Update app.py

app.py

@@ -87,7 +87,7 @@ def get_frames(video_in, step, name, resize_w):
 
 def create_video(frames, fps, type):
     print("building video result")
-    clip = ImageSequenceClip(frames, fps=fps, ismask=True)
+    clip = ImageSequenceClip(frames, fps=fps, transparent=True)
     clip.write_videofile(type + "_result.webm", fps=fps, codec="libvpx-vp9", audio=False)
     
     return type + "_result.webm"