Latency parameter on WasapiCapture not adhered to

[tbdx]

Hi,

Unless I am misunderstanding this, which is possible, I would have expected the DataAvailable event to be raised less frequently.

I am trying to process audio in near realtime although stability is important so I am happy with 100 to 200 milliseconds.

Recording in 8kHz, 16 bit, mono.

Example code

private WasapiCapture soundIn;
private SoundInSource soundInSource;
private IWaveSource finalSource;
private MMDevice AudioDeviceIn;

Debug.WriteLine(DateTime.Now.ToString("HHmmss.fff") + "\t" + "recorder format = " + AudioDeviceIn.DeviceFormat.ToString());

soundIn = new WasapiCapture(true, AudioClientShareMode.Shared, 120, new WaveFormat(8000, 16, 1));
soundIn.Device = AudioDeviceIn;
soundIn.Initialize();

soundInSource = new SoundInSource(soundIn);
soundInSource.FillWithZeros = false;

var simpleStream = new SimpleNotificationSource(soundInSource.ToSampleSource());
finalSource = simpleStream.ToWaveSource(16);

soundInSource.DataAvailable += GotAudioData;

soundIn.Start();


private void GotAudioData(object sender, DataAvailableEventArgs e)
{
	Debug.WriteLine(DateTime.Now.ToString("HHmmss.fff") + "\t" + "got bytes = " + e.ByteCount);
	
	byte[] buffer = new byte[finalSource.WaveFormat.BytesPerSecond];
	
	int read;

	int bytesPerSample;
	int howManySamples;
	
	while ((read = finalSource.Read(buffer, 0, buffer.Length)) > 0)
	{
		Debug.WriteLine(DateTime.Now.ToString("HHmmss.fff") + "\t" + "read = " + read + " from finalSource");
				
		bytesPerSample = finalSource.WaveFormat.BytesPerSample;
		howManySamples = read / bytesPerSample;

	}
}

Debugging shows the DataAvailable event seems to be triggered every 20ms, sometimes as low as 10ms. (2 bytes per sample)

092727.219	recorder format = ChannelsAvailable: 1|SampleRate: 8000|Bps: 16000|BlockAlign: 2|BitsPerSample: 16|Encoding: Extensible|SubFormat: 00000001-0000-0010-8000-00aa00389b71|ChannelMask: SpeakerFrontCenter
092727.298	got bytes = 320
092727.302	read = 320 from finalSource
092727.315	got bytes = 320
092727.316	read = 320 from finalSource
092727.336	got bytes = 320
092727.337	read = 320 from finalSource
092727.355	got bytes = 320
092727.356	read = 320 from finalSource
092727.375	got bytes = 320
092727.376	read = 320 from finalSource
092727.395	got bytes = 320
092727.396	read = 320 from finalSource
092727.416	got bytes = 320
092727.417	read = 320 from finalSource
092727.436	got bytes = 320
092727.436	read = 320 from finalSource
092727.456	got bytes = 320
092727.457	read = 320 from finalSource
092727.476	got bytes = 320
092727.476	read = 320 from finalSource
092727.496	got bytes = 320
092727.496	read = 320 from finalSource
092727.515	got bytes = 320
092727.516	read = 320 from finalSource
092727.535	got bytes = 320
092727.536	read = 320 from finalSource
092727.555	got bytes = 320
092727.557	read = 320 from finalSource
092727.575	got bytes = 320
092727.577	read = 320 from finalSource
092727.595	got bytes = 320
092727.597	read = 320 from finalSource
092727.605	got bytes = 160
092727.606	read = 160 from finalSource
092727.625	got bytes = 320
092727.626	read = 320 from finalSource
092727.636	got bytes = 160
092727.637	read = 160 from finalSource

[filoe]

You're right. It was an old relict. I've fixed it. Should be stable now. Decreased the default latency to 25ms. Should be quite stable now.