pyACA.FeatureTimePeakEnvelope Namespace Reference

Functions
	FeatureTimePeakEnvelope (x, iBlockLength, iHopLength, f_s)
	computes the peak envelope of a time domain signal
	ppm (x, filterbuf, alpha)

Function Documentation

FeatureTimePeakEnvelope()

FeatureTimePeakEnvelope	(		x,
			iBlockLength,
			iHopLength,
			f_s )

computes the peak envelope of a time domain signal

Parameters

x	array with floating point audio data (dimension samples x channels)
iBlockLength	block length in samples
iHopLength	hop length in samples
f_s	sample rate of audio data

Returns

vppm: peak envelope (1: max, 2: PPM)

t: time stamp

Definition at line 16 of file FeatureTimePeakEnvelope.py.

def FeatureTimePeakEnvelope(x, iBlockLength, iHopLength, f_s):
 
    # create blocks
    xBlocks, t = pyACA.ToolBlockAudio(x, iBlockLength, iHopLength, f_s)
 
    # number of results
    iNumOfBlocks = xBlocks.shape[0]
 
    alpha = 1 - np.array([np.exp(-2.2 / (f_s * 0.01)), np.exp(-2.2 / (f_s * 1.5))])
 
    # allocate memory
    vppm = np.zeros([2, iNumOfBlocks])
    v_tmp = np.zeros(iBlockLength)
 
    for n, block in enumerate(xBlocks):
        x_block = np.abs(block)
 
        # detect the maximum per block
        vppm[0, n] = np.max(x_block)
 
        # calculate the PPM value - take into account block overlaps
        # and discard concerns wrt efficiency
        v_tmp = ppm(x_block, v_tmp[iHopLength - 1], alpha)
        vppm[1, n] = np.max(v_tmp)
 
    # convert to dB
    epsilon = 1e-5  # -100dB
 
    vppm[vppm < epsilon] = epsilon
    vppm = 20 * np.log10(vppm)
 
    return vppm, t
 
 

Here is the call graph for this function:

ppm()

ppm	(		x,
			filterbuf,
			alpha )

Definition at line 50 of file FeatureTimePeakEnvelope.py.

def ppm(x, filterbuf, alpha):
 
    # initialization
    ppmout = np.zeros(x.shape[0])
 
    alpha_AT = alpha[0]
    alpha_RT = alpha[1]
 
    for i in range(0, x.shape[0]):
        if filterbuf > x[i]:
            # release state
            ppmout[i] = (1 - alpha_RT) * filterbuf
        else:
            # attack state
            ppmout[i] = alpha_AT * x[i] + (1 - alpha_AT) * filterbuf
 
        filterbuf = ppmout[i]
 
    return ppmout

Here is the caller graph for this function: