The Battle Video exploit is a means of luck manipulation in Pokémon Emerald. It allows the player to store an RNG seed for future use, as opposed to waiting for a given one to appear every time the game is loaded and the linear congruential generator is reset to 0. This is made possible by the simple fact that a Battle Video is intended to replay a battle accurately, which includes randomness in damage calculation and opponent move selection.
To perform this exploit, reach an RNG seed that occurs before a target value, enter a battle in any of the Battle Frontier facilities, either win or lose, and then save the Battle Video. Forfeiting by selecting "Run" does not allow this option. When the game is next saved, the Battle Video and its corresponding initial seed will be saved along with it, so whenever it is viewed, the RNG will be advanced to a handful of frames after that seed. The lack of idle RNG advancement in battle while in the Frontier makes the difference between the two significantly less than in most other cases.
- Discovered by Hozu from Smogon