When I copy any movie on the Oculus (using either adb or Android File Transfer) , I cannot view it using the default viewer unless I restart the Oculus. The video shows a black thumbnail in the list and an error when I play it. I tried with countless files, countless encodings. It always work when I reboot the Oculus though.
I guess the Oculus does not detect new files or refresh its filesystem somehow.
So after searching a bit I found out it's because a media scan of the sdcard is not triggered. It seems to me that when you open the Oculus Galery, this scan should always happen.