this can be done directly if you have a firewire video capture box.
I have a canopus advc100 which is an excellent dv capture box with high quality AtoD converter and rock solid video/audio sync. There is a undocumented easy hack to with this unit to remove macrovision, which enables high quality copies of retail vhs tapes to dvd.
However the hack does not remove the cgms flag so retail dvds still cannot be copied.
But if you connect the firewire to the Liteon 5055 dv input, the cgms is circumvented and you can do direct copies either to another dvd or to the hard drive of the liteon. With a region hack on the player you can even make pal copies of ntsc dvds with very high quality.
I rip on the pc generally anyway to make fairuse copies, but this is a useful extra function to have under the belt, and solves the problem of getting retail dvds onto the Liteon hard drive, albeit in real time.