Answer by Chris D

I've been working with rendering to textures recently in Unity 5 and also ran into some issues on import. My adjusted workflow as of now is: 1. Process file (working with MP4s) using ffmpeg2theora from command line 2. Import new .ogv file into Unity 3. Create new material to house my video 4. Assign video to material's Albedo map 5. Trigger video playback in scene as desired. As I understand it, Unity uses theora internally. The conversion step seemed to be the rough bit for me so this has been my work-around until I figure out a proper workflow.