I've just bought a Blu-ray and on the back where it lists the formats etc. it says "MPEG-4 AVC/MGVC" and has a "Master Grade Video Coding" logo next to it. Google isn't being particularly helpful so does anyone know what this is? From the little information that I've been able to find, it seems to be an extra "layer" that sits on top of AVC and somehow increases the quality. Does anyone know how this works?