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Mpeg-4 Overview

Gerhard Roth

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Overview

• Much more general than all previous mpegs– standard finished in the last two years

• standardized ways to support:– coding

• representing units of audio, visual, audiovisual content

– composition• describing how these objects are composed together to produce

compound media objects

– multiplex• multiplex and synchronize data associated with media objects

– interaction• interacting with user

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System overview

• a number of decoders for each type of media• a composition process which puts the decoded

parts together• composition ideas are similar to VRML

– scene graph of objects

– composition information is defined in the links

– hierarchical structure, not necessarily static

– composition stream has extra information for mp4• spatial relationships

• temporal relationships

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Receiver/Decoder architecture

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Multiplex synchronization

• timing and synchronization of media• three layers

– specific information for timing and synchronization of the coded media (synchronization layer)

– multiplex streams with different characteristics (flexible multiplex layer)

– add the multiplex stream to a particular network (transport multiplex layer)

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Multiplex/synchronization layer

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Intellectual property protection

• ipmp = intellectual property management and protection

• interface that permits mp4 to host one or more ipmp systems

• ipmp framework has– normative interface that permits mpeg-4 terminal to

host one or more IPMP systems

– non normative component that provides intellectual property management

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Video

• Tools for efficient compression of • images, video, 2d textures

• time varying geometry (animated meshes)

• efficient random access

• extended manipulation functionality

• content based coding and scalability

• error robustness and resilience

• based on video object– entity in scene that user can manipulate and access

• video object planes– instances of video objects at a given time

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Video

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Media integration of text and graphics

• 3d graphics– like VRML including script nodes

• face animation– face definition parameters (FDPs)

– face animation parameters (FAPs)

• 2d mesh encoding– dynamic mesh, a temporal sequence of 2d triangular

meshes

• texture coding via wavelets

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Face definition parameters

• a number of feature points on a neutral face

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Face animation parameters

• a number of face • animation points

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2d mesh decoding

• mesh vertices points can move in 2d

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2d mesh of fish

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2d mesh augmentation of fish– the letters are synthetically overlaid on the video object

and move in synchronization with it

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Conclusion

• a superset of old VRML and Mpeg-1 and Mpeg-2• very general, many concepts

– can mix and match many different compression algorithms for different objects

– handles everything (audio, video, 2d-3d, faces, mesh…)

– is a first attempt at integrating 2d and 3d worlds

• DivX is a software application that uses the MPEG-4 standard to compress digital video

• DivX is done with the open source community– much better compression than ordinary DVDs

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URLs