MFCC similar to NWaves in librosa about nwaves

[ar1st0crat]

Hi!
I guess you should check first this wiki. You'll find a paragraph related to librosa here.

Still, there are couple of important nuances in librosa:

1. htk = true or false
   This parameter essentially defines the weights of mel-filterbank (HTK-style or Slaney-style).
2. centering
   In NWaves, like in many other frameworks, frames are not centered the way they are in librosa (in fact, I don't quite understand its purpose...), so this parameter must be set to False.

Let's just consider an example:

int sr = 22050;                  // sampling rate
int fftSize = 1024;
double lowFreq = 100;     // if not specified, will be 0
double highFreq = 8000; // if not specified, will be samplingRate / 2
int filterbankSize = 40;     // or 24 for htk=true (usually)

// if 'htk' parameter in librosa will be set to False:
var melBank1 = FilterBanks.MelBankSlaney(filterbankSize, fftSize, sr, lowFreq, highFreq);

// if 'htk' parameter in librosa will be set to True:
var melBands = FilterBanks.MelBands(filterbankSize, sr, lowFreq, highFreq);
var melBank2 = FilterBanks.Triangular(fftSize, sr, melBands, null, Scale.HerzToMel);

var opts = new MfccOptions
{
    SamplingRate = sr,
    FrameDuration = (double)fftSize / sr,
    HopDuration = 0.010,
    FeatureCount = 12,
    Filterbank = melBank1,  // or MelBank2
    NonLinearity = NonLinearityType.ToDecibel, // mandatory
    Window = WindowTypes.Hamming,     // in librosa 'hann' is by default
    LogFloor = 1e-10f,  // mandatory
    DctType="2N",
    LifterSize = 0
};
var e = new MfccExtractor(opts);

In librosa:

mfccs = librosa.feature.mfcc(y, sr, n_mfcc=13,
dct_type=2, norm='ortho', window='hamming',
htk=False, n_mels=40, fmin=100, fmax=8000,
n_fft=1024, hop_length=int(0.010*sr), center=False)

Actually there are even more options. Feel free to ask, if you have any questions.

[jodusan]

@ar1st0crat Thank you for the detailed response!