python - Python麦克风输入和低通滤镜效果实时

Question

我正在尝试使用覆盆子pi接收麦克风输入，并添加一种效果，以对麦克风输入实时输出低通音频滤波器效果。他们那里有许多python音频库，例如声音pi / py音频。如果有人可以帮助我实现这一目标。

亲切的问候。

Answer 1

我没有树莓派，但是我已经在Windows上尝试了类似python的方法。我假设您可以修改此程序以适合您的需求。

为此，您将需要安装pyaudiopip install pyaudio
可以从here下载的python sounddevice
该程序:
记录麦克风的音频
用限制器限制音频
播放修改后的音频
绘制原始和修改后的音频

Python代码

from pyaudio import PyAudio, paContinue, paFloat32
from time import sleep
from numpy import array, random, arange, float32, float64, zeros
import matplotlib.pyplot as plt
import sounddevice as sd

################################### Constants ##################################

fs            = 44100   # Hz
threshold     = 0.8     # absolute gain
delay         = 40      # samples
signal_length = 1      # second
release_coeff = 0.5555  # release time factor
attack_coeff  = 0.5     # attack time factor
dtype         = float32 # default data type
block_length  = 1024    # samples

############################# Implementation of Limiter ########################

class Limiter:
    def __init__(self, attack_coeff, release_coeff, delay, dtype=float32):
        self.delay_index = 0
        self.envelope = 0
        self.gain = 1
        self.delay = delay
        self.delay_line = zeros(delay, dtype=dtype)
        self.release_coeff = release_coeff
        self.attack_coeff = attack_coeff

    def limit(self, signal, threshold):
        for i in arange(len(signal)):
            self.delay_line[self.delay_index] = signal[i]
            self.delay_index = (self.delay_index + 1) % self.delay

            # calculate an envelope of the signal
            self.envelope *= self.release_coeff
            self.envelope  = max(abs(signal[i]), self.envelope)

            # have self.gain go towards a desired limiter gain
            if self.envelope > threshold:
                target_gain = (1+threshold-self.envelope)
            else:
                target_gain = 1.0
            self.gain = ( self.gain*self.attack_coeff +
                          target_gain*(1-self.attack_coeff) )

            # limit the delayed signal
            signal[i] = self.delay_line[self.delay_index] * self.gain



################### Record Audio from Microphone #########################    

print "Recording Audio"
signal = sd.rec(signal_length * fs, samplerate=fs, channels=1, dtype=dtype)
sd.wait()
print "Audio recording complete , Play Audio"



################################# Play the Audio ###############################

original_signal = array(signal, copy=True, dtype=dtype)
limiter = Limiter(attack_coeff, release_coeff, delay, dtype)

def callback(in_data, frame_count, time_info, flag):
    if flag:
        print("Playback Error: %i" % flag)
    played_frames = callback.counter
    callback.counter += frame_count
    limiter.limit(signal[played_frames:callback.counter], threshold)
    return signal[played_frames:callback.counter], paContinue

callback.counter = 0

pa = PyAudio()

stream = pa.open(format = paFloat32,
                 channels = 1,
                 rate = fs,
                 frames_per_buffer = block_length,
                 output = True,
                 stream_callback = callback)

while stream.is_active():
    sleep(0.1)

stream.close()
pa.terminate()

############################## Plot results ####################################

plt.figure()
plt.plot(original_signal, color='green', label='original signal')
plt.plot(signal, color='red', label='limited signal')
plt.legend()
plt.show(block=True)
############################## End Program ####################################

终端输出

Python 2.7.9 (default, Dec 10 2014, 12:24:55) [MSC v.1500 32 bit (Intel)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> ================================ RESTART ================================
>>> 
Recording Audio
Audio recording complete , Play Audio
>>> 

影像输出