CHAPTER ELEVEN

THE DVD FAMILY

CGMB113/ CITB 123: MULTIMEDIA TECHNOLOGY

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SARASWATHY SHAMINI

Adapted from Notes Prepared by:Noor Fardela Zainal Abidin

© UNITEN 2004/2005

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Objectives

At the end of this chapter, students should be able to:

• understand the history and evolution of digital video disc (DVD) and Blu-ray technologies

• define basic terms and concepts related to digital video disc (DVD) and Blu-ray technologies

• Describe the DVD and Blu-ray technologies and how it works

DVD HISTORY• 1996: DVD Technology Introduced.

Prices of Recorders and CD-R Media go down significantly.High Demands cause World-Wide CD-R Media Shortage.

• 1997: DVD Released. DVD Players/Movies hit consumer market.DVD-R standard created (3.9 Gig).

• 1998: DVD-RAM, DVD-Recordable systems/equipment hits market.DVD-Video/ROM authoring tools hits the market.CD-R prices continue to drop.

• 1999: DVD-Video Becomes main stream.Consumers begin purchasing DVD Players & Movies on a mass level.Most major film studios have titles on DVD.DIVX Dies (DIgital Video eXpress).Second Generation DVD Burners. 4.7 Gig DVD-R Media Developed.

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DVD: THE BASICs• The first DVD player hit the market in March 1997. • A DVD has a much larger data capacity. Holds about seven times

more data than a CD does. • Typical contents of a DVD movie: ▫ Up to 133 minutes of high-resolution video▫with 720 dots of horizontal resolution (The video compression

ratio is typically 40:1 using MPEG-2 compression.) ▫ Soundtrack presented in up to eight languages using 5.1 channel

Dolby digital surround sound ▫ Subtitles in up to 32 languages

• DVD can also be used to store almost eight hours of CD-quality music per side

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DVD Advantage•Better picture quality•DVD movies have an on-screen index. And go to one

scene to another with the remote, no need to rewind or fast-forward.

•DVD players are compatible with audio CDs. •DVD movies may have several soundtracks on them,

and they may provide subtitles in different languages.

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Storing Data in DVD• Like CD, data on a DVD is encoded in the form of

small pits and bumps in the track of the disc. •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

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Storing Data in DVD• 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.

• For single-sided discs, the label is silk-screened onto the nonreadable side. Double-sided discs are printed only on the nonreadable area near the hole in the middle (refer to picture on next slide)

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DVD Formats

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Cross sections of the various types of completed DVDs (not to scale)

Single Layer DVD

• has a spiral track of data • the track always circles

from the inside of the disc to the outside. That the spiral track starts at the center means that a single-layer DVD can be smaller than 12 centimeters if desired.

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Data tracks on a DVD

Single Sided DVD•The data track is incredibly tiny -- 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. (see next slide for illustration)

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DVD Pit Layout

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Single Sided DVD• You will often read about "pits" on a DVD instead of

bumps. They appear as pits on the aluminum side, but on the side that the laser reads from, they are bumps.

• The microscopic dimensions of the bumps make the spiral track on a DVD extremely long.

• If you could lift the data track off a single layer of a DVD, and stretch it out into a straight line, it would be almost 7.5 miles long

• To read bumps this small you need an incredibly precise disc-reading mechanism

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DVD vs CD•DVDs can store more data than CDs for a few

reasons: ▫Higher-density data storage ▫Less overhead, more area ▫Multi-layer storage

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Double_Layer DVD•The technique for double-layering a DVD disc is of

particular importance:▫outer layer is semi-transparent [18-30% reflectivity]▫ inner layer is more reflective [50-80% reflectivity]▫pickup lens is refocused to read desired layer▫extra lead-out space required on inner layer▫ two methods of writing the layers

Parallel track path (PTP) Opposite track path (OTP) - allows near continuous read

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DVD vs CD

• 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

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DVD vs CD• Less Overhead, More Area▫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

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DVD vs CD

• Multi-Layer Storage▫ To increase the storage capacity even more, a DVD can have up to

four layers, two on each side. ▫ The laser that reads the disc can actually focus on the second layer

through the first layer.

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

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The DVD Player

•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.

•Considering how small the bumps are, the DVD player has to be an exceptionally precise piece of equipment.

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The DVD Player

• The drive consists of three fundamental components: ▫A drive motor to spin the disc - The drive motor 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.

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Other DVD•DVD-R•DVD-RW•DVD-Audio

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Blu-Ray Discs

• Blu-ray Discs (BD) has high storage capacity• Can hold and playback large quantities of high-

definition video and audio, as well as photos, data and other digital content

• The Blu-ray name is a combination of "blue," for the color of the laser that is used, and "ray," for optical ray. The "e" in "blue" was purposefully left off, according to the manufacturers, because an everyday word cannot be trademarked.

21Photo courtesy Blu-ray Disc Association

What is a Blu-ray Disc?• A current, single-sided, standard DVD can hold 4.7 GB

(gigabytes) of information. That's about the size of an average two-hour, standard-definition movie with a few extra features. But a high-definition movie, which has a much clearer image takes up about five times more bandwidth and therefore requires a disc with about five times more storage.

• As TV sets and movie studios make the move to high definition, consumers are going to need playback systems with a lot more storage capacity.

• Blu-ray is the next-generation digital video disc. It can record, store and play back high-definition video and digital audio, as well as computer data

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What is a Blu-ray Disc?

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Photo courtesy Blu-ray Disc Association

BD-ROM disc researcher

Blu-ray Advantages• Record high-definition television (HDTV) without any quality

loss • Provide interactivity• Instantly skip to any spot on the disc • Record one program while watching another on the disc • Create playlists • Edit or reorder programs recorded on the disc • Automatically search for an empty space on the disc to avoid

recording over a program • Access the Web to download subtitles and other extra

features

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Blu-ray vs DVD•A single-layer Blu-ray disc, ▫ can hold up to 27 GB of data ▫ two hours of high-definition video ▫13 hours of standard video.

•A double-layer Blu-ray disc ▫54 GB of data, ▫4.5 hours of high-definition video ▫more than 20 hours of standard video.

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Blu-ray vs DVD

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How Does Blu-ray Work? • DVDs, se a red laser to read and write data. Blu-ray uses a

blue laser (which is where the format gets its name). • A blue laser has a shorter wavelength (405 nanometers) than

a red laser (650 nanometers). • The smaller beam focuses more precisely, enabling it to read

information recorded in pits that are only 0.15 microns (µm) (1 micron = 10-6 meters) long -- this is more than twice as small as the pits on a DVD.

• Plus, Blu-ray has reduced the track pitch from 0.74 microns to 0.32 microns

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How Does Blu-ray Work? •The smaller the pits (and therefore the bumps), the

more precise the reading laser must be.•The smaller pits, smaller beam and shorter track

pitch together enable a single-layer Blu-ray disc to hold more than 25 GB of information -- about five times the amount of information that can be stored on a DVD.

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DVD Vs Blu-Ray Construction

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Source: Blu-ray Disc Association

Reference

•OneOff Media, Inc. History of CD. 2000, 2001 •Karim Nice, How DVDs Works,

http://www.stuffo.com. 1998-2005•Stephanie Watson, How Blu-ray Works,

http://www.stuffo.com. 1998-2005• Lachlan L. Mackinnon. Notes: Multimedia

Technology (F291G2). Heriot_Watt University. Edinburgh. Scotland

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