GStreamer Python example showing changing of videomixer position

test_videomixer_pos.py

import os
import sys
import time

def _prepend_env_path(name, value):
    os.environ[name] = os.pathsep.join(value +
                                       os.environ.get(name, "").split(os.pathsep))
CONFIGURED_GSTREAMER_PATH = r'C:\gstreamer\1.17\x86_64'
_prepend_env_path("PATH", [os.path.join(CONFIGURED_GSTREAMER_PATH, 'bin')])
sys.path.insert(0, os.path.join(CONFIGURED_GSTREAMER_PATH, 'lib', 'python3.7', 'site-packages'))

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

Gst.init(None)
desc = "videomixer name=mix sink_1::xpos=290 sink_1::ypos=10 ! videoconvert ! autovideosink sync=false " \
       "videotestsrc pattern=red ! video/x-raw,width=500,height=500 ! mix. " \
       "videotestsrc pattern=white ! video/x-raw,width=200,height=200 ! mix."
playbin = Gst.parse_launch(desc)

playbin.set_state(Gst.State.PLAYING)
mix = playbin.get_by_name('mix')
pad = mix.get_static_pad('sink_1')
time.sleep(1)
pad.set_property('xpos', 200)
time.sleep(1)
playbin.set_state(Gst.State.NULL)
Gst.deinit()