720p movie with black bars

Check the aspect ratio

1.78:1 - fill the entire screen

1.85:1 - small black bars at the top and bottom of the screen

2.35:1, 2.39:1, or  2.40:1 - black bars on the top and bottom of the image (common for cinematic movies) 

Examples:

MOVIE

Starting playback...

Movie-Aspect is 2.39:1 - prescaling to correct movie aspect.

VO: [xv] 1280x536 => 1280x536 Planar YV12 

TV SHOW

Starting playback...

Movie-Aspect is 1.78:1 - prescaling to correct movie aspect.

VO: [xv] 1280x720 => 1280x720 Planar YV12