DVD-ROM drives have been shipping from several manufacturers. This is a fast changing area. Also see the newest DVD recorder from Pioneer, the DVR-A03 . Next you do your editing, add titles, etc. Then you use an encoder card to compress the signal to mpg2 video standards.
Some systems do the encoding first, then edit the encoded video since it's then a smaller file size.
After that you record the finished file to the DVD recorder using DVD premastering software. As you can see, the DVD-R is only used as the final step in the process. It's also one of the cheapest parts of the process as a good compression board can be expensive, depending on your video source. You can record from a DVD-player, but keep in mind that nearly all commercial DVD discs have copy protection built into them so they can not be copied. Also keep in mind that the DVD-Recorder is DVD5 only while a commercial disc could be DVD5, DVD9, DVD10, DVD 14, or DVD18.