MULTIMEDIA MULTIMEDIA TECHNOLOGYTECHNOLOGY

SMM 3001SMM 3001

MEDIA - VIDEOMEDIA - VIDEO

In this chapterIn this chapter

How digital video differs from How digital video differs from conventional analog videoconventional analog video

The advantages & limitations of The advantages & limitations of digital video compared with those of digital video compared with those of analog videoanalog video

The basic components of a desktop The basic components of a desktop video systemvideo system

Capturing & digitizing videoCapturing & digitizing video Tools & techniques for editing digital Tools & techniques for editing digital

videovideo

INTRODUCTIONINTRODUCTION

What is digital video?What is digital video? Video is usually composed of Video is usually composed of

visual images depicting live action visual images depicting live action with accompanying audio with accompanying audio soundtracksoundtrack

Digital video – creates the illusion Digital video – creates the illusion of full motion by displaying rapid of full motion by displaying rapid sequence of changing images on sequence of changing images on display devicedisplay device

Digital video requires methods to Digital video requires methods to capture, store and present videocapture, store and present video

CAPTURECAPTURE

Video captureVideo capture Involves digitizing an analog Involves digitizing an analog

source for live action scenesource for live action scene Example – video camera/VCR Example – video camera/VCR

tape can serve as sources for the tape can serve as sources for the images, composed of a time images, composed of a time sequence of framessequence of frames

Each frames is an analog or Each frames is an analog or continuous video imagescontinuous video images

CAPTURECAPTURE

Video captureVideo capture Signal from videotape (video & Signal from videotape (video &

audio components) must be audio components) must be captured & digitisedcaptured & digitised

Can be achieved by using Can be achieved by using integrated components called integrated components called video capture cardsvideo capture cards

EDITINGEDITING

Conventional editing film & Conventional editing film & videotape is constrained by videotape is constrained by sequence – linear editingsequence – linear editing

Digital video can be accessed Digital video can be accessed randomly – nonlinear editing; randomly – nonlinear editing; making editing individual frames making editing individual frames faster and more precisefaster and more precise

Non linear editing is non Non linear editing is non destructive; they do not alter the destructive; they do not alter the original source materialoriginal source material

PLAYBACKPLAYBACK

Process of digital video Process of digital video playback, the stored data must playback, the stored data must be fetched, processed & be fetched, processed & converted to analog signals for converted to analog signals for video display devices & video display devices & speakersspeakers

Data is usually stored in a file in Data is usually stored in a file in secondary memory eg. hard secondary memory eg. hard disk/CD-ROMdisk/CD-ROM

PLAYBACKPLAYBACK

Compared to analog video, it’s Compared to analog video, it’s confined to linear organization of confined to linear organization of its mediaits media

Most digital video playback Most digital video playback systems offer additional modes systems offer additional modes for viewingfor viewing

Frames may be displayed Frames may be displayed individually like a slide show, individually like a slide show, fast forward, rewind, reverse fast forward, rewind, reverse playback and random accessplayback and random access

DIGITAL VIDEO FEATURESDIGITAL VIDEO FEATURES

Digital video offers several Digital video offers several advantages over analog formsadvantages over analog forms

Advantages are due to 2 factors:Advantages are due to 2 factors: Discrete nature of digital video, Discrete nature of digital video,

therefore it’s easier for computer therefore it’s easier for computer to process data in new & to process data in new & interesting waysinteresting ways

Data is represented digitally, Data is represented digitally, therefore can be stored efficiently therefore can be stored efficiently and transmitted over computer and transmitted over computer networksnetworks

DIGITAL VIDEO FEATURESDIGITAL VIDEO FEATURES

Other features :Other features : Digital video is easily scalableDigital video is easily scalable

Picture resolution & colour Picture resolution & colour information can be adjusted to fit the information can be adjusted to fit the capabilities of computer displaying capabilities of computer displaying the videothe video

Digital video is randomly Digital video is randomly accessibleaccessible Video frames are discrete, they can Video frames are discrete, they can

be marked & stored for random be marked & stored for random accessaccess

DIGITAL VIDEO FEATURESDIGITAL VIDEO FEATURES

Other features :Other features : Digital video is stored & Digital video is stored &

transmitted efficientlytransmitted efficiently Inherits some of the advantages & Inherits some of the advantages &

capabilities shared by other forms of capabilities shared by other forms of computer datacomputer data

Eg. video conferencing – audio and Eg. video conferencing – audio and video is transmitted in real timevideo is transmitted in real time

DIGITAL VIDEO FEATURESDIGITAL VIDEO FEATURES

Other features :Other features : Digital video offers powerful Digital video offers powerful

editing capabilitiesediting capabilities Digital editing exploits the power of Digital editing exploits the power of

the computer to insert, delete, the computer to insert, delete, combine, copy & move frames like combine, copy & move frames like any form of dataany form of data

