureCallbacks()
+    {
+        var buffer = new AdaptivePcmBuffer(1, 20);
+        short[] half = Enumerable.Range(0, 480).Select(value => (short)value).ToArray();
+        short[] full = new short[960];
+
+        Assert.True(buffer.TryWrite(half));
+        Assert.Equal(0, buffer.Read(full));
+        Assert.Equal(480, buffer.CountFrames);
+
+        Assert.True(buffer.TryWrite(half));
+        Assert.Equal(960, buffer.Read(full));
+        Assert.Equal(0, buffer.CountFrames);
+        Assert.Equal(half, full.AsSpan(0, 480).ToArray());
+        Assert.Equal(half, full.AsSpan(480, 480).ToArray());
+    }
+
+    [Theory]
+    [InlineData(20)]
+    [InlineData(40)]
+    [InlineData(60)]
+    public void AdaptivePcmBufferSustainsIosSizedCaptureCallbacks(int bufferMilliseconds)
+    {
+        var buffer = new AdaptivePcmBuffer(1, bufferMilliseconds);
+        short[] callback = new short[1_024], encoded = new short[960];
+        long producedFrames = 0;
+        int lateStarvation = 0, fullReads = 0;
+
+        // AVAudioEngine commonly delivers 1,024 frames every 21 1/3 ms while the codec owner
+        // requests 960 frames every 20 ms. Replay those independent clocks for two minutes.
+        for (long consumerFrame = 0; consumerFrame < 48_000L * 120; consumerFrame += 960)
+        {
+            while (producedFrames <= consumerFrame)
+            {
+                for (int i = 0; i < callback.Length; i++) callback[i] = (short)(producedFrames + i);
+                Assert.True(buffer.TryWrite(callback));
+                producedFrames += callback.Length;
+            }
+
+            int read = buffer.Read(encoded);
+            if (read == encoded.Length) fullReads++;
+            // A 20 ms target initially contains one 1,024-frame callback, so the codec's
+            // second deadline precedes the next callback by 1.33 ms. Re-priming once during
+            // that first second is expected; recurring starvation is the audible defect.
+            else if (consumerFrame >= 48_000) lateStarvation++;
+        }
+
+        Assert.Equal(0, lateStarvation);
+        Assert.True(fullReads > 5_000);
+    }
+
     [Fact]
     public void OneCaptureMissDoesNotRestartTalkspurtButSustainedStarvationDoes()
     {
@@ -40,6 +113,8 @@ public class AudioEngineTests
         engine.ProcessCycle();
         engine.FeedPcm(1, tone, 1); engine.ProcessCycle();
         Assert.Equal(2, sent.Count); Assert.True((sent[0].Flags & VoiceFrameFlags.Marker) != 0); Assert.Equal(VoiceFrameFlags.None, sent[1].Flags & VoiceFrameFlags.Marker);
+        LocalAudioDiagnostics diagnostic = engine.GetLocalDiagnostics(1);
+        Assert.Equal(3, diagnostic.Cycles); Assert.Equal(1, diagnostic.StarvedCycles); Assert.Equal(2, diagnostic.EncodedPackets);
         for (int i = 0; i < 10; i++) engine.ProcessCycle();
         engine.FeedPcm(1, tone, 1); engine.ProcessCycle();
         Assert.True((sent[^1].Flags & VoiceFrameFlags.Marker) != 0);
@@ -193,6 +268,14 @@ public class AudioEngineTests
         Assert.True(energy > 100000);
     }
 
+    private static string FindRoot()
+    {
+        DirectoryInfo? directory = new(AppContext.BaseDirectory);
+        while (directory is not null && !File.Exists(Path.Combine(directory.FullName, "VoiceCat.slnx")))
+            directory = directory.Parent;
+        return directory?.FullName ?? throw new DirectoryNotFoundException("Repository root not found.");
+    }
+
     private sealed class ManualAudioClock : TimeProvider
     {
         private long milliseconds;