Example of using input from a Blackmagic Decklink or Ultrastudio card in kivy with the use of OpenCV and GStreamer.

kivy_decklink.py

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.image import Image
from kivy.clock import Clock
from kivy.graphics.texture import Texture

import cv2
import numpy as np

class CamApp(App):

    def build(self):
        self.img1 = Image()
        layout = BoxLayout()
        layout.add_widget(self.img1)

        self.capture = cv2.VideoCapture('decklinksrc mode=7 connection=0 ! videoconvert ! appsink')

        Clock.schedule_interval(self.update, 1.0/33.0)
        return layout

    def update(self, dt):
        ret, frame = self.capture.read()
        
        if frame:
            buf1 = cv2.flip(frame, 0)
            buf = buf1.tostring()
            texture1 = Texture.create(size=(frame.shape[1], frame.shape[0]), colorfmt='bgr')
            texture1.blit_buffer(buf, colorfmt='bgr', bufferfmt='ubyte')
    
            self.img1.texture = texture1
        else:
            print("No frame read.")

if __name__ == '__main__':
    CamApp().run()