DVD - Technology

The DVD Family

● The Technologies– DVD-ROM– DVD-RAM– DVD-R– DVD+RW– DVD-Audio– DVD-Video– http://www.pctechguide.com/10dvd.htm

DVD History

● Originally two competing developments– MMCD backed by Sony & Philips– SD backed by Toshiba, Matsushita & Time Warner

● 1995 - group of computer companies led by IBM insisted on single standard

● 1997 - DVD Forum created● International standards developed by ECMA

DVD Technology

● Like CDs, DVDs use a track of pits signifying binary information on a disc, which is read by an optical pickup. DVD has the same dimensions as CD, but a much higher capacity and data transfer rate.

● Differences between DVD and CD– Track pitch: DVD = 0.74m v. CD = 1.6m – Minimum Pit Length: DVD= 0.4m v. CD = 0.84m

DVD Technology

● DVD  can hold anywhere from seven times to over 25 times the digital data on a CD

● There are three reasons for DVD's greater data capacity:1. Smaller pit size2. Tighter track spacing3. Multiple layer capability

DVD Technology

A comparison of a CD's pit size and track spacing vs. that of a DVD

DVD Technology (cont.)

● Data density of DVD is 4.5 times CD– Capacity of one-sided, single layer disc is 4.7GB– Higher capacities can be achieved by using both sides of the disc

and up to two layers per side:● Single-sided, single-layer (4.7 GB)

– known as DVD-5– The "5" in "DVD-5" signifies the nearly 5 GBytes worth of data

capacity● Single-sided, double-layer (8.5GB)

– DVD-9– the DVD player automatically switches to the second

layer in a fraction of a second, by re-focusing the laser pickup on the deeper second layer.  This capability allows for uninterrupted playback of long movies up to four hours

DVD Technology

● Double-sided, single-layer (9.4GB)– Known as DVD-10, this construction features a capacity of

9.4 GBytes of data.  DVD-10s are commonly used to put a widescreen version of the movie on one side, and a full frame version of the same movie on the other side

● Double-sided, double-layer (17.0GB)– The DVD-18 construction can hold approximately 17 GBytes

(almost 26 times the data capacity of a CD), or about 8 hours of video and audio as a DVD-Video.  Think of DVD-18 as a double-sided DVD-9, where up to four hours of uninterrupted video and audio can be stored on one side

● 1 hour of MPEG-2 video = 2.2 GB

DVD Technology (cont.)

● 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

Recordable DVD

● Most common form is DVD-RAM– uses phase-change recording to provide rewriteable,

erasable discs with 2.6GB per side capacity– phase-change uses a recording medium that can exist

in both a crystalline and an amorphous state– recording takes place by changing surface of disc to

amorphous state, to represent the presence of data, by heating it with a laser

Recordable DVD

● DVD-R– compatible with DVD-ROM– interchangeable with all other formats– take-up slow, so drives are very expensive

● DVD+RW– not adopted by DVD Forum as official standard– similar technique to DVD-RAM, 3GB per side– actively supported by HP [drive], Philips & Sony

New Stuff

● DVD-Audio– no audio standard in 1996 release– DVD-Audio 1.0 standard approved by DVD Forum

and released in March 1999– release of products slowed by compliance with SDMI,

uses Verance encryption & watermarking– DVD-Video players have better than CD sound

New Stuff (cont.)

– Universal players will not be available for some time, so DVD-Audio discs will not necessarily play on existing DVD-Video players

– Sony & Philips have developed a competing format, Super Audio CD (SACD)

● provides a two layer approach, one for existing CD players plus one for high-density DVD-Audio

● extremely expensive!!– Incompatibility between DVD-Audio, DVD-Video and

DVD-ROM remains a problem