Title: Final Fantasy IV (ファイナルファンタジーIV)
Undub: audio swap
Final Fantasy IV for Nintendo DS is a pretty easy undub. All the cut scenes are rendered in real-time, so all you need to do is replace the voice samples. Extract your U.S. rom with the DS tool of your choice (we used dsbuff) and locate the \data\voice directory. Copy the voice files from the Japanese version into that directory.
Note that the U.S. game contains 730 voice files (6 with unique names) while the Japanese one has 868. We're not sure if some of the excess Japanese files are pieced together during gameplay to make up longer samples. If that's the case, the speech should theoretically skip in a few places. Please report if you observe this or other strange behavior. Your undubbed voice directory should contain 874 files.
Re-pack the ROM and enjoy this remake in all its low-polygon glory.