如何在输入流上播放声音

Question

我在想，能不能直接从Python里把声音播放到一个输入设备上。我现在用的是Linux系统，同时还在用OSS、ALSA和Pulseaudio这些工具。

Answer 1

我想这要看你拿到数据后想用它做什么。如果你想处理声音的话，我推荐你看看scikits.audiolab这个库。这个库可以帮助你绘制声音的频谱图，我猜这正是你想要做的事情吧？

Answer 2

你完全可以用Python来播放（和生成）声音。

这里有一个示例代码，它会生成一个正弦波，打开默认的Alsa播放设备，并通过这个设备播放正弦波。

#!/usr/bin/env python3
import math
import struct
import alsaaudio
from itertools import *

def sine_wave(frequency=440.0, framerate=44100, amplitude=0.5):
    """Stolen from here: http://zacharydenton.com/generate-audio-with-python/"""
    period = int(framerate / frequency)
    if amplitude > 1.0: amplitude = 1.0
    if amplitude < 0.0: amplitude = 0.0
    lookup_table = [float(amplitude) * math.sin(2.0*math.pi*float(frequency)*(float(i%period)/float(framerate))) for i in range(period)]
    return (lookup_table[i%period] for i in count(0))

sound_out = alsaaudio.PCM()  # open default sound output
sound_out.setchannels(1)  # use only one channel of audio (aka mono)
sound_out.setrate(44100)  # how many samples per second
sound_out.setformat(alsaaudio.PCM_FORMAT_FLOAT_LE)  # sample format

for sample in sine_wave():
    # alsa only eats binnary data
    b = struct.pack("<f", sample)  # convert python float to binary float
    sound_out.write(b)

或者你可以把麦克风的声音回放到扬声器上。

#!/usr/bin/env python3
import struct
import alsaaudio

sound_out = alsaaudio.PCM()  # open default sound output
sound_out.setchannels(1)  # use only one channel of audio (aka mono)
sound_out.setperiodsize(5) # buffer size, default is 32

sound_in = alsaaudio.PCM(type=alsaaudio.PCM_CAPTURE)  # default recording device
sound_in.setchannels(1)  # use only one channel of audio (aka mono)
sound_in.setperiodsize(5) # buffer size, default is 32

while True:
    sample_lenght, sample = sound_in.read()
    sound_out.write(sample)

在Python的alsaaudio库中还有很多其他的例子可以找到，链接是 http://pyalsaaudio.sourceforge.net/libalsaaudio.html

如何在输入流上播放声音

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