T.Sharon-A.Frank1

Multimedia

Media/Tools Comparisons

T.Sharon-A.Frank

2

Media/Tools Comparisons

• Comparison Parameters

• Discrete Media

• Continuous Media

• Multimedia System Characteristics

• Software Requirements/Tools

T.Sharon-A.Frank

3

• Size

• Bandwidth

• Burstiness (peak to average ratio)

• Delay

• Jitter (variance of delay)

• Error/Loss Tolerance

• Synchronization

Comparison Parameters

T.Sharon-A.Frank

4

Discrete Media

• High Throughput

• Bursty in General

• Tolerate Delays/Jitter (between media)

• Ansichronous (not equal in time)

T.Sharon-A.Frank

5

Text

• Text/Binary Files/Commands– various sizes

• Response Time Requirements– file transfer (seconds)– RPC (milliseconds)

• Error Sensitive– use error control codes – use retransmissions

T.Sharon-A.Frank

6

Notes on Text

• Slower and more difficult to read than same text in hardcopy form.

• Present only a few paragraphs of text per page.

• Display whole paragraphs on screen.

• Avoid forcing users to bounce back and forth between pages to read paragraphs.

T.Sharon-A.Frank

7

Vector Graphics

• Size:– Graphics Page - 3KB

• Tolerate few errors

T.Sharon-A.Frank

8

Bitmapped Images

• Size:– color image - 2-4MB

– typical: color screen, 1K*1K pixels,

24 Bit = 3 MB

• Accepts data loss

T.Sharon-A.Frank

9

• Vectors – drawing programs:– Select individual graphic objects (shapes,

paths, etc)

– Transform size, position, angle, etc

– Change attributes such as stroke, fill, etc

• Bitmaps – painting programs:– Select areas of pixels

– Apply effects and filters

Image Editing

T.Sharon-A.Frank

10

• Vectors:– Scaling is a simple mathematical operation

on stored description (before rendering)

– Curves and lines remain smooth at all sizes.

• Bitmaps:– Interpolate pixel values

– Usually produces loss of quality, blurring, jaggedness.

Image Scaling

T.Sharon-A.Frank

11

Continuous Media

• Isochronous (equal in time)– Fixed Throughput

– Constant Rate

– Constant Delay

– Reduced Jitter

• Not bursty in general

• Soft Real-Time (RT) constraints

T.Sharon-A.Frank

12

Audio

• Bandwidth (medium-high)– 8-200 Kb/s

– Typical: 64Kb/s (8000 samples * 8 bit)

• Sensitive to delay/jitter

• Medium tolerance to data loss

• Human ear more sensitive than human eye

T.Sharon-A.Frank

13

Audio Quality Factors

• Sampling rate

• Bit depth (Sample size)

• Both factors set at capture time.

• Suggested rule:

– initially capture at 16bit resolution at 44.1 KHz sampling rate.

– can always reduce later.

T.Sharon-A.Frank

14

MIDI or Digital Audio?

• Use MIDI (Musical Instrument Digital Interface) when:– limited RAM or MHz, and– You have a hi-quality MIDI source, and– You’ll play ONLY on your PC, and– There is no spoken dialog.

• Use Digital Audio when:– The playback may be on another PC– You have sufficient RAM and MHz– You need spoken dialog.

T.Sharon-A.Frank

15

Steps to Create an Animation

1. Determine type of animation

2. Choose software

3. Create or select graphic to animate

4. Create color palette

5. Render (draw) graphic

6. Set display buffers for transformations

7. Generate basic design

8. Select and initialize palette

9. Create animation special effects

16

• “Easy to describe but much harder to do”.

• Properties of 3D models (shape, size, position, rotation, surface characteristics, etc), light sources and cameras are numerically defined.

• Animate a scene by changing the numbers, rendering a new frame, changing further …

• Can make objects move, or move the camera.

• Requires 3D visualization and animation skills and great amount of processing power.

