 Coding efficiency/Compression ratio:  The loss of information or distortion measure:

 The functional elements of the generalized model: Spatial operator Quantizer Variable length coding  The elements required in the feedback loop: Inverse operators Delayed frame memory Motion estimation Motion compensation

 A fundamental issue facing the design of video compression systems: the tradeoff between bitrate and quality or distortion  Factors in design and selection of a video compression system: Video characteristic Transmission requirement Compression system characteristics and performance Rate-distortion requirement Standards requirement

 Sampling of Analog Video Signals Two-dimensional spatial sampling and one- dimensional temporal sampling Nyquist sampling theorem: defines the conditions under which sampled analog signals can be perfectly reconstructed.

 Digital Video Formats

 Entropy and Predictive Coding Discrete memoryless source (DMS) – VLC coding: Huffman and arithmetic coding Markov source – predictive coding: differential pulse code modulation coding (DPCM)

 Block Transform Coding: The Discrete Cosine Transform Has fast implementations using real calculations Does not produce any significant discontinuities at the block edges when reconstruction

 Block Transform Coding: The Discrete Cosine Transform Has fast implementations using real calculations Does not produce any significant discontinuities at the block edges when reconstruction

 Quantization Uniform scalar quantizer Non-uniform quantization Vector quantizers

 Motion Compensation and Estimation Motion estimation and compensation are common techniques used to encode the temporal aspect of a video signal. Three stages of motion compensated video coding: 1. motion estimation 2. motion compensation 3. encode the prediction error

 Motion Compensation and Estimation Motion estimation is an interframe prediction process falling in two general categories: 1. pel-recursive algorithms 2. block-matching algorithms: measure and search

 The H.261 recommendation is targeted at the videophone and videoconferencing application market running on connection-based ISDN at p x 64 kbps, p = 1,...,30.  It explicitly defines the encoded bit stream syntax and decoder, while leaving the encoder design to be compatible with the decoder specification.  The video encoder is required to carry a delay of less than 150 ms so that it can operate in real-time bidirectional videoconferencing applications.

 The H.261 is part of a group of related ITU recommendations that define visual telephony systems.  This group includes the following:

 Motion Compensation  Transformation and Quantization  Scalabilities --one scalable coded file that offers increasingly greater spatial resolution, higher frame rates, or a better signal-to-noise ratio.

 Hybrid Wavelet Coder temporal differential PCM (DPCM)+wavelet based coders in the spatial dimension  Spatiotemporal Wavelet Coder Without motion compensation With motion compensation  Zero Coding and Embedding

 Segmenting objects  Temporal linking of objects  Encoding objects  “Inter” mode—encoding objects by the motion parameters (I objects)  “Intra” mode—encoding those that can not be predicted (P objects)

 Joint Motion Estimation and Segmentation The likelihood functional that describes how well the observed images match the motion field data:

 Joint Motion Estimation and Segmentation A priori density of motion and enforces prior constraints on the motion field:

 Joint Motion Estimation and Segmentation A priori expectations for the object label field itself:

 Maximation Approach MAP solution Two-step iterative hierarchical procedure: motion estimation & segmentation

 Coding of Video Objects I mode: motion compensated predictive (MCP) coding in hybrid object-based (OB)-MCP P mode: spatial wavelet coding

 Object Motion/Segmentation Coding Object-based 3-D wavelet coding (OB- 3DSBC) coder

 Represent visual data in terms of regions, defined by their contour and texture, possibly corresponding to objects or to parts of objects.  emphasize visually sensitive data while neglecting visually insignificant information  Second-generation concept is now widely accepted and has become the basic philosophy of the new MPEG-4 standard  Is called dynamic coding

 Intramode(I)—an object is coded independently  Intermode(P)—a video object is coded taking into account information available on its past

 Object Shape and Geometry Coding A progressive contour coding based on a polygonal approximation of the shape boundary is used to code the outline of object. Suitable for sketch-based retrieval that is based on video object shapes A geometrical shape boundary description can be integrated into an object-based mesh coding scheme

Lossless shape representation-- altered boundary triangles

 Object Motion Estimation, Compensation, and Coding  Texture Representation