Here's the new 'Trim' function in action, here on my Lumia 830:
Now appearing on an 'Edit' menu near you - in Windows 10 Mobile Photos, this pops up for videos now....
As you'd expect for a 'Trim' function, you get to set the start and end points of the video, before saving the trimmed video 'as a copy'.
This takes roughly real time on my test Lumia 830. I'd expect it to be similar for 4K video on the Lumia 930/950 etc.
Of course, a little lateral thinking means that this is not really just a 'trimming' function - it's a way of 'extracting' segments of video too - just go into the same source several times, trimming different sections and then you'll have multiple clips, as needed.
Very nice to have this included out of the box, anyway. In other Photos news, you can now share and edit the contents of 'Albums' - do you use this feature?
Editing a Photos 'Album', you can change the title, cover and contents as you see fit, then share (a link to) the album directly with the world via normal comms and social apps on your phone....
Comments welcome!