Video Codec Design Developing Image and Video Compression Systems

Transcription

1 Video Codec Design Developing Image and Video Compression Systems Iain E. G. Richardson The Robert Gordon University, Aberdeen, UK JOHN WILEY & SONS, LTD

2 Contents 1 Introduction l 1.1 Image and Video Compression Video CODEC Design Structure of this Book 2 2 Digital Video Introduction Concepts, Capture and Display The Video Image Digital Video Video Capture Sampling Display Colour Spaces RGB YCrCb The Human Visual System Video Quality Subjective Quality Measurement Objective Quality Measurement Standards for Representing Digital Video Applications Platforms Summary 25 References 26 3 Image and Video Compression Fundamentals Introduction Do We Need Compression? Image and Video Compression DPCM (Differential Pulse Code Modulation) Transform Coding Motion-compensated Prediction Model-based Coding Image CODEC Transform Coding Quantisation 35

3 vi CONTENTS Entropy Coding Decoding Video CODEC Frame Differencing Motion-compensated Prediction Transform, Quantisation and Entropy Encoding Decoding Summary 45 4 Video Coding Standards: JPEG and MPEG Introduction The International Standards Bodies The Expert Groups The Standardisation Process Understanding and Using the Standards JPEG (Joint Photographic Experts Group) JPEG Motion JPEG JPEG MPEG (Moving Picture Experts Group) MPEG MPEG MPEG Summary 76 References 76 5 Video Coding Standards: H.261, H.263 and H.26L Introduction H H Features The H.263 Optional Modes/H H.263 Profiles H.26L Performance of the Video Coding Standards Summary 91 References 92 6 Motion Estimation and Compensation Introduction Motion Estimation and Compensation Requirements for Motion Estimation and Compensation Block Matching Minimising Difference Energy Full Search Motion Estimation Fast Search Three-Step Search (TSS) 102

4 CONTENTS vii Logarithmic Search Cross Search One-at-a-Time Search Nearest Neighbours Search Hierarchical Search Comparison of Motion Estimation Algorithms Sub-Pixel Motion Estimation Ill 6.7 Choice of Reference Frames Forward Prediction Backwards Prediction Bidirectional Prediction Multiple Reference Frames Enhancements to the Motion Model Vectors That can Point Outside the Reference Picture Variable Block Sizes Overlapped Block Motion Compensation (OBMC) Complex Motion Models Implementation Software Implementations Hardware Implementations Summary 125 References Transform Coding Introduction Discrete Cosine Transform Discrete Wavelet Transform Fast Algorithms for the DCT Separable Transforms Flowgraph Algorithms Distributed Algorithms Other DCT Algorithms Implementing the DCT Software DCT Hardware DCT Quantisation Types of Quantiser Quantiser Design Quantiser Implementation Vector Quantisation Summary 160 References Entropy Coding Introduction Data Symbols Run-Level Coding 164

5 CONTENTS Other Symbols Huffman Coding True' Huffman Coding Modified Huffman Coding Table Design Entropy Coding Example Variable Length Encoder Design Variable Length Decoder Design Dealing with Errors Arithmetic Coding Implementation Issues Summary 192 References 193 Pre- and Post-processing Introduction Pre-filtering Camera Noise Camera Movement Post-filtering Image Distortion De-blocking Filters De-ringing Filters Error Concealment Filters Summary 208 References 209 Rate, Distortion and Complexity Introduction Bit Rate and Distortion The Importance of Rate Control Rate-Distortion Performance The Rate-Distortion Problem Practical Rate Control Methods Computational Complexity Computational Complexity and Video Quality Variable Complexity Algorithms Complexity-Rate Control Summary 232 References 232 Transmission of Coded Video Introduction Quality of Service Requirements and Constraints QoS Requirements for Coded Video Practical QoS Performance Effect of QoS Constraints on Coded Video 241

6 CONTENTS ix 11.3 Design for Optimum QoS Bit Rate Error Resilience Delay Transmission Scenarios Digital Television Broadcasting: MPEG-2 Systems/Transport Packet Video: H.323 Multimedia Conferencing Summary 254 References Platforms Introduction General-purpose Processors Capabilities Multimedia Support Digital Signal Processors Embedded Processors Media Processors Video Signal Processors Custom Hardware Co-processors Summary 269 References Video CODEC Design Introduction Video CODEC Interface Video In/Out Coded Data In/Out Control Parameters Status Parameters Design of a Software CODEC Design Goals Specification and Partitioning Designing the Functional Blocks Improving Performance Testing Design of a Hardware CODEC Design Goals..._ Specification and Partitioning Designing the Functional Blocks Testing Summary 287 References Future Developments Introduction 289

7 x CONTENTS 14.2 Standards Evolution Video Coding Research Platform Trends Application Trends Video CODEC Design 292 References 293 Bibliography 295 Glossary 297 Index 301