Ok, so I am having this video playback issue with our GearVR app built in Unity3D. If I run the Oculus app from the phone screen, go to our app, and then put the phone into the headset the video will play just fine. If I follow this same pattern with Samsung VR the video plays just fine as well.
However, if I plug the phone into the headset and then navigate to my app it will not play. Just goes to a black screen for a few seconds and then goes back to my app menu. If I use the Samsung VR app I get a "This video cannot be played" on the screen.
The video is Stereoscopic and 4k (4096x2048) Top Bottom, if that makes any difference. The end of the video filename is *_360_TB.mp4
I also noticed that if I convert the video down to 1080p it will play starting that app both ways. So I know it must be linked to the video size (Either resolution, or filesize) The 4k version is 253 MB and the 1080p is 60.5MB.