Batch Convert videos

[hbelouf]

I have (lets say) 3 movs/mkv/avi that are different sizes. 1 - 1156X404; 2 - 1180x536; 3 - 1280x720. I would like to "resize" each one so that it would fit on 1920x1080, now here is the catch each video would be centered and would have black boders added so it would appear on 1920x1080. So basically it would be adding black boders automatically to each sides so it would be centered.

I have let say about 400 videos that I need to do this, do it manually would be just .

Thanks in advance.