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
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...