E.G.M. Petrakis The MPEG Standard 1 The MPEG Standard MPEG-1 (1992) actually a video player plays out audio/video streams same type of access as home VCR MPEG-2 (1995) introduced for compression and transmission of digital TV signals still limited interactivity MPEG-4 (1999) is completely different high level of interactivity MPEG-7 (2002) for the description of metadata only
The MPEG Standard. MPEG-1 (1992) actually a video player plays out audio/video streams same type of access as home VCR MPEG-2 (1995) introduced for compression and transmission of digital TV signals still limited interactivity MPEG-4 (1999) is completely different - PowerPoint PPT Presentation
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E.G.M. Petrakis The MPEG Standard 1
The MPEG StandardMPEG-1 (1992) actually a video player
plays out audio/video streamssame type of access as home VCR
MPEG-2 (1995) introduced for compression and transmission of digital TV signalsstill limited interactivity
MPEG-4 (1999) is completely different high level of interactivity
MPEG-7 (2002) for the description of metadata only
E.G.M. Petrakis The MPEG Standard 2
MPEG-4MPEG-4 addresses the need towards
Mixing of natural and synthetic audiovisual information
High interactivity in the presentation of multimedia content
Deployment of communication systems for real-time or broadcast delivery of coded data streams
A new approach for describing, coding and presenting a scene
MPEG-4 combines different coding tools for Audio/video Synthetic objects and graphics
E.G.M. Petrakis The MPEG Standard 3
MPEG-4 ObjectsThe audio/video components of MPEG-4
Objects are coded, transmitted separately and composed at the decoder site
They can exist independentlyMultiple objects can be grouped together
to form complex objectsVideo and audio can be easily manipulatedPermits choosing appropriate coding tools
for audio, video and graphics objects
E.G.M. Petrakis The MPEG Standard 4
MPEG-4 Object Based Coding
E.G.M. Petrakis The MPEG Standard 5
MPEG-4 CodingThe scene is composed and rendered at the
sender sitevideo frames, audio are coded,
multiplexed and transmitted tools for coding arbitrarily shaped objects
At the receiver the stream is demultiplexedvideo and audio are decoded, composed,
synchronized and presented as defined at the senders site
E.G.M. Petrakis The MPEG Standard 6
Object CodingObjects are described mathematically
(e.g. by their positions)similarly for audio and graphics objectsan object need only be defined oncethe viewer can change their positiontransmit calculations to update the scene
at the receiverthis is a critical feature when the response
has to be fast and bit-rate is limited
E.G.M. Petrakis The MPEG Standard 7
Binary Format for Scenes (BIFS)
MPEG-4’s language for describing and dynamically changing a scene
Borrows concepts from VRMLBoth define representations of the same dataVRML defines objects and actions in textBIFS code is binary (10-15 times shorter)Unlike VRML, MPEG-4 uses BIFS for real-time
streaming: a scene can be built-up and played on the fly
VRML and BIFS evolve consistently
E.G.M. Petrakis The MPEG Standard 8
scene graph
E.G.M. Petrakis The MPEG Standard 9
The Scene GraphRepresents a scene as independent
or compound objects e.g., father and child the audio track of his voicefloor and walls (sprites: for backgrounds)the web site the synthetic image of the furniturea synthetic HDTV set playing a movie
from the families DVD library
E.G.M. Petrakis The MPEG Standard 10
Elementary Streams (ES)The scheme for preparing content for
transmission, storage and decodingObjects are placed in ESsProbably two or more ESs per objectA sound track or a video may have a single
ESScalable objects way have one ES for basic
quality information + one or more enhancement layers for improved quality (e.g., finer detail, faster motion)
ESs are split into packets and sent along with timing information for proper synchronization
E.G.M. Petrakis The MPEG Standard 11
Object Descriptors (OD)MPEG-4s mechanism that informs
the system which ES belongs to a certain objectOD contain Elementary Stream
