Contents. xv xxi xxiii xxiv. 1 Introduction 1 References 4

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1 Contents List of figures List of tables Preface Acknowledgements xv xxi xxiii xxiv 1 Introduction 1 References 4 2 Digital video Introduction Analogue television Interlace Picture sizes Standard definition television formats (SDTV) Standard input format (SIF) Common intermediate format (CIF) Quarter common intermediate format (QCIF) Video graphics array (VGA) Quarter video graphics array (QVGA) High definition television Chrominance formats Bit depth and uncompressed video bit rates Concluding remarks Summary 20 References 20 3 Picture quality assessment Introduction Subjective viewing tests Analogue video quality measurements Linear distortions Non-linear distortions Noise Measurement Digital video quality Peak signal-to-noise ratio (PSNR) Objective perceptual video quality measurement techniques 27

2 viii Video compression systems Picture quality monitoring using watermark signals Testing picture quality analysers Video quality measurements inside encoders or decoders Double-ended video quality measurements 30 in encoders Single-ended video quality measurements on compressed bit streams Concluding remarks Summary 31 References 31 4 Compression principles Introduction Basic audio compression techniques Frequency response Frequency masking Temporal masking Transformation and quantisation Introduction to video compression Redundancy in video signals Exploiting spatial redundancy Example transformation and quantisation Exploiting statistical redundancy Exploiting temporal redundancy Motion estimation Example transformation of a predicted block Block diagrams Quantisation control Bi-directional prediction Mode decision Rate control Concluding remarks Summary 51 References 51 5 MPEG video compression standards Introduction MPEG MPEG Interlace coding tools Film coding tools Low-delay mode Profiles and levels Block diagram MPEG MPEG-4 Part 2 (Visual) Motion prediction Intra-prediction Object coding 64

3 Contents ix MPEG-4 Part 10 (AVC) New transforms Entropy coding Intra-predictions Motion prediction In-loop filter Rate-distortion optimisation (RDO) Block diagram Structure of MPEG bit streams Elementary streams Sequence Group of pictures Picture Slice Macroblock Block Differences in MPEG-4 (AVC) Transport stream Timing synchronisation Adaptation fields Program-specific information (PSI) Current MPEG activities Concluding remarks Summary 80 Exercise 5.1 Encoder evaluation 81 Exercise 5.2 Bit-rate saving 81 Exercise 5.3 PSNR limit 81 References 82 6 Non-MPEG compression algorithms Introduction VC-1 SMPTE 421M Adaptive block-size transform Motion compensation Advanced entropy coding De-blocking filter Advanced B frame coding Low-rate tools Fading compensation Audio Video Coding Standard (AVS) Transform Intra-predictions Motion compensation Entropy coding De-blocking filter B frame coding modes Wavelet compression JPEG Dirac Dirac Pro Concluding remarks 95

4 x Video compression systems 6.8 Summary 96 Exercise 6.1 Clip encoding 96 Exercise 6.2 Codec comparison 96 References 96 7 Motion estimation Introduction Block-matching algorithms in the spatial domain Exhaustive motion estimation Hierarchical motion estimation Other block-matching methods Spiral search Sub-sampling method Telescopic search Three-step search Correlation algorithms in the frequency domain Phase correlation Cross-correlation Sub-block motion estimation Sub-pixel motion refinement Concluding remarks Summary 114 Exercise 7.1 Motion estimation search range 114 References Pre-processing Introduction Picture re-sizing Horizontal down-sampling Vertical down-sampling in SDTV systems Temporal sub-sampling Intra-field down-sampling Vertical-temporal down-sampling De-interlacing Motion-adaptive de-interlacing Motion-compensated de-interlacing De-interlacing and compression Noise reduction Introduction Types of noise Bit-rate demand of noisy video signals Noise reduction algorithms Temporal noise reduction algorithms Spatial noise reduction algorithms Noise-level measurement Impulse noise reduction De-blocking and mosquito filters De-blocking filters Mosquito noise filters 128

5 Contents xi 8.5 Forward analysis Introduction Film mode detection Scene cuts, fades and camera flashes Picture criticality measurement Global coding mode decisions Detection of previously coded picture types Concluding remarks Summary 131 Exercise 8.1 De-interlacing 131 Exercise 8.2 Vertical down-sampling 131 Exercise 8.3 HD to SD conversion 131 Exercise 8.4 Encoder optimisation 132 References High definition television (HDTV) Introduction Compression of HDTV Spatial scalability Progressive versus interlaced Compression of 1080p50/ Bit-rate requirement of 1080p Test sequences Test configuration Bit-rate results Qualification of these results Concluding remarks Summary 145 Exercise 9.1 HDTV contribution 145 References Compression for mobile devices Introduction Compression algorithms for mobile applications Pre-processing for TV to mobile Compression tools for TV to mobile CABAC B frames Main Profile Decode time Scalable video coding (SVC) Transmission of text to mobile devices Concluding remarks Summary 157 Exercise 10.1 Compression for mobile devices 157 References 157

