During his Eurogamer Expo talk Microsoft Corporate Vice President Phil Harrison showed off Xbox One's game recording features in a short demonstration of the console's Upload Studio. Although no specifics were given as to the length of recording time available, he stated that players can record "as much or as little as they want."
To demonstrate the features the video showed a short 45 second clip of game-making game Project Spark. Once a player has captured their clip, they are able to record a separate video of themselves commentating on the clip using the Kinect camera. The clip and your commentary will then be played side-by-side in a picture-in-picture view. There are then several sharing options: you might choose to keep it private, you can share with friends, or you can share with the wider public. He referred to this as a 'powerful virality tool.'
It looked like an intuitive system. Some basic editing features were shown such as transitions, which looked simple and easy to use. Still, it was a short segment, and, given the talk's focus on the social aspects of Xbox One, we can hope to see more of these editing and sharing features soon.