Try BSPlayer's feature "Extend picture to" (assuming that you have a 4:3 TV and (e.g.) a 16:9 movie).
In Options > Preferences > Video > [Video rendering] just below the radio-buttons Mode 1 / Mode 2 there is a box offering several possibilities to "Extend picture to". Assuming that you have PAL as TV-standard: select "576 lines" (For NTSC it should be 480).
Any result?