private void HandleFftData(object sender, FftDataAvailableHandlerArgs e) {
float[] rawFft = e.FftData;
float deltaFreq = (float)AudioIn.SAMPLE_RATE / FftProcessor.FFT_LENGTH;
// Operate only on frequencies through MAX_FREQ that may be involved in formants
float[] newFft = rawFft.Take((int)(Analyzer.MAX_FREQ / deltaFreq + 0.5f)).ToArray();
// Normalize the fft
newFft = newFft.Select(a => (float)(a / Math.Sqrt(FftProcessor.FFT_LENGTH))).ToArray();
// Negative values differ only by phase, use positive ones instead
newFft = newFft.Select(a => Math.Abs(a)).ToArray();
// Remove DC component (and close to it)
newFft[0] = newFft[1] = newFft[2] = 0;
fft = newFft;
prepareVisualization();
}
private void HandleFftData(object sender, FftDataAvailableHandlerArgs e) {
float[] rawFft = e.FftData;
float[] newFft = new float[fft.Length];
// Normalize and then square for power instead of amplitude
for (int i = 0; i < newFft.Length; i++) {
float n = rawFft[i] / (float)Math.Sqrt(FftProcessor.FFT_LENGTH);
newFft[i] = n * n;
}
// Remove DC component (and close to it)
newFft[0] = newFft[1] = newFft[2] = 0;
// Remove noise in the fft with a high-pass filter
float lastIn = newFft[0];
float lastOut = lastIn;
float alpha = 0.96f;
for (int i = 1; i < newFft.Length; i++) {
float inValue = newFft[i];
float outValue = alpha * (lastOut + inValue - lastIn);
lastIn = inValue;
lastOut = outValue;
newFft[i] = outValue;
}
// Z-score it, put negative values at 0.
float average = newFft.Average();
float sumSquareDiffs = 0;
for (int i = 0; i < newFft.Length; i++) {
sumSquareDiffs += (newFft[i] - average) * (newFft[i] - average);
}
float stdDev = (float)Math.Sqrt(sumSquareDiffs / newFft.Length);
for (int i = 0; i < newFft.Length; i++) {
newFft[i] = (newFft[i] - average) / stdDev;
}
// Consider it noise/silence if the stdDev is too low
Debug.WriteLine(stdDev);
if (stdDev > 1e7) {
fft = newFft;
// Shift in the new fft
Array.Copy(lastFfts, 1, lastFfts, 0, lastFfts.Length - 1);
lastFfts[lastFfts.Length - 1] = fft;
// Shift in new fundamental
Array.Copy(lastFundamentals, 1, lastFundamentals, 0, lastFundamentals.Length - 1);
lastFundamentals[lastFundamentals.Length - 1] = IdentifyFundamental(fft);
prepareVisualization();
} else {
// Shift in null and 0 values to clear out the buffer.
Array.Copy(lastFfts, 1, lastFfts, 0, lastFfts.Length - 1);
lastFfts[lastFfts.Length - 1] = null;
Array.Copy(lastFundamentals, 1, lastFundamentals, 0, lastFundamentals.Length - 1);
lastFundamentals[lastFundamentals.Length - 1] = 0;
Array.Copy(lastDrawnPointsRoundness, 1, lastDrawnPointsRoundness, 0, lastDrawnPointsRoundness.Length - 1);
lastDrawnPointsRoundness[lastDrawnPointsRoundness.Length - 1] = Tuple.Create(new PointF(-1, -1), 0f); // Set to not draw it
updateUI();
}
}