private void CalculateFFT()
{
if (WindowFunction != null)
{
WindowFunction.Apply(inputBuffer);
}
fft.Forward(inputBuffer);
FFTUtil.Results(inputBuffer, outputBuffer, windowFunctionNormalizationDecibelOffset);
OnWindowAnalyzed();
}
/// <summary>
/// Calculates a normalization offset for the current window function. Every window function leads to
/// a different FFT result peak value, and since the peak value of each windowed FFT means 0dB, this
/// offset can be used to adjust the calculated dB values.
/// </summary>
private void CalculateWindowFunctionNormalizationOffset()
{
if (windowFunction == null)
{
windowFunctionNormalizationDecibelOffset = 0;
}
else
{
SineGeneratorStream sine = new SineGeneratorStream(1024, 16, new TimeSpan(0, 0, 1));
float[] input = new float[WindowSize];
float[] output = new float[input.Length / 2];
WindowFunction wf = WindowUtil.GetFunction(windowFunction.Type, input.Length);
sine.Read(input, 0, input.Length);
wf.Apply(input);
fft.Forward(input);
int maxIndex = FFTUtil.Results(input, output);
float maxValue = output[maxIndex];
windowFunctionNormalizationDecibelOffset = 1f - maxValue;
}
}
