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<span class="fxxl"><b>dvdisaster</b></span>
<i>Version 0.72.4 / 0.72 (pl4)</i>
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<tr><td style="width:1%; vertical-align:top;">·</td><td colspan=2><span class="fs">Examples of the error correction</span></td></tr>
<tr><td style="width:1%; vertical-align:top;">·</td><td colspan=2><span class="fs"><a href="index20.html">dvdisaster complements quality scans</a></span></td></tr>
<tr><td style="width:1%; vertical-align:top;">·</td><td colspan=2><span class="fs"><a href="index30.html">Pro and con of dvdisaster</a></span></td></tr>
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<h3 class="top">Examples of the error correction</h3>
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<b>Recovery of aged media.</b> 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.
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<tr><td><span class="fs">Reading the defective medium.</span></td></tr>
<tr><td><a href="index10_expand=1.html#snap1"><img src="thumbnails/recover-linear.png" alt="" class="noborder"></a></td></tr>
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<b>Repairing the defective image.</b> 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.
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<tr><td><span class="fs">Repairing the defective image.</span></td></tr>
<tr><td><a href="index10_expand=2.html#snap2"><img src="thumbnails/fix-image.png" alt="" class="noborder"></a></td></tr>
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<b>Recovery needs error correction data:</b> 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
<i>before</i> the medium goes defective.<p>
So if you have a defective medium but never created ecc data for it - sorry,
your data is probably lost.<p>
<a href="index20.html">Why quality scans won't suffice...</a>
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<i> Copyright 2004-2012 Carsten Gnörlich.<br>
Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved.
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