I previously asked more than one user about whether JRiver's zoom control allowed user positioning of the zoomed image and they said yes. But Movieman said that such up/down, left/right control is NOT available after zooming on an image.
https://yabb.jriver.com/interact/index.php/topic,125815.msg873953.html#msg873953Cyberlink's PowerDVD can do this, albeit slowly with mouse dragging, though possibly not with BDs-and may not be compatible with AnyDVD HD to insure this. With VLC player you can zoom and reposition DVDs but it's a very clunky process. And to play BDs you first have to go to some strange website and carefully download these special "lbb codes' and install them in the right VLC directory.
Here I was expecting that by now complete zoom control would be accessible via a handheld remote, when it still can't even be done with keyboard commands or mouse clicks.
Like with slow motion (which VLC can do with ease), I can't believe that after all of this time something so basic is missing from JRiver player, and after asking JRiver developers numerous times to include it in the next version.