如何在GStreamer中使用Opencv VideoWriter？

import cv2
import gi
gi.require_version('Gst', '1.0')
from gi.repository import Gst

Gst.init(None)

pipeline = Gst.Pipeline()

src = Gst.ElementFactory.make("appsrc", "source")
caps = Gst.Caps.from_string("video/x-raw, format=BGR")
src.set_property("caps", caps)
pipeline.add(src)

filter = Gst.ElementFactory.make("capsfilter", "filter")
filter.set_property("caps", caps)
pipeline.add(filter)

encoder = Gst.ElementFactory.make("videoconvert", "encoder")
pipeline.add(encoder)

muxer = Gst.ElementFactory.make("avimux", "muxer")
pipeline.add(muxer)

sink = Gst.ElementFactory.make("filesink", "sink")
sink.set_property("location", "output.avi")
pipeline.add(sink)

src.link(filter)
filter.link(encoder)
encoder.link(muxer)
muxer.link(sink)

pipeline.set_state(Gst.State.PLAYING)

cap = cv2.VideoCapture("input.mp4")
while True:
    ret, frame = cap.read()
    if not ret:
        break

    data = frame.tostring()
    buf = Gst.Buffer.new_allocate(None, len(data), None)
    buf.fill(0, data)
    src.emit("push-buffer", buf)

cap.release()

pipeline.set_state(Gst.State.NULL)