public float[][] CreateSpectrogram(AudioSamples audioSamples, int overlap, int wdftSize)
{
float[] samples = audioSamples.Samples;
int width = (samples.Length - wdftSize) / overlap;
float[][] frames = new float[width][];
for (int i = 0; i < width; i++)
{
float[] complexSignal = fftService.FFTForward(samples, i * overlap, wdftSize);
float[] band = new float[(wdftSize / 2) + 1];
for (int j = 0; j < (wdftSize / 2) + 1; j++)
{
double re = complexSignal[2 * j];
double img = complexSignal[(2 * j) + 1];
re /= (float)wdftSize / 2;
img /= (float)wdftSize / 2;
band[j] = (float)((re * re) + (img * img));
}
frames[i] = band;
}
return(frames);
}
public FingerprintSignature CreateFingerprint(AudioSamples audioSamples, SpectrogramConfig configuration)
{
absEnergy = new double[(Frequencies.Length - 1) * 4]; // number of frequencies bands (33)
lowpassFilters = new LowpassFilters(Frequencies.Length - 1); // 33 bands
try
{
int width = (audioSamples.Samples.Length - configuration.WdftSize) / configuration.Overlap; // WdftSize=2048 / Overlap=64
if (width < 1)
{
return(null);
}
// reserve memory for 32 bit fingerprint hashes
byte[] hashes = new byte[width * sizeof(uint)];
byte[] reliabilities = new byte[width * 32]; // elke subfinger (32 bits) heeft voor elke bit een waarde tussen 0 en 31 voor relibility (dus 5 bits), we ronden dit af naar 1 byte
FingerprintSignature fingerprintSignature = new FingerprintSignature(null, 0, hashes, (long)(width * 11.6));
fingerprintSignature.Reliabilities = reliabilities;
// Calculate a hamming windows
float[] hammingWindow = new float[configuration.WdftSize];
for (int i = 0; i < hammingWindow.Length; i++)
{
// Hamming (watch it peak is at beginning not as in real hamming in the middle)
hammingWindow[i] = 0.54f + 0.46f * (float)System.Math.Cos((6.283f * (float)i / hammingWindow.Length));
//hammingWindow[i] = 0.54f - (0.46f * (float)System.Math.Cos(((6.283f * (float)i) / (hammingWindow.Length - 1)))); // real hamming window
} //for
int[] frequenciesRange = Frequencies; // 34 freqencies
float[] samples = new float[configuration.WdftSize];
for (int i = 0; i < width; i++)
{
if (((samples.Length - 1) + (i * configuration.Overlap)) >= audioSamples.Samples.Length)
{
// we hebben niet voldoende data meer!
// dus we stoppen nu en nemen het "laaste" stukje niet mee!
break;
}
for (int j = 0; j < samples.Length; j++)
{
samples[j] = audioSamples.Samples[j + (i * configuration.Overlap)] * hammingWindow[j];
} // for j
float[] complexSignal = fftService.FFTForward(samples, 0, configuration.WdftSize);
byte[] reliability;
uint subFingerprint = CalculateSubFingerprint(complexSignal, frequenciesRange, 5512, out reliability);
Buffer.BlockCopy(BitConverter.GetBytes(subFingerprint), 0, hashes, i * sizeof(uint), sizeof(uint));
Buffer.BlockCopy(reliability, 0, reliabilities, i * reliability.Length, reliability.Length);
// sequencenumber = i;
// timestamp = (i / audioSamples.Samples.Length) * configuration.SampleRate
} //for
return(fingerprintSignature);
}
finally
{
absEnergy = null;
lowpassFilters = null;
}
}