DVD is an optical disc storage format that was invented in 1995 and offers higher storage capacity than CDs. DVDs use a shorter wavelength laser to place pits more densely, allowing more data to be stored in the same physical space as a CD. DVDs can have multiple layers, with later versions supporting up to 8 layers, greatly increasing potential storage capacity over single-layer discs.

1. DVD

2. DVD A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than CDs while having the same dimensions.

3. The DVD Video format was first introduced by Toshiba in Japan in November 1996, in the United States in March 1997 (test marketed), in Europe in October 1998, and in Australia in February 1999. The official DVD charter documents specify that the basis of the DVD name stems from the term digital versatile disc . Usage in the present day varies, with Digital Versatile Disc, Digital Video Disc , and DVD being the most common.

4. Design Comparison of several forms of disk storage showing tracks (not-to-scale); green denotes start and red denotes end.

5. Just like in a CD, the information is coded as a series of tiny pits in the disk. The pits are organized on a spiral track in a structure similar to vinyl records. When a smooth surface is read, the machine interprets the data point as a 0. When a pit is encountered, the data point is read as a 1. DVDs use a shorter-wavelength, red laser that can place pits more densely on the surfaces of the disks. This not only allows for more data, it also requires that the disks be only half as thick as conventional CDs.

7. Layers A DVD is composed of several layers of plastic, totaling about 1.2 millimeters thick. Each layer is created by injection molding polycarbonate plastic. This process forms a disc that has microscopic bumps arranged as a single, continuous and extremely long spiral track of data.

8. Once the clear pieces of polycarbonate are formed, a thin reflective layer is sputtered onto the disc, covering the bumps. Aluminum is used behind the inner layers, but a semi-reflective gold layer is used for the outer layers, allowing the laser to focus through the outer and onto the inner layers. After all of the layers are made, each one is coated with lacquer, squeezed together and cured under infrared light.

9. The data track is just 740 nanometers separate one track from the next (a nanometer is a billionth of a meter). And the elongated bumps that make up the track are each 320 nanometers wide, a minimum of 400 nanometers long and 120 nanometers high.

10. DVD Storage Capacity Higher Density Data Storage Single-sided, single-layer DVDs can store about seven times more data than CDs. A large part of this increase comes from the pits and tracks being smaller on DVDs. Specification CD DVD Track Pitch 1600 nanometers 740 nanometers Minimum Pit Length (single-layer DVD) 830 nanometers 400 nanometers Minimum Pit Length (double-layer DVD) 830 nanometers 440 nanometers

11. DVD Storage Capacity Less Overhead, More Area On a CD, there is a lot of extra information encoded on the disc to allow for error correction -- this information is really just a repetition of information that is already on the disc. The DVD format doesn't waste as much space on error correction, enabling it to store much more real information. Another way that DVDs achieve higher capacity is by encoding data onto a slightly larger area of the disc than is done on a CD.

12. DVD Storage Capacity Multi-Layer Storage To increase the storage capacity even more, a DVD can have up to four layers, two on each side. Format Capacity Approx. Movie Time Single-sided/single-layer 4.38 GB 2 hours Single-sided/double-layer 7.95 GB 4 hours Double-sided/single-layer 8.75 GB 4.5 hours Double-sided/double-layer 15.9 GB Over 8 hours

13. DVD drive speeds Drive speed Data rate ~Write time (min) (Mbit/s) (MB/s) (MiB/s) SL DL 1× 11.08 1.39 1.32 57 103 2× 22.16 2.77 2.64 28 51 2.4× 26.59 3.32 3.17 24 43 2.6× 28.81 3.60 3.43 22 40 4× 44.32 5.54 5.28 14 26 6× 66.48 8.31 7.93 9 17 8× 88.64 11.08 10.57 7 13 10× 110.80 13.85 13.21 6 10 12× 132.96 16.62 15.85 5 9 16× 177.28 22.16 21.13 4 6 18× 199.44 24.93 23.78 3 6 20× 221.60 27.70 26.42 3 5 22× 243.76 30.47 29.06 3 5 24× 265.92 33.24 31.70 2 4

14. DVD Players A DVD player is very similar to a CD player. It has a laser assembly that shines the laser beam onto the surface of the disc to read the pattern of bumps. The drive consists of three fundamental components: A drive motor to spin the disc; It is precisely controlled to rotate between 200 and 500 rpm, depending on which track is being read. A laser and a lens system to focus in on the bumps and read them - The light from this laser has a smaller wavelength (640 nanometers) than the light from the laser in a CD player (780 nanometers), which allows the DVD laser to focus on the smaller DVD pits. A tracking mechanism that can move the laser assembly so the laser beam can follow the spiral track - The tracking system has to be able to move the laser at micron resolutions.

