Following command giving

I am trying to capture a webcam using the ffmpeg command in a Python script and process the frame for my work. For my work, I need to capture and forward through the pipe to my function, but I always get an empty frame. I tried many SO solutions, but they are not helping.

I use this code to slide previous and next pages up, the problem is the [v]tpad=stop_mode=clone:stop_duration=10[s1]; is clone the first frame not last frame of [s0], how can I use last frame of [s0] to countdown?