Undisker - Open, Create and Extract ISO Files

Invalid CD Volume Header

During the CD capturing process you get the popup error message like following:

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Is it a bug of Undisker?

No, it is not a bug. This message means that the source drive to be captured has been validated and Undisker has identified the logical inconsistency of CD technical data.

What does this problem mean?

It means that the number of logical sectors stored in CD Volume Header differs from the actual number of physical sectors. This information is created by CD Recording software during the mastering process, so this is not a physical damage or incorrect behaviour of Undisker.

Why it could happen?

It may be, for example, a simple copy protection mechanism, which theoretically can lock a standard access to CD sectors out of range indicated in CD Volume Header. However normally all CD burning programs simply ignore this value.

Another reason can be a CD layout with mutliple data tracks. In this case, number of sectors in each session is always less than the total amount of sectors on CD.

What can be done?

You can choose one of two available options - value can be either kept or corrected.

• Keep the existing value. If CD is captured "as is", last portion of image may be not accesible by other programs which use the information about logical amount of sectors (from CD header). However the data will be captured completely, and Undisker itself is able to acces all virtual sectors of such disk image, but compatibility with third-party software can not be guaranteed.
• Correct the value. To prevent inconsistencies in work of third-party software, CD Volume Header should be corrected during capturing. Corrected ISO image contains the complete and valid data, but it's not 100% identical to the original disk anymore. For example, CRC calculated for such image will be different from the CRC of original CD content.

Undisker asks user for the action, which other programs normally do not do. If you don't want to be asked for this, you can customize Undisker to perform a selected action automatically. For further details please refer to Undisker Customizing Options.