Python读取输出声音没有输入

Question

有关读取系统声级的最简单方法的任何线索是什么？

我打算用短的LED灯带制作均衡器并将它们连接到Arduino或RaspberryPi上。我已经看到很多例子如何使用输入，麦克风等，但总体输出不是那么多。在这一点上，我不关心程序特定或系统范围，当我真正获得读数时，我很高兴。任何建议都会受到欢迎。

- 编辑 -

基于How get sound input from microphone in python, and process it on the fly?我将PCM_CAPTURE更改为PCM_PLAYBACK，这导致python表示在输出/回放时无法读取。

我现在正在尝试创建一个环回设备，想法是将播放回送到单独的捕获并然后读取它但是到目前为止没有运气，我不知道这种方式是多么干净/干净。我无法想象这是要走的路。

Answer 1

有人使用Python和PulseAudio实现了这一点，请参阅this blog posting。作者编写了一个脚本，用于调查系统范围的峰值声级，将其提供给VU表。他还在Bitbucket上提供了源代码，here。

我在Ubuntu上测试了它，它适用于我（虽然只能从命令行，而不是在交互式Python会话中）。一些额外的工作是安装一个ctypes PulseAudio包装器，用于连接Python（源代码中的链接），并可能在脚本中将SINK_NAME设置为正确的值。

我从博客中收集的内容PulseAudio非常适合这项工作，但也许有更好的方法。

Answer 2

几乎任何类型的混音器（软件或硬件）都应该能够将声音输出重新路由到输入。对于Windows，内置Stereo Mix，对于Linux有几种解决方案（我听过PulseAudio的好消息，但我无法证明自己 - {{3}中的一些步骤可能有帮助）。

这样你可以将它路由到Python - 你读过的读取麦克风级别的例子应该也可以正常工作。

Answer 3

我发现了这个github solution：

我将 python 程序设置为一个单独的实例，因此它不会滞后于我的主程序。然后每 33 毫秒 (30 fps) 轮询一次 IPC 泡菜。我对代码进行了一些修改，如下所示：

#!/usr/bin/env python
# -*- coding: utf-8 -*-

#==============================================================================
#
#       vu_meter.py - Listen to microphone left/right and generate vu level
#
#==============================================================================
"""

FROM: https://github.com/kmein/vu-meter

.gitignore          NOT INSTALLED
LICENSE             NOT INSTALLED
README.md           NOT INSTALLED
amplitude.py                        THIS MODULE
record.py           NOT INSTALLED
vu_constants.py                     THIS MODULE
vu_meter.py                         THIS MODULE

ENHANCEMENTS:

    1) Support Python environment variable for automatic python 2 / 3 selection
    2) Add UTF-8 to support Python 2 (not necessary in this program though)
    3) Reset maximal between songs (gap when 10 samples of zero strength)
    4) Remove console output and write values to ramdisk (/run/user/1000)
    5) Optional 'stereo' parameter to measure left & right channels
    6) Utilize numpy which is usually auto-installed on distros
    7) Include separate amplitute.py & vu_constants.py in main
    8) Remove unused functions from Amplitude class

"""

from __future__ import print_function       # Must be first import
from __future__ import with_statement       # Error handling for file opens

import pyaudio
import numpy as np              # January 24, 2021 support separate 2 channels
import sys
import math
import struct
#from amplitude import Amplitude

RATE = 44100
INPUT_BLOCK_TIME = 0.05
INPUT_FRAMES_PER_BLOCK = int(RATE*INPUT_BLOCK_TIME)
SHORT_NORMALIZE = 1.0 / 32768.0
# Mono output
VU_METER_FNAME  = "/run/user/1000/mserve.vu-meter-mono.txt"
# Stereo output (Left and Right)
VU_METER_LEFT_FNAME  = "/run/user/1000/mserve.vu-meter-left.txt"
VU_METER_RIGHT_FNAME  = "/run/user/1000/mserve.vu-meter-right.txt"


class Amplitude(object):
    ''' an abstraction for Amplitudes (with an underlying float value)
    that packages a display function and many more
    
