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  1. #1
    Registered User Lyubo_lvl's Avatar
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    DVD

    DVD - "+R" "-R".

  2. #2
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  3. #3
    Registered User Lyubo_lvl's Avatar
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    . ? - +R -R, +R 20-30% -?

  4. #4
    Registered User Neotrace's Avatar
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    / -/ .... . +/- ...
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    Registered User Lyubo_lvl's Avatar
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    , NEC 1100A 119

  6. #6
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    :

    DVD-R and DVD-RW
    DVD-R/W was the first DVD recording format released that was compatible with standalone DVD Players.
    DVD-R is a non-rewriteable format and it is compatible with about 91% of all DVD Players and most DVD-ROMs.
    DVD-RW is a rewriteable format and it is compatible with about 74% of all DVD Players and most DVD-ROMs.
    DVD-R/W supports single side 4.7 GB* DVDs(called DVD-5) and double side 9.4 GB* DVDs(called DVD-10).
    These formats are supported by DVDForum.

    DVD+R and DVD+RW
    DVD+R/W has some better features than DVD-R/W such as lossless linking and both CAV and CLV writing.
    DVD+R is a non-rewritable format and it is compatible with about 86% of all DVD Players and most DVD-ROMs.
    DVD+RW is a rewritable format and is compatible with about 74% of all DVD Players and most DVD-ROMs.
    DVD+R/W supports single side 4.7 GB* DVDs(called DVD-5) and double side 9.4 GB* DVDs(called DVD-10).
    These formats are supported by the DVD+RW Alliance.

    .. - DVD+R lossless linking - gap ...
    (justlink) (.. ) DVD-R gap.

    ( , DVD-RAM )

    Why DVD+R(W) is superior to DVD-R(W) , ( ), ( ) ....

  7. #7
    Registered User Neotrace's Avatar
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    Originally posted by georgebg
    Why DVD+R(W) is superior to DVD-R(W) , ( ), ( ) ....
    ...10x.... + - - :

    Not only are the pre-pits more error prone than phase modulation, but data they carry are also less protected. In one ECC block pre-pits carry 192 bits of information (one pre-pit block). Out of these 192 bits, 48 are not protected by any error correction mechanism, 24 bits are protected by 24 bits of parity (A parity), and the last 56 bits are also protected by 24 bits of parity (B parity). All in all, this strange heterogeneous structure finally gives a pretty weak protection to the information bits carried by pre-pits.

    On the other hand the corresponding DVD+R(W) structure is 4 times smaller : one ADIP word is 52 bits large, consisting of 1 sync bit, 31 data bits and 20 parity bits (which protect all data bits). One ECC block contains 4 ADIP words, so 204 bits of information in total. Also each ADIP word contains the full ECC block address, while 4 times this size are needed in the - technology to extract this address : this gives significant speedups when seeking uses this method.

    Defect management and recording quality

    Another major advantage of DVD+RW format over DVD-RW (although no drive support it yet) is hardware defect management provided by the DVD+MRW standard (Mt Rainier for DVD+RW). On a DVD+MRW disc, when an error occur during a read or write access to an ECC block, this block is flagged as bad and the drive will not use it any more. Instead, when writing to the disc, data which should have been stored in this bad block are relocated elsewhere ; likewise, when the drive is asked to read these data again, it will fetch them from the new location. These operations are completely transparent for any software (whatever operating system, driver or burning application is used), and while the initiator is requesting consecutive sectors the drive will actually read data from various locations : this new abstraction layer is called Logical to Physical address translation.

    As a side note, popular belief is that defect management is only useful when burning new discs (where data which are being written can also be read back, checked and moved to another location if needed), but that it is helpless on discs which get damaged after they have been burned. This is wrong, because when an ECC block is partially damaged and requires several retries to be read (or for instance give too many PI/PO errors), these data can proactively be moved to another clean location on the disc before media wear-out makes them unreadable. Of course, if an ECC block is damaged beyond error correction capabilities, data are definitely lost ; however, only very serious damages can make such a thing happen, as PI/PO correction can handle burst errors larger than 6 mm.

    As with formatting, DVD+RW standard enables background verifications, i.e. the disc is checked for defects when the drive is idle. Of course, at any time the user can still read or write to the disc, or eject it from the drive ; background verification would then resume later from where it was stopped. Combining these features together gives a very powerful system which can continuously try to improve the longevity of discs : while the user performs its usual operations, the drive can check in the background the complete surface of the disc and move data from damaged locations to clean areas. Such advanced use of defect management are already described in the DVD+MRW specification, for instance with the Self Monitoring Analysis and Reporting Technology (SMART, a technology inspired from hard discs). Finally, it is important to mention that DVD+MRW provides full read-only compatibility for players which don't understand MRW.

    :

    Also a DVD+R(W) disc allows a drive to achieve better writing quality (independently of media quality), because it gives more information to a drive than a DVD-R(W). Indeed, just like with CD-R(W), the best writing settings for a given disc are found at startup during the OPC (Optimum Power Control) algorithm, which use data contained in the pre-pits blocks/ADIP words. And regarding OPC, a DVD+R(W) gives not only more information (e.g. power dependency on wavelength) but also more precise ones (e.g. startup laser power). Moreover, all these information are available for 4 different speed ranges (primary and upper speeds, normal and 4x+ mode), while - format only provides one set of data. This is very important because optimal writing settings are very sensitive to burning speeds. Also the OPC test area of DVD+ is 32768 sectors in total, compared to 7088 sectors for DVD-.
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