Techincally, it is possible to back up DVD-Video discs on-the-fly but in your case (as geno88 pointed out) you need to consider:
- your laptop dvd burner will usually read/burn at 8x CAV max, which will start at 4x and increase to 8x at the end, or at layer break. Meanwhile your external DVD burner, if you purchase a newer model it will usually supported at higher speed (16-20x).
- Due to difference of read/burn speed method, there will be lag of data transfer to one of the burner.
- Most DVD-Video discs are protected as you already know but on top of that, most of them are DVD-Video dual layer. If you plan on burning dual layer (DL) to single layer (SL) then on-the-fly won’t work as you need to encode first.
- If you plan on burning SL to SL and DL to DL, would you be willing sacrifice a blank DL media if something goes wrong during on-the-fly burning?
In any case, for on-the-fly burning you will need a tool to remove the copy protection, ie AnyDVD, and to burn ie ImgBurn. I have tried burning on-the-fly copy protected DVD-Video disc, single layer with these two tools. However it was a simple CSS protection and not the newer and difficult ones. The title was Thunderbolt region 1, it’s a single layer DVD-Video disc.
If you want to try:
- enable AnyDVD
- run ImgBurn in Build Mode
- drag Audio_TS and Video_TS folders from original disc to ImgBurn
- In ImgBurn, select the second burner as destination
- Burn at lower speed, ie 4x, 6x or 8x.
Let us know.