Initial commit: RemSound v1.0

src/RemSound.Sender/SilentRenderKeepAlive.cs

@@ -0,0 +1,61 @@
+using NAudio.CoreAudioApi;
+using NAudio.Wave;
+
+namespace RemSound.Sender;
+
+/// <summary>
+/// Pins a continuous silent render stream on a WASAPI device so the device stays "warm".
+/// Some USB audio interfaces (Audient EVO8, RME, Focusrite, etc.) only fire WASAPI loopback
+/// callbacks when something is actively rendering to the device — when the render endpoint
+/// goes idle, the loopback path stops delivering frames until an application starts rendering
+/// again. By pinning a zero-volume silent render stream on the same device we capture from,
+/// loopback callbacks keep firing regardless of whether other apps are playing audio.
+///
+/// Same idea the legacy "silence.exe" used; folded into the sender so it's automatic, sized
+/// to the device's actual mix format (no resampler stage), and ties to capture lifetime.
+/// We do not own the MMDevice — AudioSender does — so we never dispose it.
+/// </summary>
+internal sealed class SilentRenderKeepAlive : IDisposable
+{
+    private readonly WasapiOut output;
+    private readonly Action<string>? onDiagnostic;
+
+    public SilentRenderKeepAlive(MMDevice device, Action<string>? onDiagnostic = null)
+    {
+        this.onDiagnostic = onDiagnostic;
+        // Shared mode with a 50 ms buffer. Latency doesn't matter for silence; longer buffers
+        // mean fewer wakeups per second. Event sync still gives us efficient blocking turnover.
+        output = new WasapiOut(device, AudioClientShareMode.Shared, useEventSync: true, latency: 50);
+        output.Init(new SilenceProvider(output.OutputWaveFormat));
+    }
+
+    public void Start()
+    {
+        try
+        {
+            output.Play();
+            onDiagnostic?.Invoke($"silence keepalive started ({output.OutputWaveFormat.SampleRate} Hz, {output.OutputWaveFormat.Channels} ch)");
+        }
+        catch (Exception ex)
+        {
+            onDiagnostic?.Invoke($"silence keepalive start failed: {ex.GetType().Name}: {ex.Message}");
+        }
+    }
+
+    public void Dispose()
+    {
+        try { output.Stop(); } catch { /* ignore */ }
+        try { output.Dispose(); } catch { /* ignore */ }
+    }
+
+    private sealed class SilenceProvider(WaveFormat format) : IWaveProvider
+    {
+        public WaveFormat WaveFormat { get; } = format;
+
+        public int Read(byte[] buffer, int offset, int count)
+        {
+            Array.Clear(buffer, offset, count);
+            return count;
+        }
+    }
+}