What goes wrong in Scratched CD

Please let me know what goes wrong when a CD is scratched and thus why data cannot be read from it.

Hi and welcome to the coolest forum in the world

Your initiation task is to read the following little article http://en.wikipedia.org/wiki/CD-ROM

and come back to give us a short summary

:iagree::bigsmile:

deanimator thanks for providing
http://www.itl.nist.gov/iad/894.05/docs/StabilityStudy.pdf
http://www.memorex.com/downloads/whitepapers/WhitePaper_Reference_Guide_Optical_Media_Mar2406.pdf

i will revert bak for more help :slight_smile:

regards

experts i need a bit more input. So pls pour in your thoughts.
regards

Basically, a disc contains a series of “0” and “1” in form of pits and lands on the spiral of the data track.

When a disc is scratched, some pits and lands cannot be read by the laser. In other words, the drive is not able to understand if in the track there is a pit or a land. Consequently, it is not able to understand if it is reading a “0” or a “1”, and then it is not able to extract data from the disc.

Actually, [B]all[/B] discs contains errors on the data track, but most of times these errors are correctable (both by hardware and software mechanisms). When a disc is scratched, the amount of errors is higher, and if the scratch is located on a critical sector of the disc (i.e. in the sector used by hardware and software mechanisms to recover data), these recovery data cannot be retrieved, and consequently the disc data cannot be read at all.

I know that this is not exactly the most precise formal description of what happen on a disc, but basically this is what happens on a scratched media :flower:

When a CD is scratched, the laser is not able to see the track containing “pits” and “lands” properly, and if it misses too many of these, the error correction circuits are not able to output correct data and errors are reported through Windows (or whatever operating system you use).

If the scratches are really bad, the laser may not even be able to follow the track on the CD properly forcing it to seek back and forth to find the track.

Some drives are better than others in reading scratched CDs, and some programs like IsoPuzzle can sometimes help you copy a damaged CD.

thanks a lot to all of you nice people for helping.:slight_smile:

vinay453 ;If you have a scratched disc you need to recover you may be able to have someone with a commercial disc polisher resurface it for you.
You might have to pay a little .I suggest your local movie rental store or your local library.There are probably even businesses in some areas that do this.
If it just one that can be easily replaced it’s not worth the bother but some discs are irreplacable.

[quote=cholla;2035040]vinay453 ;If you have a scratched disc you need to recover you may be able to have someone with a commercial disc polisher resurface it for you.
You might have to pay a little .I suggest your local movie rental store or your local library.There are probably even businesses in some areas that do this.
If it just one that can be easily replaced it’s not worth the bother but some discs are irreplacable.[/quote]

My local movie rental store ( going for 20years) uses Brasso.
I spoke to them ,They have a Commercial disc polisher . But Brasso workes Best.
I think you have to be trained to use that Machine( 1 microsecond to long and * poof * all is gone :eek: :bigsmile: