Presumably the graphics controller fills up a frame buffer for display,
so, if one is not at a certain point using the controller to draw
something, could one write to the frame buffer directly?

Also, AIUI, the RPi communicates with the GPU via memory-based
message buffers, so the GPU must be running some form of background
kernel?

I assume that this must be the purpose of only one of the GPU
processors as running full motion video, say, in an MPEG stream,
must take quite a lot of computer time?

One part of the GPU must be simply concerned with taking the frame
buffer and emitting it as a composite video stream, so I wonder how
the aspect ratio is set up?

Sorry, a bit unstructured in the above, just musing; it's something
that I pick up after a few months before dropping it again; I'm
struggling  to get to grips with the whole GPU thing.

--- SoupGate-Win32 v1.05