正如這些看似簡(jiǎn)單的問(wèn)題似乎總是如此，魔鬼在細(xì)節(jié)中。我最終寫(xiě)了一些代碼來(lái)解決這個(gè)問(wèn)題。pip 依賴(lài)項(xiàng)可以使用python3 -m pip install ffmpeg-python PyOpenAL. 代碼的工作流程可以分為兩步：
代碼必須從在線流中下載 mp3 文件數(shù)據(jù)的二進(jìn)制塊，并將它們轉(zhuǎn)換為原始 PCM 數(shù)據(jù)（基本上是簽名的 uint16_t 幅度值）以進(jìn)行播放。這是使用ffmpeg-python 庫(kù)完成的，它是FFmpeg的包裝器。此包裝器在單獨(dú)的進(jìn)程中運(yùn)行 FFmpeg，因此此處不會(huì)發(fā)生阻塞。
然后代碼必須將這些塊排隊(duì)以進(jìn)行播放。這是使用PyOpenAL完成的，它是OpenAL的包裝器。在創(chuàng)建設(shè)備和上下文以啟用音頻播放后，將創(chuàng)建一個(gè) 3d 定位的源。這個(gè)源不斷地與緩沖區(qū)（模擬“環(huán)形緩沖區(qū)”）一起排隊(duì)，這些緩沖區(qū)填充了從 FFmpeg 輸入的數(shù)據(jù)。這與第一步在單獨(dú)的線程上運(yùn)行，使下載新音頻塊獨(dú)立于音頻塊播放運(yùn)行。
這是該代碼的樣子（帶有一些注釋?zhuān)Ｈ绻鷮?duì)代碼或此答案的任何其他部分有任何疑問(wèn)，請(qǐng)告訴我。
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)
