public byte[] Render(float masterVolume)
{
// due to the way NAudio works, the source files must be provided twice.
// this is because all channels are kept in sync by the mux, and the unused
// channel data is discarded. If we tried to use the same source for both
// muxes, it would try to read 2x the data present in the buffer!
// If only we had a way to create separate WaveProviders from within the
// MultiplexingWaveProvider..
try
{
using (MemoryStream sourceLeft = new MemoryStream(Data), sourceRight = new MemoryStream(Data))
{
using (RawSourceWaveStream waveLeft = new RawSourceWaveStream(new IgnoreDisposeStream(sourceLeft), Format), waveRight = new RawSourceWaveStream(new IgnoreDisposeStream(sourceRight), Format))
{
// step 1: separate the stereo stream
MultiplexingWaveProvider demuxLeft = new MultiplexingWaveProvider(new IWaveProvider[] { waveLeft }, 1);
MultiplexingWaveProvider demuxRight = new MultiplexingWaveProvider(new IWaveProvider[] { waveRight }, 1);
demuxLeft.ConnectInputToOutput(0, 0);
demuxRight.ConnectInputToOutput(1, 0);
// step 2: adjust the volume of a stereo stream
VolumeWaveProvider16 volLeft = new VolumeWaveProvider16(demuxLeft);
VolumeWaveProvider16 volRight = new VolumeWaveProvider16(demuxRight);
// note: use logarithmic scale
#if (true)
// log scale is applied to each operation
float volumeValueLeft = (float)Math.Pow(1.0f - Panning, 0.5f);
float volumeValueRight = (float)Math.Pow(Panning, 0.5f);
// ensure 1:1 conversion
volumeValueLeft /= (float)Math.Sqrt(0.5);
volumeValueRight /= (float)Math.Sqrt(0.5);
// apply volume
volumeValueLeft *= (float)Math.Pow(Volume, 0.5f);
volumeValueRight *= (float)Math.Pow(Volume, 0.5f);
// clamp
volumeValueLeft = Math.Min(Math.Max(volumeValueLeft, 0.0f), 1.0f);
volumeValueRight = Math.Min(Math.Max(volumeValueRight, 0.0f), 1.0f);
#else
// log scale is applied to the result of the operations
float volumeValueLeft = (float)Math.Pow(1.0f - Panning, 0.5f);
float volumeValueRight = (float)Math.Pow(Panning, 0.5f);
// ensure 1:1 conversion
volumeValueLeft /= (float)Math.Sqrt(0.5);
volumeValueRight /= (float)Math.Sqrt(0.5);
// apply volume
volumeValueLeft *= Volume;
volumeValueRight *= Volume;
// apply log scale
volumeValueLeft = (float)Math.Pow(volumeValueLeft, 0.5f);
volumeValueRight = (float)Math.Pow(volumeValueRight, 0.5f);
// clamp
volumeValueLeft = Math.Min(Math.Max(volumeValueLeft, 0.0f), 1.0f);
volumeValueRight = Math.Min(Math.Max(volumeValueRight, 0.0f), 1.0f);
#endif
// use linear scale for master volume
volLeft.Volume = volumeValueLeft * masterVolume;
volRight.Volume = volumeValueRight * masterVolume;
// step 3: combine them again
IWaveProvider[] tracks = new IWaveProvider[] { volLeft, volRight };
MultiplexingWaveProvider mux = new MultiplexingWaveProvider(tracks, 2);
// step 4: export them to a byte array
byte[] finalData = new byte[Data.Length];
mux.Read(finalData, 0, finalData.Length);
// cleanup
demuxLeft = null;
demuxRight = null;
volLeft = null;
volRight = null;
mux = null;
return finalData;
}
}
}
catch
{
return Data;
}
}
public void PerformanceTest()
{
var waveFormat = new WaveFormat(32000, 16, 1);
var input1 = new TestWaveProvider(waveFormat);
var input2 = new TestWaveProvider(waveFormat);
var input3 = new TestWaveProvider(waveFormat);
var input4 = new TestWaveProvider(waveFormat);
var mp = new MultiplexingWaveProvider(new IWaveProvider[] { input1, input2, input3, input4 }, 4);
mp.ConnectInputToOutput(0, 3);
mp.ConnectInputToOutput(1, 2);
mp.ConnectInputToOutput(2, 1);
mp.ConnectInputToOutput(3, 0);
byte[] buffer = new byte[waveFormat.AverageBytesPerSecond];
Stopwatch s = new Stopwatch();
var duration = s.Time(() =>
{
// read one hour worth of audio
for (int n = 0; n < 60 * 60; n++)
{
mp.Read(buffer, 0, buffer.Length);
}
});
Console.WriteLine("Performance test took {0}ms", duration);
}
public void ConnectInputToOutputThrowsExceptionForInvalidOutput()
{
var input1 = new TestWaveProvider(new WaveFormat(32000, 16, 2));
var mp = new MultiplexingWaveProvider(new IWaveProvider[] { input1 }, 1);
Assert.Throws<ArgumentException>(() => mp.ConnectInputToOutput(1, 1));
}
public void HasConnectInputToOutputMethod()
{
var input1 = new TestWaveProvider(new WaveFormat(32000, 16, 2));
var mp = new MultiplexingWaveProvider(new IWaveProvider[] { input1 }, 1);
mp.ConnectInputToOutput(1, 0);
}
public void StereoInTwoOutCanBeConfiguredToSwapLeftAndRight()
{
var input1 = new TestWaveProvider(new WaveFormat(32000, 16, 2));
// 4 bytes per pair of samples
byte[] expected = new byte[] { 2, 3, 0, 1, 6, 7, 4, 5, 10, 11, 8, 9, };
var mp = new MultiplexingWaveProvider(new IWaveProvider[] { input1 }, 2);
mp.ConnectInputToOutput(0, 1);
mp.ConnectInputToOutput(1, 0);
byte[] buffer = new byte[12];
var read = mp.Read(buffer, 0, 12);
Assert.AreEqual(12, read);
Assert.AreEqual(expected, buffer);
}
public void TwoInOneOutShouldCanBeConfiguredToSelectRightChannel()
{
var input1 = new TestWaveProvider(new WaveFormat(32000, 16, 2));
// 16 bit so left right pairs
byte[] expected = new byte[] { 2, 3, 6, 7, 10, 11, 14, 15, 18, 19 };
var mp = new MultiplexingWaveProvider(new IWaveProvider[] { input1 }, 1);
mp.ConnectInputToOutput(1, 0);
byte[] buffer = new byte[10];
var read = mp.Read(buffer, 0, 10);
Assert.AreEqual(10, read);
Assert.AreEqual(expected, buffer);
}