Xbox DVD Layout (Unknown sectors at end of Image)

Discussion in 'Xbox (Original console)' started by Delta_force, Jul 14, 2018.

  1. Delta_force

    Delta_force Spirited Member

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    I started working on a tool to strip redump-conforming XISOs of replicatable data for easier storage, however, info on XDVDs is rather scarce (the only readable info I have is from xbfuse, a thing which allows you to mount XISOs via fuse in linux).

    All XDVDs have a plain DVDVIDEO conforming filesystem at the start, which will display a "put this disk in a xbox to play" message in a couple languages. This seems to be the same across all disks from all regions, so dumping it once, stripping and appending when reconstructing is a nobrainer.
    The interesting part is this: At the very end of a XDVD, you have 16 sectors which contain non-zero data, the data itself is 32bytes in size (appears to be a set of uint32_t) with all values except two being constant, those two counting up from the first sector to the last sector in increments of 1.
    When walking backwards, after those 16 sectors you get zero-sectors until you reach the actual XDVDFS. These 16 sectors again appear to be the same across all disks (Note: I only checked 5 disks for this, dont take it for granted. If someone knows of a really big game, I can check if all sectors are still there).
    Does anyone know the purpose of those sectors or possibly a way to derive them (hardcoding them in is always an option, but I want to avoid that as much as possible)?

    (Sidenote: the "magic" sector which has the "MICROSOFT*XBOX*MEDIA" signature is followed by a sector which begins with "XBOX_DVD_LAYOUT_TOOL_SIG". A quick search with the G reveals exactly zero results for this, any info on that would be a nice bonus)
     
  2. Rocky5

    Rocky5 Site Supporter 2015

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    Last edited: Jul 14, 2018
  3. Delta_force

    Delta_force Spirited Member

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    Alright, I checked both images and they both follow the same pattern (16 non-zero sectors at the end, then blank space until XDVDFS) so Ill assume that these sectors exist as-is in all images (so hardcoding is now a viable option), but that doesnt make it any better of an option. Do the MS docs say anything about that?
     
  4. ToXZiN 1

    ToXZiN 1 Spirited Member

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  5. Delta_force

    Delta_force Spirited Member

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    oooh, nice find. this also mentiones the 16 sectors i found (as security sectors)
     
  6. ToXZiN 1

    ToXZiN 1 Spirited Member

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    Yep, commodore4eva did a lot of work on the DVD firmware side of things with the Samsung 605B drive. A quick Google search with "commodore4eva samsung 605b" will return info on it as well. The specialist made a hacked fw for the Hitachi OG xbox drive. He hardcoded the checks into the drive fw to always return a pass when burning media.
     

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