'If' not a codec issue, it could've been poorly encoded. For example, an ntcs video converted over to pal format or vice versa without taking this into consideration. ntsc & pal use different height dimensions & frame rate. Else it might have been widescreen squashed into normal ntsc/pal format. I think they call that letter-boxing when they squeeze a 16:9 aspect video into 4:3 aspect ratio.