6 xii Video compression systems 11 MPEG decoders and post-processing Introduction Decoding process Channel change time Bit errors and error concealment Post-processing Concluding remarks Summary 166 Exercise 11.1 Channel change time 166 Exercise 11.2 Filter design 166 References Statistical multiplexing Introduction Analysis of statistical multiplex systems Bit-rate saving with statistical multiplexing Statistical multiplexing of MPEG-4 (AVC) bit streams Comparison of bit-rate demand of MPEG and MPEG-4 (AVC) Bit-rate demand of MPEG-4 (AVC) HDTV System considerations Configuration parameters Noise reduction Two-pass encoding Opportunistic data Concluding remarks Summary 181 Exercise 12.1 Statistical multiplexing at median 182 bit-rate demand Exercise 12.2 Large statistical multiplex system 182 References Compression for contribution and distribution Introduction MPEG-2 4:2:2 Profile Bit-rate requirement of 4:2:2 Profile Optimum GOP structure with high-bit-rate 184 4:2:2 encoding VBI handling in MPEG-2 4:2:2 encoding MPEG-4 (AVC) CABAC at high bit rates MPEG-4 (AVC) profiles Fidelity range extension :2:2 MPEG-4 (AVC) Comparison of 8 and 10 bit coding Low-delay MPEG-4 (AVC) 196

7 Contents xiii 13.4 Concluding remarks Summary 197 Exercise 13.1 Distribution link 197 References Concatenation and transcoding Introduction Concatenation model Detection of MPEG frame types in decoded video signals Bit-rate saving MPEG-2/MPEG-4 (AVC) concatenation Fixed bit rate into variable bit rate MPEG-2 to MPEG-2 concatenation MPEG-2 to MPEG-4 (AVC) concatenation MPEG-4 (AVC) to MPEG-4 (AVC) 210 concatenation Concatenation of HDTV MPEG-4 (AVC) to MPEG-2 concatenation Variable bit rate into fixed bit rate MPEG-2 downstream encoder MPEG-4 (AVC) downstream encoder Concluding remarks Summary 215 Exercise 14.1 Concatenation with statistical multiplexing 215 Exercise 14.2 Concatenation of DTH signals into 215 MPEG-4 (AVC) encoder Exercise 14.3 Concatenation of DTH signals 215 into MPEG-2 encoder Exercise 14.4 Concatenation of 4:2:0 signals 216 References Bit-stream processing Introduction Bit-rate changers Transcoding Splicing Splicing and statistical multiplexing Insertion of pre-compressed video clips Concluding remarks Summary 223 Exercise 15.1 Bit-stream processing 223 Exercise 15.2 Splicing between different bit rates 224 References Concluding remarks 225 References 226

8 xiv Video compression systems Appendix A: Test sequences referred to in this book 227 A.1 SDTV test sequences 227 A.2 HDTV test sequences 228 Appendix B: RGB/YUV conversion 229 B.1 SDTV conversion from RGB to YUV 229 B.2 SDTV conversion from YUV to RGB 229 B.3 HDTV conversion from RGB to YUV 229 B.4 HDTV conversion from YUV to RGB 230 Appendix C: Definition of PSNR 231 Appendix D: Discrete cosine transform (DCT) and inverse DCT 232 Appendix E: Introduction to wavelet theory 233 E.1 Introduction 233 E.2 Relationship to windowed Fourier transformation 233 E.2.1 Orthonormal wavelets 234 E.2.2 Wavelets based on splines 235 References 236 Appendix F: Comparison between phase correlation and cross-correlation 237 Appendix G: Polyphase filter design 239 G.1 Down-sampling by N 239 G.1.1 Numerical example 239 G.2 Up-sampling by M 240 G.2.1 Numerical example 240 G.3 Up-sampling by M/N 240 G.3.1 Numerical example 241 G.4 Down-sampling by M/N 241 G.4.1 Numerical example 241 Appendix H: Expected error propagation time 243 Appendix I: Derivation of the bit-rate demand model 245 Bibliography 247 Useful websites 249 Glossary 251 Example answers to exercises 257 Index 263