08/03/02000 David Bown MSc CBLT/Multimedia 1 Video and DVD.

08/03/02000David Bown MSc CBLT/Multimedia 1

Video and DVD


What is DVD? DVD was the first distribution medium

designed for digital video. Hence it originally stood for Digital

Video Disc. Digital offers dramatic improvements

in transmission efficiency compared to analogue video.


Studio Quality Images DVD now stands for Digital Versatile Disc. It offers an optical (and audio) storage

medium with enormous capacity and bandwidth compared to CD-ROM.

Standard specifications include MPEG-2 video which gives studio quality 740X480 pixel images (VHS tape: 320X240).


Recordable DVD DVD-R Recordable once, read on DVD-

ROM. DVD-RAM read and write to 2.6 GB

DVD-RAM Disc and read and write once to 3.9 GB DVD-R Discs.

DVD-Ram discs readable on DVD-R and DVD-ROM drives.


High Capacity Full length films 133 minutes of MPEG-

2. Single layer discs: 4.7 Gbyte.

Dual-layer discs: 8.5 Gbyte.


Double-sided DVDs Double-sided dual layer discs with

back to back bonding. By combining with Dual layer a

massive capacity of 17 Gbytes can be obtained.


Data Storage on DVD Like CD-ROMs data is recorded in spiral of

tiny pits.


Capacity Gains over CD-ROM

DVDs obtain significantly more capacity by: Shorter wavelength laser; Smaller pits (0.4 micrometers v 1.1 on

CD-ROMS) Denser track pitch (0.74 micrometers v

1.6 on CD-ROMS) Increased efficiency in channel encoding.


Construction of DVD


Variable Bit Rate Average bit rate

for DVD is 4.7 mbs. But the rate varies

between >3 to 10.07mbs.

This enables high quality images to be generated from complex scenes.


MPEGs (Moving Pictures Expert Group)

Video standard for DVD, MPEG uses three types of video frame:

I-Frames contains all spatial info of video frame. These are used as the “hooks”, every scene change requires a new I-Frame.

B-Frames (Highest compression). P-Frames.


MPEG Advantages Universal compatibility:Universal compatibility: MPEG files are

system independent. Greater compression ratiosGreater compression ratios than any

other format (up to 200:1). Highest qualityHighest quality compression does not

lead to sacrifice in quality. MPEG delivers broadcast quality video.


Advantages of DVD Added features over Video tape. Immediate scene access. There are more than 5,600 movie and

music videos currently available. Same size as CD but can store an

entire film. DVD offers superior picture and sound.


Future of DVD? DVD or Sony’s Phase-Change Rewritables

(PCR) disc or NEC (Betamax v VHS). Hitachi propose a DVD-RAM disc with

phase-change technology that will be retrospective to CD-ROM and DVD-ROM.

Blue lasers developed in Japan mean a laser footprint even smaller than DVD can be obtained.


History of Video on the Web

Multimedia became commonplace back in 1992 with CD-ROMS.

But the Web has low bandwidth and cannot cope easily with moving pictures.

TV uses “fat” cable infrastructure, Web uses “thin” telephone infrastructure.

Moving images on the Web like “sucking a bowling ball through a garden hose”.


Video Compression Temporal compression: frame by frame. Spatial compression: deletes

information common to entire file and defines ‘areas’ rather than pixels.

In addition, file size can be reduced by cutting:

Colours frame rate audio quality.


Hardware v Software Codecs

Hardware codecs are faster and require fewer CPU resources.

Delivers high-quality results. But are more expensive. Software codecs are less expensive,

e.g. freeware versions. Take long time to analyse and

compress.


DV Filmmaking Digital Video (DV) was introduced to

U.S. consumers in 1994.

Digital Video is a high resolution video format that stores, manipulates and relays data like any other computer data.


Benefits of DV Excellent images, being digital the

copy quality is identical to the original. Three separate signals for each colour

offering good colour reproduction. Ability to use “Firewires” high speed

connections in and out of computers. Portable and relatively inexpensive

cameras.


‘FireWire’ - Wired for Speed

A high-speed serial bus cable designed by Apple to provide cheap digital interface.

Based on the port found on Nintendo Gameboy.

Provides a transfer rate of 50 megabytes/sec (Broadcast quality needs just 3.6)

It can link up to 63 devices. Unlike SCSI no device IDs need to be set.


Webmonkey Hints Use a tripod. Use tight close-ups. Use quality resources. Do not shoot very dark or light

backgrounds. Capture rate no bigger than 320 x 240

pixels at 10 frames per second.


The End

08/03/02000 David Bown MSc CBLT/Multimedia 1 Video and DVD.

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