Digital video offers additional Digital video offers additional playback playback

Digital video has interactive Digital video has interactive potentialpotential

DIGITAL VIDEO DIGITAL VIDEO REQUIREMENTSREQUIREMENTS Basic desktop video system requires Basic desktop video system requires

additional hardware & software to additional hardware & software to capture & produce video for capture & produce video for computerscomputers

To playback full motion colour movie To playback full motion colour movie with CD-quality stereo sound at full with CD-quality stereo sound at full screen resolution, ~26.5 Mbytes/sec screen resolution, ~26.5 Mbytes/sec data rate is requireddata rate is required

CD-ROM drive is able to deliver CD-ROM drive is able to deliver 150Kbits/sec, hard drive 2-5MB/sec150Kbits/sec, hard drive 2-5MB/sec

DIGITAL VIDEO DIGITAL VIDEO REQUIREMENTSREQUIREMENTS The demands for data transfer must The demands for data transfer must

be reduced drastically for desktop be reduced drastically for desktop computers to play videocomputers to play video

Trimming is done to reduce the Trimming is done to reduce the amount of data used for representing amount of data used for representing both sight & sound, less data; both sight & sound, less data; smaller picture & fewer framessmaller picture & fewer frames

Video file formats are compressed Video file formats are compressed for more compact storagefor more compact storage

Data compression, redundancy is Data compression, redundancy is eliminated for binary informationeliminated for binary information

DIGITAL VIDEO DIGITAL VIDEO REQUIREMENTSREQUIREMENTS CompressionCompression

Data compression, redundancy is Data compression, redundancy is eliminated for binary informationeliminated for binary information

When the movie is created, the file When the movie is created, the file is processed by is processed by compressorcompressor (using either hardware/CPU or by (using either hardware/CPU or by software)software)

Compressed data (less space) will Compressed data (less space) will be converted back to original form be converted back to original form before usebefore use

With compression, the demands With compression, the demands on the CPU now may be moreon the CPU now may be more

BUILDING BASIC DESKTOP BUILDING BASIC DESKTOP VIDEO SYSTEMVIDEO SYSTEM Basic desktop video system Basic desktop video system

requires 6 fundamental requires 6 fundamental components :components : Analog sourceAnalog source Video capture cardVideo capture card CPUCPU Secondary storageSecondary storage MonitorMonitor Editing & playback controlEditing & playback control

BUILDING BASIC DESKTOP BUILDING BASIC DESKTOP VIDEO SYSTEMVIDEO SYSTEM

Analog sourceVideo capture

card

Edit & PlaybackControl

CPUDISK

Video monitor

CAPTURING VIDEO CAPTURING VIDEO SEQUENCESSEQUENCES The main task is performed by The main task is performed by

video capture card to send a video capture card to send a stream of binary data to CPU; to stream of binary data to CPU; to encode data into movie fileencode data into movie file

The capture card receives an The capture card receives an analog video signal that must be analog video signal that must be converted, sampled, and converted, sampled, and quantized according to the quantized according to the specifications set by the ser & specifications set by the ser & enforced by the capture enforced by the capture programprogram

CAPTURING VIDEO CAPTURING VIDEO SEQUENCESSEQUENCES Details in capturing video :Details in capturing video :

Input source – each second of the Input source – each second of the analog video signal is composed analog video signal is composed of nearly 30 frames created by 60 of nearly 30 frames created by 60 fields. Signal is sampled fields. Signal is sampled temporallytemporally

Colour information is another Colour information is another details to be considereddetails to be considered

Most capture cards achieve some Most capture cards achieve some data compression when digitizing data compression when digitizing colourscolours

EDITING DIGITAL VIDEOEDITING DIGITAL VIDEO

Video is produced by editing – Video is produced by editing – creating composition by adding, creating composition by adding, deleting, and modifying video deleting, and modifying video segmentssegments

Example of software : Adobe Example of software : Adobe PremierePremiere

Activities involved in editingActivities involved in editing Logging – identify the appropriate Logging – identify the appropriate

statistics eg. duration & type of audio & statistics eg. duration & type of audio & videovideo

Assembling – actual sequencing of Assembling – actual sequencing of logged video clipslogged video clips

EDITING DIGITAL VIDEOEDITING DIGITAL VIDEO

Activities involved in editingActivities involved in editing Transitions – visual effects that Transitions – visual effects that

smoothes or stretches the change smoothes or stretches the change from one video segment to from one video segment to another eg. dissolve, wipeanother eg. dissolve, wipe

Rotoscoping – working with Rotoscoping – working with individual frames of video footageindividual frames of video footage

Compositing – superimposing one Compositing – superimposing one video clip with anothervideo clip with another