What is the right exp setting for play a video on Ipad?

Hi guys,
I’ve tried to package my application, and all works fine but when I play my video from my UI, it start very slow with some lagging but the audio works very well.
I’m working on an Ipad Pro 12.9 year 2017 (last update iOs 10.3.2), with Unreal 4.13.2.
I tried to see all the forum and guide about the compression on mobile and iOs ( Play a video in IOS 4.9 [SOLVED] - Rendering - Unreal Engine Forums ),
but finally I didn’t find solutions.

This is my exportation settings (the same for After Effect, Premiere, and Media Encore)

I tried also to use different video and different format, I’ve tried to change Unreal version (4.14 and 4.15) but I have the same issue. In the preview the video works.
I’ve seen that when I increase the bitrate the video is more smooth (now the bitrate is on 25 Mbps).
Someone could help me please?
Thank You