Splitting into chapters without quality loss

[skypilotpete]

I am trying to work out the best way of splitting a DVD into individual chapter files with minimal or no quality loss. As far as I can see, Clone DVD Mobile is the only Slysoft program which has the option to split into chapter files, but I cannot find any profile which gives me no quality loss. I thought that Generic Mpeg-2 Passthrough might do this, but I have never been able to get that to work - I always get an error message saying that Clone DVD Mobile is unable to process the file, no matter how many DVDs I try it on. I then tried VOB File (passthrough), and this works, but I am confused. The total size of the original DVD Video_TS folder is always much larger than the combined size of the VOB chapter files. For example, for a 4.18 GB Video_TS folder, the total size of the chapter VOB files is 2.51 GB, which is considerably less than the total size of the VOB files in the original VIDEO_TS folder. The process of splitting into VOB files is extremely quick, so I can't see that any re-encoding can be taking place. Can someone please explain what is happening here, and if there is a better way to split into chapter files without losing quality?

I run Windows 7 64 Home, Clone DVD Mobile 1.9.0.1, Clone DVD2 2.9.3.0, AnyDVD 7.5.3.0.

EDIT: Oops - I think I have found the blindingly obvious answer to the reduced file size - there are some special features on the DVD which are presumably not included in the main feature chapters.