Not all videos can be made into working Live Wallpapers in iOS 17. Keep reading to find out why.
iOS 17 Live Wallpaper is still very new, buggy and quite different from the previous Live Wallpapers which is causing a lot of confusion.
There is no official document from Apple regarding the specifics of the new Live Wallpaper. Here are some tips on creating Live Wallpaper for iOS 17 and some of the things I was able to figure out.
Minimum video length is 3 seconds. If the video is only 3 seconds, you won't be able to choose the cover photo (ending). It will automatically be the middle of the video.
Use the lock button above the right trimmer handle and drag the right handle to find the right position. If the video is too short, you can create a new video by appending same video at the end until it's long enough.
Once you set it as a Live Wallpaper, often you will find that it is too short. You can make it longer by create a new video by speeding up. If the video is too slow you won't see much motion. You can speed up a video by tapping the S button to toggle through the different speeds and tap make video.
When setting the Live Wallpaper, you often get Motion Not Available message and all you have to do is tap Cancel and set it again. This is probably a bug. You can read more about it here, How to fix Motion Not Available Message.
There seems to be some processing going on by iOS trying to add motion effect. If it is unable to apply the motion effect, it will not work.
Try to pick a part of the video where the subject is shown continuously up until the cover photo. This will make it easy for iOS to try to add the motion effect.
You can also try changing the video position slightly. You can use the end button.
This video shows the newly added Lock button to help with creating the Live Wallpaper. Tapping on the lock button will lock the duration to 3 seconds. After locking, you can drag the right handle and move it to the desired position. Video preview will automatically show the cover photo.
Here is resulting Live Wallpaper.
Hope this cleared up some of the questions you had. Let's make some cool Live Wallpapers!