Rivergate Software Inc. - makers of DVDAfterEdit

There are two different types of HD DVD - those which use only Standard Content, and those which feature Advanced Content.

Standard Content HD DVDs are very similar to "normal" Standard Definition DVDs. So, they have EVOB files, ( HD versions of VOBs ) plus IFO and BUP files, just like an SD DVD - and corresponding Titles, Pre and Post-Commands and all the other familiar elements of the DVD spec, all contained in an HVDVD_TS folder. Disc structure and navigation are largely defined by the EVOB files, which, like SD VOB files, contain chapter points, button commands and subtitles.

In contrast, Advanced Content DVDs don't use IFO files. They have TMAP files, which contain indexing information for the EVOBs, but everything else is contained in a separate folder on the DVD, the ADV_OBJ folder. The EVOBs have no internal structure, so no chapter points, cells, button commands or subpictures. All the interactive content starts out in the ADV_OBJ folder. ( Strictly speaking, this data can be muxed into the HVDVD_TS folder to improve access times, but this is not a requirement, and happens at the pre-mastering stage. )

Most of the currently available HD DVD authoring solutions can create Standard Content only. The exceptions are Sonic Scenarist and the proprietary Toshiba system. There is a wide range of Standard Content authoring tools available, meaning that anyone familiar with SD DVD can start authoring in HD today, and move to Advanced Content in the near future.