Gedo Senki, "Tale of Gedo", is an upcoming film from Studio Ghibli based on the famous book series "Earthsea" by Ursula K. Leguin. It is to be known in English language release as "Tales from Earthsea".
For an English synopsis, look here please.
http://www.ursulakleguin.com/GedoSenkiSynopsis.html