Archiving live photos

the live photo gets divided into two pieces on export, without loss of quality, and is reassembled into one live photo if put back into the photos app.

Yes, the key metadata item in Live photos is ContentIdentifier. It has to be identical in both the image and the movie, even the file names do not have to match. When importing such pair, Photos.app shows only the imported image's filename. Also the matching movie can be from a completely different footage such as .mp4.

Sorry but I don't quite understand how they go to waste and what resolution you are asking?

Apple "Live Photo" .jpg or .heic has the "sidecar" .mov file. Usually they is imported via USB. Or via AirDrop select a Live Photo > Share [that arrow-up widget] > Options: All photos info (sp?), Ready > AirDrop widget [select target device] > [in the target device] Accept: Save to Downloads or Open in Photos.

On the other hand Android "Motion Photos" has the movie embedded inside the the .jpg and can be extracted with exiftool.

maviszook wrote:

Okay, I think I finally understand: the live photo gets divided into two pieces on export, without loss of quality, and is reassembled into one live photo if put back into the photos app.

That's correct. Only the Photos app can view a Live photo as a single entity. You can view the movie and image file individually outside of the Photos library but not together.