correct settings for making a DVD with XDcam footage

I've edited a show for clients using FCP 6. Footage was shot with the XDCam and looks beautiful in FCP. I then exported using Quicktime Movie setting and made a DVD with iDVD. Footage doesn't look so great - a bit jagged and pixelated. Is this due to shooting in HD and finishing in HD?

Any suggestions how to improve the final output? i.e. change settings - if so, to what?
Use Compressor?

Thank you,
Laura