Well, I'll need more info really. What are you watching on, and what/where is the server? What is the source material? DVD? Blu-ray? Is it a direct, 1:1 rip or was it encoded to a smaller file at a lesser bitrate?
By default, it should be configured to direct play, which means it's not transcoding the file...it's playing it as is. A lot of devices have issues playing a direct stream with, say, a native blu-ray rip. My AppleTv 4, LG tv, and any idevice have the same issue. The PS4 seems to be ok.