public List <SoundFeature> GetLPCAndCepstralSeries(string lpcNamePrefix, int lpcOrder, string cepstralNamePrefix, int cepstralOrder)
{
List <SoundFeature> lpcSoundFeatureList = new List <SoundFeature>();
for (int ii = 0; ii < lpcOrder; ii++)
{
SoundFeature soundFeature = new SoundFeature();
soundFeature.Name = lpcNamePrefix + (ii + 1).ToString(); // LPCs enumerated from 1.
soundFeature.SetSize(frameList.Count);
lpcSoundFeatureList.Add(soundFeature);
}
List <SoundFeature> cepstralSoundFeatureList = new List <SoundFeature>();
for (int ii = 0; ii <= cepstralOrder; ii++)
{
SoundFeature soundFeature = new SoundFeature();
soundFeature.Name = cepstralNamePrefix + ii.ToString();
soundFeature.SetSize(frameList.Count);
cepstralSoundFeatureList.Add(soundFeature);
}
List <double> lpcCoefficients = null;
for (int iFrame = 0; iFrame < frameList.Count; iFrame++)
{
WAVSound frame = frameList[iFrame];
lpcCoefficients = frame.ComputeLPCCoefficients(lpcOrder);
for (int ii = 0; ii < lpcOrder; ii++)
{
lpcSoundFeatureList[ii].ValueList[iFrame] = lpcCoefficients[ii];
}
List <double> cepstralCoefficients = frame.ComputeCepstralCoefficients(lpcCoefficients, cepstralOrder);
for (int ii = 0; ii <= cepstralOrder; ii++)
{
cepstralSoundFeatureList[ii].ValueList[iFrame] = cepstralCoefficients[ii];
}
}
//
// The first cepstral coefficient (c0) is equal to the (non-normalized) autocorrelation,
// and can usually be removed in speech recognition (the autocorrelation is typically computed
// elsewhere, as a separate feature).
//
// Moreover the second cepstral coefficient (c1) is identical to the first LPC coefficient,
// and so can also be removed.
//
cepstralSoundFeatureList.RemoveAt(0); // Remove c0
cepstralSoundFeatureList.RemoveAt(0); // Remove c1
List <SoundFeature> soundFeatureList = new List <SoundFeature>();
soundFeatureList.AddRange(lpcSoundFeatureList);
soundFeatureList.AddRange(cepstralSoundFeatureList);
return(soundFeatureList);
}