Screen format

[nickdunc]

I tried a test and played it back using VLC, and the format was 'square'.
I am used to it being rectangular to fill a whole screen.
Am I missing something?
I would ideally like to stream this via a Roku from a hard drive, and so the final format will make a big difference.
Thanks

[nickdunc]

I have not found this with other ones and so suspect it is a function of the film itself