1. Joined : Sep 2015
    Posts : 7
    Windows 8.1
       17 Sep 2015 #1

    Could this CD be read


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ID:	38013So i hear once a cd is broke in half it can never be read again. why is that. i know the cd has to spin. If you take a dime sized piece of the memory layer from a broke cd and place it or tape it to a whole cd and place it in a PC like the pic above why wouldnt it read its spining would the laser know its not part of the disk or see it as dirt?
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  2. Joined : Jun 2014
    UK
    Posts : 623
    W10 pro x64 and W10 x86
       17 Sep 2015 #2

    No chance for that. A CD player should cope with a 400uM (micrometer) interruption in the reflective layer. This disc is an official Philips test disc. A good player can cope with all these defects even up to the 1000um shown. The large rectangular defect is a simulated fingerprint.
    Attached Thumbnails Attached Thumbnails Test Disc.png  
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  3. Joined : Sep 2015
    Posts : 7
    Windows 8.1
       17 Sep 2015 #3

    What of it wasn't dime sized but more like a small thin piece the size of a finger nail or scratch
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  4. Joined : Jun 2014
    UK
    Posts : 623
    W10 pro x64 and W10 x86
       17 Sep 2015 #4

    Minor scratches should be easily handled. You can work out the scale for yourself by looking at the attached image, anything bigger than those defects will give un-correctable errors in the recovered data stream. At that point a player uses 'interpolation' to insert what it thinks the data could be, basing that on previous samples. Beyond that point and its unknown... some players will mute the signal, and a point is reached where the laser can not keep on track, the result is the player rejects the disc in some way, either as a controlled stop/eject or even locking up where the disc takes of at rapid speed.
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  5. Joined : Aug 2014
    Forever West
    Posts : 2,581
    Win10 Home and Pro, Win10 Insider Preview, Win7 Home, Linux Mint
       17 Sep 2015 #5

    jon92 said: View Post
    What of it wasn't dime sized but more like a small thin piece the size of a finger nail or scratch
    CDs and DVDs are read by the laser beam in the drive, any scratch, scuff, fingerprint or interruption of the recorded track screws up what the laser is reading leading to failure. It doesn't take much, more pronounced on the R and RW discs than with what commercial programs come on, an example would be the way youngsters, and some oldsters, handle the discs without them being in a sleeve or jewel case.
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  6. Joined : May 2015
    Posts : 1,377
    Win 10 14393.51
       17 Sep 2015 #6

    Compact disc - Wikipedia, the free encyclopedia

    The data are laid in a spiral track. The analog equivalent is vinyl phonograph record, which has a spiral groove. The CD reads from the center out, though. An audio CD is also a CLV device (constant linear velocity), so the spin rate is lower at the edge than the center. (It ranges from 200 to 500 RPM.)

    If you stuck a piece of a CD onto a platter and spun it, you'd have to align it so that its tracks approximately lay along the possible tracks of a CD. Whether a regular CD device could actually acquire the bits of track and any useful data, I have no idea. (I'd bet no.)

    The total length of the CD spiral is something over 5km (3 mi). A 1.7 cm length of the track (diameter of a US dime) would hold about 2.5kB. That's more than I expected.

    It might be more practical to scan the piece of CD with a high resolution device and extract the track data using software.

    What do you want to know for? Are you trying to spy on someone, or are you afraid that someone will spy on you?
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  7. Joined : Sep 2015
    Posts : 7
    Windows 8.1
       17 Sep 2015 #7

    i afraid that i may have backed up viruses to a cd years ago . i broke the cd think "there its gone no change of it ever infect another one of me pc's" but when you snap a cd is creates a bunch of type pieces of the memory layer. i have this stuipd situation that these tiny piece will get on my hand then i touch a cd and put it in the pc , it will read the cd plus the tiny piece and boom i;ll be infected. i know sounds like a stupid plot to a sci fi movie but Anxiety is a bitch
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  8. Joined : Oct 2014
    Posts : 655
    Windows 7
       17 Sep 2015 #8

    jon92 said: View Post
    i afraid that i may have backed up viruses to a cd years ago . i broke the cd think "there its gone no change of it ever infect another one of me pc's" but when you snap a cd is creates a bunch of type pieces of the memory layer. i have this stuipd situation that these tiny piece will get on my hand then i touch a cd and put it in the pc , it will read the cd plus the tiny piece and boom i;ll be infected. i know sounds like a stupid plot to a sci fi movie but Anxiety is a bitch
    You are being paranoid.

    A virus is a computer program. In order for it to infect a computer it must be intact. Random pieces of a virus on a CD fragment are just junk that couldn't infect anything.

    There are more than enough real threats to your computers security and you should concern yourself with them, not imaginary ones.
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