为什么MFCC提取libs返回不同的值？

Question

我使用两个不同的库提取MFCC功能：

• python_speech_特性库
• 鲍勃图书馆

但是两者的输出是不同的，甚至形状也不一样。这正常吗？或者我缺少一个参数？在

我的代码的相关部分如下：

import bob.ap
import numpy as np
from scipy.io.wavfile import read
from sklearn import preprocessing
from python_speech_features import mfcc, delta, logfbank

def bob_extract_features(audio, rate):
    #get MFCC
    rate              = 8000  # rate
    win_length_ms     = 30    # The window length of the cepstral analysis in milliseconds
    win_shift_ms      = 10    # The window shift of the cepstral analysis in milliseconds
    n_filters         = 26    # The number of filter bands
    n_ceps            = 13    # The number of cepstral coefficients
    f_min             = 0.    # The minimal frequency of the filter bank
    f_max             = 4000. # The maximal frequency of the filter bank
    delta_win         = 2     # The integer delta value used for computing the first and second order derivatives
    pre_emphasis_coef = 0.97  # The coefficient used for the pre-emphasis
    dct_norm          = True  # A factor by which the cepstral coefficients are multiplied
    mel_scale         = True  # Tell whether cepstral features are extracted on a linear (LFCC) or Mel (MFCC) scale

    c = bob.ap.Ceps(rate, win_length_ms, win_shift_ms, n_filters, n_ceps, f_min,
                    f_max, delta_win, pre_emphasis_coef, mel_scale, dct_norm)
    c.with_delta       = False
    c.with_delta_delta = False
    c.with_energy      = False

    signal = np.cast['float'](audio)           # vector should be in **float**
    example_mfcc = c(signal)                   # mfcc + mfcc' + mfcc''
    return  example_mfcc


def psf_extract_features(audio, rate):
    signal = np.cast['float'](audio) #vector should be in **float**
    mfcc_feature = mfcc(signal, rate, winlen = 0.03, winstep = 0.01, numcep = 13,
                        nfilt = 26, nfft = 512,appendEnergy = False)

    #mfcc_feature = preprocessing.scale(mfcc_feature)
    deltas       = delta(mfcc_feature, 2)
    fbank_feat   = logfbank(audio, rate)
    combined     = np.hstack((mfcc_feature, deltas))
    return mfcc_feature



track = 'test-sample.wav'
rate, audio = read(track)

features1 = psf_extract_features(audio, rate)
features2 = bob_extract_features(audio, rate)

print("--------------------------------------------")
t = (features1 == features2)
print(t)

Answer 1

你试过用宽容的眼光来比较这两者吗？我相信这两个mfcc是浮点数数组，测试是否完全相等可能不是明智之举。尝试使用带有一定公差的numpy.testing.assert_allclose，并确定该公差是否足够好。在

尽管如此，我想你说即使形状不匹配，我没有经验鲍勃.ap自信地对此发表评论。然而，由于窗口化的原因，一些库经常在输入数组的开始或结尾用零填充输入，如果其中一个库的操作方式不同，这可能是造成这种情况的原因。在

Answer 2

However the output of the two is different and even the shapes are not the same. Is that normal?

是的，有不同种类的算法，每个实现都有自己的风格

or is there a parameter that I am missing?

它不仅仅是关于参数，还有一些算法上的差异，如窗口形状（hamming vs hanning）、mel过滤器的形状、mel过滤器的开始、mel过滤器的规范化、提升、dct风格等等。在

如果你想要相同的结果，只需使用单一的库进行提取，同步它们是非常无望的。在