MULTIMEDIA TECHNOLOGY SMM 3001 MEDIA - VIDEO

In this chapter How digital video differs from conventional analog video How digital video differs from conventional analog video The advantages & limitations of digital video compared with those of analog video The advantages & limitations of digital video compared with those of analog video The basic components of a desktop video system The basic components of a desktop video system Capturing & digitizing video Capturing & digitizing video Tools & techniques for editing digital video Tools & techniques for editing digital video

INTRODUCTION What is digital video? What is digital video? Video is usually composed of visual images depicting live action with accompanying audio soundtrack Video is usually composed of visual images depicting live action with accompanying audio soundtrack Digital video – creates the illusion of full motion by displaying rapid sequence of changing images on display device Digital video – creates the illusion of full motion by displaying rapid sequence of changing images on display device Digital video requires methods to capture, store and present video Digital video requires methods to capture, store and present video

CAPTURE Video capture Video capture Involves digitizing an analog source for live action scene Involves digitizing an analog source for live action scene Example – video camera/VCR tape can serve as sources for the images, composed of a time sequence of frames Example – video camera/VCR tape can serve as sources for the images, composed of a time sequence of frames Each frames is an analog or continuous video images Each frames is an analog or continuous video images

CAPTURE Video capture Video capture Signal from videotape (video & audio components) must be captured & digitised Signal from videotape (video & audio components) must be captured & digitised Can be achieved by using integrated components called video capture cards Can be achieved by using integrated components called video capture cards

EDITING Conventional editing film & videotape is constrained by sequence – linear editing Conventional editing film & videotape is constrained by sequence – linear editing Digital video can be accessed randomly – nonlinear editing; making editing individual frames faster and more precise Digital video can be accessed randomly – nonlinear editing; making editing individual frames faster and more precise Non linear editing is non destructive; they do not alter the original source material Non linear editing is non destructive; they do not alter the original source material

PLAYBACK Process of digital video playback, the stored data must be fetched, processed & converted to analog signals for video display devices & speakers Process of digital video playback, the stored data must be fetched, processed & converted to analog signals for video display devices & speakers Data is usually stored in a file in secondary memory eg. hard disk/CD-ROM Data is usually stored in a file in secondary memory eg. hard disk/CD-ROM

PLAYBACK Compared to analog video, it’s confined to linear organization of its media Compared to analog video, it’s confined to linear organization of its media Most digital video playback systems offer additional modes for viewing Most digital video playback systems offer additional modes for viewing Frames may be displayed individually like a slide show, fast forward, rewind, reverse playback and random access Frames may be displayed individually like a slide show, fast forward, rewind, reverse playback and random access

DIGITAL VIDEO FEATURES Digital video offers several advantages over analog forms Digital video offers several advantages over analog forms Advantages are due to 2 factors: Advantages are due to 2 factors: Discrete nature of digital video, therefore it’s easier for computer to process data in new & interesting ways Discrete nature of digital video, therefore it’s easier for computer to process data in new & interesting ways Data is represented digitally, therefore can be stored efficiently and transmitted over computer networks Data is represented digitally, therefore can be stored efficiently and transmitted over computer networks

DIGITAL VIDEO FEATURES Other features : Other features : Digital video is easily scalable Digital video is easily scalable Picture resolution & colour information can be adjusted to fit the capabilities of computer displaying the video Picture resolution & colour information can be adjusted to fit the capabilities of computer displaying the video Digital video is randomly accessible Digital video is randomly accessible Video frames are discrete, they can be marked & stored for random access Video frames are discrete, they can be marked & stored for random access

DIGITAL VIDEO FEATURES Other features : Other features : Digital video is stored & transmitted efficiently Digital video is stored & transmitted efficiently Inherits some of the advantages & capabilities shared by other forms of computer data Inherits some of the advantages & capabilities shared by other forms of computer data Eg. video conferencing – audio and video is transmitted in real time Eg. video conferencing – audio and video is transmitted in real time

