从 pyaudio-stream 获取音频样本作为浮点数 [英] Get an audio sample as float number from pyaudio-stream

问题描述

由于我目前正准备构建一个基于 Raspberry Pi 的设备，用于测量用声卡记录的噪声(例如方差)中的一些东西，并尝试在 python 中执行此操作，我陷入了弄清楚如何获得音频样本作为浮点数以供进一步计算.

As I am currently about to build a device based on a Raspberry Pi for measuring some stuff from noise recorded with a sound card (e.g. variance), and trying to do this within python, I got stuck figuring out how to get a an audiosample as float-number for further calculations.

我做了什么:
使用 Line-In-to-chinch-Adapter 并接触插头以生成某种测试信号.
录制到例如 Audacity 或 Matlab 会显示合理的结果，例如

What did I do:
Took a Line-In-to-chinch-adapter and touching the plugs for generating some sort of test signal.
Recording to for example Audacity or Matlab shows plausible results, like

我想得到什么:
理想情况下，我想从声卡中获取例如 5 帧和 1024 个样本，并将它们转换为列表、元组或 numpy 数组作为浮点数以供进一步计算.

What I want to get:
In ideal, I want to get for example 5 frames á 1024 samples from the sound card, and convert them into a list, tuple or numpy array as a float number for further calculations.

当试图用 python/pyaudio 和本文末尾的代码实现这一点时，我得到了这样的东西:

When trying to achieve this with python/pyaudio with the code at the end of this post, I got something like this:

由于我使用 python 获得的值似乎与 Matlab(和其他)中的值相差大约两倍，我想我已经监督了某些事情或做错了什么.我想我在 struct.unpack 区域的某个地方犯了一个错误，但无法弄清楚究竟在哪里或为什么.我想请你帮忙，指出错误在哪里，我做错了什么.

Due to the fact that the values I got with python seem to differ from them in Matlab (and others) by the factor of about two, I think I've overseen something or did something wrong. I think I made a mistake somewhere at the struct.unpack region, but can't figure out where exactly or why. I'd like to ask you for help, pointing out where the error is and what I did wrong.

用于获取一些样本并绘制它们的小测试代码:

Little testcode for getting some samples and plotting them:

import pyaudio
import struct
import matplotlib.pyplot as plt

FORMAT = pyaudio.paFloat32
SAMPLEFREQ = 44100
FRAMESIZE = 1024
NOFFRAMES = 220
p = pyaudio.PyAudio()
print('running')

stream = p.open(format=FORMAT,channels=1,rate=SAMPLEFREQ,input=True,frames_per_buffer=FRAMESIZE)
data = stream.read(NOFFRAMES*FRAMESIZE)
decoded = struct.unpack(str(NOFFRAMES*FRAMESIZE)+'f',data)

stream.stop_stream()
stream.close()
p.terminate()
print('done')
plt.plot(decoded)
plt.show()

推荐答案

尝试使用numpy.fromstring"函数替换struct.unpack":

Try use "numpy.fromstring" function to replace "struct.unpack":

import numpy
stream = p.open(format=FORMAT,channels=1,rate=SAMPLEFREQ,input=True,frames_per_buffer=FRAMESIZE)
data = stream.read(NOFFRAMES*FRAMESIZE)
decoded = numpy.fromstring(data, 'Float32');

让我知道这是否适合您

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