Monday, April 19, 2010

DVD capacity

Capacity and nomenclature[19][20]
SS = single-sided, DS = double-sided, SL = single-layer, DL = dual-layer
Designation Sides Layers
(total)
Diameter Capacity
(cm) (GB) (GiB)
DVD-1[21] SS SL 1 1 8 1.46 1.36
DVD-2 SS DL 1 2 8 2.66 2.47
DVD-3 DS SL 2 2 8 2.92 2.72
DVD-4 DS DL 2 4 8 5.32 4.95
DVD-5 SS SL 1 1 12 4.70 4.38
DVD-9 SS DL 1 2 12 8.54 7.95
DVD-10 DS SL 2 2 12 9.40 8.75
DVD-14[22] DS DL/SL 2 3 12 13.24 12.33
DVD-18 DS DL 2 4 12 17.08 15.90
Capacity and nomenclature of (re)writable discs
Designation Sides Layers
(total)
Diameter Capacity
(cm) (GB) (GiB)
DVD-R SS SL (1.0) 1 1 12 3.95 3.68
DVD-R SS SL (2.0) 1 1 12 4.70 4.37
DVD-RW SS SL 1 1 12 4.70 4.37
DVD+R SS SL 1 1 12 4.70 4.37
DVD+RW SS SL 1 1 12 4.70 4.37
DVD-R DS DL 2 2 12 9.40 8.75
DVD-RW DS DL 2 2 12 9.40 8.75
DVD+R DS DL 2 2 12 9.40 8.75
DVD+RW DS DL 2 2 12 9.40 8.75
DVD-RAM SS SL 1 1 8 1.46 1.36*
DVD-RAM DS DL 2 2 8 2.65 2.47*
DVD-RAM SS SL (1.0) 1 1 12 2.58 2.40
DVD-RAM SS SL (2.0) 1 1 12 4.70 4.37
DVD-RAM DS DL (1.0) 2 2 12 5.16 4.80
DVD-RAM DS DL (2.0) 2 2 12 9.40 8.75*

The basic types of DVD (12 cm diameter, single-sided or homogenous double-sided) are referred to by a rough approximation of their capacity in gigabytes. In draft versions of the specification, DVD-5 indeed held five gigabytes, but some parameters were changed later on as explained above, so the capacity decreased. Other formats, those with 8 cm diameter and hybrid variants, acquired similar numeric names with even larger deviation.

The 12 cm type is a standard DVD, and the 8 cm variety is known as a MiniDVD. These are the same sizes as a standard CD and a mini-CD, respectively. The capacity by surface (MiB/cm2) varies from 6.92 MiB/cm2 in the DVD-1 to 18.0 MiB/cm2 in the DVD-18.

As with hard disk drives, in the DVD realm, gigabyte and the symbol GB are usually used in the SI sense (i.e., 109, or 1,000,000,000 bytes). For distinction, gibibyte (with symbol GiB) is used (i.e., 230, or 1,073,741,824 bytes). Most computer operating systems display file sizes in gibibytes, mebibytes, and kibibytes, labeled as gigabyte, megabyte, and kilobyte, respectively.

Size comparison: a 12 cm DVD+RW and a 19 cm pencil.

Each DVD sector contains 2,418 bytes of data, 2,048 bytes of which are user data. There is a small difference in storage space between + and - (hyphen) formats:

Capacity differences of writable DVD formats
Type Sectors Bytes MB MiB GB GiB
DVD−R SL 2,298,496 4,707,319,808 4,707.320 4,489.250 4.707 4.384
DVD+R SL 2,295,104 4,700,372,992 4,700.373 4,482.625 4.700 4.378
DVD−R DL 4,171,712 8,543,666,176 8,543.666 8,147.875 8.544 7.957
DVD+R DL 4,173,824 8,547,991,552 8,547.992 8,152.000 8.548 7.96

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