Inside the UDF filesystem - Sectornumber & filesize ?

[marsoupilami]

Hi there!

I have recovered a VideoDVD as far as possible to an iso-image.
The bad thing is: both the ISO-filesystem and the UDF-system are partly corrupted...
Well - my approach now is to recover the files fixing the UDF entries using information obtained from the other filesystem - or vice versa.

Any ideas where to find filesize and starting sector inside the UDF area?

Many thanks in advance!

[Rufus210]

Look at the specs (http://www.osta.org/specs/)?

[setarip_old]

@marsoupalami

Hi!

I've got to believe that if you get in touch with "LIGHTNING UK!" (author of DVD Decrypter and IMGBurn), he/she can tell you all you want to know about this topic...

[awhitehead]

Any ideas where to find filesize and starting sector inside the UDF area?

Many thanks in advance!


Take a look at this (http://forum.doom9.org/showthread.php?p=995404#post995404) post where I ramble on and on on how to obtain the LBA Extend for Blu-Ray discs. Read the specs, they tell things. :-P

Basically you are looking at tracing the following sequence (Shamelessly stolen from FreeBSD's udf_vfsops.c, since scottl can draw better ASCII art then I can) to obtain the actual LBA for the file, and in process of reading file ID descriptor you get to learn the size and starting sector.


* Sector:
* 256:
* n: Anchor Volume Descriptor Pointer
* n - 256: |
* |
* |-->Main Volume Descriptor Sequence
* | |
* | |
* | |-->Logical Volume Descriptor
* | |
* |-->Partition Descriptor |
* | |
* | |
* |-->Fileset Descriptor
* |
* |
* |-->Root Dir File Entry
* |
* |
* |-->File data:
* File Id Descriptor
* |
* |
* |-->File Entry
* |
* |
* |-->File data



AVDP can be at 256's sector of the disk (using LBA, so 256 + 16 physical sector), at the last block of the disc, or at the last - 256 block.

The rest are highly variable.

[setarip_old]

@awhitehead

I couldn't help but notice that your posting refers to BluRay DVDs.

Is this information equally applicable to standard video DVDs (which is what "Marsoupilami" is inquiring about)?

[marsoupilami]

Many thanks to everyone!
This sounds a little complicated but I will see how to get my files out...
Thank´s again!

[awhitehead]

@awhitehead

I couldn't help but notice that your posting refers to BluRay DVDs.

Is this information equally applicable to standard video DVDs (which is what "Marsoupilami" is inquiring about)?

To the best of my knowledge, it is. At least my laptop doesn't have a Blu-Ray or HD-DVD drive, so currently I test my code with a standard burned DVD in a drive.

But basically, we are talking about reading a UDF filesystem. Standard DVDs tend to use version 1.02 of the UDF filesystem with an ISO 9660 bridge. ISO9660 bridge is actually somewhat irritating, because it makes things look like DOS files if you can't grok UDF 1.02 natively. DVDs recorded in a TOC mode tend to use UDF 1.5, since main change from 1.02 to 1.5 is the support of the virtual rewritable structure, that permits you to add (in reality overlay) files to the session . DVD-VRs tend to use UDF-2.0 since 1.5 to 2.0 primarily added support for real-time recording (hence AVDP can end up in the last sector of the disc) and added better virtual rewritability support. Blu-Ray and HD-DVD tend to use wither UDF 2.5 or UDF 2.6. Big thing in 2.5 is ability to duplicate data multiple times on disc. In PS3 games this functionality is used to spread identical file in multiple locations on the same optical disc, and permit better seek times. There is also metadata support that got added, somewhat similar to streams under NTFS or resource forks under HFS+. Basically used for indexing and searching, although I don't know of anyone actually using it.

But note that all of the above did not change the basics all that much. You still get to look for AVDP in 3 standard locations. You still use AVDP to figure out where LVD is, and from there find the Fileset Descriptor. Then you traverse the FD to find what you need.

I think.

[setarip_old]

To the best of my knowledge, it is.That's all I wanted to be sure of. Thanks ;>}