On the fly mp4 rewrapping server

#!/usr/bin/env python3

import asyncio
import sanic

app = sanic.Sanic("VOD Downloader")

STREAM_TPL = "https://vod.nebulabroadcast.com/sport5/{key}/index-f1-v1-f4-a1.m3u8"

class Rewrapper():
    def __init__(self, vod_key):
        source_url = STREAM_TPL.format(key=vod_key)
        self.args = [
            "-i", source_url,
            "-c:v", "copy",
            "-c:a", "copy",
            "-movflags", "frag_keyframe+empty_moov",
            "-bsf:a", "aac_adtstoasc",
            "-f", "mp4", "-"]

    async def start(self):
        self.proc = await asyncio.create_subprocess_exec("ffmpeg", *self.args, stdout=asyncio.subprocess.PIPE)

    async def read(self):
        return await self.proc.stdout.read(1024*1024)

    async def finish(self):
        await self.proc.wait()
        self.proc = None

    def __del__(self):
        if self.proc:
            print("Terminating rewrapper")
            self.proc.kill()
            asyncio.shield(self.proc.wait())

@app.route("/download/<vod_key:string>.mp4")
async def test(request, vod_key):

    async def streaming_fn(response):
        rewrapper = Rewrapper(vod_key)
        await rewrapper.start()
        while True:
            buff = await rewrapper.read()
            if not buff:
                break
            await response.write(buff)
        await rewrapper.finish()

    return sanic.response.stream(streaming_fn, content_type='video/mp4')

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=8910)