I use nPlayer to access my files over the network/sftp/Dropbox/WebDAV/put.io/HTTP and download to my local device. But like I said, streaming directly from the network works too. But for a high bitrate 4k file downloading first is better since the server=>phone=>ATV transfer can be too slow. (Resolution doesn’t matter, it’s all about bitrate. Some 4k HEVCs are lower bitrate/smaller files than 1080p h264s)