Thank you for your work but the communication is difficult.
My use case is:
an GL window is created by the app, the pipeline app sink get the frame and display the frame inside the existing window/GL context.
processing -> pipeline -> appsink
!
!
!
gui_app <-------------- create texture
(create window, (without copy of frame data)
create GL context) !
swap buffers
This impossible that it is not working this a the basic of graphic engine (ask for support)
Michel