Programs such as Roxio Media Creator Suite 8 and 9 have a "straight to DVD" mode.
Ulead MovieFactory 4/5 also has that it is called straight to disc ( see below)
What you are asking the is that the PC capture DV AVI, convert it to mpeg2, futher make a DVD structure ( author: turn the mpeg to VOB) and burn.all "on the fly"
This is possible but is processor intensive and requires a "well oiled" system to work very well ,all the time. It is also fraught with the risk of failing should any of these processes not function well. The Settop DVD recorded is a dedicated hardware ( With hardware mpeg encoder and a much more simplififed software than a PC : hence its ability to be better at doing this)
Even with this software it infact doesnt happen real time as a lot of caching is done and background processes are taking place
Pinnacle Studio can import your footage via firewire as mpeg2 ( encoding "on the fly") and you can make movie to DVD disc straight away. It is only if you edit that it will rerender . As a 2 stage MiniDV tape to DVD it isnt IMHO, too bad
PS: As an aside, I can only get this function to work on one of 3 PCs : I really dont use it as such For straight capture, I use my settop DVD recorder ( with HDD). It is great for simple DVD authoring though.