3. H.261 Video Codec for A/V Services at px64 kbits

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1 3. H.261 Video Codec for A/V Services at px64 kbits /ß ÃOÔ³tŸ» MEDAL Multimedia Engineering & Design ASIC Lab. 3 Ô Ã khrhee@vlsi.chosun.ac.kr Chosun Univ. Multimedia ASIC Lab. 1 Outline H.261 Video Coding Basic H.261 Video Coding Algorithm H.261 Video Multipex Coder H.261 Transmission Coder Reference Chosun Univ. Multimedia ASIC Lab. 2

2 H.261 Video Coding Basic H.261 System Block Diagram H.261 System Feature H.261 Encoder/Decoder H.261 Data Structure Video Signal Format Samples of Luma & Chroma Chosun Univ. Multimedia ASIC Lab. 3 H.261 System Block Diagram Chosun Univ. Multimedia ASIC Lab. 4

3 H.261 System Feature Audiovisual ÀèH: eù9$üø EÌ: px64kbps, p=1,2,...,30 8 e: Y œ X e Ü: NTSC(525 lines;480), PAL (625 lines;576) e d ù9 INTER L : ME& MC INTRA L : DCT Yh L : VLC d : 4 hù ˆµø t ÀX: BCH(511,493) Chosun Univ. Multimedia ASIC Lab. 5 H.261 Encoder Chosun Univ. Multimedia ASIC Lab. 6

4 H.261 Decoder Chosun Univ. Multimedia ASIC Lab. 7 H.261 Data Structure Chosun Univ. Multimedia ASIC Lab. 8

5 Video Signal Format Chosun Univ. Multimedia ASIC Lab. 9 H.261 Video Multiplex Coder H.261 Stream 4 hù Picture Layer GOB layer Macroblock Layer Block Layer Multipoint Functions Chosun Univ. Multimedia ASIC Lab. 10

6 H.261 Stream 4 ƒô +/ Picture GOB data Header... GOB data Picture Layer GOB MB data Header... MB data Group of Block Layer MB Header block data... block data MacroBlock Layer TCOEF... TCOEF EOB Block Layer Chosun Univ. Multimedia ASIC Lab. 11 Picture Layer PSC (20) TR (5) PTYPE (6) PEI (1) PSPARE (0/8/16...) PEI (1) GOB data (...) PSC(Picture Start Code) : 20 bits; TR(Temporal Reference) : 5 bits PTYPE( Type Information) : 6 bits bit 1 : Split screen indicator; off(0)/on(1) bit 2 : