正交傅立叶梅林矩特征提取程序
时间: 2023-09-24 22:10:58 浏览: 44
对于正交傅立叶梅林矩特征提取,可以使用以下程序进行实现:
```python
import numpy as np
from scipy.fftpack import dct
def mel_filterbank(num_filters, num_fft, sample_rate, low_freq=0, high_freq=None):
if high_freq is None:
high_freq = sample_rate / 2
# 将线性频率转换为梅尔频率
low_mel = freq_to_mel(low_freq)
high_mel = freq_to_mel(high_freq)
# 在梅尔频率轴上均匀分布滤波器的中心
mel_centers = np.linspace(low_mel, high_mel, num_filters + 2)
# 将梅尔频率转换为线性频率
hertz_centers = mel_to_freq(mel_centers)
# 在FFT中计算滤波器的位置
fft_bins = np.arange(num_fft // 2 + 1) * sample_rate / num_fft
# 为每个滤波器计算其在FFT中的位置
filterbank = np.zeros((num_filters, num_fft // 2 + 1))
for i in range(num_filters):
# 计算滤波器在FFT中的左、中、右的三个位置
left = np.argmax(fft_bins >= hertz_centers[i])
center = np.argmax(fft_bins >= hertz_centers[i + 1])
right = np.argmax(fft_bins >= hertz_centers[i + 2])
# 线性上升
increment = 1 / (center - left)
for j in range(left, center):
filterbank[i, j] = (j - left) * increment
# 线性下降
decrement = 1 / (right - center)
for j in range(center, right):
filterbank[i, j] = 1 - ((j - center) * decrement)
return filterbank
def freq_to_mel(freq):
return 2595 * np.log10(1 + freq / 700)
def mel_to_freq(mel):
return 700 * (10 ** (mel / 2595) - 1)
def extract_mfcc(signal, sample_rate, num_mfcc=13, num_filters=26, num_fft=512, low_freq=0, high_freq=None):
if high_freq is None:
high_freq = sample_rate / 2
# 计算MFCC所需的滤波器组
filterbank = mel_filterbank(num_filters, num_fft, sample_rate, low_freq, high_freq)
# 计算信号的功率谱密度
spectrum = np.abs(np.fft.rfft(signal, num_fft)) ** 2
# 将功率谱密度转换为dB
spectrum = 20 * np.log10(spectrum / np.max(spectrum))
# 将信号传递到滤波器组中,并将结果转换为dB
filtered = np.dot(spectrum, filterbank.T)
filtered = 20 * np.log10(filtered / np.max(filtered))
# 计算MFCC系数
mfcc = dct(filtered, type=2, axis=1, norm='ortho')[:, 1:num_mfcc + 1]
return mfcc
```
这个程序实现了一个函数`extract_mfcc`,它接受一个音频信号、采样率以及一些参数,返回一个MFCC系数矩阵。具体而言,它使用傅立叶变换计算信号的功率谱密度,然后将其传递到一个滤波器组中,以获得每个滤波器的幅度响应。然后,它对每个滤波器的响应进行离散余弦变换,并返回前num_mfcc个系数作为MFCC特征。