DVD plays differently on VLC vs other software/hardware?

[PartyRambo]

I should consider this a 'learning' experience... but right now, I'm just pi&&ed off...
I've been backing up, stripping junk & compressing to DVD5, a pile of DVDs from my collection, to put on the media player for quick access. VideoLan (VLC) is my preferred player.
I've been testing my exported edit in VLC; if it looks OK, I shrink it to ISO, and test the ISO on the media player - and so far it's been a perfect run.
For the most part, all I've been doing is stripping out junk & extra languages.
Occasionally, I have to fix a menu glitch, which has so far been easy to do as the references on those have been bare-bones & a simple Jump to VTS correction was all that's been needed.

After spending much of yesterday, trying to fix the menu of just one movie, and totally failing to get it to work correctly, I discovered this morning that it plays just fine in other software players & my media player.

It jumps to VTS1, PGC5 in VLC, but to VTS1, PGC6 in the others. As a result, it gives a sub-menu first in VLC, but the main menu in the others (which, had I known, would have saved me many hours yesterday!).
I have not seen this behaviour before, but a post elsewhere on this site, directed me to check another player, and voila!

I haven't yet completely tried tracing the R[x] settings, but there are a crapload of what appear to be redundant references, and I don't know what they are anyway!
I use DVDRemakePro to edit; I don't fully understand the tech specs of a DVD, and have only recently started to get some understanding of how the menus jump around. So my level of DVD knowledge is better-than-layman, but not-yet-author.

So - I'm now aware I should test in multiple environments, but does anyone have any suggestions/answers/guides as to WHY a DVD would behave differently in VLC vs another?
And/or, why a DVD would behave differently between players, in general?

Thanks...

[loster]

I have had issues with VLC and dvd's might be related to the feature that skips straight to the menu.

[DB83]

What you describe is technically impossible.

A player beit software or hardware simply reads the instructions generated from the ifo file, reads or sets registers accordingly and then performs the actions which result in what you see or hear.

The instructions are the same since they are burnt into the ifo file.They can not be magically altered by a player. But I do wonder if software players are more likely to cache certain registers. The instructions then read those saved registers and the disk behaves somewhat differently to what you expected.

So in your scenario, that jump can only happen if another condition is set. You use the debug feature of dvdremakepro to trace though a disk. You can then see what registers are being set etc.

[loster]

http://forum.videolan.org/viewtopic.php?f=7&t=87336
also
http://forum.videolan.org/viewtopic.php?f=2&t=10564

[DB83]

Well neither of those two links work for me.

I have only used VLC as a dvd player occassionaly and only for non-edited disks. But if it is to work it MUST read the read the IFO instructions.

Maybe the OP would like to post the instructions so that we can see the logic of why a different PGC is being called.

[DB83]

Just a little addition to the last post.

I checked two dvds using VLC and PowerDVD. One is a commercial disk, the other one I totally authored myself (not an edit). Both of these disks have first-play videos before they should go to the main menu. PowerDVd plays the first-play and goes to the main menu. VLC does not play the first-play and goes straight to the main menu - that is the only difference I can see between these two players. Looking at the VMG instructions for the first-play I do not see any critical registers being set so it appears that VLC can safely skip these.

Checking the instructions for the main menu, some registers are being checked so it now follows that if these have been inadvertingly set then the menu, although being called, is behaving differently.