public static SpectralDecomp Decompose(
IBGCStream stream,
int windowCount = 400,
int windowOrder = 12,
int targetChannel = 0,
double minFreq = 0.0,
double maxFreq = double.PositiveInfinity)
{
//WindowSize is 2 ^ windowOrder
int windowSize = 1 << windowOrder;
if (stream.Channels <= targetChannel)
{
throw new ArgumentException(
$"TargetChannel ({targetChannel}) exceeded stream channels ({stream.Channels})",
nameof(targetChannel));
}
float[] samples = stream.IsolateChannel(targetChannel).HardClip().Cache().Samples;
int sampleOffset = (int)((samples.Length - windowSize) / (double)(windowCount - 1));
//Adjust windowSize to conform to sample size and requirements
while (sampleOffset <= 0 && windowOrder > 4)
{
--windowOrder;
windowSize = 1 << windowOrder;
windowCount /= 2;
sampleOffset = (int)((samples.Length - windowSize) / (double)(windowCount - 1));
}
if (windowOrder == 4)
{
throw new ArgumentException("Clip too short to evaluate");
}
//Limit Max Frquency by the size of the window
maxFreq = Math.Min(maxFreq, FrequencyDomain.GetComplexSampleFrequency(windowSize, windowSize / 2));
//Limit Min Frequency by the
minFreq = Math.Max(minFreq, FrequencyDomain.GetComplexSampleFrequency(windowSize, 1));
//Our output will be just the real-valued amplitudes
SpectralDecomp decomp = new SpectralDecomp(minFreq, maxFreq, windowSize, windowCount);
Complex64[] fftBuffer = new Complex64[windowSize];
IBGCEnvelopeStream windowStream = new BlackmanHarrisEnvelope(windowSize);
for (int window = 0; window < windowCount; window++)
{
int specificOffset = sampleOffset * window;
windowStream.Reset();
//Copy samples into buffer
for (int i = 0; i < windowSize; i++)
{
//Set real value
fftBuffer[i] = samples[specificOffset + i] * windowStream.ReadNextSample();
}
Fourier.Forward(fftBuffer);
decomp.Add(window, fftBuffer);
}
decomp.Rescale();
return(decomp);
}
public static (double[] psd, double offset) Decompose(
IBGCStream stream,
int windowOrder = 12,
int targetChannel = 0)
{
//WindowSize is 2 ^ windowOrder
int windowSize = 1 << windowOrder;
if (stream.Channels <= targetChannel)
{
throw new ArgumentException(
$"TargetChannel ({targetChannel}) exceeded stream channels ({stream.Channels})",
nameof(targetChannel));
}
float[] samples = stream.IsolateChannel(targetChannel).HardClip().Cache().Samples;
int sampleOffset = windowSize / 2;
if (windowOrder == 4)
{
throw new ArgumentException("Clip too short to evaluate");
}
int windowCount = 1 + (int)Math.Ceiling((samples.Length - windowSize) / (double)sampleOffset);
if (windowCount < 1)
{
windowCount = 1;
}
//Our output will be just the real-valued amplitudes
double[] spectralValues = new double[windowSize / 2];
Complex64[] fftBuffer = new Complex64[windowSize];
IBGCEnvelopeStream windowStream = new BlackmanHarrisEnvelope(windowSize);
// 2 x due to negative frequencies
// 0.5 x due to overlap
double amplitudeAdjustant = 1.0 / (windowCount * windowSize);
for (int window = 0; window < windowCount; window++)
{
int specificOffset = sampleOffset * window;
windowStream.Reset();
//Copy samples into buffer
for (int i = 0; i < windowSize; i++)
{
//Set real value
if (specificOffset + i >= samples.Length)
{
fftBuffer[i] = Complex64.Zero;
}
else
{
fftBuffer[i] = samples[specificOffset + i] * windowStream.ReadNextSample();
}
}
Fourier.Forward(fftBuffer);
for (int i = 0; i < fftBuffer.Length / 2; i++)
{
spectralValues[i] += amplitudeAdjustant * fftBuffer[i].MagnitudeSquared;
}
}
double maxValue = double.MinValue;
double minValue = double.MaxValue;
for (int i = 0; i < spectralValues.Length; i++)
{
spectralValues[i] = 10.0 * Math.Log10(spectralValues[i]);
if (!double.IsNaN(spectralValues[i]) && !double.IsNegativeInfinity(spectralValues[i]))
{
if (spectralValues[i] > maxValue)
{
maxValue = spectralValues[i];
}
if (spectralValues[i] < minValue)
{
minValue = spectralValues[i];
}
}
}
for (int i = 0; i < spectralValues.Length; i++)
{
if (double.IsNaN(spectralValues[i]) || double.IsNegativeInfinity(spectralValues[i]))
{
spectralValues[i] = minValue - maxValue;
}
else
{
spectralValues[i] -= maxValue;
}
}
return(spectralValues, maxValue);
}