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Technical University of CreteDepartment of Electronic and Computer Engineering

Multimedia Data Management

Euripides G.M. Petrakis

Chania 2010



  • 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



  • The most common type of information

  • The least space intensive data type

  • The 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.)



  • 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, speakers

  • Digital waveform audio: digital,

    • less sensitivity to noise and distortion

    • involves larger processing and storage capacities

    • Digital Audio Tape (DAT), Compact discs (CD)

    • WAV (Microsoft’s wave file format)


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



  • Digital images: sequences of pixels

  • Pixels: 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.


Image Concepts and Structures

  • Binary images: 1 bit/pixel

    • black & white photos, facsimile images

  • Computer Graphics: 4 bits/pixel

  • Grayscale images: 8 bits/sample

  • Color images: 16, 24 bits/pixel


RGB Representation

  • A color is produced by adding

    • red, green and blue

  • The straight line R=G=B specifies gray values ranging from black to white


YUV Representation

  • YUV describes the luminance and chrominance components of an image

    • 1 luminance: gray scale version of an image

      • Y = 0.299R + 0.587G + 0.114B

    • 2 chrominance components:

      • U = 0.564(B - Y)

      • V = 0.713(R - Y)



  • Conversion between RGB and YUV requires multiplication operations

    • an approximation:

    • Y = R/4 + G/2 +B/2, U=(B-Y)/2, V=(R-Y)/2

    • R = Y + 2V, G = Y – (U + V), B = Y + 2U

  • YCbCr is another color format

    • for compression

    • Cb = U/2 + 0.5, Cr = V/1.6 + 0.5



  • The most space intensive data type

  • A sequence of frames

  • Realistic 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


Audio-video Modes of Operation


  • Can be either stored or used / transmitted live in real-time

  • Can be used interactively or non-interactively



  • Objects described through their basic elements (e.g., 2D, 3D shapes)

    • these elements can have different sizes, position, orientation, surface, fill etc.

    • compact representations

    • generated and can be manipulated by design tools (e.g., CAD tools)

    • Their descriptions are stored in files


2D and 3D graphics objects


Baker 96



  • 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.)


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)


Multimedia Technologies

  • Technologies integrated within a mdbms

  • HSM support

  • IR support (exact and approximate)

  • Spatial data types and queries

  • Interactive querying, relevance feedback, refining

  • Automatic feature extraction

  • Automatic content retrieval and indexing

  • Query optimization


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


Hierarchical Storage Management (HSM)

  • Support storage of multimedia objects

    • On-line: on RAM, magnetic disk

    • Near-on-line: on optical storage

    • Off-line: on tapes, shelves

  • Each level has different

    • Performance: decreases from top to bottom

    • Capacity: increases from top to bottom

    • Cost: decreases from top to bottom


Information Retrieval (IR) Capabilities

  • Retrieval is the most common operation

    • Deletions and updates are less common

    • Exact match: search based on exact information

    • Inexact: 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 refinement

    • Iterate over query results

    • Adjust weights of query terms or features

    • And finally resubmit queries


MDBMS architecture


Baker 96


MDBMS Implementation

  • Relies on 3rd party vendors for each component

    • Relational dbms for typical records

    • separate optical storage module for text/audio/graphics/images/video

    • Text retrieval system (e.g. Lucene)

    • Audio/image/video retrieval system

    • Feature extraction system

    • Multimedia object interface system


Object-Oriented Multimedia Databases

  • Better design, better suited for multimedia applications

    • Uniform handling of data and operations

    • Data 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 requirements

    • Provides primitives for object handling

    • Multimedia components need to be implemented or integrated


Multimedia Applications

  • Multimedia Systems suggest a variety of applications

    • Multimedia conferencing

    • Multimedia on demand (interactive TV, news on demand)

    • See next page for more …


Multimedia Applications



Multimedia Conferencing (MC)

  • Multimedia conferencing enable a number of participants to exchange multimedia information

    • Each 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


A video conference system


  • The biggest performance challenge occurs when the participants transmit voice and video

    • These are mixed together to form a composite stream consisting of video and voice streams


Software Architecture




  • Fully distributed: direct connections between the participants

    • Processing and mixing of media at every location

    • Shortest delay

    • The connections increase rapidly

  • Centralized (star) network: a central is connected to every participant

    • Processing and mixing at central node

    • The central node waits until all media is received before mixing and broadcasting


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 hierarchically

    • intermediate nodes perform mixing and processing

    • the completely mixed data is sent to root who broadcasts directly to the leaves

    • reduces network traffic significantly


Multimedia conferencing network architectures



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 services

    • interactive entertainment

    • video news distribution

    • video rental services

    • digital multimedia libraries


Interactive Television (ITV)

  • An ITV system must be capable of providing

    • basic TV

    • subscription TV

    • pay per view

    • video on demand

    • shopping

    • education

    • electronic newspaper

    • financial transactions

    • single-user and multi-user games


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


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