python - 如何接收 “icecast”网络广播流以使用Python立即播放？

Question

我想获取互联网音频/广播流(特别是Longplayer，单击以获取直接流URL)并用python播放。

最好是在后台运行，以使脚本能够继续运行其主循环。 (例如，作为游戏背景音乐或其他东西，尽管Pyglet，PyGame等可能会为此提供自己的工具。)

我已经看到一些使用requests录制网络广播并将其转储到文件中的可能过时的示例，但这不是我想要的，答案的注释似乎包含有关requests的争论，尤其是其他问题？ (请参阅here)

我愿意使用可以pip的任何软件包，只要它可以在Python 3.X中使用。 (当前使用3.6纯粹是因为我还没有花大力气安装3.7)

重申一下，我不想保存该流，只需立即将其播放(或在需要时进行缓冲？)再返回给用户即可。最好是在不阻止脚本的情况下进行脚本，我想这需要多线程/多处理，但这仅次于播放。

Answer 1

这些似乎很简单的问题似乎总是如此，细节在于魔鬼。我最终写了一些代码来解决这个问题。可以使用python3 -m pip install ffmpeg-python PyOpenAL安装pip依赖项。代码的工作流程可以分为两个步骤:

该代码必须从在线流中下载mp3文件数据的二进制块并将其转换为原始PCM数据(基本带符号的uint16_t振幅值)以进行播放。这是使用the ffmpeg-python library(它是FFmpeg的包装器)完成的。该包装器在单独的进程中运行FFmpeg，因此此处不会发生阻塞。

然后，代码必须将这些块排队播放。这是使用PyOpenAL(它是OpenAL的包装器)完成的。创 build 备和上下文以启用音频播放后，将创建一个3d位置的源。该源连续与缓冲区(模拟“环形缓冲区”)排队，缓冲区中填充了从FFmpeg传入的数据。从第一步开始，它就在单独的线程上运行，从而使下载新的音频块独立于音频块回放而运行。

这是该代码的样子(带有一些注释)。如果您对代码或此答案的任何其他部分有任何疑问，请告诉我。

import ctypes
import ffmpeg
import numpy as np
from openal.al import *
from openal.alc import *
from queue import Queue, Empty
from threading import Thread
import time
from urllib.request import urlopen

def init_audio():
    #Create an OpenAL device and context.
    device_name = alcGetString(None, ALC_DEFAULT_DEVICE_SPECIFIER)
    device = alcOpenDevice(device_name)
    context = alcCreateContext(device, None)
    alcMakeContextCurrent(context)
    return (device, context)

def create_audio_source():
    #Create an OpenAL source.
    source = ctypes.c_uint()
    alGenSources(1, ctypes.pointer(source))
    return source

def create_audio_buffers(num_buffers):
    #Create a ctypes array of OpenAL buffers.
    buffers = (ctypes.c_uint * num_buffers)()
    buffers_ptr = ctypes.cast(
        ctypes.pointer(buffers), 
        ctypes.POINTER(ctypes.c_uint),
    )
    alGenBuffers(num_buffers, buffers_ptr)
    return buffers_ptr

def fill_audio_buffer(buffer_id, chunk):
    #Fill an OpenAL buffer with a chunk of PCM data.
    alBufferData(buffer_id, AL_FORMAT_STEREO16, chunk, len(chunk), 44100)

def get_audio_chunk(process, chunk_size):
    #Fetch a chunk of PCM data from the FFMPEG process.
    return process.stdout.read(chunk_size)

def play_audio(process):
    #Queues up PCM chunks for playing through OpenAL
    num_buffers = 4
    chunk_size = 8192
    device, context = init_audio()
    source = create_audio_source()
    buffers = create_audio_buffers(num_buffers)

    #Initialize the OpenAL buffers with some chunks
    for i in range(num_buffers):
        buffer_id = ctypes.c_uint(buffers[i])
        chunk = get_audio_chunk(process, chunk_size)
        fill_audio_buffer(buffer_id, chunk)

    #Queue the OpenAL buffers into the OpenAL source and start playing sound!
    alSourceQueueBuffers(source, num_buffers, buffers)
    alSourcePlay(source)
    num_used_buffers = ctypes.pointer(ctypes.c_int())

    while True:
        #Check if any buffers are used up/processed and refill them with data.
        alGetSourcei(source, AL_BUFFERS_PROCESSED, num_used_buffers)
        if num_used_buffers.contents.value != 0:
            used_buffer_id = ctypes.c_uint()
            used_buffer_ptr = ctypes.pointer(used_buffer_id)
            alSourceUnqueueBuffers(source, 1, used_buffer_ptr)
            chunk = get_audio_chunk(process, chunk_size)
            fill_audio_buffer(used_buffer_id, chunk)
            alSourceQueueBuffers(source, 1, used_buffer_ptr)

if __name__ == "__main__":    
    url = "http://icecast.spc.org:8000/longplayer"

    #Run FFMPEG in a separate process using subprocess, so it is non-blocking
    process = (
        ffmpeg
        .input(url)
        .output("pipe:", format='s16le', acodec='pcm_s16le', ac=2, ar=44100, loglevel="quiet")
        .run_async(pipe_stdout=True)
    )

    #Run audio playing OpenAL code in a separate thread
    thread = Thread(target=play_audio, args=(process,), daemon=True)
    thread.start()

    #Some example code to show that this is not being blocked by the audio.
    start = time.time()
    while True:
        print(time.time() - start)