python - 在Python中给定NumPy数组的情况下，如何流式传输MP3 block ？

Question

我正在努力寻找一种解决方案，用于从Python服务器流式传输合成音频。合成的音频将增量生成，并作为np.float32 NumPy数组返回。然后需要将其从NumPy数组转换为MP3块。最后，MP3块通过flask提供服务。

这是一些伪代码:

import numpy

from flask import Flask
from flask import Response

app = Flask(__name__)
sample_rate = 24000


def pcm_to_mp3():
    raise NotImplementedError()


def get_synthetic_audio():
    """ Mock function for synthetic audio. """
    while True:
        yield numpy.random.rand(1024) * 2 - 1  # Return: 32-bit Floating Point PCM


@app.route('/stream', methods=['GET'])
def get_stream():
    """ Stream synthetic audio. """

    def response():
        for numpy_array in get_synthetic_audio():
            # NOTE: The raw audio needs additional metadata to be playable like sample rate.
            yield pcm_to_mp3(numpy_array, sample_rate=sample_rate)

    return Response(
        response(),
        headers={
            # NOTE: Ensure stream is not cached.
            'Cache-Control': 'no-cache, no-store, must-revalidate',
            'Pragma': 'no-cache',
            'Expires': '0',
            # NOTE: Enable streaming.
            'Transfer-Encoding': 'chunked'
        },
        mimetype='audio/mpeg')


if __name__ == "__main__":
    app.run()

虽然类似的设置适用于WAV文件，但我无法弄清楚如何对MP3文件执行类似的操作。

谢谢!

来源

通过PyDub将NumPy数组转换为MP3文件:How to read a MP3 audio file into a numpy array / save a numpy array to MP3?

带有 flask 的

流音频WAV文件:HTTP realtime audio streaming server

使用PyAudio流音频WAV文件:Python: realtime audio streaming with PyAudio (or something else)?

带有FFMpeg和Flask的

流:https://gist.github.com/anthonyeden/f3b3bdf6f62badd8f87bb574283f488a

Answer 1

我能够找出一种可行的方法:

import select
import subprocess

import numpy

from flask import Flask
from flask import Response

app = Flask(__name__)


def get_synthetic_audio(num_samples):
    audio = numpy.random.rand(num_samples).astype(numpy.float32) * 2 - 1
    assert audio.max() <= 1.0
    assert audio.min() >= -1.0
    assert audio.dtype == numpy.float32
    return audio


def response():
    pipe = subprocess.Popen(
        'ffmpeg -f f32le -acodec pcm_f32le -ar 24000 -ac 1 -i pipe: -f mp3 pipe:'
        .split(),
        stdin=subprocess.PIPE,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE)
    poll = select.poll()
    poll.register(pipe.stdout, select.POLLIN)
    while True:
        pipe.stdin.write(get_synthetic_audio(24000).tobytes())
        while poll.poll(0):
            yield pipe.stdout.readline()


@app.route('/stream.mp3', methods=['GET'])
def stream():
    return Response(
        response(),
        headers={
            # NOTE: Ensure stream is not cached.
            'Cache-Control': 'no-cache, no-store, must-revalidate',
            'Pragma': 'no-cache',
            'Expires': '0',
        },
        mimetype='audio/mpeg')


if __name__ == "__main__":
    app.run(host='0.0.0.0', port=8000, debug=True)

在探索过程中，我了解到 flask不支持分块传输编码。这是令人惊讶的，因为分块传输编码是1997年作为HTTP 1.1的一部分引入的。

无论如何，令我惊讶的是， ffmpeg的流与 flask兼容，并且Safari，Firefox和Chrome支持该流。