For the 4.7 "screens of (like the iPhone 6s) it seems to have a ratio of problem when playing videos in landscape format. The video stretches far across the width but the proportions are not maintained, the image is distorted. Are you planning an update to allow the application to change these settings either manually or automatically depending on the mobile?
videos are showing correctly on my iPhone 6s. Can you post some screen shots of how the video looks in portrait and landscape modes?
Also can you let us know the video format and resolution? If possible can you share a video with us using a drop box link or something? If you do not want to share the video link in public you can PM me with the link.