

If you upload rather or less than 16:9 frame video then Youtube will add a black bar to adjust the size.
So try to upload to according to that size.
Well, some software export video according to this ratio and some software.
I use Camtasia9 for screen recording video and there I do not have to adjust the size.
But in above premier pro, I have to adjust size.
If you try to with Adobe then after editing then go to File>Export>Media>Format>H.264.





