DVD Video (*.VOB) frames filtering good from bad data

[IsoBuster]

I am trying to figure out something ...

I extract VOB data, and often when I extract a *.VOB file it doesn't play well in all players. Hickups, audio issues, players only see the first 6 seconds or so etc.
This is, if I understand correctly, because of other-than-mpeg data in the VOB files, such as titles and other meta data.

In my soft I have a simple filter (always had that in place) that allows to "extract but filter MPG frames".
I simply check for the signature 0xBA010000 and throw away blocks that don't have this signature.
That however doesn't seem to be enough in this case. It looks as if the "bad" blocks also have this signature.

I was wondering if there is an 'easy' way to detect blocks that shouldn't be there to get a clean mpeg stream ?
So besides the signature I mentioned, is there another signature I can check for to distinguish between the pure mpeg data and other data that shouldn't be there ?

Or am I putting it too simple and is there more to it ?
If so I'd love to know what it is that I'm missing or what I don't seem to understand (yet)

Cheers !
Looking forward to an answer.

[hech54]

You only use IsoBuster if the disc is corrupt and it will not rip with a normal DVD ripper like DVDfabDecrypter.

[IsoBuster]

Thanks hech54 ... though I'm not sure how this helps ? I use IB whenever I like But that's besides the point.

My Q is more in depth (coding) and I hope some people with inside knowledge on VOB file structures will be able to respond.

Cheers.

[hech54]

There is no mystery to VOB files. They are created when a DVD is authored and are basically useless outside of the DVD environment. Removing one VOB file is completely useless since all of the VOB files in the title/titleset are linked together and basically "cannot survive alone without the others".
It's not brain surgery....messing with VOB files, especially individual VOB files from the entire movie, causes problems.

[IsoBuster]

Still, my question stands. Is there a way, other than the obvious 0xBA010000 signature, to distinguish a pure mpeg frame from one that has other information such as title information etc.

[KBeee]

VOB2MPEG will extract the "pure" mpeg file from the VOB's

[IsoBuster]

Thanks, still not really what I'm after, but thanks.

[boardbuilder]

Try this:

http://www.mpucoder.com/DVD/vobov.html

MPUCoder's website has lots of DVD related technical information. Other great sources of DVD tech info: The Unofficial DVD Specifications Guide, found at:

www.dvd-replica.com

And Jim Taylor's excellent book, DVD Demystified. I was able to buy a used, early edition of this book from www.valorebooks.com for only a penny! (Plus $3.95 shipping, of course.) These sources go into some pretty deep technical nitty gritty. Hope this helps.

[IsoBuster]

Thanks boardbuilder. I will need to dive into that !

Meanwhile, if somebody has a small code example to do what I ask, please don't hold back

[IsoBuster]

And Jim Taylor's excellent book, DVD Demystified.

It just hit me, I know Jim (although I can't seem to recall what we talked about), he's a LinkedIn contact. I'll ask him the same question.

[boardbuilder]

You may be able to get some code samples from open source projects (such as FFMPEG, avidemux, etc) that are able to demux mpeg program streams, including DVD video objects. I would assume that their code is well commented, and maybe sifting through the rubble would yield some clues. Googling ISO 13818-1 will yield a PDF file for the MPEG systems standard, to which DVD VOBs comply. The other sections of ISO 13818 describe the details of the elementary streams.

As you probably already know, DVD VOB files belonging to the same titleset are separated into 1 gigabyte chuncks merely for the convenience of the various operating systems, and they may be concatenated into a single file for more convenient use outside a DVD player. A single VOB file may also contain more than one video object (audio/visual program -- MPEG audio/video contiguous extent). Also note that audio that is not mpeg (AC3, DTS, PCM, etc) is contained in the private data streams.

[boardbuilder]

And Jim Taylor's excellent book, DVD Demystified.

It just hit me, I know Jim (although I can't seem to recall what we talked about), he's a LinkedIn contact. I'll ask him the same question.

ur... umm... ahem... please don't tell him I only paid a penny for his book! (It was worth every penny, by the way!) I did buy the second and third edition of DVD Demystified from the same website, also for a great price (but not as great as the penny deal). The book is actually very much worth its full price IMHO.

[IsoBuster]

LOL ... your secret is safe with me boardbuilder