CS Spring 2012 CS 414 – Multimedia Systems Design Lecture 12 – MPEG-2/ MPEG-4 (Part 6) Klara Nahrstedt Spring 2012

CS Spring 2012 Administrative MP1

Outline MPEG-2/MPEG-4 Reading:  Media Coding book, Section –  broadcasting/kiev/References/mpeg-4.html broadcasting/kiev/References/mpeg-4.html  Available software  Xvid – free software  video-codec-for-pc video-codec-for-pc CS Spring 2012

MPEG-2 Standard Extension MPEG-1 was optimized for CD-ROM and apps for 1.5 Mbps (video strictly non- interleaved) MPEG-2 adds to MPEG-1:  More aspect ratios: 4:2:2, 4:4:4  Progressive and interlaced frame coding  Four scalable modes spatial scalability, data partitioning, SNR scalability, temporal scalability CS Spring 2012

MPEG-1/MPEG-2 Pixel-based representations of content  takes place at the encoder Lack support for content manipulation  e.g., remove a date stamp from a video  turn off “current score” visual in a live game Need support manipulation and interaction if the video is aware of its own content CS Spring 2012

MPEG-4 Compression CS Spring 2012

Interact With Visual Content CS Spring 2012

Original MPEG-4 Conceived in 1992 to address very low bit rate audio and video (64 Kbps) Required quantum leaps in compression  beyond statistical- and DCT-based techniques  committee felt it was possible within 5 years Quantum leap did not happen CS Spring 2012

The “New” MPEG-4 Support object-based features for content Enable dynamic rendering of content  defer composition until decoding Support convergence among digital video, synthetic environments, and the Internet CS Spring 2012

MPEG-4 Components Systems – defines architecture, multiplexing structure, syntax Video – defines video coding algorithms for animation of synthetic and natural hybrid video (Synthetic/Natural Hybrid Coding) Audio – defines audio/speech coding, Synthetic/Natural Hybrid Coding such as MIDI and text-to-speech synthesis integration Conformance Testing – defines compliance requirements for MPEG-4 bitstream and decoders Technical report DSM-CC Multimedia Integration Framework – defines Digital Storage Media – Command&Control Multimedia Integration Format; specifies merging of broadcast, interactive and conversational multimedia for set-top-boxes and mobile stations CS Spring 2012

MPEG-4 Example ISO N3536 MPEG4 CS Spring 2012

MPEG-4 Example ISO N3536 MPEG4 CS Spring 2012

MPEG-4 Example Daras, P. MPEG-4 Authoring Tool, J. Applied Signal Processing, 9, 1-18, 2003 CS Spring 2012

Interactive Drama CS Spring 2012

MPEG-4 Characteristics and Applications CS Spring 2012

Example of MPEG-4 Scene Source:

Media Objects An object is called a media object  real and synthetic images; analog and synthetic audio; animated faces; interaction Compose media objects into a hierarchical representation  form compound, dynamic scenes CS Spring 2012

Logical Structure of Scene CS Spring 2012

Example of Composed Scene CS Spring 2012 Sprite Object Player Object Composed Scene

Video Syntax Structure CS Spring 2012 New MPEG-4 Aspect: Object-based layered syntactic structure

Content-based Interactivity Achieves different qualities for different objects with a fine granularity in spatial resolution, temporal resolution and decoding complexity Needs coding of video objects with arbitrary shapes Scalability  Spatial and temporal scalability  Need more than one layer of information (base and enhancement layers) CS Spring 2012

Examples of Base and Enhancement Layers CS Spring 2012

Coding of Objects Each VOP corresponds to an entity that after being coded is added to the bit stream Encoder sends together with VOP  Composition information where and when each VOP is to be displayed Users are allowed to change the composition of the entire scene displayed by interacting with the composition information CS Spring 2012

Spatial Scalability CS Spring 2012 VOP which is temporally coincident with I-VOP in the base layer, is encoded as P-VOP in the enhancement layer. VOP which is temporally coincident with P-VOP in the base layer is encoded as B-VOP in the enhancement layer.

Examples of Base and Enhancement Layers CS Spring 2012

Temporal Scalability CS Spring 2012

High Level Codec for Generalized Scalability CS Spring 2012

Composition (cont.) Encode objects in separate channels  encode using most efficient mechanism  transmit each object in a separate stream Composition takes place at the decoder, rather than at the encoder  requires a binary scene description (BIFS) BIFS is low-level language for describing:  hierarchical, spatial, and temporal relations CS Spring 2012

MPEG-4 Part 11 – Scene Description BIFS – Binary Format for Scenes  Coded representation of the spatio-temporal positioning of audio-visual objects as well as their behavior in response to interactions  Coded representation of synthetic 2D and 3D objects that can be manifested audibly and/or visibly BIFS – MPEG-4 scene description protocol to  Compose MPEG-4 objects  Describe interaction about MPEG-4 objects  Animate MPEG-4 objects BIFS Language Framework – XMT (textual representation of multimedia content using XML)  Accommodates SMIL, W3C scalable vector graphics and VRML (now X3D) CS Spring 2012

MPEG-4 Rendering ISO N3536 MPEG4 CS Spring 2012

Major Components on MPEG-4 Terminal CS Spring 2012

Integration and Synchronization of Multiple Streams CS Spring 2012 Source:

Synchronization Global timeline (high-resolution units)  e.g., 600 units/sec Each continuous track specifies relation  e.g., if a video is 30 fps, then a frame should be displayed every 33 ms. Others specify start/end time CS Spring 2012

Data Recovery CS Spring 2012 Reversible Variable Length Codes (RVLC) : variable length code words are designed such that they can be read both in forward and reverse directions QP – quantization parameter HEC – header extension code MP – macro-block

MPEG-4 parts MPEG-4 part 2  Includes Advanced Simple Profile, used by codecs such as Quicktime 6 MPEG-4 part 10  MPEG-4 AVC/H.264 also called Advanced Video Coding  Used by coders such as Quicktime 7  Used by high-definition video media like Blu- ray Disc CS Spring 2012

MPEG-4 System Layer Model SL – sync layer DMIF – Delivery Multimedia Integration Framework

MPEG-4 File with Media Data OD – Object Descriptor BIFS – Binary Format for Scenes Mdat – media data atoms

Interaction as Objects Change colors of objects Toggle visibility of objects Navigate to different content sections Select from multiple camera views  change current camera angle Standardizes content and interaction  e.g., broadcast HDTV and stored DVD CS Spring 2012

Hierarchical Model Each MPEG-4 movie composed of tracks  each track composed of media elements (one reserved for BIFS information)  each media element is an object  each object is a audio, video, sprite, etc. Each object specifies its:  spatial information relative to a parent  temporal information relative to global timeline CS Spring 2012

Conclusion A lot of MPEG-4 examples with interactive capabilities Content-based Interactivity  Scalability  Sprite Coding Improved Compression Efficiency (Improved Quantization) Universal Accessibility  re-synchronization  data recovery  error concealment CS Spring 2012