assuming you have a mpeg or avi file, you have to demux (split video and sound). I use avidemux.
After this you have to mplex the two files with mplex (mjpegtools) or tcmplex (transcode) and tell the programm how to encode (DVD, SVCD, VCD).
After this "DVDWIZARD" will prepare the file for burning the video on dvd.
In k3b you will find the project type DVD-Video. Drag the resultfiles from DVDWIZARD in the VIDEO_TS directory and burn.
You can find this tools as rpms on www.rpmseek.com.