straight backups and "get VTS sectors"

[rudeboymcc]

hi. i just ripped all the files from FRIDAY onto my computer with DVD decryptor, and then loaded VIDEO_TS.IFO in IfoEdit.

when i clicked GET VTS SECTORS it had to change loads of things. i would have though it would have said no problems found, but how can a proper DVD have incorrect VTS sectors?

[DMagic1]

Ive had a copy of dvds like that too. I cant remember which ones right now.

[Kedirekin]

I suspect it something like this.

On the DVD, the files look like this.
xxxxxxxxxeof....xxxxxxxeof.......xxxxxxxxeof

where xxx is file data, eof is end of file, and ... is basically blank space.

When you rip to files you get
xxxxxxxxxeofxxxxxxxeofxxxxxxxxeof

This changes the location of the VTS sectors.

I'm just guessing of course, but I think there is a requirement that IFO and BUP files cannot be written to the same block on disk, which either means that IFO and BUP files are exactly the size of a block or that they are separated by unused (blank) space, so the guess is plausible.

[Dimmer]

I've been wondering about this too: whenever I do Get VTS sectors on any DVD I authored in Scenarist, it always corrects VIDEO_TS.IFO file. Couldn't find an explanation to this so far, but the discs play fine on a standalone even without correcting sectors.

[Mr.Shine]

This has been answered before here. Some authoring softwares put *.ifo and *.bup are in different ECC blocks (8 sectors / 16kb) - otherwise that would defeat the purpose of a backup file (*.bup is a backup of *.ifo), since if the ECC block is unreadable, both copies of the ifo are gone. It is the image formatter's responsibility to check the sector pointers in the ifo and put the vobs at the right place on the disc, separated by blank space, as Kedirekin said.
I do not know, however, which image formatters actually do this properly, so when I really have to copy a DVD file-based and create a new image, I do a "Get VTS sectors" to be on the safe side. If you copy the DVD via read/write image (e.g. with DVDDrecrypter), as well as if your authoring program creates the image on its own, the copy will be fine without "Get VTS sectors".

Many newer DVD players don't parse the DVD via the sector pointers but using the file system (like software DVD players), so it can happen that even with wrong sector pointers, the DVD plays fine in your player.

[Dimmer]

Originally posted by Mr.Shine
This has been answered before here. Some authoring softwares put *.ifo and *.bup are in different ECC blocks (8 sectors / 16kb) - otherwise that would defeat the purpose of a backup file (*.bup is a backup of *.ifo), since if the ECC block is unreadable, both copies of the ifo are gone. It is the image formatter's responsibility to check the sector pointers in the ifo and put the vobs at the right place on the disc, separated by blank space, as Kedirekin said.
I do not know, however, which image formatters actually do this properly, so when I really have to copy a DVD file-based and create a new image, I do a "Get VTS sectors" to be on the safe side. If you copy the DVD via read/write image (e.g. with DVDDrecrypter), as well as if your authoring program creates the image on its own, the copy will be fine without "Get VTS sectors".

Many newer DVD players don't parse the DVD via the sector pointers but using the file system (like software DVD players), so it can happen that even with wrong sector pointers, the DVD plays fine in your player. Thanks Mr.Shine, this makes sense. Perhaps I should look into this further. I read somewhere that Scenarist produces discs that have better compatibility with different DVD players than discs authored with lower-end programs. I guess it's because of the little things like that.