15. As the laser moves outward from the center of the disc, the bumps move past the laser at an increasing speed.

16. Special DVDs

17. DVD-ROM Digital Versatile Disc-Read Only Memory, or DVD-ROM , is a media storage disk that closely resembles a CD or compact disk. The major difference is that the DVD-ROM is formatted to hold far more data. DVD-ROM refers to a read-only disc, or a disc that cannot be written over. Capacity: Single-sided single-layer disc — 4.38 GB Single-sided double-layer disc — 7.95 GB Double-sided single-layer disc — 8.75 GB Double-sided double-layer disc — 15.9 GB

18. DVD-RAM DVD-RAM (DVD – Random Access Memory) is a disc specification presented in 1996 by the DVD Forum. DVD-RAM media have been used in computers as well as camcorders and personal video recorders since 1998. The on-disc structure of DVD-RAM is closely related to hard disk and floppy disk technology, as it stores data in concentric tracks. DVD-RAMs can be accessed just like a hard or floppy disk and usually without any special software.

19. Physically smaller, 80 mm in diameter, DVD-RAM discs also exist with a capacity of 1.46 GB for a single-sided disc and 2.8 GB for a double-sided disk. DVD-RAMs were originally solely sold in cartridges; recent DVD recorders can work with discs either with or without cartridge. A DVD-RAM Type 2

20. Advantages Long life — without physical damage, data is retained for an estimated 30 years. For this reason, it is used for archival storage of data. Can be rewritten over 100,000 times for the lowest write speed discs. Reliable writing of discs. DVD-burning software may not be required — discs can be used and accessed like a removable hard disk. Very fast access of small files on the disc. Small 2 KB disc block size wastes less space when writing small files. Disadvantages Media unavailability: Lower popularity of the format makes blank media harder to find at stores. High-speed media unavailability: Higher media cost. Less compatibility than DVD+RW and DVD-RW, despite predating both formats.

21. DVD-R DVD-R is a DVD recordable format. The DVD-R format was developed by Pioneer in 1997. Data on a DVD-R cannot be changed, whereas a DVD-RW (rewritable DVD) can be rewritten multiple (1000+) times. DVD capacity Disk Type Data sectors (2,048 B each) Capacity bytes GB DVD-R (SL) 2,298,496 4,707,319,808 4.7 DVD+R (SL) 2,295,104 4,700,372,992 4.7 DVD-R DL 4,171,712 8,543,666,176 8.5 DVD+R DL 4,173,824 8,547,991,552 8.5 SL / DL – Single/Dual layer

22. Speed Drive speed Data rate (MB/s) Data rate (Mbit/s) Write time for single-layer DVD-R 1X 1.32 MB/s 10.56 Mbit/s 60 minute 2X 2.64 MB/s 21.12 Mbit/s 30 minutes (CLV) 4X 5.28 MB/s 42.24 Mbit/s 15 minutes (CLV) 8X 10.56 MB/s 84.48 Mbit/s 8 minutes (Z-CLV) 16X 21.12 MB/s 168.96 Mbit/s 5.75 minutes (CAV) 18X 23.76 MB/s 190.08 Mbit/s 5.5 minutes (CAV) 20X 26.40 MB/s 211.20 Mbit/s 5 minutes (CAV) 22X 29.04 MB/s 232.32 Mbit/s 4.5 minutes (CAV) 24x 31.68 MB/s 253.44 Mbit/s ~4.0 minutes (CAV)

23. DVD-R vs. DVD+R DVD+R has more robust error management system than DVD-R, allowing for more accurate writing to media independent of the quality of the media. Session linking in DVD+R results in fewer damage in discs. DVD-R use LPP (Land Pre Pit) system for tracking and speed control. While DVD+R uses an improved ADIP (ADdress In Pregroove) system which makes the ADIP system more accurate at higher speeds.

24. DVD-RW DVD-RW disc is a rewritable optical disc with equal storage capacity to a DVD-R, typically 4.7 GB. The format was developed by Pioneer in November 1999. The smaller Mini DVD-RW holds 1.46 GB, with a diameter of 8 cm. According to Pioneer, DVD-RW discs may be written to about 1,000 times before needing replacement. DVD-RW discs are commonly used to store data in a non-volatile format, such as when creating backups or collections of files.

25. DVD+RW Similar to DVD-RW, is a rewriteable 4.7gb DVD disc. DVD+RW, does have a couple of technical advantages — (1) lossless linking (which enables some editing after recording without a full erasure that DVD-RW requires), (2) a special drag-and-drop file support on the desktop (otherwise known as DVD+MRW). Unfortunately, the DVD+RW disc type does not compare well with DVD-R as far as DVD playback compatibility.

26. DVD-Audio DVD-Audio (commonly abbreviated as DVD-A ) is a digital format for delivering high-fidelity audio content on a DVD. The first discs entered the marketplace in 2000. Compared to the CD, the much higher capacity DVD format enables the inclusion of either: Considerably more music (with respect to total running time and quantity of songs) or Far higher audio quality, reflected by higher linear sampling rates and higher bit-per-sample resolution, and/or Additional channels for spatial sound reproduction.

27. DVD-Video DVD-Video is a consumer video format used to store digital video on DVD discs, and is currently the dominant consumer video format in Asia, North America, Europe, and Australia. It was first available for retail around 1997. To record moving pictures, DVD-Video uses either MPEG-2 compression at up to 9.8 Mbit/s (9,800 kbit/s) or MPEG-1 compression at up to 1.856 Mbit/s (1,856 kbit/s).

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