e.g.m. petrakisintroduction1 technical university of crete department of electronic and computer...
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1E.G.M. Petrakis Introduction
Technical University of CreteDepartment of Electronic and Computer
Engineering
Multimedia Data Management
Euripides G.M. Petrakishttp://www.intelligence.tuc.gr/~petrakis
http://courses.ced.tuc.gr
Chania 2010
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Definition
Multimedia: composite entities combining text, audio, images, video (bit-stream objects), graphics
Multimedia Information Systems: database systems that support all multimedia data types and handle very large volumes of information
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TEXT
The most common type of information
The least space intensive data typeThe form in which text is stored
varies (plain ascii, word files, spreadsheets, annotations, database fields etc.)
Text fonts are becoming complex allowing special effects (color, shade, fill etc.)
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AUDIO Space intensive (one minute can take up
Mbytes), presented as analog, digital or MIDI
Analog waveform: electrical signal, amplitude specifies the loudness of the sound in microphones, tapes, records, amplifiers,
speakersDigital waveform audio: digital,
less sensitivity to noise and distortion involves larger processing and storage
capacitiesDigital Audio Tape (DAT), Compact discs (CD)WAV (Microsoft’s wave file format)
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MIDI (Musical Instrument Digital Interface)
Commands that describe how the music should be played are stored (instead of sound)
A music synthesizer generates sound Provides high data compression, Widely accepted
Furht et.al.96
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IMAGES
Digital images: sequences of pixelsPixels: numbers interpreted to
display intensity, color, contrast etc Binary (0-1 values), gray-scale (8
bits/pixel), colour (3x8 values for RGB)Space overhead depends on image
type, resolution, compression scheme
Image formats: tiff, bmb, jpeg etc.
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Image Concepts and Structures
Binary images: 1 bit/pixel black & white photos, facsimile images
Computer Graphics: 4 bits/pixelGrayscale images: 8 bits/sampleColor images: 16, 24 bits/pixel
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RGB Representation
A color is produced by addingred, green and blue
The straight line R=G=B specifies gray values ranging from black to white
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YUV Representation
YUV describes the luminance and chrominance components of an image1 luminance: gray scale version of an
imageY = 0.299R + 0.587G + 0.114B
2 chrominance components:U = 0.564(B - Y)V = 0.713(R - Y)
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Conversions
Conversion between RGB and YUV requires multiplication operationsan approximation: Y = R/4 + G/2 +B/2, U=(B-Y)/2, V=(R-
Y)/2R = Y + 2V, G = Y – (U + V), B = Y + 2U
YCbCr is another color format for compressionCb = U/2 + 0.5, Cr = V/1.6 + 0.5
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VIDEO
The most space intensive data typeA sequence of framesRealistic video playback, transmission,
compression/decompression require transfer rates about 30frames/sec
Microsoft’s AVI and Apple’s Quicktime file formats integrate video and audio in the same presentation
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Audio-video Modes of Operation
Can be either stored or used / transmitted live in real-time
Can be used interactively or non-interactively
Furht et.al.96
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GRAPHICS
Objects described through their basic elements (e.g., 2D, 3D shapes)these elements can have different sizes,
position, orientation, surface, fill etc. compact representationsgenerated and can be manipulated by
design tools (e.g., CAD tools)Their descriptions are stored in files
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Khoshafian Baker 96
2D and 3D graphics objects
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MULTIMEDIA objects
Text, audio, images, video, graphics are elements of complex multimedia objects
Various tools or applications integrate, process and combine multimedia
Applications: multimedia authoring applications that output documents and databases and end-user applications (e.g., video on demand)
Tools: for viewing, updating, querying (presentation viewers, browsers etc.)
