How to extract HDMI input to a custom app

Hi all,

I have cameras connected to a raspberry pi i, the pi preforms some image processing on the camera streams then outputs the images to a hdmi output. I have connected a hdmi cable between the herelink air unit and the raspberry pi, but now im stuck, how do i actually read the data coming from the HDMI through a custom android app?

I would also like to be able to send commands to the raspberry pi from the herelink controller.

You may try to study this video app