Change to watermark from File to Image so it can be seen in the examples.

app.py

@@ -10,7 +10,7 @@ def generate_video(original_video, watermark):
     return gr.Video(original_video, watermark=watermark)
 
 
-demo = gr.Interface(generate_video, [gr.Video(), gr.File()], gr.Video(),
+demo = gr.Interface(generate_video, [gr.Video(), gr.Image(type='filepath')], gr.Video(),
                     examples=[[a, w1], [b, w2]])
 
 if __name__ == "__main__":