Since you are writing directly to a DVD, I’m guessing that you file is in MPEG2. You will need an mpeg2 editing software. Roxio and Nero can do this, but are the lowest level of programs. Next up are programs like Ulead Video Studio and Pinnacle Studio. Then there is Adobe PRemiere, and Vegas Movie Studio. Womble MPEG, and a slew of others. You may want to look at www.videohelp.com/tools, and also read some of the stuff in the forum for video editing.