133 lines
5.7 KiB
PHP
133 lines
5.7 KiB
PHP
<?php
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# dvdisaster: English homepage translation
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# Copyright (C) 2004-2012 Carsten Gnörlich
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#
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# UTF-8 trigger: äöüß
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#
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# Include our PHP sub routines, then call begin_page()
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# to start the HTML page, insert the header,
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# navigation and news if appropriate.
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require("../include/dvdisaster.php");
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require("../include/screenshot.php");
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begin_page();
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howto_headline("Recovering media images", "Advanced settings", "images/create-icon.png");
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?>
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The first attempt of <a href="howtos42.php">reading the defective medium</a>
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will usually provide enough data for the error correction. If it did not,
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try the following:<p>
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<?php begin_screen_shot("Estimating the chance of recovery","adaptive-failure.png"); ?>
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<b>Estimating the chance of recovery</b><p>
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Examine the output of the reading process. Under the "Sectors processed" section
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you will find the actual percentage of readable sectors and how many percent will
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be needed for a full recovery. Using the difference between the two values
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(85.6% - 81.3% = 4.3% in the example) you can estimate the likelyhood of being able
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to collect enough sectors for a successful recovery:<p>
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<?php end_screen_shot(); ?>
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<table cellspacing="0" cellpadding="10">
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<tr style="background-color:#c0ffc0;">
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<td class="w10p" align="center" valign="top">< 5%</td>
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<td>Chances are good that you will get enough data using more reading attempts.
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</td></tr>
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<tr style="background-color:#ffffc0;">
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<td class="w10p" align="center" valign="top">5%-10%</td>
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<td> If you have several drives with different reading characteristics
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you may get the required data by being persistent and patient.
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</td></tr>
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<tr style="background-color:#ffe0c0;">
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<td class="w10p" align="center" valign="top">10%-20%</td>
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<td> You are in trouble. If the missing sectors do not drop significantly
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below 10% during the next 2-3 reading attempts the medium is probably unrecoverable.
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</td></tr>
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<tr style="background-color:#ffc0c0;">
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<td class="w10p" align="center" valign="top">> 20%</td>
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<td>Too much data loss; you can write this medium off as unrecoverable.
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To prevent this from happening again, use error correction data with
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higher redundancies and shorten the intervals for defect scanning.
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</td></tr>
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</table><p>
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Try the following settings one by one in further read attempts.
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Please perform a complete reading pass for each setting so that you
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learn how it affects the outcome (sometimes the results also differ
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depending on the drive used for reading). When you have gone through the list
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you may combine them into more powerful configurations.
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<hr>
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<?php begin_screen_shot("Perform another reading attempt","fix-prefs-read-attempts1.png"); ?>
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<b>Perform another reading attempt</b><p>
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Do not alter any values except for setting a smaller value for terminating the
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reading process. Recommended values are: 32 for BD, 16 for DVD and 0 for CD (use
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the slider marked green). Perform another reading attempt using this setting.
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You can repeatedly read the medium as long as any pass
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provides a significant number of new sectors.<p>
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<b>Hint:</b> Let the drive cool down between the reading passes. Eject and load
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the medium before each pass; sometimes the medium comes to rest in a better
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position and the number of readable sectors improves.
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<p>
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<?php end_screen_shot(); ?>
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<hr>
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<b>Complete the image using different drives</b><p>
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Perform additional reading attempts using different drives. Transfer the
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image to other computers to see if their drives can contribute more readable
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sectors.<p>
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<hr>
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<?php begin_screen_shot("Increase the number of reading attempts","fix-prefs-read-attempts2.png"); ?>
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<b>Increase the number of reading attempts</b><p>
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<i>For all media types (CD, DVD, BD):</i><p>
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Set the number of reading attempts per sector to a minimum of 5 and a maximum of 9
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(green markings).<p>
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<i>Only for CD media:</i><p>
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Some drives are capable of partially reading defective sectors on CD media.
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Activate the "Raw sector caching" option and specify a directory where
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fragments of defective sectors should be stored (yellow markings).
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If enough fragments of a defective sector have been collected it may be possible
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to fully reconstruct it from that information.
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<?php end_screen_shot(); ?>
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<?php begin_screen_shot("Multiple reading attempts","fix-reread-dvd.png"); ?>
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<i>Examining results of multiple reading attempts (CD, DVD, BD):</i><br>
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Not all drives show an improvement after increasing the number of reading attempts.
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Watch for messages of the form "Sector ..., try x: success" (highlighted in yellow).
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These indicate that
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the drive could read a sector after several reading attempts. If you never see such
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messages, increasing the number of reading attempts does not pay off for the
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respective drive.
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<?php end_screen_shot(); ?>
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<a name="21h"></a>
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<i>Examining partial reading of defective CD sectors:</i><br>
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When the whole medium has been processed, look into the directory you entered
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above (/var/tmp/raw in the example). If no raw files have been created
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the drive may not support the required reading mode.
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However if you have several drives which do create raw files, then let them all
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work in the same raw file directory. Collecting raw sector fragments from
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different drives hightens the chance of reconstructing the defective sectors.
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<p>
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<?php begin_screen_shot("Use different raw reading mode","fix-prefs-drive2.png"); ?>
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<i>Use a different raw reading mode for CD media:</i><br>
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Using the preset "20h" raw reading mode might not work on some drives.
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Perform another reading attempt using raw reading mode "21h" (see the screenshot).
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Check again whether some raw files have been created.
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<?php end_screen_shot(); ?>
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<!-- do not change below -->
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<?php
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# end_page() adds the footer line and closes the HTML properly.
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end_page();
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?>
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