    January 25, 2021 - Remove unused add, subb, gt, eq, int & str functions
    '''

    def __init__(self, value=0):
        self.value = value

    def __lt__(self, other):
        return self.value < other.value

    def to_int(self, scale=1):
        ''' convert an amplitude to an integer given a scale such that one can
        choose the precision of the resulting integer '''
        return int(self.value * scale)

    @staticmethod
    def from_data(block):
        ''' generate an Amplitude object based on a block of audio input data '''
        count = len(block) / 2
        shorts = struct.unpack("%dh" % count, block)
        sum_squares = sum(s**2 * SHORT_NORMALIZE**2 for s in shorts)
        return Amplitude(math.sqrt(sum_squares / count))

    def display(self, mark, scale=50, fn=VU_METER_FNAME):
        ''' display an amplitude and another (marked) maximal Amplitude
        graphically '''
        int_val = self.to_int(scale)
        mark_val = mark.to_int(scale)
        delta = abs(int_val - mark_val)
        # print(int_val * '*', (delta-1) * ' ', '|',mark_val,int_val,delta)
        # January 23, 2021: Write values to ramdisk instead of displaying
        with open(fn, "w") as vufile:
            vufile.write(str(mark_val) + " " + str(int_val))


def parse_data(data, channel_ndx, channel_cnt, maximal):
    '''
        Process data from one channel
    '''
    data = np.fromstring(data,dtype=np.int16)[channel_ndx::channel_cnt]
    data = data.tostring()
    amp = Amplitude.from_data(data)
    gap = amp.value      # For signal test below.
    if amp > maximal:
        maximal = amp
    return amp, maximal, gap


def main():

    # January 24, 2021 separate left and right channels
    parameter = 'mono'
    if (len(sys.argv)) == 2:
        parameter = sys.argv[1]     # Null = 'mono', 'stereo' = Left & Right

    audio = pyaudio.PyAudio()
    reset_baseline_count = 0
    try:
        stream = audio.open(format=pyaudio.paInt16,
                            channels=2,
                            rate=RATE,
                            input=True,
                            frames_per_buffer=INPUT_FRAMES_PER_BLOCK
                           )

        maximal = Amplitude()
        maximal_l = maximal_r = maximal

        while True:
            data = stream.read(INPUT_FRAMES_PER_BLOCK)

            # January 24, 2021 separate left and right channels
            if parameter == 'stereo':
                ampl, maximal_l, gap = parse_data(data, 0, 2, maximal_l)
                ampr, maximal_r, gap = parse_data(data, 1, 2, maximal_r)
                if maximal_r < maximal_l:
                    # A momentary spike to left channel inherited by right
                    maximal_r = maximal_l
                if maximal_l < maximal_r:
                    # A momentary spike to right channel inherited by left
                    maximal_l = maximal_r
            else:
                # Mono - processing all dadta
                amp = Amplitude.from_data(data)
                gap = amp.value      # For signal test below.
                if amp > maximal:
                    maximal = amp

            # New code January 23, to reset next song's maximal during gap
            if gap == 0.0:
                reset_baseline_count += 1
                if reset_baseline_count == 10:
                    maximal = Amplitude()
                    maximal_l = maximal_r = maximal
                    # print('maximual reset', maximal.value)
            else:
                reset_baseline_count = 0

            # January 24, 2021 separate left and right channels
            if parameter == 'stereo':
                ampl.display(scale=200, mark=maximal_l, fn=VU_METER_LEFT_FNAME)
                ampr.display(scale=200, mark=maximal_r, fn=VU_METER_RIGHT_FNAME)
            else:
                # Mono processing one channel combined sound
                amp.display(scale=200, mark=maximal, fn=VU_METER_FNAME)

    finally:
        stream.stop_stream()
        stream.close()
        audio.terminate()

if __name__ == "__main__":
    main()