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Existing Video Coding Standards. ITU. H.120 (1984). ISO. H.261 (1990) p ×64Kbps. MPEG-1 (1992) 1.5Mbps, VCD. H.263 8-512Kbps. MPEG-2/H.262 (1996) 2-10Mbps, DVD. MPEG-4 (2000) 8-1024Kbps. H.263+(1998). windows media player or real player. H.264/AVC coding standard. - PowerPoint PPT Presentation

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  • Existing Video Coding StandardsISOITUMPEG-1 (1992)1.5Mbps, VCDMPEG-2/H.262 (1996)2-10Mbps, DVDMPEG-4 (2000)8-1024KbpsH.261 (1990)p64KbpsH.2638-512KbpsH.263+(1998)

    windows media playeror real player

    H.264/AVC coding standardH.120 (1984)

    EE569 Digital Video Processing

  • H.261 Coding StandardBackground:Facilitate video conferencing and videophone service over ISDNp64 kbps (p=1:videophone; p>5: videoconference; p=30: VHS-quality)Basis of MPEG-1 and MPEG-2FeaturesMaximum coding delay of 150msAmenable to low-cost VLSA implementation

    EE569 Digital Video Processing

  • Input Image Formats

    EE569 Digital Video Processing

  • Video MultiplexIt defines a data structure so that a decoder can interpret the received bit stream without any ambiguityHierarchical data structurePicture layerGroup of blocks (GOB) layerMacroblock (MB) layerBlock layerEach layer has a distinct header

    EE569 Digital Video Processing

  • Picture and GOB LayersPicture layer consists of picture header followed by the data for GOBsPicture header contains data such as picture format (CIF or QCIF)GOB layer is always composed of 33 macroblocksGOB header contains a MB address and compression mode followed by the data for the blocks

    EE569 Digital Video Processing

  • Macroblock and Block LayersMacroblock: the smallest unit to select the compression modeY1Y2Y4Y3CrCbA MB always consists of 6 blocks (Y1 Y4, Cr, Cb)

    EE569 Digital Video Processing

  • Compression Modes Intra ModeSimilar to JPEG codingSupport two compression modesInter ModeME is not specified (MC is optional)Usually, 16-by-16 BMA, integer-pel accuracy, search range [-15,15]Support various compression modes

    EE569 Digital Video Processing

  • Selecting a Compression ModeShould a MV be transmitted?Should we use intra or inter compression mode?Should the quantizer stepsize be changed?We can choose the optimal compression mode based onthe variance of the original MB, the MB difference (bd),the displaced MB difference (dbd) and the best MV estimate

    EE569 Digital Video Processing

  • Selection MethodIf the variance of dbd is smaller than bd, then we select Inter mode and MC is neededNeed to transmit MVDThe transmission of DCT coefficients is optionalOtherwise, no MV will be transmittedIf the original MB has a smaller variance, select Intra mode; otherwise select Inter mode (but with a zero MV)For MC blocks, prediction errors can be modified by a 2D spatial filter (the prototype of deblocking filter)

    EE569 Digital Video Processing

  • H.261 Compression Modes

    EE569 Digital Video Processing

  • InterpretationMQUANT: when it is on, a new value of quantizer stepsize will be transmitted;MVD: when it is on, the motion vector difference will be transmitted;CBP: when it is on, it means at least one transform coefficient in MB will be transmitted;TCOEFF: when it is on, transform coeffients will be transmitted

    EE569 Digital Video Processing

  • Variable ThresholdingT=g, Tmax=g+g/2Coeff
  • ExampleCoef>TCoefT

    EE569 Digital Video Processing

  • Run-Length CodingZigzag Scan(run,level)(0,3) (1,2) (7,1) EOB

    EE569 Digital Video Processing

  • H.261 Rate/Buffer ControlThe coded video data rate is controlled byPre-processingQuantization step-sizeBlock significance criterion (CBP flag)Temporal sampling ratio The fullness of buffer is controlled byQuantization step-sizeMaximum allowable coding delay (150ms)

    EE569 Digital Video Processing

  • MPEG-I Standard Features Syntax based no specific algorithm is standardized, the parameters defining the encoded bit stream and decoder are contained in the bit stream itself. Random accessAllow independent access points (I-frame) to the bitstream. Fast forward and reverse search Reasonable coding/decoding delay

    EE569 Digital Video Processing

  • Input Video Format Progressive video (interlaced video is handled by MPEG2) Input video is first converted into the MPEG standardinput format (SIF).SIF format: Y - 352 240, Cr/Cb - 176 120, 30 frames/secYCrCb

    EE569 Digital Video Processing

  • MPEG-I Constrained Parameter Set-maximum number pixels/line: 720-maximum number of lines/picture: 576-maximum number of pictures/sec: 30-maximum number of macro-blocks/picture: 396-maximum number of macro-blocks/sec: 9900-maximum bit rate: 1.86 Mbps-maximum decoder buffer size: 376,832 bits

