This depends on the aspect ratio of the video and your screen. If your screen has an aspect ratio of 16:10 and the video is 16:9, there will be gaps on the top and bottom. If the ratio is something like 3:4, there will be gaps on the left and right.
However, you can use VLC media player to do what you want. When the video starts playing, select your aspect ratio from the video menu in the menu bar. Be warned though that if you select a ratio that is drastically different from the video's native ratio, it might become terribly disproportional.
Feel free to shoot any other queries.
widescreen issue!!
Linear Mode
