The iPhone (and a few other devices) will always record videos in a horizontal orientation. If the video is a vertical / portrait video, the iPhone requests the video decoder to rotate the video back to vertical during playback.
Unfortunately, many Android TV devices ignore (or are incapable of honoring) this rotation. Since the decoder fails to rotate the video correctly, the horizontal recording is played onto a vertical surface. However, the rotation is wrong!
In my experience, the Google TV with Chromecast dongle correctly plays all vertical iPhone videos. As of 2021, the Amazon Fire TV Sticks and Sony Bravia TVs will not rotate videos to the vertical. Possibly this will change in the future, but right now those devices are incapable of hardware decoding vertical iPhone videos. You must turn off hardware acceleration in my apps to correctly orient these videos.
So what can you do?
- If the videos are 1080p or less, try turning off hardware acceleration to bypass the device’s decoder. You can do this by entering the app settings, go to Display, and uncheck “Hardware Accelerate Videos”. While this will work for 4K videos too, those typically require HEVC / h.265 hardware decoding and turning off acceleration will result in choppy playback.
- You can install VLC and use it has your video player by entering the app settings, go to Display, and then check “Use VLC”. VLC falls back to software decoding if it runs into any problems with the hardware decoder so 4K videos will likely be too slow there as well.
- You can upload the files to a service that automatically transcodes videos into widely compatible formats, such as Flickr or Google Photos. Those services will correctly rotate the video as part of their conversion process.
- You can manually re-encode the videos to remove the rotation requirement, to increase compatibility and to convert the videos into more efficient bandwidth versions that will help with streaming. It is important to realize that many cloud drive services are not video streaming services and playing raw 4K videos from them can use up to 8 MB/s. This is a high requirement for a lot of internet connections.