DIGITAL VIDEO FEATURES Other features : Other features : Digital video offers powerful editing capabilities Digital video offers powerful editing capabilities Digital editing exploits the power of the computer to insert, delete, combine, copy & move frames like any form of data Digital editing exploits the power of the computer to insert, delete, combine, copy & move frames like any form of data Digital video offers additional playback Digital video offers additional playback Digital video has interactive potential Digital video has interactive potential

DIGITAL VIDEO REQUIREMENTS Basic desktop video system requires additional hardware & software to capture & produce video for computers Basic desktop video system requires additional hardware & software to capture & produce video for computers To playback full motion colour movie with CD-quality stereo sound at full screen resolution, ~26.5 Mbytes/sec data rate is required To playback full motion colour movie with CD-quality stereo sound at full screen resolution, ~26.5 Mbytes/sec data rate is required CD-ROM drive is able to deliver 150Kbits/sec, hard drive 2-5MB/sec CD-ROM drive is able to deliver 150Kbits/sec, hard drive 2-5MB/sec

DIGITAL VIDEO REQUIREMENTS The demands for data transfer must be reduced drastically for desktop computers to play video The demands for data transfer must be reduced drastically for desktop computers to play video Trimming is done to reduce the amount of data used for representing both sight & sound, less data; smaller picture & fewer frames Trimming is done to reduce the amount of data used for representing both sight & sound, less data; smaller picture & fewer frames Video file formats are compressed for more compact storage Video file formats are compressed for more compact storage Data compression, redundancy is eliminated for binary information Data compression, redundancy is eliminated for binary information

DIGITAL VIDEO REQUIREMENTS Compression Compression Data compression, redundancy is eliminated for binary information Data compression, redundancy is eliminated for binary information When the movie is created, the file is processed by compressor (using either hardware/CPU or by software) When the movie is created, the file is processed by compressor (using either hardware/CPU or by software) Compressed data (less space) will be converted back to original form before use Compressed data (less space) will be converted back to original form before use With compression, the demands on the CPU now may be more With compression, the demands on the CPU now may be more

BUILDING BASIC DESKTOP VIDEO SYSTEM Basic desktop video system requires 6 fundamental components : Basic desktop video system requires 6 fundamental components : Analog source Analog source Video capture card Video capture card CPU CPU Secondary storage Secondary storage Monitor Monitor Editing & playback control Editing & playback control

BUILDING BASIC DESKTOP VIDEO SYSTEM Analog source Video capture card Edit & Playback Control CPU DISK Video monitor

CAPTURING VIDEO SEQUENCES The main task is performed by video capture card to send a stream of binary data to CPU; to encode data into movie file The main task is performed by video capture card to send a stream of binary data to CPU; to encode data into movie file The capture card receives an analog video signal that must be converted, sampled, and quantized according to the specifications set by the ser & enforced by the capture program The capture card receives an analog video signal that must be converted, sampled, and quantized according to the specifications set by the ser & enforced by the capture program

CAPTURING VIDEO SEQUENCES Details in capturing video : Details in capturing video : Input source – each second of the analog video signal is composed of nearly 30 frames created by 60 fields. Signal is sampled temporally Input source – each second of the analog video signal is composed of nearly 30 frames created by 60 fields. Signal is sampled temporally Colour information is another details to be considered Colour information is another details to be considered Most capture cards achieve some data compression when digitizing colours Most capture cards achieve some data compression when digitizing colours

EDITING DIGITAL VIDEO Video is produced by editing – creating composition by adding, deleting, and modifying video segments Video is produced by editing – creating composition by adding, deleting, and modifying video segments Example of software : Adobe Premiere Example of software : Adobe Premiere Activities involved in editing Activities involved in editing Logging – identify the appropriate statistics eg. duration & type of audio & video Logging – identify the appropriate statistics eg. duration & type of audio & video Assembling – actual sequencing of logged video clips Assembling – actual sequencing of logged video clips

EDITING DIGITAL VIDEO Activities involved in editing Activities involved in editing Transitions – visual effects that smoothes or stretches the change from one video segment to another eg. dissolve, wipe Transitions – visual effects that smoothes or stretches the change from one video segment to another eg. dissolve, wipe Rotoscoping – working with individual frames of video footage Rotoscoping – working with individual frames of video footage Compositing – superimposing one video clip with another Compositing – superimposing one video clip with another