Add difference video files!

[blackboy]

Hello Everyone!
Sorry, I just speak English a little. I am making a SVCD output disc by Ulead DVD MovieFactory. I have some questions. May anyone help me:
-In new project, add video flies, I combine alternately 3 slideshows files(MPEG2) with 4 AVI-DV files. I'm wondering:
+ Need I convert AVI-DV files to MPEG2 (by convert software) before add files ? Although the Ulead can add many kinds of format file (AVI, MPEG...) but I worry about quality output SVCD.
+ Can I change MPEG settings (Mpeg properties for file Conversion) in project settings? (convert 4 AVI files to MPEG2)
Please help me so that I get the best quality SVCD.
Many thanks everyone.