Problems when presenting portrait mode jpg files by a single mp4 with the Canvas II

Hi to all,

I edit my photos for a Canvas II with Photoshop, scale them 1080x1920 or 1920x1080 pixel respectively and optimize for 100 dpi. 

Then I use lightroom to combine series of several jpgs by exporting them as one mp4 file. While my Canvas II - hanging in portrait mode -  correctly presents the landscape files of the mp4 file (just one black border above and another below), it incorrectly presents the portrait mode files with a two inch black border on all 4 sides of the image.

Does anybody know what happens with portrait mode jpg files when they are part of a mp4 file on the Canvas II?  

Thank you, Klaus-Henning