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Advanced Multimedia and Graphics

Advanced Multimedia and Graphics Dr. Serhan Dagtas 12:15-1:30 pm Tue & Thu Introduction Introduction to the course Outline, objectives, material, etc. Introduction to multimedia Course Outline Introduction to various media types; still images, video, audio, speech, text, graphics

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Advanced Multimedia and Graphics

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  1. Advanced Multimedia and Graphics • Dr. Serhan Dagtas • 12:15-1:30 pm Tue & Thu

  2. Introduction • Introduction to the course • Outline, objectives, material, etc. • Introduction to multimedia

  3. Course Outline • Introduction to various media types; still images, video, audio, speech, text, graphics • Acquisition • Compression techniques • Analysis and indexing of multimedia content • Multimedia retrieval • Storage • Applications

  4. Course Objectives • Understand the basics of multimedia systems • Store, process, and present multimedia data • Image, audio, and video indexing & retrieval • Work on research projects • Computer graphics and virtual reality

  5. Course Materials • Textbooks • Mutimedia Fundementals Vol. I, • Multimedia Comm. Systems • Handouts and web material

  6. Exams and projects • Exams • Midterm • Final • Projects • 3-5 assignments • Group project

  7. Policies • Reading • Read the chapters • Assignments may not be from lecture • Attendance is expected

  8. Multimedia • Media (plural of medium) • Virtually any means of conveying information • Mostly text, audio, images, video • Also music, raw data, graphic objects, etc. • Multimedia • More than one media type simultaneously manipulated

  9. Multimedia Information Systems • Storage, Retrieval, Management and Analysis of information in any form • Images • Video • Audio • Graphics, charts, etc. • Text • Data

  10. multiMEDIA what? • Medium (media): A means by which information is perceived… Or: A means of affecting or conveying something (information) “Multimedia” is an adjective!

  11. Multimedia Information Systems • The confluence of several technologies • Digital signal processing • Image processing • Computer graphics • Digital Video technology • Visual interactive languages • Advanced databases • Operating systems • Computer networks

  12. Some Enabling Factors • Optical disc technology • large volumes • preserve quality • Shift from analog to digital processing • high resolution image • high fidelity audio

  13. Analog Video Digital Video • loss of quality in copying • cannot be annotated • consumers cannot edit • duplication without loss • index, search, editing • fast random access • high quality playback • interactive

  14. Enabling Factors (cont’d) • Fiber optics technology • high bandwidth • accuracy • speed • Fast specialized processors • audio boards • video boards • Better software, • real-time OS • codec (software only)

  15. Example application • PTV & HMS

  16. Properties of Multimedia System • Combination of Media • Is any combination of media a multimedia? • Independence • Tightly coupled media are not considered multimedia, e.g., a computer controlled video recorder stores audio and video but they are tightly connected • Computer supported integration • Communication systems

  17. Continuous vs. Discrete • Discrete media • time-independent: text and graphics • Continuous media • time-dependent: sound and full motion video

  18. Analog vs. Digital • Analog • Media represented using real values • Digital • Media represented using discrete values • (integers, quantized numbers, floating point representations)

  19. Sampled media • Sampled media • Represented by discrete points (which may be real valued) • Notice: • Sampled does not imply Digital

  20. Sampling Sampling - simply taking voltage readings at fixed points in time Uniform sampling – sampling at regular intervals

  21. Digital Conversion • Given voltage readings at points in time: • Convert the readings to digital • Options for digital representation: • Integers • Floating point values

  22. We’ll focus on... • Digital sampled media • But… • We have to understand the underlying continuous media...

  23. An Overview of Media Types We will look at: • text • Image • Sound • Video

  24. Text • Plain text: • alphanumeric characters • Most common representation is ASCII • Structured text • Text documents are structured (title, sections, …) • There are many standards and formats: • Word processor formats • LaTex, PDF

  25. Text Compression • Compression is either lossy or lossless • Text compression is lossless • Text compression uses the fact that some characters and phrases appear more often than others

  26. Text compression: Huffman coding • Idea: assign fewer bits to symbols that appear more often and more bits to symbols that are less often • Example: • Assume a file with 1000 characters • Characters are e, t, x, and z • Probability of occurrence 0.8, 0.16, 0.02, and 0.02 • In normal coding we need 2 bits for each symbol  2000 bits for the entire file • Using Huffman: 1 for e, 01 for t, 001 for x, and 000 for z • Total number of bits = 1000(1*.8+2*.16+3*.02+3*.02) = 1240

  27. Text compression: run length coding • Directly reduce the number of repeating characters • A run of any length is represented by: Sc, X, C • Sc special character • X is the repeated character • C is the character count

  28. Represent the phrase by its token Input file Yes Phrase No add phrase to dictionary and generate a token Did it appear before? Text compression: Lampel-Ziv-Welch (LZW) • Idea: build a dictionary of phrases from the input file.

  29. LZW example • Assume a file with 10,000 characters • If we use 8 bits for each character, we need 80,000 bits for the file • Suppose the file has 2000 words or phrases out of which 500 are distinct • We can use 9 bit tokens for each word or phrase  total number of bits is 18,000 bits

  30. Image • human and computer vision • Vision • to see an image and to understand its contents • capturing, analysis, and extracting features • Computer vision/image processing • intensity levels • resolution • distances and areas • the role of color • Images vs. Graphics • images are captured, graphics are created. • images are sequences of picture elements, graphics are a series of commands. • graphics may be converted into (synthetic) images

  31. REAL WORLD IMAGE Vision, Image Processing and Visualization Photography Image Processing Computer Vision Computer Graphics/ Visualization SCENE DESCRIPTION

  32. What kind of images…? • Face photos: Mug shots • Finger prints • CAT-scan data • News photos (general. Usually accompanied with explanatory text) • Surveillance (semi-specific domain,we may or may not know what to look for). • Video segments • Movies:general • surveillance • News broadcast • Sports

  33. Summary • Multimedia • Multimedia information systems • Enabling factors • Continuous vs. discrete • Analog vs. digital • Text • image

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