
Secret: How to Play 3840x3840 360° 3D Video on iPhone
In fact, with these tricks 360° 3D videos will look better on an iPhone through VR Goggles than on Samsung Gear Goggles even though some Samsung phone screens are higher resolution.
Of course, you need a few steps to make this possible.
Step 1: Realize that most media encoding software imposes limitations on the dimensions that an h264 video can be.4096x2048 is pretty much the max and therefore only really useful for 2D 360°.
Step 2: Realize that iTunes sucks and was never meant to be the music, photo, and video management system that Apple claims it is. You can't upload a video over 3840x1920 through iTunes.
Step 3: Stitch and encode your 360° 3D video at 3840x3840 in the ProRes or another codec that doesn’t limit the height of your videos. This will be your master file that we will later encode as an h264. Make sure the left eye’s information is stacked on top of right eye. This is sometimes referred to as Top - Bottom or Half over - Half under stereoscopic configuration.
Step 4: Download Handbrake for encoding your video https://handbrake.fr/. Handbrake doesn’t adhere to the recommended h264 limitations like other programs. Yay! Drag your 3840x380 video into Handbrake. Set the format to h264. Set your frame rate to whatever was your original frame rate. Leave Video quality at RF 22. Select Web Optimized checkbox. Select Fast Decode. Choose the Picture tab and make sure you type in 3840x3840 into the screen dimensions. Make sure the Crop is set to 0 in all directions otherwise it will slightly alter your dimensions.

Handbrake Media Encoding Desktop App
Now, name your file
Step 5: Download a VR Player for your iPhone that allows you to add files to it’s directory. We like VR Player Pro.

https://itunes.apple.com/us/app/vrplayer-pro-2d-3d-360-video-player-for-vr/id1065311870?mt=8
Step 6: Download Ecamm Phoneview desktop app as your iPhone file management tool. http://www.ecamm.com/mac/phoneview/.
You can try for free and only costs $29.95 when you realize how easy it is to manage your files on your iPhone. You can actually access all your Phone apps, voice messages, and use your iPhone like a hard drive. We love using it for many things.
Plug your iPhone’s lightning cable into your desktop. Start up Phoneview. Disregard that inferior iTunes is bouncing and wants your attention. Sorry, iTunes you are going to sit this one out. On the left hand side of Phoneview you should see an Apps folder. Select that and then find VR Player Pro. Drag your 3840x3840 360 video onto the root of VR Player Pro. Wait for it to copy over and then unplug lightning cable.

Phone View Desktop App - Showing VR Player Pro file path
Step 7: Start up the VR Player Pro app on your iPhone. There will be many tutorials that you will need to swipe through before you use it. Keep swiping through until you finally can use the app. Select the gear-looking settings icon in the top left, scroll down and change the following:
Screen Layout for VR
Screen Gap: 0 Pt
Screen Size: 1.00 X
360° Video
Max Resolution: 3840x3840
Frames Per Second: 30 fps
Anti-Aliasing (Segment Count of Sphere): 72

VR Player Pro Settings Screen
Step 8: Select "Done" in the upper right corner to close out of the settings menu. Now, swipe until you see your mp4 file. Select the file and then slide into your VR Goggles. Be amazed. Now you are seeing full, high resolution 3840x3840 360° stereoscopic 3D video on your iPhone. Enjoy.