[4candles]

Originally Posted by RainDawg

Just to chime in here....

The way around these problems is to burn with Nero as a data disc, but with a VIDEO_TS and a blank AUDIO_TS folder. If the VIDEO_TS folder (which is what you'll download from TTD) was authored correctly, this will still play in 99% of standalone players fine. Nero seems to alter the info files to perfectly match one standard, but it's not necessary.

Sadly, I don't think it's as simple as that - and I would be surprised if 99% of all DVD players could play a VIDEO_TS folder burned in data mode.

When a DVD is authored, the IFO files contain "relative sector pointers" to other files on the DVD. Hardware DVD players use these pointers to locate the content on the DVD - it's only the "VIDEO_TS.IFO" file that a hardware player will actually look for by name. After that file has been found, everything is based on sectors, not files.

In order for the sector pointers to point to the correct parts of the correct files, the files must be ordered correctly on the DVD - and this is not alphabetical order, which is probably how Nero burns data DVDs.

A typical VIDEO_TS folder on a correctly burned DVD would have the files located in the following order:

VIDEO_TS.IFO
VIDEO_TS.VOB
VIDEO_TS.BUP
VTS_01_0.IFO
VTS_01_0.VOB
VTS_01_1.VOB
VTS_01_2.VOB
VTS_01_0.BUP
VTS_02_0.IFO
VTS_02_0.VOB
VTS_02_1.VOB
VTS_02_0.BUP

Notice that the order is IFO -> VOB -> BUP which is where the alphabetical sorting fails.

This is why DVDs burnt as data discs shouldn't work - it's simply a matter of the files being placed on the disc in the wrong order, so the pointers are no longer pointing where they should be. It's possible that by co-incidence that some or even all of the pointers could still point to the right place, but it isn't guaranteed.

Under Linux, the "mkisofs" program understands the .IFO files, and when you ask it to generate a DVD-Video compliant .ISO file for burning a DVD, it uses the pointers in the IFO files to decode where the files should be placed on the DVD.

Nero may well have it's own views on where files should go on a DVD (which could be different to the decisions made by the DVD Authoring program), and change some of the pointers in the IFO files. This is probably even more likely for DVDs authored using a standalone DVD recorder - I've seen some very odd structures being generated by standalone DVD recorders.

An interesting experiment (which I can't do as I don't use Windows) would be to burn a DVD in DVD-Video mode using Nero, copy the files back the hard disk, and then burn another copy of the DVD and see if Nero changes files that it has already changed.

If it turns out that Nero does indeed create MD5-identical burns after at least one generation, and considering the fact that Nero is more or less the de-facto standard for DVD burning, maybe a solution would be for seeders to pass the files through Nero before seeding.

Another solution (if it's only the IFO files that are being changed by Nero), would be to burn those (along with the torrent's text file and original MD5 checksums) in a seperate folder on the DVD. When extracting the DVD for trading, you could just copy the VOBs from the VIDEO_TS folder, and everything else from the data folder.