can framebuffer be smaller than sceen?

[MichaelJPCT]

i have an idea that i want to keep the game window's aspect ratio, for example 16:9, while the screen of device is usually not accurately 16:9.
can i have a framebuffer smaller than the screen and keep some black margins around the framebuffer?

[EgonOlsen]

I think it can, but I'm not sure that would be displayed. It might be a better idea to render into a NPOT-texture and blit that instead.

[MichaelJPCT]

i tried creating a smaller framebuffer , the app just couldn't start.
so your suggested way may be the only way.