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  1. Does a scratched DVD result in lost data?

  2. How do I fix a scratched DVD?

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1. Not always, error-detecting and error-correcting codes are used in DVDs (as in CDs, ECC RAM, etc..), see here for more infos on them: en.wikipedia.org/wiki/Error_detection_and_correction –  Shadok May 23 '12 at 13:32
    
Thanks @Shadok for answering Q1 –  Suman Krishna Saha May 23 '12 at 13:33
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5 Answers

up vote 20 down vote accepted

1.yes but not completely

enter image description here

It will depend on how much it is scratched . If it is negligible just ignore it . If it is in the moderate level some utility programs may help you . If it is in very high level no hope , (still you may can recover some data if you have luck :) )

2.Try your luck using following apps

  1. CD Recovery Toolbox Free CD Recovery Toolbox Free was developed for recovering damaged files CD, DVD, HD DVD, Blu-Ray and etc disks. You can use it to restore information lost as a result of some mechanical damage of the disk (scratches, chips, different spots on the surface) or as a result of incorrect recording. Program can recover data that was considered lost. Tool scans any CD and DVD disks and finds files and folders located there

    enter image description here

  2. Roadkil's Unstoppable Copier

    Recovers files from disks with physical damage. Allows you to copy files from disks with problems such as bad sectors, scratches or that just give errors when reading data. The program will attempt to recover every readable piece of a file and put the pieces together. Using this method most types of files can be made useable even if some parts of the file were not recoverable in the end.

enter image description here

Or Try to fix the DVD

  • First clean the surface of the disc with a soft lint-free cloth. You can use a gentle detergent (or rubbing alcohol) if there are some grease spots. Make sure there are no finger prints or dust particles. Don’t scrub too hard as you may do more harm than good this way.
  • Now apply some toothpaste or polish on the scratched surface. It is best to start with a minimum amount of either, or else you will have your work really cut out trying to buff away the remainder.
  • Now rub gently with a cloth moving from the center outwards.

Links

  1. http://www.makeuseof.com/tag/how-to-repair-and-recover-data-from-damaged-cds-or-dvds/
  2. http://www.makeuseof.com/tag/free-cddvd-file-recovery-tool-cd-recovery-toolbox/
  3. http://www.roadkil.net/program.php?ProgramID=29
  4. http://www.google.com
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+1 for Unstoppable Copier, that software is fantastic for grabbing data off bad/dying drives as well. –  Evan Wondrasek May 29 '12 at 14:21
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Yeah, the important thing, when trying to remove scratches, is to NOT do circular motions, which will tend to put new microscratches parallel to the recording tracks but instead use radial (in-out) motions. And likely a Radio Shack or Best Buy near you has a kit for scratch removal. –  Daniel R Hicks Oct 10 '13 at 23:41
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Does a scratched DVD result in lost data?

Not necessarily. The data is not actually stored on the surface of the disk - it's actually stored more towards the center. There is a protective layer of plastic-coating (polycarbonate) surrounding the data.

DVD layers


How do I fix a scratched DVD?

If only the protective layer is scratched, it can be filled in using the CD/DVD repair kits available at electronics stores (or even Wal-mart). If the scratch is deep enough to damage the data, however, you're out of luck.

(Others have mentioned that DVDs use error-correction codes. This is true, but if the drive is saying the data is corrupt/can't be read, that already means the ECC wasn't able to recover the data, so that knowledge does not really help you)

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+1 for the diagram –  Joshua Drake May 23 '12 at 17:52
    
Thanks @BlueRaja –  Suman Krishna Saha May 24 '12 at 6:17
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The diagram is really awesome . Diagram tells more than text. –  Tachyons May 24 '12 at 12:06
    
@BlueRaja Is there an tool /device available to restore data inside the protective layer ? –  Tachyons May 25 '12 at 4:50
    
This diagram seems like one for the dual layer discs or is it? –  Power-Inside Jun 24 '12 at 14:51
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1- Yes, all DVD/CD are burned using a digital redundancy technique. On DVDs I know that Reed-Solomon code is used:

Reed–Solomon codes have since found important applications from deep-space communication to consumer electronics. They are prominently used in consumer electronics such as CDs, DVDs, Blu-ray Discs, in data transmission technologies such as DSL and WiMAX, in broadcast systems such as DVB and ATSC, and in computer applications such as RAID 6 systems.

This code allow you to have some scratches on your DVD/CD because data redundancy, however it goes only to a limit(not deterministic), after that, every new scratch will result on more data loss.

2- Fortunatelly there are some methods that allow you to try to recover your scratched media and the data on it. On Wikihow you can found a good way:

While compact discs (CDs) are remarkably durable, it’s nearly impossible to prevent scratches and scuffs from occurring from time to time, especially with frequent use. The resulting damage can mean either a skip in your favorite music track or, in the case of data CDs, the loss of that spreadsheet you worked on for two weeks.

Don’t despair — repair! While commercial CD repair kits and CD refinishing machines are available, you may be able to repair the damage on your own with products you already have.

  1. Steps:

    1.1 Clean the disc

    1.2 Identify the scratch

    1.3 Repair foil scratches

    1.4 Do data recovery

    1.5 Polish the CD with a slight abrasive

    1.6 Wax method

    1.7 Light bulb method

    1.8 Professional refinishing

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+1 for the toothpaste method; it works. –  Shinrai May 23 '12 at 14:21
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Scratches on the bottom (clear) portion of the disk cause data read errors by interrupting the laser beam's path to the data. The actual data may still be intact, just unreachable (think overwriting words on a page with a black marker, the words are still there but not visible.) Such scratches may be filled in or polished out using various products/techniques. Try googling for "CD repair".

Scratches on the top (metallic) portion of the disk actually remove the data bearing layer and are not physically recoverable. If you can see light through the disk, the data is no longer there.

In either case the error correction protocols noted in other answers are used to rebuild lost data, up to a point.

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Also, Disks with surface damage on the bottom can fairly easily be repaired, a lot of Movie rental places have a machine that can resurface disks and make them work again. –  Jeff F. May 23 '12 at 16:21
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"Such scratches may be filled in or polished out using various products/techniques. Try googling for "CD repair"." Good point about the rental place though, you may try asking your local rental place if they are willing to process your disk. –  Chris Nava May 23 '12 at 17:30
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  1. Yes, it can cause. Depends on the location/depth/type of the scratch. But yes, it may cause data loss. (Even if the DVD features a "Scratch protection layer".)
  2. You can't repair a damaged DVD. Back in the days, we used Alcohol 120% software to read the DVD even with the damaged blocks, and managed to save the data. You can give that a try.

To prevent all this: You can use WinRAR's "Recovery record". If the DVD gets damaged, and if the corrupted part falls under the recovery record, WinRAR will be able to repair the archive itself.
(You can enable it at the "General" tab of "Add to archive", and set the Recovery record's percentage at the "Advanced" tab. How much? Depends on how big your data is.)

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On bad scratches I used a dab baby oil on the scratches to help the laser read the blocks, worked amazingly well, clear fingernail polish works well also, but is a more permanent solution that requires dry time. Then there is polishing the disc to remove light to moderate scratches. –  Moab May 23 '12 at 13:49
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I disagree on 2. You can fix damaged DVD as long as it is surface damage. A lot of movie rental places have a machine that will resurface a DVD and restore it to like new condition. –  Jeff F. May 23 '12 at 16:23
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