We currently have mediatextures playing video on windows 7, iOS, and Android using MPEG-4 at 24fps and 1280x720 resolution, as this is the only format that seems to work accross all of these platforms.
It does not, however, play media on the Surface Pro 3 running Windows 8.1 Pro, and the texture remains black.
Does anyone have any idea why this might be an issue?