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Multimedia Databases (MDB)
Means stored information or database management systems (dbms)
Multimedia dbms (mdbms) integrate conventional database capabilities together with different technologies such as Hierarchical storage management (HSM) and Information retrieval (IR)
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Multimedia Technologies
Technologies integrated within a mdbms HSM support IR support (exact and approximate)Spatial data types and queriesInteractive querying, relevance feedback,
refiningAutomatic feature extractionAutomatic content retrieval and indexing Query optimization
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Database capabilities
Persistence: object persist through invocations Transactions: content is inserted, deleted,
updated Concurrency control: transactions run
concurrently Recovery: failed transactions are not propagated
to the db Querying: content can be retrieved Versioning: access previous states of objects Integrity: transactions guarantee consistency of
content Security: constraints for accessing/updating
objects Performance: optimal data structures and
programs
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Hierarchical Storage Management (HSM)
Support storage of multimedia objects On-line: on RAM, magnetic diskNear-on-line: on optical storageOff-line: on tapes, shelves
Each level has differentPerformance: decreases from top to
bottomCapacity: increases from top to bottomCost: decreases from top to bottom
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Information Retrieval (IR) Capabilities
Retrieval is the most common operationDeletions and updates are less commonExact match: search based on exact
informationInexact: search based on inexact information
e.g., partial, neighborhood search, can be fuzzy or probabilistic
The results are ranked by order of relevance to the query
Query refinementIterate over query results Adjust weights of query terms or featuresAnd finally resubmit queries
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Khoshafian Baker 96
MDBMS architecture
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MDBMS Implementation
Relies on 3rd party vendors for each componentRelational dbms for typical records separate optical storage module for
text/audio/graphics/images/videoText retrieval system (e.g. Lucene)Audio/image/video retrieval systemFeature extraction systemMultimedia object interface system
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Object-Oriented Multimedia Databases
Better design, better suited for multimedia applications Uniform handling of data and operationsData types are objects with internal structures
and operations that capture the behavior of objects (e.g., audio playback, video browsing)
OO dbms does not satisfy all MM requirementsProvides primitives for object handling Multimedia components need to be
implemented or integrated
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Multimedia Applications
Multimedia Systems suggest a variety of applicationsMultimedia conferencing Multimedia on demand (interactive TV,
news on demand)See next page for more …
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Furht et.al.96
Multimedia Applications
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Multimedia Conferencing (MC)
Multimedia conferencing enable a number of participants to exchange multimedia informationEach participant has a workstation
linked to other workstations over high-speed networks
Each participant can send or receive mm data and perform certain collaborative activities
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Furht et.al.96
The biggest performance challenge occurs when the participants transmit voice and videoThese are mixed together to form a composite
stream consisting of video and voice streams
A video conference system
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Furht et.al.96
Software Architecture
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Architectures
Fully distributed: direct connections between the participants Processing and mixing of media at every
locationShortest delayThe connections increase rapidly
Centralized (star) network: a central is connected to every participantProcessing and mixing at central nodeThe central node waits until all media is
received before mixing and broadcasting
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Architectures (cont.)
Double star network: a central node from one star network is connected to another central node of another star network
Hierarchical network: intermediate nodes, root and leaves (participants) connected hierarchicallyintermediate nodes perform mixing and
processingthe completely mixed data is sent to root who
broadcasts directly to the leavesreduces network traffic significantly
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Furht et.al.96
Multimedia conferencing network architectures
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Video on Demand (VoD)
Fast networks coupled with powerful computers and compression techniques will be capable of delivering stream data in real-time
On-demand multimedia servicesinteractive entertainment video news distributionvideo rental services digital multimedia libraries
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Interactive Television (ITV)
An ITV system must be capable of providingbasic TVsubscription TVpay per viewvideo on demandshoppingeducationelectronic newspaperfinancial transactionssingle-user and multi-user games
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This Course
Emphasis on Text, images, video Information retrieval & systems Data organization Web information systems Semantic Web Video & MPEG standards
No emphasis on Architectures Specific applications (VoD, ITV,MC) Services
E.G.M. Petrakis Introduction