3D Animation

T.Sharon-A.Frank

17

Video

• Bandwidth (very high)– 2-50MB/s

– typical: VHS quality, 6MHz bandwidth,• 100 Mb/s uncompressed• 1.5-6 Mb/s compressed

• Bounded delay/jitter

• Loss tolerant

T.Sharon-A.Frank

18

Video Creation

• Video captures the real world:– therefore video cannot be created in the same sense

that images can be created– video must be captured.

• Animation can create a virtual world:– but this is not video– and we’ve already talked about animation.

T.Sharon-A.Frank

19

Video Quality

• People are more accepting of poor image quality (Frame dropping ) than poor sound quality.

T.Sharon-A.Frank

20

Video Quality Factors

• Source Format: VHS tape is acceptable for home use. Professional projects demand highest quality given only by BetaCam and digital tape.

• Source Content: MPEG-1 and software only codecs have difficulty with high-speed action sequences. MPEG-2 can handle such content.

• Quality of Encoding System: generic encoding typically produces lower quality video. When parameters can be controlled, resulting video is of higher quality.

T.Sharon-A.Frank

21

Multimedia System Characteristics

• Multimedia data is stored in the file system like other ordinary data.

• Multimedia files can be quite large.

• Continuous-media data is data with specific rate requirements and may require extremely high data rates.

• Multimedia applications may be sensitive to timing delays during real-time playback of the media.

T.Sharon-A.Frank

22

Some data rates for multimedia and high-performance I/O devices

.

23

• Text: editors, layout programs.• Images: image editing, painting and

drawing (Photoshop, Illustrator, GIMP).• Sound: editing and effects (Audacity,

Audition, Bias Peak).• Animation: drawing and interpolation

(Flash, Silverlight).• Video: editing and post-production

(Premiere, After Effects, Final Cut Pro).

Applications for different media types

T.Sharon-A.Frank

24

Purpose of Multimedia Authoring Tools

• Provide a framework for organizing, combining and editing elements of multimedia projects.

• Used for:

– designing interactivity

– designing user interface

– presenting projects

– assembling multimedia elements in coherent, cohesive project.

T.Sharon-A.Frank

25

Multimedia Authoring Tools

• Allow for creation of:

– video productions

– animations

– games

– interactive training

– simulations

– prototypes

– visualizations

T.Sharon-A.Frank

26

Authoring Tool Metaphors

1. Page-based (Card-based)

2. Icon-based Event-driven

3. Timeline-based

4. Object-oriented• May require some programming in a scripting

language to provide interactivity– Behaviors provide prefabricated parameterized

actions.

T.Sharon-A.Frank

27

Page-based (Card-based) Tools

• Elements organized as pages in a book (or a stack of cards).

• Best used when elements can be viewed individually.

• Authoring tool organizes sequence of viewing.

• Examples:– HyperCard (Mac), SuperCard (Mac/Win)

– Media Object (Mac/Win), ToolBook (Win)

– PowerPoint (Win), Visual Basic (Win), Astound, SST3.0

T.Sharon-A.Frank

28

Icon-based Event-driven Tools

• Elements and events are organized in a structural framework (or process).

• Typically display flow diagrams of activities along branching paths.

• When navigation is complex, charts are useful for development.

• Similar to visual programming - graphically depict the projects logic and then add content.

• Examples:– Authorware Professional (Mac/Win)

– Icon Author (Win), Quest (Win)

T.Sharon-A.Frank

29

Timeline-based Tools

• Elements and events are organized along a timeline.

• Best used when project has a beginning and end with a message to send.

• Developer sets playback speed.

• Elements are triggered at given time in sequence of events.

• Very popular.• Examples: Flash, Director (Mac/Win), Action!

T.Sharon-A.Frank

30

Object-oriented Tools

• Elements and events are objects that have a hierarchical order (parents and children).

• Message passing allows objects to do things depending on their property settings.

• Particularly useful for games and for simulating real-life situations.

• Examples:– mTropolis (Mac/Win)– AppleMedia Tool– MediaForge (Win)

T.Sharon-A.Frank

31

Other Important Features

• Organizing

• Interactivity

• Performance Tuning

• Playback

• Delivery

• Cross-Platform