From DVD5 to DVD5, just like ADM202E mentioned.
From DVD9 to DVD5, you can use DVDshrink.
DVDshrink compresses the contents so they would fit in a single DVD5.
However, most orig DVDs are DVD9.
If you back-up a single DVD9 to a single DVD5, you are sacrificing quality.
To me this doesn't make sense kasi you already have the original - you shouldn't sacrifice quality.
So what I do is this:
DVD9 = DVD5 + DVD5
1. I use DVDDecrypter to transfer the DVD9 contents to harddisk.
2. Then I use DVDFab to process the contents into 2 discs.
3. Then I use Nero to burn the 2 discs.
Pros: Bitrate is not reduced. No compression done. Therefore, quality is the same as the original.
Cons: You are using 2 discs. Hence you will get the "Insert disc2" message at the end of disc1.
DVDFab splits the contents into 2 discs. The special features and bonuses of the movie are placed as much as possible in disc1. The first part of the movie is also placed in disc1. The remaining part of the movie is placed on disc2.
Why back-up (in case Edu Manzano is reading)? To protect the original discs from my 3year old boy. Nabasagan na ako ng disc dahil sa malikot kong anak.