VR audio vedio Stream

we all know that Unreal engine support all the VR hard device, there is a question I have about the basic tech ,that Some VR device can see image on computer screen and head-up device the same time. the point is that the head-up device how to get the vedio and audio stream. it’s just like a implement of live stream service? I will appreciate a official answer.
I am a graduate in UESTC, answer my email tqzsoft@foxmail.com . Waitting…