This project is based off the efforts of the people at TASVideos . For a full description of what they do, take a look at their Welcome Page .
Every approved submission (called “movies”, even though they contain no audio or video data) on their website is simply a series of recorded button presses that in theory can be played back on the actual console for which they are intended. In most cases however the emulator differs too greatly from the actual consoles to make this possible, but in the case of the NES the difference is significantly smaller.
The game choice also makes a big difference as to whether the button presses can be played back or not. If the game relies on any uninitialized memory for randomness, or if it is heavily based on console timing, it may not work. In the case of Super Mario Bros however, as long as the button presses start play back at the right time, the movie will play back correctly.