I'm actually working on using video in VR on a Vive, but regardless of that effort it seems that in general the new video player doesn't seem to be using my hardware for help. I have a 3.5 GHZ quad core cpu and a GTX1080 Video card, but anything in the 4K range is tough to playback. I've tried MP4's using H264 and AVI formats using FFMPEG to try different settings, but nothing works. Playing the videos outside of Unity works great, and/or if I use something like the AVPro Asset, or another asset that uses FFMPEG on it's own I've tried lowering the FPS, and changing the bitrate, and doing power of 2 resolutions, but I haven't found anything that seems to help with the built in player. I would say it can't do it, but in searching the forums I see people say it doesn't work for them either, but other people saying it works fine for them with 4K content.