I am trying to watch a 4k HDR (.mkv, HEVC) movie on iPhone XS Max. It is about 2 hours long and 18 GB. I know 4k is overkill on a phone screen, but this is the only size I could obtain in HDR. I cannot find an app that can play this movie without lagging. Tried VLC, iPlayerExtreme, etc. Playback is choppy. When it's not lagging it looks incredible. Now I know that this is a high bitrate, but shouldn't the phone be able to handle this easily due to HEVC hardware decoding? According to MediaInfo, the bitrate of this file is slightly lower than the bitrate of 4k30 footage recorded using the phone, and obviously the iPhone can smoothly play its own footage.