Do you want to stretch the video or to enlarge it (this way the aspect ratio is kept but some video portions will be cut)
To go into fullscreen mode just press F, then you can use several keys:
If you want to stretch
- Use CTRL+NumKEYS (2,8,4,6) to resize the video area
If you want to keep Aspect Ratio
- Use M key to achieve Movie mode (you can use this even if you didn't entered full screen)
- Use SHIFT+O to use custom Pan-Scan settings
Or just select "Cut top and bottom of video in fullscreen mode" under Video settings (CTRL+P)
Plus if you want to freely resize the movie window while in Windowed mode, just un-check the "Keep aspect ratio" menu item (right-click to open menu -> Video -> un-check that option)
