Examples of the error correction

Recovery of aged media. The medium processed here has become discolored and partly unreadable in its outer region. A surface scan yields about 23.000 unreadable sectors of 342.000 sectors total; resulting in about 7,2% defective sectors.

Reading the defective medium.

Repairing the defective image. The resulting image is still incomplete since about 23.000 sectors could not be read. These sectors are now reconstructed using the error correction data created with dvdisaster. During the recovery a maximum of 20 errors per error correction block is encountered. This results in a peak error correction load of 63%, meaning that this degree of damage is handled well by error correction data created with default settings.

Repairing the defective image.

Recovery needs error correction data: The recovery process described above uses error correction ("ecc") data. Think of this data as a special form of backup data (it needs less space than a normal backup, though). Like an ordinary backup, the ecc data needs to be created before the medium goes defective.

So if you have a defective medium but never created ecc data for it - sorry, your data is probably lost.

Why quality scans won't suffice...