Jumping cells without cell commands ?

[Kayaker]

I was fooling around with an ( apparently ) protected movie.
Ripit4ME clearly detects what are the protected cells and by de-selecting them the PGC can be extrated with DVDDecrypter with no problem.

Let's state clearly that I don't care about the ripping itself, but I want to undestand technically how the cells are skiped and what is going on.

Copying the IFOs to the hard disk and single stepping wiht PGCEdit the PGC ( VTS3 PGc 1 in this case ) is eventually being played.

There are NO cells command prior to the protected cells. Actually there are no cells commands in the complete PGC.
Nor anything that old PSL2 plugin detect as protected.

I don't undestand how the cells are skipped in a standalone player or PowerDVD.
I puzzles me.

What tricky DVD commands can be used to skip a couple ofcells in a PGC without a cell command ?

Or can it be jumped with tricky NAV packs in the VOB stream ?

Thanks.

[r0lZ]

Maybe the PGC is always entered at a specific cell, PG or PTT?
Or are there angles or ILVed cells?
Or BOVs that are automatically executed after some time?

I'm not sure it is possible to use "trcky NAV packs", but who knows?

[Kayaker]

sorry for my imaginative "tricky navpack" .. :)

I'll single step it again with your great PGCEdit.

But as far as I can see ( that's not much for sure ) the PGC is entered in the first cell.

I'll be back said Arnold ....

[Kayaker]

thare are no Buttons over video.

I guess as fas as I remember ... I have the VOBs at home. Here at work I bring only the Ifos.

but I'm pretty sure there were no BOV.

lemme check the other thing...

[mpucoder]

Without seeing the vobs I can only guess that the NAV packs are used to cause the skip. Cells are linked, and not assumed to be contiguous. If the skip is small enough (less than 20000 sectors) it can be performed seamlessly. Look at the pointer at offset 0x4f1 or 0x541 (enable VOBU_SRI in VobEdit)

Is this a commercial DVD that I might be able to get and look at? all demuxers I know proceed without checking the links. Even those that are able to follow angles and stories, as MuxMan can, do not look at the linkages within a cell (only the ILVU links)

[blutach]

You see this a bit in menus using the post commands. For example:

1 if ( gprm(13) == 1 ) then { Goto line 5 }
2 Set gprm(10) +=(add) 1
3 if ( gprm(10) == 3 ) then { Goto line 5 }
4 LinkCN Cell 3
5 LinkPGCN PGC 8

This would loop a menu 3 times then go to PGC 8, where it might jump to a title.

Regards

[Kayaker]

I'll take the look at those pointers.

Do you think that cells can be skipped with NAV Packs ( I was just teorizing )
If that is standard DVD spec why don't have them done it before (as a protection schema I mean ) ?
I supponse as you say no demuxer is THAT attached to specs and look as those pointers.

Interesting stuff from the point of view of someody designing protections is how standard it is and if it will work in the real world of standalones player.

Anyway I'm suspecting there were not protected cells at all but really scratches in the DVD (please don't kill me :) ).
Remember al this is aiming at educating myself ( and drive you all nuts :) )

The thing begins in the layer break. but it's strange PowerDVD sikps them. Or at least it seems so.

I you start to fool around with "jump to .." in the bad zone the DVD eventually tries to read bad sectors.

BTW the DVD is zone 1 INSOMNIA.

I was thinking the other day that there is no point now in "skipping cells" protection schemes, if you can debug it with PGCedit and take a look at the real played ones.

[blutach]

The thing begins in the layer break. but it's strange PowerDVD skips them. Or at least it seems so.
If you are talking about the playback of a burned DVD, then I would immediately suspect a bad burn. Ensure you are using only Verbatim DL media and burning only with ImgBurn (www.imgburn.com).

Regards

[Kayaker]

No. No.

I'm talking about the original DVD.
Which visually have some minimal scratches ( very minimal) but I got worse DVD's which read fine.

Anyway I'm getting interested in tricky stuff that can be done.
Whether this is the case or not in this particular DVD.