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Wednesday, November 12, 2008

How to copy the perfect CD or DVD

If I can first draw a quick parallel between 2 Vauxhall Vectra's parked next to each both look the same but one has a 3.0 V6 engine the other a lean 1.4 are they really the same? The same can be said of the discs, disc printing and more so the copy process also.
As you know you can copy DVD data at between 1x and 16x. We do not recommend using more than 2X. Why - a disc spinning at 16X on a DVD is equivalent to 72X on a CD. The faster you burn 1> the more errors will be written to disc 2> the more gear changes are required on your drive to keep burning at a constant speed which in itself causes more errors to occur.
How can you tell if a disc is burned too fast? Most times you can see with the naked eye by looking at the back of your disc and see if you can see subtly different coloured bands/ rings on the data area. If so you will most likely find CRC errors where it changes from one band to another. This can be checked by downloading CRC Checking software (Sorry CRC = Cyclic Redundancy Check error - its the check digits on your packets of data)
Next you need to ask are all discs verified? This takes as long as the burn process itself where every single disc is validated against the original data to be copied and rejects highlighted. So copying is not just copying as you will see.
Same goes for the blank media itself. Ever wondered why some discs cost more than others? Its down to a number of factors a> thickness of material this should be 1.2mm thick exactly. Thinner media is produced by some manufacturers to avoid paying Phillips royalties there is also a double saving of polycarbonate and royalty fee, downside, compatibility of disc with players. Ever had a disc that refuses to play? b> amount of Nickel (for DVD) or silver (for CD) put down on the disc. This is the reflective surface for the laser. 70 Microns is the minimum recommended - some will skip and put less on this reduces readability of the disc, some put the minimum, quality discs put more. Why? to increase readability and longevity of disc life. c> quality of the dye in the disc. although all DVD-r's are blue the dye in the disc is affected by UV light (why we always recommend keeping DVD in a black backed case). Some dyes are more stable than others. Sony, TDK and Verbatim offer 80 year guarantees others 50 some no guarantee, why could this be, similar analogy to sun cream could be drawn here, it all looks the same but some says factor 50 some factor 5. d> In manufacture of the disc, rejects occur. There are only 4 companies globally who make all CD-r and DVD-r and sell them to the branded companies you know and love. Every DVD-r will have a small amount of errors built into the plastic through imperfection in the polycarbonate, dye, nickel etc. different manufacturers have acceptable levels of errors. Sony TDK, Verbatim having the lowest acceptable error rates IE Reject more discs from the manufacturing process. The rejects are then graded where lesser brands accept the top tier of discs, low quality brands take the next, A grade media the next then unbranded the bottom tier.

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