/// <summary>
/// Starts rendering audio data.
/// </summary>
/// <param name="maxBufferSeconds">
/// The maximum duration of audio that can be buffered for playback.
/// </param>
/// <param name="targetLatencyInMs">
/// The target maximum number of milliseconds of acceptable lag between
/// playback of samples and live sound being produced.
/// </param>
/// <param name="gain">
/// The gain to be applied prior to rendering the audio.
/// </param>
/// <param name="inFormat">
/// The input audio format.
/// </param>
public void StartRendering(double maxBufferSeconds, int targetLatencyInMs, float gain, WaveFormat inFormat)
{
if (this.wasapiRenderer != null)
{
this.StopRendering();
}
// Create an audio buffer to buffer audio awaiting playback.
this.audioBufferStream = new CircularBufferStream((long)Math.Ceiling(maxBufferSeconds * inFormat.AvgBytesPerSec), false);
this.wasapiRenderer = new WasapiRenderer(this.audioDevice);
// Create a callback delegate and marshal it to a function pointer. Keep a
// reference to the delegate as a class field to prevent it from being GC'd.
this.callbackDelegate = new AudioDataRequestedCallback(this.AudioDataRequestedCallback);
// initialize the renderer with the desired parameters
this.wasapiRenderer.Initialize(targetLatencyInMs, gain, inFormat, this.callbackDelegate);
// tell WASAPI to start rendering
this.wasapiRenderer.Start();
}
/// <summary>
/// Initialize the renderer.
/// </summary>
/// <param name="engineLatency">
/// Number of milliseconds of acceptable lag between playback of samples and live sound being produced.
/// </param>
/// <param name="gain">
/// The gain to be applied to the audio before rendering.
/// </param>
/// <param name="inFormat">
/// The format of the input audio samples to be rendered. If this is NULL, the current default audio
/// format of the renderer device will be assumed.
/// </param>
/// <param name="callback">
/// Callback function delegate which will supply the data to be rendered.
/// </param>
public void Initialize(int engineLatency, float gain, WaveFormat inFormat, AudioDataRequestedCallback callback)
{
// Create our shutdown event - we want a manual reset event that starts in the not-signaled state.
this.shutdownEvent = new ManualResetEvent(false);
// Now activate an IAudioClient object on our preferred endpoint and retrieve the mix format for that endpoint.
object obj = this.endpoint.Activate(ref audioClientIID, ClsCtx.INPROC_SERVER, IntPtr.Zero);
this.audioClient = (IAudioClient)obj;
// Load the MixFormat. This may differ depending on the shared mode used.
this.LoadFormat();
// Remember our configured latency
this.engineLatencyInMs = engineLatency;
// Set the gain
this.gain = gain;
// Check if the desired format is supported
IntPtr closestMatchPtr;
IntPtr inFormatPtr = WaveFormat.MarshalToPtr(inFormat);
int hr = this.audioClient.IsFormatSupported(AudioClientShareMode.Shared, inFormatPtr, out closestMatchPtr);
// Free outFormatPtr to prevent leaking memory
Marshal.FreeHGlobal(inFormatPtr);
if (hr == 0)
{
// Replace _MixFormat with inFormat. Since it is supported, we will initialize
// the audio render client with that format and render without resampling.
this.mixFormat = inFormat;
this.mixFrameSize = (this.mixFormat.BitsPerSample / 8) * this.mixFormat.Channels;
}
else
{
// In all other cases, we need to resample to OutFormat
if ((hr == 1) && (closestMatchPtr != IntPtr.Zero))
{
// Use closest match suggested by IsFormatSupported() and resample
this.mixFormat = WaveFormat.MarshalFromPtr(closestMatchPtr);
this.mixFrameSize = (this.mixFormat.BitsPerSample / 8) * this.mixFormat.Channels;
// Free closestMatchPtr to prevent leaking memory
Marshal.FreeCoTaskMem(closestMatchPtr);
}
}
this.inputBufferSize = (int)(this.engineLatencyInMs * inFormat.AvgBytesPerSec / 1000);
this.outputBufferSize = (int)(this.engineLatencyInMs * this.mixFormat.AvgBytesPerSec / 1000);
DeviceUtil.CreateResamplerBuffer(this.inputBufferSize, out this.inputSample, out this.inputBuffer);
DeviceUtil.CreateResamplerBuffer(this.outputBufferSize, out this.outputSample, out this.outputBuffer);
// Create resampler object
this.resampler = DeviceUtil.CreateResampler(inFormat, this.mixFormat);
this.InitializeAudioEngine();
// Set the callback function
this.dataRequestedCallback = callback;
}