What we did was check the flags set by XGetVideoFlags() and XGetVideoStandard() and then set the appropriate screen size for PAL50, PAL60 and NTSC.
When using XGetVideoStandard() with XC_VIDEO_STANDARD_PAL_I make sure to use == and not & as NTSC/PAL are not mutually exclusive.
Didn't require much special coding just changing the FPS and screen size when creating the Direct3D device.
