pyACA.computeMelSpectrogram Namespace Reference

Functions
	computeMelSpectrogram (x, f_s, afWindow=None, bLogarithmic=True, iBlockLength=4096, iHopLength=2048, iNumMelBands=128, fMaxInHz=None)
	computes a mel spectrogram from the audio data
	generateMelFb_I (iFftLength, f_s, iNumFilters, f_max)
	computeMelSpectrogramCl (cPath)
	main

Variables
	parser = argparse.ArgumentParser(description='Compute key of wav file')
	metavar
	required
	help
	args = parser.parse_args()
	cPath = args.infile

Function Documentation

computeMelSpectrogram()

computeMelSpectrogram	(		x,
			f_s,
			afWindow = None,
			bLogarithmic = True,
			iBlockLength = 4096,
			iHopLength = 2048,
			iNumMelBands = 128,
			fMaxInHz = None )

computes a mel spectrogram from the audio data

Parameters

x	array with floating point audio data (dimension samples x channels)
f_s	sample rate of audio data
bLogarithmic	levels (true) or magnitudes (false)
afWindow	FFT window of length iBlockLength (default: hann), can be [] empty
iBlockLength	internal block length (default: 4096 samples)
iHopLength	internal hop length (default: 2048 samples)
iNumMelBands	number of mel bands (default: 128 bands)
fMaxInHz	maximum frequency (default: None)

Returns

M: Mel spectrum

f_c: Center frequencies of mel bands

t: time stamps

Definition at line 26 of file computeMelSpectrogram.py.

def computeMelSpectrogram(x, f_s, afWindow=None, bLogarithmic=True, iBlockLength=4096, iHopLength=2048, iNumMelBands=128, fMaxInHz=None):
 
    if not fMaxInHz:
        fMaxInHz = f_s / 2
 
    # Pre-process: down-mix, normalize, zero-pad
    x = ToolPreprocAudio(x)
 
    if afWindow is None:
        # Compute window function for FFT
        afWindow = ToolComputeHann(iBlockLength)
 
    assert(afWindow.shape[0] == iBlockLength), "parameter error: invalid window dimension"
 
    # Compute spectrogram (in the real world, we would do this block by block)
    [X, f, t] = computeSpectrogram(x, f_s, None, iBlockLength, iHopLength)
 
    # Compute Mel filters
    H, f_c = generateMelFb_I(iBlockLength, f_s, iNumMelBands, fMaxInHz)
 
    M = np.matmul(H, X)
 
    if bLogarithmic:
        # Convert amplitude to level (dB)
        M = 20 * np.log10(M + 1e-12)
 
    return M, f_c, t
 
 

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computeMelSpectrogramCl()

computeMelSpectrogramCl

(

cPath

)

main

Definition at line 86 of file computeMelSpectrogram.py.

def computeMelSpectrogramCl(cPath):
    from pyACA.ToolReadAudio import ToolReadAudio
 
    # read audio file
    [f_s, x] = ToolReadAudio(cPath)
    
    # compute feature
    [M, f, t] = computeMelSpectrogram(x, f_s)
 
    return M, f, t
 
 

generateMelFb_I()

generateMelFb_I	(		iFftLength,
			f_s,
			iNumFilters,
			f_max )

Definition at line 55 of file computeMelSpectrogram.py.

def generateMelFb_I(iFftLength, f_s, iNumFilters, f_max):
 
    # initialization
    f_min = 0
    f_max = min(f_max, f_s / 2)
    f_fft = np.linspace(0, f_s / 2, iFftLength // 2 + 1)
    H = np.zeros((iNumFilters, f_fft.size))
 
    # compute center band frequencies
    mel_min = ToolFreq2Mel(f_min)
    mel_max = ToolFreq2Mel(f_max)
    f_mel = ToolMel2Freq(np.linspace(mel_min, mel_max, iNumFilters + 2))
 
    f_l = f_mel[0:iNumFilters]
    f_c = f_mel[1:iNumFilters + 1]
    f_u = f_mel[2:iNumFilters + 2]
 
    afFilterMax = 2 / (f_u - f_l)
 
    # compute the transfer functions
    for c in range(iNumFilters):
        H[c] = np.logical_and(f_fft > f_l[c], f_fft <= f_c[c]) * \
            afFilterMax[c] * (f_fft-f_l[c]) / (f_c[c]-f_l[c]) + \
            np.logical_and(f_fft > f_c[c], f_fft < f_u[c]) * \
            afFilterMax[c] * (f_u[c]-f_fft) / (f_u[c]-f_c[c])
 
    return H, f_c
 
 

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Variable Documentation

args

args = parser.parse_args()

Definition at line 107 of file computeMelSpectrogram.py.

cPath

str cPath = args.infile

Definition at line 108 of file computeMelSpectrogram.py.

help

help

Definition at line 104 of file computeMelSpectrogram.py.

metavar

metavar

Definition at line 103 of file computeMelSpectrogram.py.

parser

parser = argparse.ArgumentParser(description='Compute key of wav file')

Definition at line 102 of file computeMelSpectrogram.py.

required

required

Definition at line 103 of file computeMelSpectrogram.py.