如何在Linux系统中使用Python获取系统音频输出的相对音量？

Got it, let's tackle this problem—you want to grab the relative loudness of audio being played through your Linux speakers using Python, not just the system volume level (like the slider setting). Here are a couple of reliable, distro-agnostic approaches that work for most setups:

Approach 1: Use PulseAudio's parec + Numpy (Simple & Effective) #

Most Linux systems use PulseAudio as their audio server, so we can leverage its built-in tools to capture the "monitor" output (the audio being sent to speakers) and calculate relative loudness via RMS (Root Mean Square) — this metric directly correlates to perceived sound intensity.

Step 1: Install Dependencies #

First, make sure you have the required tools and libraries:

# For Debian/Ubuntu-based distros
sudo apt install pulseaudio-tools python3-numpy

# For Fedora/RHEL-based distros
sudo dnf install pulseaudio-utils python3-numpy

Step 2: Python Code to Calculate Relative Loudness #

This script will capture the monitor audio stream, compute the RMS value, and print the relative loudness (higher = louder):

import subprocess
import numpy as np

def get_relative_loudness():
    # Configure parec to capture monitor output (16-bit, mono, 44.1kHz)
    cmd = [
        "parec",
        "--format=s16le",
        "--rate=44100",
        "--channels=1",
        "--monitor-stream"
    ]
    
    # Start the parec process and read raw audio data
    process = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)
    
    # Read a chunk of audio data (adjust chunk size for responsiveness)
    chunk = process.stdout.read(44100 * 2)  # 1 second of data (16-bit = 2 bytes per sample)
    if not chunk:
        return 0.0
    
    # Convert raw bytes to numpy array of integers
    audio_data = np.frombuffer(chunk, dtype=np.int16)
    
    # Calculate RMS (relative loudness) — normalize to 0-1 range
    rms = np.sqrt(np.mean(audio_data**2))
    normalized_rms = rms / np.iinfo(np.int16).max  # Max value for 16-bit audio
    
    process.terminate()
    return round(normalized_rms, 4)

# Example usage
if __name__ == "__main__":
    loudness = get_relative_loudness()
    print(f"Relative Loudness: {loudness}")

Approach 2: Use PyAudio (More Control Over Audio Streams) #

If you prefer a pure-Python approach without relying on external CLI tools, PyAudio can access the PulseAudio monitor device directly.

Step 1: Install Dependencies #

pip install pyaudio
sudo apt install portaudio19-dev  # Required for PyAudio on Debian/Ubuntu

Step 2: Python Code with PyAudio #

First, find your monitor device name using pactl list sources — look for entries like "Monitor of Built-in Audio Analog Stereo". Then use this script:

import pyaudio
import numpy as np

def get_monitor_device_index(p, device_name_substring="Monitor"):
    # Find the index of the PulseAudio monitor device
    for i in range(p.get_device_count()):
        info = p.get_device_info_by_index(i)
        if device_name_substring in info["name"]:
            return i
    raise ValueError("Monitor device not found — check your PulseAudio setup")

def get_relative_loudness():
    p = pyaudio.PyAudio()
    monitor_index = get_monitor_device_index(p)
    
    # Configure audio stream (match monitor device parameters)
    stream = p.open(
        format=pyaudio.paInt16,
        channels=1,
        rate=44100,
        input=True,
        input_device_index=monitor_index,
        frames_per_buffer=44100
    )
    
    # Read audio data
    chunk = stream.read(44100)
    audio_data = np.frombuffer(chunk, dtype=np.int16)
    
    # Calculate normalized RMS
    rms = np.sqrt(np.mean(audio_data**2))
    normalized_rms = rms / np.iinfo(np.int16).max
    
    stream.stop_stream()
    stream.close()
    p.terminate()
    
    return round(normalized_rms, 4)

# Example usage
if __name__ == "__main__":
    try:
        loudness = get_relative_loudness()
        print(f"Relative Loudness: {loudness}")
    except ValueError as e:
        print(e)

Key Notes #

• RMS Explained: The normalized RMS value ranges roughly from 0 (silent) to 1 (maximum loudness). It’s a great proxy for perceived relative loudness.
• Permissions: Make sure your user is in the audio group to access PulseAudio devices: sudo usermod -aG audio $USER (log out and back in after this).
• Responsiveness: Adjust the chunk size in either script if you want faster updates (smaller chunks) or smoother readings (larger chunks).

内容的提问来源于stack exchange，提问作者Corey Campbell