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