When freeze frames and menus are written to a (S)VCD, Nero will make the necessary conversions automatically and retain the correct aspect ratio (the ratio of width to height). This is necessary because the pixels in (S)VCD are not square even though this is the case with most computer settings.
Example: A computer image with a resolution of 640x480 fits exactly into a PAL SVCD image with a resolution of 704x576.
The actual resolution depends on the 'Encoding resolution' option on the 'VideoCD' tab in the compilation window.