See attached video.
All Emby videos played in Edge are extremely jittery, as if it plays frames in this order: 1, 2, 3, 4, 5, 1, 6, 7, 8, 9, 10, 6...
All Emby videos played from FireFox are not jittery, they are transcoded and have frequent pauses because my server is a Xeon 3060 from the Core2 era.
Emby documentation says that Emby transcodes only when necessary. This is false.
All videos play just fine over local network using Media Player Classic.