Modifying a Disc Image

[Kao]

Why is it when I modify a cd-i disc image with a hex editor, that disc refuses to work anymore? Even if I modify the image by just one byte, the disc simply cannot be read! Any ideas?

[cdifan]

It might depend on what you modify...

There is error-detection (EDC) and -correction (ECC) data in the disc image, but most (I'm tempted to say all) CD-i players aren't supposed to use this data unless they get error signals from the CD-drive; the primary reason for this is that error detection/correction is done in software and thus expensive performancewise. Or so the Philips technical notes say...

OTOH, they *might* do EDC in hardware; I don't really know. There are tools that reconstruct the EDC/ECC bytes after editing; the "cdedit" program which used to come with the "master" program is one such.

[WindowsKiller]

I think you can get around of this by converting the image to 2336 bytes/sector. The EDC/ECC stuff is then no longer part of the image file but generated when burning.

[cdifan]

For data sectors, the EDC/ECC is inside those 2336 bytes.

[Kao]

Thanks for the information! I'll give that conversion a try.

How might I go about doing such a conversion, though? Can it be done through Isobuster?

[WindowsKiller]

I would say mount it with Daemon Tools and then rip it from the virtual drive with CDRWin. You have to deselect "RAW" to get an image with 2336 bytes/sector.

But if cdifan is right, it probably won't help.

[Gir Draxa]

You may also try an editor that will not change the file structure like ULTRA EDIT32. I've used that in the past for modifying 3DO titles.

Gir Draxa

[Kao]

Thank you, I will definately give that a try!