I am getting started with some mmal based code to process video from the raspberry pi camera. I am trying to render a preview to the screen, and there's something that's confusing me.
In all the examples I can find, you can either render full screen, in which case you set:
param.set |= MMAL_DISPLAY_SET_FULLSCREEN;
param.fullscreen = 1;
OR you can render to a rect, in which case the example code is:
param.set |= (MMAL_DISPLAY_SET_DEST_RECT | MMAL_DISPLAY_SET_FULLSCREEN);
param.fullscreen = 0;
param.dest_rect = [...];
(see, for example, here: https://github.com/raspberrypi/userland ... iew.c#L120)
My question is: why do you set the MMAL_DISPLAY_SET_FULLSCREEN flag in the case when you're not rendering full screen? If you remove it, no rendering appears. With it included, rendering to the specified dest_rect occurs. This seems pretty confusing, but maybe I'm missing something.