I m working on a project that captures the game windows and send it to another node. As long as game is in focus or maximize, the rendering is smooth and steady. When the game is out of focus or minimized, the streaming shows jerky effect. When you maximize the windows, the affect again disappears. Is that an issue of directx game rendering or something else? How this problem can be solved?
If the system is not under heavy load, there is nothing inherent in DirectX that will reduce performance for a minimized or background window's process. If the system is under heavy load, the OS may prioritize scheduling of the foreground window's process above other processes.
As @AlexandreVaillancourt mentioned, games will often intentionally throttle back their rendering when their primary window is minimized or goes out of focus, in order to enable a better experience for users who temporarily alt+tab to another process (e.g. Teamspeak, a web browser, etc.).