Descriptors (ESD) which tell the system which decoders to use
ODs are sent in their own stream which allows them to be added or deleted as the scene changes
E.G.M. Petrakis The MPEG Standard 12
Profiles and LevelsMPEG-4 provides a set of tools for coding
multimedia contentsan application may use only subsets of these
toolsProfiles: MPEG-4s definitions of these
subsets for audio, visual, graphics information
Levels: define the computational complexity of the profile’s tool subset
Certain combinations of profiles fit well together
E.G.M. Petrakis The MPEG Standard 13
MPEG-4 Profiles
E.G.M. Petrakis The MPEG Standard 14
MPEG-4 Visual ObjectsArbitrarily shaped objects are coded apart
from their background Binary shape coding: a pixel is or is not
part of an object simple, crude technique, suitable for low-bit
rates, suffers from aliasingAlpha shape (gray scale) coding: each pixel
is assigned a value for its transparencyobjects can be smoothly blended into a
background or with other objects
E.G.M. Petrakis The MPEG Standard 15
Visual ObjectsRectangular natural images and
scenes are coded using MPEG-1, 2Texture is coded separately by a DCT,
block based coding scheme or wavelets
E.g., weather reports: the weatherman’s image seems to be standing in front of a map which is actually generated elsewhere
E.G.M. Petrakis The MPEG Standard 16
Object SegmentationMPEG does not specify how objects
are extracted video object segmentation is difficult e.g., record weatherman’s image in
front of a color background MPEG-4 specifies decoding
implementation of encoding is left to the industry to decide
E.G.M. Petrakis The MPEG Standard 17
MPEG-4 ApplicationsMPEG-4 makes video possible even
at very low bit-rates (e.g., 10 kb/s)mobile devices, internet
Scalable objects for low bit-ratesa base layer conveys all the information
in some basic quality one of more enhancement layers can be
sent to get better qualitysend only the most important objects
E.G.M. Petrakis The MPEG Standard 18
SpritesFor coding unchanged backgrounds The background is defined and coded
only onceMust be updated for each change (e.g.,
when the viewing angles changes) The sprite is sent only onceNew views are created by sending the
new positions
E.G.M. Petrakis The MPEG Standard 19
Advanced FeaturesMap images into computer generated shapes
a 2D or 3D mesh may have an image mapped onto ita few parameters to deform the mesh generate the
impression of a moving picture rather than sending new images for each change,
send commands and parameters to the viewerpre-defined faces are particularly interesting meshesthe appearance of a face may be left to the decoder
(e.g., custom facial models can be downloaded)
E.G.M. Petrakis The MPEG Standard 20
MPEG-4 FacesImages laid over a
wire-frame face Send wire-frame plus
parametersImage reconstruction
at receivers siteSpeech is generated
from text in steps with motions of the mouth, eyes and lips
E.G.M. Petrakis The MPEG Standard 21
MPEG-7MPEG-7 (2002) focuses on description of
multimedia contentmodalities: image, speech, video, graphics and
their combinationsMPEG-7 complements existing MPEG
standards and is applicable even to non-MPEG formats (compressed or uncompressed)
MPEG-7 is driven by trends in technology, market and user needs
Applications: VideoOnDemand, NewsOnDemand, InteractiveTV, multimedia information systems etc.
E.G.M. Petrakis The MPEG Standard 22
Scope of the StandardProvides the means for indexing,
searching, filtering and managing audio-visual contentbroadcast media selection (e.g.,
Some software for extracting descriptors is also included (visual, audio descriptors)
E.G.M. Petrakis The MPEG Standard 36
References1. “MPEG-4 Multimedia for our Time” R. Koenen,
IEEE Spectrum, Feb. 1999, pp. 26-332. “
Applying and Implementing the MPEG-4 Multimedia Standard”, J. Kneip et.al. IEEE Micro, Nov-Dec 1999, pp. 64-74
3. “Overview of the MPEG-7 Standard”, S.-Fu Chang, T. Sikora and A. Puri, IEEE Transactions on Circuits and Systems for Video Technology, special issue on MPEG-7, June 2001
4. “Everything You Wanted to Know about MPEG-7” F. Nack and A.T. Lindsay, Part I, II, IEEE Multimedia, Aug-Dec1999