Passing OpenCV Mats to GStreamer pipeline without VideoWriter

main.py

import cv2
import gi

gi.require_version("Gst", "1.0")
from gi.repository import Gst  # isort:skip

WIDTH = 320
HEIGHT = 240
FPS = 30


def need_data(bus, msg):
    try:
        ret, frame = cap.read()
        buf = Gst.Buffer.new_wrapped(frame.tostring())
        appsrc.emit("push-buffer", buf)
    except StopIteration:
        appsrc.emit("end-of-stream")


Gst.init(None)

pipeline = Gst.Pipeline.new(None)

appsrc = Gst.ElementFactory.make("appsrc")
caps = Gst.Caps.from_string(
    f"video/x-raw,format=BGR,width={WIDTH},height={HEIGHT},framerate={FPS}/1"
)
appsrc.set_property("caps", caps)
appsrc.connect("need-data", need_data)

cap = cv2.VideoCapture(0)
cap.set(cv2.CAP_PROP_FRAME_WIDTH, WIDTH)
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, HEIGHT)
cap.set(cv2.CAP_PROP_FPS, FPS)

videoparse = Gst.ElementFactory.make("videoconvert")
xvimagesink = Gst.ElementFactory.make("xvimagesink")

pipeline.add(appsrc)
pipeline.add(videoparse)
pipeline.add(xvimagesink)

appsrc.link(videoparse)
videoparse.link(xvimagesink)

pipeline.set_state(Gst.State.PLAYING)
bus = pipeline.get_bus()
bus.timed_pop_filtered(Gst.CLOCK_TIME_NONE, Gst.MessageType.ERROR | Gst.MessageType.EOS)
pipeline.set_state(Gst.State.NULL)