Fullscreen streaming issue

[Alame]

I'm trying to stream Riot's League of Legends game. The game switches between a lobby client and the actual game client, and "game" streaming is only available for the actual game client. To prevent offline periods between games, I stream as "screen" instead of the game. However, once I enter the game client, the full-screen game shows up in a windowed mode and still displays some of my desktop. I've seen other livestreams streaming the game that don't have this problem, and am wondering what the issue is.
Any help would be much appreciated.

[freekers]

Run the game in windowed mode.

[Alame]

no, that's the problem. Despite the fact that I'm running the game fullscreen, the livestream shows it as if I'm in windowed mode. I want it to run fullscreen.

[coryfrans]

You have to use the zoom functions to zoom in the video capture to the part of the screen you want to cast.