Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 1!Overview: Video Coding Standards! Video coding standards: applications and common structure! ITU-T Rec. H.261 ! ISO/IEC MPEG-1 ! ISO/IEC MPEG-2! State-of-the-art: H.264/AVC!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 2!Applications of Video Compression!Efficient and flexible video compression standard needed Adapted from [Srinivasan et al., 2004]Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 3!Applications of Video Compression!Digital television broadcasting!2 . . . 6 Mbps!(10…20 Mbps for HD)!MPEG-2!(H.264/AVC)!DVD video!Blu-ray Disk!5 . . . 8 Mbps!up to 40 Mbps!MPEG-2!MPEG-2, H.264/AVC, VC-1 (up to 1080p)!Internet video streaming!100 . . . 2000 kbps! MPEG-1, H.264/AVC, VC-1, or similar proprietary!Videoconferencing, videotelephony!20 . . . 2000 kbps! H.261, H.263,#H.264/AVC!Video over 3G wireless! 100 . . . 500 kbps! H.263, MPEG-4, H.264/AVC!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 4!Motion-compensated Hybrid Coding# H.261, MPEG-1, MPEG-2, H.263, MPEG-4, H.264/AVC!Entropy Coding Deq./Inv. Transform Motion- Compensated Predictor Control Data Quant. Transf. coeffs Motion Data 0 Intra/Inter Coder Control Decoder Motion Estimator Transform/ Quantizer -Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 5!Video Compression Standards:#Hierarchical Syntax!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 6!ITU-T Rec. H.261! International standard for ISDN picture phones and for video conferencing systems (1990)! Image format: CIF (352 x 288 Y samples) or #QCIF (176 x 144 Y samples), frame rate 7.5 ... 30 fps! Bit-rate: multiple of 64 kbps (= ISDN-channel), #typically 128 kbps including audio! Picture quality: for 128 kbps acceptable with limited motion in the scene! Stand-alone videoconferencing system or #desk-top videoconferencing system, integrated with PC!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 7!Macroblocks! Macroblock (MB) of 16x16 pixels! Sampling format: 4:2:0! MB consists of 4 luminance and 2 chrominance blocks!16x16 luminance!samples !0! 1!2! 3!4! 5!8x8 Cb-!samples!8x8 Cr-!samples!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 8!H.261 Motion-Compensated Prediction! Integer-pel accuracy! One displacement vector per macroblock! Maximum displacement vector range +/-16 horizontally and vertically! Adaptive loop filter, separable in 1-D horizontal and vertical!!impulse response: [¼, ½, ¼] !! Differential encoding of motion vectors!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 9!H.261 Residual Coding! 8x8 DCT! Quantization! Uniform quantizer (Δ=8) for intra-mode DC coefficients! Uniform threshold quantizer (Δ=2,4,…,62) for AC coefficients in intra-mode and all coefficients in inter-mode! Zig-zag scan! Run-level coding for entropy coding ! (zero-run, value) symbols! zero-run: the number of coefficients quantized to zero since the last nonzero coefficient! value: the amplitude of the current nonzero coefficient!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 10!H.261 Macroblock Types (VLC Table)!Prediction! MQUANT! MVD! CBP! TCOEFF! VLC!Intra! X! 0001!Intra! X! X! 0000 001!Inter! X! X! 1!Inter! X! X! X! 0000 1!Inter+MC! X! 0000 0000 1!Inter+MC! X! X! X! 0000 0001!Inter+MC! X! X! X! X! 0000 0000 01!Inter+MC+FIL! X! 001!Inter+MC+FIL! X! X! X! 01!Inter+MC+FIL! X! X! X! X! 0000 01!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 11!MPEG-1/2: GOP Structure!Group of Pictures = GOP! 1 3 4 2 6 7 8 5!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 12!MPEG-1/2 Encoder!Pre-processing!8x8 DCT!Weighting! Quantization! VLC!Video multiplex!Buffer!Picture reordering!Inverse quantization!Inverse weighting!Inverse "8x8 DCT!Picture store 1!Picture store 2!Motion compensation!+-!+1/2!zero!Motion vectors, macroblock info, start codes!Video in !Bitstream !Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 13!MPEG-1: coding of I-pictures! I-pictures: intraframe coded! 8x8 DCT! Arbitrary weighting matrix for coefficients! Differential coding of DC-coefficients! Uniform quantization! Zig-zag-scan, run-level-coding! Entropy coding! Unfortunately, not quite JPEG!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 14!MPEG-1: coding of P-pictures! Motion-compensated prediction from an encoded I-picture or P-picture (DPCM)! Half-pel accuracy of motion compensation, bilinear interpolation! One displacement vector per macroblock! Differential coding of displacement vectors! Coding of prediction error with 8x8-DCT, uniform threshold quantization, zig-zag-scan as in I-pictures!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 15!MPEG-1: coding of B-pictures! Motion-compensated prediction from two consecutive P- or I-pictures! either!• only forward prediction (1 vector/macroblock)! or!• only backward prediction (1 vector/macroblock)! or!• Average of forward and backward prediction = interpolation (2 vectors/macroblock)! Half-pel accuracy of motion compensation, bilinear interpolation! Coding of prediction error with 8x8-DCT, uniform quantization, zig-zag-scan as in I-pictures!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 16!MPEG-2 vs. MPEG-1! Efficiently compress interlaced digital video at broadcast quality! Frame pictures or field pictures! Adaptive frame/field prediction! Adaptive frame/field DCT! Improved coding efficiency by different quantization, VLC tables, and additional coefficient scan patterns! Spatial, temporal and SNR scalability profiles (rarely used)!Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 17!• Field 1Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 18!• Field 2Bernd Girod: EE398A Image and Video Compression! Video Coding Standards no. 19!Frame = Both Fields