The player's name is Morimoto. He specializes in what the Japanese call "God Technique" videos. All God Technique demonstrations involve the use of emulators and save-states. In the case of many of Morimoto's replays, he actually plays the game set to 50% speed (or even slower... his FC/NES Gradius replay is done at something like 25% speed) and uses per-frame save-states (so if he makes a mistake, he can go back to the exact frame where he messed up). After completing the run (which normally takes him about 18 months), he takes each frame of saved replay data and compiles it all together in Premier to produce the final video.
He issued a public apology some time ago for his videos, as many thought that what was being done in the videos was 100% human skill (which it isn't). Since then, any videos that he has done come with a disclaimer at the beginning describing the process used to create the video (such as in his more recent DDP

OJ Hibachi video).