Yes it's necessary to convert the avi to DVD format, if your goal is to burn and playback on standard DVD player..These come to mind..DVDflick, FAVC, ConvertxtoDVD(Trialware)..
You can set whichever tool/app of the three you choose, to directly burn after conversion..
FYI, the quality of the video after conversion will degrade (from original DV-AVI), since the encoder will use a lower bitrate deemed necessary for best results and of course to fit the projected media size used (4.7gb, 8.5gb disc)..
If you need to do some simple editing before the conversion, try AviDemux..
There are other tools/methods available...These have worked for me, with good results..
EDIT:man do I type sloooow or what!...But as Kerry56 would say, I did do more work!..