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。
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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