Python实现PCM编码，LPC编码和ADPCM编码【语音信号处理实战】.zip

import numpy as np def adpcm_decoder(code, sign_bit): """ APDCM解码函数 :param code: :param sign_bit: :return: """ l = len(code) y = np.zeros(l) ss2 = np.zeros(l) ss2[0] = 1 # 生成步长查找表 index = [-1, 4] currentIndex = 0 startval = 1 endval = 127 base = np.exp(np.log(2) / 8) # 近似步长 const = startval / base numSteps = int(round(np.log(endval / const) / np.log(base))) n = [i + 1 for i in range(numSteps)] base = np.exp(np.log(endval / startval) / (numSteps - 1)) const = startval / base tabel2 = np.round(const * np.power(base, n)) for n in range(1, l): neg = code[n] >= sign_bit if neg: temp = code[n] - sign_bit else: temp = code[n] temp2 = (temp + 0.5) * ss2[n - 1] if neg: temp2 = -temp2 y[n] = y[n - 1] + temp2 if y[n] > 127: y[n] = 127 elif y[n] < -127: y[n] = -127 # 计算新的步长 currentIndex += index[int(temp)] if currentIndex < 0: currentIndex = 0 elif currentIndex > numSteps: currentIndex = numSteps ss2[n] = tabel2[currentIndex] return y / 128 def adpcm_encoder(x, sign_bit): """ APDCM编码函数 :param x: :param sign_bit: :return: """ x *= 128 l = len(x) # 生成步长查找表 index = [-1, 4] currentIndex = 1 startval = 1 endval = 127 base = np.exp(np.log(2) / 8) # 近似步长 const = startval / base numSteps = int(round(np.log(endval / const) / np.log(base))) n = [i + 1 for i in range(numSteps)] base = np.exp(np.log(endval / startval) / (numSteps - 1)) const = startval / base tabel2 = np.round(const * np.power(base, n)) ss = np.zeros(l) ss[0] = tabel2[0] z = np.zeros(l) code = np.zeros(l) d = np.zeros(l) neg = 0 for n in range(1, l): d[n] = x[n] - z[n - 1] if d[n] < 0: neg = 1 code[n] += sign_bit d[n] = -d[n] else: neg = 0 if d[n] >= ss[n - 1]: code[n] += 1 if neg: temp = code[n] - sign_bit else: temp = code[n] temp2 = (temp + 0.5) * ss[n - 1] if neg: temp2 = -temp2 z[n] = z[n - 1] + temp2 if z[n] > 127: z[n] = 127 elif z[n] < -127: z[n] = -127 # 计算新的步长 currentIndex += index[int(temp)] if currentIndex < 0: currentIndex = 0 elif currentIndex > numSteps: currentIndex = numSteps ss[n] = tabel2[currentIndex] return code