The Difference Between DVD- & DVD+

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DVD- and DVD+ media look the same, but there are important differences.
DVD- and DVD+ media look the same, but there are important differences.

During your most recent visit to the electronics section of a local store, you may have found yourself wondering just what the difference is between a DVD+R(W) and DVD-R(W). The discs look the same, physically. They're also about the same price and boast similar speeds. There are some subtle differences, however, that you might want to consider before making a purchase.

  1. Legacy

    • The DVD- format was developed in 1997 by the DVD Forum, and it was designed as a natural extension of the CD-R format using a smaller-wavelength laser and narrower tracks on the disc surface. The DVD+ format was not released until 2002 by the DVD+RW Alliance, giving DVD- a five-year advantage in the consumer market. As a result, the DVD Forum was reluctant to recognize DVD+ as an official format until the DVD6C Licencing Group added DVD+ to its licenced formats list in 2008.

    Compatibility

    • Since the DVD- format was available to consumer markets for five years before DVD+ was introduced, many DVD video players and DVD computer drives sold prior to 2004 were not designed to read DVD+ discs. These drives might therefore be incompatible with the newer DVD+ specification. However, in an independent test of 252 DVD devices by IntelliKey Labs on behalf of the DVD+RW Alliance in 2003, over 95 percent of devices were able to read and write to DVD+R discs compared to over 85 percent for DVD-R discs. As of 2010, nearly all consumer-grade DVD devices support both media formats.

    Recording Modes

    • One of the main differences between DVD- and DVD+ is the available recording modes. The DVD Forum released the DVD-VR standard in 1999 for DVD-RW and DVD-RAM discs. The DVD-VR standard allows the disc contents to be written, edited and rewritten at any time during the recording process (i.e., you need not rewrite the entire disc to edit one file). Unfortunately, many DVD video players will not recognize the DVD-VR standard; the user must choose to use either the DVD-VR or DVD-Video standard. DVD+RW discs use the DVD+VR standard, which allows for on-the-fly editing and remains compatible with DVD video players.

    Addressing Methods

    • One technical difference between the two formats is the addressing method used. DVD- technology uses a method known as Land Pre-Pit. This method uses the "land" space between the grooves on the DVD- disc as header space. Each address is approximately 0.5 micrometers wide on the disc surface. DVD+ technology uses a different method called Address In Pre-Groove. ADIP uses the "wobble" frequency of the disc track to determine physical location. Because four wobble cycles are used for each address, each header is approximately 17 micrometers long, making them slightly more resistant to defects and read/write errors.

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