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+<?php
+# dvdisaster: English homepage translation
+# Copyright (C) 2004-2012 Carsten Gnörlich
+#
+# UTF-8 trigger: äöüß 
+#
+# Include our PHP sub routines, then call begin_page()
+# to start the HTML page, insert the header, 
+# navigation and news if appropriate.
+
+require("../include/dvdisaster.php");
+require("../include/screenshot.php");
+
+begin_page();
+?>
+
+<!-- Insert actual page content below -->
+
+<h3 class="top">The adaptive reading strategy</h3>
+
+dvdisaster contains two different reading strategies.<p>
+
+<b>The adaptive reading strategy is recommended for:</b><p>
+<ul>
+<li><a href="howtos42.php">extracting data</a> from damaged media
+</li>
+</ul>
+
+<b>The <a href="qa34.php">linear reading strategy</a> is recommended for:</b><p>
+<ul>
+<li><a href="howtos23.php">creating images</a> from undamaged media, e.g. to generate the error correction file</li>
+<li><a href="howtos12.php">scanning the medium</a> for reading speed and read errors</li>
+</ul>
+
+<pre> </pre>
+
+<b>Properties of the adaptive reading strategy.</b><p>
+
+The adaptive reading strategy uses a "divide and conquer" approach for locating
+still readable portions of a damaged medium. The strategy is based upon an article
+published by Harald Bögeholz in c't-Magazin 16/2005 where it was published together
+with the program <i>h2cdimage</i>:
+
+<ol>
+<li> 
+At the beginning the medium is considered as a single unread interval. Reading begins
+with sector zero.<p>
+</li>
+<li>
+The reading process continues sequentially unless either the end of the current interval
+or a read error is encountered.<p>
+</li>
+<li>
+The reading process is terminated if either (3a) sufficient sectors for a successful
+error correction have been read or (3b) no unreadable intervals exceeding a given size
+remain.
+<p>
+</li>
+<li>
+Otherwise the largest remaining unread interval will be determined. Reading continues in the middle
+(e.g. second half) of this interval; 
+the first half of this interval is kept for a later reading pass.
+</li>
+</ol>
+
+<?php begin_screen_shot("Adaptive reading in progress","adaptive-progress.png"); ?>
+The termination criterium (3a) is especially efficient: Reading will stop as soon
+as enough sectors have been collected for a successful image recovery using the
+error correction file. This can reduce the reading time by as much as 90 percent
+compared with a full read attempt, but does of course only work when 
+an error correction file is available.<p>
+<?php end_screen_shot(); ?><p>
+
+<pre> </pre>
+
+<a name="configure"></a>
+<b>Configuration</b><p>
+
+<b>Error correction file.</b> 
+Adaptive reading works best when error correction data is available. 
+Obviously the error correction data must have been 
+<a href="howtos21.php">created</a>
+at a time where the medium was still fully readable. To use a error correction file
+during adaptive reading, 
+<a href="howtos42.php#select_eccfile">enter its name</a> before starting the reading process.<p>
+
+<b>Limiting the adaptive reading range.</b> Reading can be 
+<a href="howtos11.php#image">limited</a> to a part of the medium.
+
+This is not recommended when error correction data is used since the limit
+might prevent sectors from being read which are required 
+for a succesful error correction. 
+If no error correction data is available, 
+limiting the reading range might be helpful
+during multiple reading attempts.<p>
+
+<b>Early reading termination.</b>
+If no error correction data is available, adaptive reading will stop when no unread
+intervals
+<a href="howtos41.php#reading_attempts">larger than a selectable size</a> remain.<p>
+
+The termination value should not be smaller than 128.
+Otherwise the laser head will have to carry out lots of repositioning moves during the
+final phase of the reading process. This will negatively affect both the life expectancy
+of the drive and its reading capability. A better approach is to stop adaptive 
+reading earlier and then try reading the remaining sectors with an additional
+<a href="qa34.php">linear reading</a> pass.
+
+<!-- do not change below -->
+
+<?php
+# end_page() adds the footer line and closes the HTML properly.
+
+end_page();
+?>