Update app.py

app.py

@@ -139,8 +139,8 @@ def infer(url_in,interpolation,fps_output):
       if ret == False:
         break
       nxt = cv2.cvtColor(fr2, cv2.COLOR_RGBA2GRAY)
-      cv2.calcOpticalFlowFarneback(prvs, nxt, flow, 0.5, 3, 15, 3, 5, 1.2, 0)
-      mag, ang = cv2.cartToPolar(flow[..., 0], flow[..., 1])
+      fl = cv2.calcOpticalFlowFarneback(prvs, nxt, flow, 0.5, 3, 15, 3, 5, 1.2, 0)
+      mag, ang = cv2.cartToPolar(fl[..., 0], fl[..., 1])
       hsv[..., 0] = ang*180/np.pi/2
       hsv[..., 2] = cv2.normalize(mag, None, 0, 255, cv2.NORM_MINMAX)
       rgba = cv2.cvtColor(hsv, cv2.COLOR_HSV2RGBA)