    EE569 Digital Video Processing

  • Perspective Video Formats

    EE569 Digital Video Processing

  • Hierarchical Data Structure (I) Sequences are formed by Group Of Pictures (GOP) GOP are made up of pictures Pictures consist of slices Slices are made up of macro-blocks Macro-blocks (MB) consist of blocks Blocks are 88 pixels arrays

    EE569 Digital Video Processing

  • GOPGOPGOPGOPGOPGOPframeframeframeframeframeframeslicesliceslicesliceslicesliceMBMBMBMBMBMBblockblockblockblockHierarchical Data Structure (II)

    EE569 Digital Video Processing

  • Four Compression Modes I frame : Intra-frame JPEG-like coding P frame : forward Prediction from previous frames B frame : forward, backward or bi-directional Prediction D frame : contain only the DC component of each blockIPPBBBBBB0 1 2 3 4 5 6 7 8GOP

    EE569 Digital Video Processing

  • GOP ReorderingIPPBBBBBB0 1 2 3 4 5 6 7 8GOPProcessing order: 0,4,1,2,3,8,5,6,7

    EE569 Digital Video Processing

  • MB Types in MPEG-I

    EE569 Digital Video Processing

  • Intra-frame Compression Mode88 DCTQuantizationRun-length codingJPEG-like coderDefault quantization matrix Q0spatially adaptive quantizationMQUANT parameter MB types- IntraQ0- Intra-AQ

    EE569 Digital Video Processing

  • Inter-frame Compression Mode (P) MB types- Intra- Intra-A- Inter-D- Inter-DA- Inter-F- Inter-FD- Inter-FDA- skippedDirectly copy from the block at thesame position in the previous frame A new MQUANT value and DCT ofprediction error will be codedWe need to transmit MV and DCT ofprediction error We need to transmit MV, DCT ofprediction error and a new MQUANT

    EE569 Digital Video Processing

  • Interframe Compression Mode (B) Advantages Disadvantagesallow efficient handling of problems associated withcovered/uncovered backgroundMC averaging over two frames suppresses noise betterthan prediction from just one frameSince B-frames are not used in predicting future frames,they can be coded with fewer bits without causing errorpropagationTwo frame buffers are neededLonger coding delay

    EE569 Digital Video Processing

  • Theoretical Framework behind B-frame CodingWhy does it improve coding efficiency?Multi-hypothesis motion compensation (MHMC)B frame is one of the simplest MHMC (two hypotheses: forward and backward)Why does it facilitate scalable coding?Temporal scalabilityWe can skip B-frames without affecting the decoding of other frames

    EE569 Digital Video Processing

  • MPEG-I Encoder and Decoder Encoder modules Decoder modulesmotion estimation, selection of compression mode (MTYPE)per MB, setting MQUANT value, MCP, quantizer and dequantizer, DCT and IDCT, VLC, multiplexer, buffer and buffer regulator Demultiplexer, VLC decoder, MCP, dequantizer and IDCT relative number of I,P,B pictures in a GOP is application dependent. The use of B-pictures is optional. There is at least one I picture every 132 pictures. half-pixel accuracy in motion estimation m.v. that refer to pixels outside of picture is not allowed

    EE569 Digital Video Processing

  • Software ImplementationsBellcore versionivy.ee.princeton.edu (not publically accessible)Berkeley version toe.cs.berkeley.edu (128.32.149.117)/pub/multimedia/mpeg/mpeg-2.0.tar.ZStanford versionftp://havefun.stanford.edu/ (36.2.0.35)/pub/mpeg/MPEGv1.2.tar.Z

    EE569 Digital Video Processing

  • MPEG-I vs. H.261

    EE569 Digital Video Processing

  • MPEG-2 Standard Features it allows for interlaced input, higher-definition inputsand alternative subsampling of chrominance channels it offers scalable bit stream it provides improved quantization and coding options Profiles simple profile, main profile, SNR scalable profile,spatially scalable profile and high profile

    EE569 Digital Video Processing

  • Chrominance Subsampling 4:2:0 (same as MPEG-I) 4:2:2 (chroma subsampled in the horizontal direction only) 4:4:4 (no chroma subsampling)luminancechrominanceluminancechrominance

    EE569 Digital Video Processing

  • Interlaced Video Coding Frame pictures Field picturesInterleave lines of even and odd fields to form composite framesodd fieldeven field8888Even and odd fields are treated as separate picturesQ: For video containing significant motion, which format is preferred?

    EE569 Digital Video Processing

  • Frame and Field PicturesGOP can be composed of mixture of frame and field picturesField pictures always appear in pair (top field and bottom field)If the top field is

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