Cepstrogram

class audioflux.Cepstrogram(radix2_exp=12, samplate=32000, window_type=WindowType.RECT, slide_length=1024)

Cepstrogram algorithm

Parameters

radix2_exp: int

fft_length=2**radix2_exp

samplate: int

Sampling rate of the incoming audio

window_type: WindowType

Window type for each frame.

See: type.WindowType

slide_length: int or None

Window sliding length.

Examples

Read guitar chord audio data

>>> import audioflux as af
>>> audio_path = af.utils.sample_path('guitar_chord2')
>>> audio_arr, sr = af.read(audio_path)

Extract Cepstrogram

>>> from audioflux.type import ReassignType, WindowType
>>> import numpy as np
>>> obj = af.Cepstrogram(radix2_exp=12, samplate=sr)
>>> cepstrums_arr, envelope_arr, details_arr = obj.cepstrogram(audio_arr)

Show Cepstrogram plot

>>> import matplotlib.pyplot as plt
>>> from audioflux.display import fill_spec
>>> audio_len = audio_arr.shape[-1]
>>>
>>> fig, ax = plt.subplots()
>>> img = fill_spec(cepstrums_arr, axes=ax,
>>>                 x_coords=obj.x_coords(audio_len),
>>>                 y_coords=obj.y_coords(),
>>>                 x_axis='time', y_axis='log',
>>>                 title='Cepstrogram - Cepstrums')
>>> fig.colorbar(img, ax=ax)
>>>
>>> fig, ax = plt.subplots()
>>> img = fill_spec(envelope_arr, axes=ax,
>>>                 x_coords=obj.x_coords(audio_len),
>>>                 y_coords=obj.y_coords(),
>>>                 x_axis='time', y_axis='log',
>>>                 title='Cepstrogram - envelope')
>>> fig.colorbar(img, ax=ax)
>>>
>>> fig, ax = plt.subplots()
>>> img = fill_spec(details_arr, axes=ax,
>>>                 x_coords=obj.x_coords(audio_len),
>>>                 y_coords=obj.y_coords(),
>>>                 x_axis='time', y_axis='log',
>>>                 title='Cepstrogram - details')
>>> fig.colorbar(img, ax=ax)
>>>

Methods

cal_time_length(data_length)	Calculate the length of a frame from audio data.
cepstrogram(data_arr[, cep_num])	Get cepstrogram data
x_coords(data_length)	Get the X-axis coordinate
y_coords()	Get the Y-axis coordinate

cal_time_length(data_length)

Calculate the length of a frame from audio data.

• fft_length = 2 ** radix2_exp

• (data_length - fft_length) / slide_length + 1

Parameters

data_length: int

The length of the data to be calculated.

Returns

out: int

cepstrogram(data_arr, cep_num=4)

Get cepstrogram data

Parameters

data_arr: np.ndarray [shape=(…, n)]

Input audio data

cep_num: int, 4~128

formant estimate number

Returns

cepstrums: np.ndarray [shape=(…, fre, time), dtype=(np.float32)]

The matrix of cepstrums

envelope: np.ndarray [shape=(…, fre, time), dtype=(np.float32)]

The matrix of envelope(formant)

details: np.ndarray [shape=(…, fre, time), dtype=(np.float32)]

The matrix of details(tone)

y_coords()

Get the Y-axis coordinate

Returns

out: np.ndarray [shape=(fre,)]

x_coords(data_length)

Get the X-axis coordinate

Parameters

data_length: int

The length of the data to be calculated.

Returns

out: np.ndarray [shape=(time,)]