DVD Studio Pro - What Do You Mean a 4.7 GB DVD Won’t Hold 4.7 Gigabytes?

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What Do You Mean a 4.7 GB DVD Won’t Hold 4.7 Gigabytes?

With computers, memory and disk size are commonly expressed in terms such as kilobyte,
megabyte, and gigabyte. Technically, a kilobyte should represent 1000 bytes, but due to
the binary numbering system computers use, a kilobyte actually represents 1024 bytes.
Similarly, a megabyte represents 1,048,576 bytes (and not 1,000,000 bytes) and a gigabyte
represents 1,073,741,824 bytes (and not 1,000,000,000 bytes).

Unfortunately, with DVD discs the terms megabyte and gigabyte do not use the same
binary-based standard; they literally refer to the technically accurate 1,000,000 bytes for
a megabyte and 1,000,000,000 bytes for a gigabyte. This means that a 4.7 GB DVD disc
will actually hold only 4.37 binary-based gigabytes. While the difference is not large
(relatively speaking), it must be accounted for if you intend to come close to filling the


Chapter 2

Planning Your Project

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When displaying estimated sizes, DVD Studio Pro uses the “1000 bytes equals

a kilobyte” system. This means that the estimated sizes refer to the amount of space they
will require on the DVD and will be a bit larger than the file sizes shown in the Finder.
While the Finder shows binary-based file sizes, you can use its File > Get Info command
to see both the binary-based file size and, in parentheses, the “1000 bytes equals a kilobyte”