How to use the av.CodecContext.create function in av

# We haven't exposed bitstream filters yet, so we're gonna use the `ffmpeg` CLI.
h264_path = 'night-sky.h264'
if not os.path.exists(h264_path):
    subprocess.check_call([
        'ffmpeg',
        '-i', av.datasets.curated('pexels/time-lapse-video-of-night-sky-857195.mp4'),
        '-vcodec', 'copy',
        '-an',
        '-bsf:v', 'h264_mp4toannexb',
        h264_path,
    ])


fh = open(h264_path, 'rb')

codec = av.CodecContext.create('h264', 'r')

while True:

    chunk = fh.read(1 << 16)

    packets = codec.parse(chunk)
    print("Parsed {} packets from {} bytes:".format(len(packets), len(chunk)))

    for packet in packets:

        print('   ', packet)

        frames = codec.decode(packet)
        for frame in frames:
            print('       ', frame)

def __init__(self) -> None:
        self.codec = av.CodecContext.create("h264", "r")

def _encode_frame(
        self, frame: av.VideoFrame, force_keyframe: bool
    ) -> Iterator[bytes]:
        if self.codec and (
            frame.width != self.codec.width or frame.height != self.codec.height
        ):
            self.codec = None

        if self.codec is None:
            self.codec = av.CodecContext.create("libx264", "w")
            self.codec.width = frame.width
            self.codec.height = frame.height
            self.codec.pix_fmt = "yuv420p"
            self.codec.time_base = fractions.Fraction(1, MAX_FRAME_RATE)
            self.codec.options = {
                "profile": "baseline",
                "level": "31",
                "tune": "zerolatency",
            }

        packages = self.codec.encode(frame)
        yield from self._split_bitstream(b"".join(p.to_bytes() for p in packages))