pyACA.FeatureSpectralPitchChroma Namespace Reference

computes the pitch chroma from the magnitude spectrum More...

Functions
	FeatureSpectralPitchChroma (X, f_s)
	computes the pitch chroma from the magnitude spectrum
	generatePcFilters (iSpecLength, f_s)

Detailed Description

computes the pitch chroma from the magnitude spectrum

Args: X: spectrogram (dimension FFTLength X Observations) f_s: sample rate of audio data

Returns: v_pc: pitch chroma

Function Documentation

FeatureSpectralPitchChroma()

FeatureSpectralPitchChroma	(		X,
			f_s )

computes the pitch chroma from the magnitude spectrum

Parameters

X	spectrogram (dimension FFTLength X Observations)
f_s	sample rate of audio data

Returns

v_pc: pitch chroma

Definition at line 23 of file FeatureSpectralPitchChroma.py.

def FeatureSpectralPitchChroma(X, f_s):
 
    isSpectrum = X.ndim == 1
    if isSpectrum:
        X = np.expand_dims(X, axis=1)
 
    # generate filter matrix
    H = generatePcFilters(X.shape[0], f_s)
 
    # compute pitch chroma
    v_pc = np.dot(H, X**2)
 
    # norm pitch chroma to a sum of 1 but avoid div by zero
    norm = v_pc.sum(axis=0, keepdims=True)
    norm[norm == 0] = 1
    v_pc = v_pc / norm
 
    return np.squeeze(v_pc) if isSpectrum else v_pc
 
 

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generatePcFilters()

generatePcFilters	(		iSpecLength,
			f_s )

Definition at line 43 of file FeatureSpectralPitchChroma.py.

def generatePcFilters(iSpecLength, f_s):
 
    # initialization at C4
    f_mid = 261.63
    iNumOctaves = 4
    iNumPitchesPerOctave = 12
 
    # sanity check
    while f_mid * 2**iNumOctaves > f_s / 2.:
        iNumOctaves = iNumOctaves - 1
 
    H = np.zeros([iNumPitchesPerOctave, iSpecLength])
 
    # for each pitch class i create weighting factors in each octave j
    for i in range(0, iNumPitchesPerOctave):
        afBounds = np.array([2**(-1 / (2 * iNumPitchesPerOctave)), 2**(1 / (2 * iNumPitchesPerOctave))]) * f_mid * 2 * (iSpecLength - 1) / f_s
        for j in range(0, iNumOctaves):
            iBounds = np.array([math.ceil(2**j * afBounds[0]), math.ceil(2**j * afBounds[1])])
            H[i, range(iBounds[0], iBounds[1])] = 1 / (iBounds[1] - iBounds[0] + 1)
 
        # increment to next semi-tone
        f_mid = f_mid * 2**(1 / iNumPitchesPerOctave)
 
    return H

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