用 Python 在多个输出设备上播放多个声音文件

有想过用一台主机给不同的设备同时播放不同的音频文件吗？如果你正准备搭建一个DJ应用，需要实现一副耳机和一组扬声器的混音效果；又或者你需要构建一组包含许多个扬声器的音乐系统，而每个扬声器都需要播放不同的音频文件，彼此之间需要实现同步……

下面这个 DEMO 演示了用树莓派驱动8个不同的扬声器，分别播放8种不同的单声道音频文件，不仅有视频，更有必要的说明：

下面是所用的的零部件清单。

• 功放板
• USB 声卡
• DC/DC变压器
• USB HUB
• DC 接线端子

所需要的项目源代码在这里：
https://github.com/esologic/pear

参照图片连接树莓派、USB 声卡、功放、USB HUB、扬声器和电源。

Multi-Audio 范例

首先给树莓派安装 sounddevice，用下面的命令即可。

sudo apt-get install python3-pip python3-numpy libportaudio2 libsndfile1 
python3 -m pip install sounddevice soundfile

这里有4个音频文件，和 multi.py 在同一个目录下，目录结构如下。

multi_audio/
├── 1.wav
├── 2.wav
├── 3.wav
├── 4.wav
└── multi.py

这段代码基于 Python 的 sounddevice 库。

"""
multi.py, uses the sounddevice library to play multiple audio files to multiple output devices at the same time
Written by Devon Bray (dev@esologic.com)
"""

import sounddevice
import soundfile
import threading
import os


DATA_TYPE = "float32"


def load_sound_file_into_memory(path):
    """
    Get the in-memory version of a given path to a wav file
    :param path: wav file to be loaded
    :return: audio_data, a 2D numpy array
    """

    audio_data, _ = soundfile.read(path, dtype=DATA_TYPE)
    return audio_data


def get_device_number_if_usb_soundcard(index_info):
    """
    Given a device dict, return True if the device is one of our USB sound cards and False if otherwise
    :param index_info: a device info dict from PyAudio.
    :return: True if usb sound card, False if otherwise
    """

    index, info = index_info

    if "USB Audio Device" in info["name"]:
        return index
    return False


def play_wav_on_index(audio_data, stream_object):
    """
    Play an audio file given as the result of `load_sound_file_into_memory`
    :param audio_data: A two-dimensional NumPy array
    :param stream_object: a sounddevice.OutputStream object that will immediately start playing any data written to it.
    :return: None, returns when the data has all been consumed
    """

    stream_object.write(audio_data)


def create_running_output_stream(index):
    """
    Create an sounddevice.OutputStream that writes to the device specified by index that is ready to be written to.
    You can immediately call `write` on this object with data and it will play on the device.
    :param index: the device index of the audio device to write to
    :return: a started sounddevice.OutputStream object ready to be written to
    """

    output = sounddevice.OutputStream(
        device=index,
        dtype=DATA_TYPE
    )
    output.start()
    return output


if __name__ == "__main__":

    def good_filepath(path):
        """
        Macro for returning false if the file is not a non-hidden wav file
        :param path: path to the file
        :return: true if a non-hidden wav, false if not a wav or hidden
        """
        return str(path).endswith(".wav") and (not str(path).startswith("."))

    cwd = os.getcwd()
    sound_file_paths = [
        os.path.join(cwd, path) for path in sorted(filter(lambda path: good_filepath(path), os.listdir(cwd)))
    ]

    print("Discovered the following .wav files:", sound_file_paths)

    files = [load_sound_file_into_memory(path) for path in sound_file_paths]

    print("Files loaded into memory, Looking for USB devices.")

    usb_sound_card_indices = list(filter(lambda x: x is not False,
                                         map(get_device_number_if_usb_soundcard,
                                             [index_info for index_info in enumerate(sounddevice.query_devices())])))

    print("Discovered the following usb sound devices", usb_sound_card_indices)

    streams = [create_running_output_stream(index) for index in usb_sound_card_indices]

    running = True

    if not len(streams) > 0:
        running = False
        print("No audio devices found, stopping")

    if not len(files) > 0:
        running = False
        print("No sound files found, stopping")

    while running:

        print("Playing files")

        threads = [threading.Thread(target=play_wav_on_index, args=[file_path, stream])
                   for file_path, stream in zip(files, streams)]

        try:

            for thread in threads:
                thread.start()

            for thread, device_index in zip(threads, usb_sound_card_indices):
                print("Waiting for device", device_index, "to finish")
                thread.join()

        except KeyboardInterrupt:
            running = False
            print("Stopping stream")
            for stream in streams:
                stream.abort(ignore_errors=True)
                stream.close()
            print("Streams stopped")

    print("Bye.")

运行之后将分别在3个设备上播放 1.wav、2.wav 和 3.wav 音频文件。

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