OBS let's you edit video on the fly and the pipe the output somewhere else. For example, you can take the video of you playing a game, add a video of your face

OBS let's you edit video on the fly and the pipe the output somewhere else. For example, you can take the video of you playing a game, add a video of your face from your webcam to the corner, add text overlays of your channel name and then send the result to twitch.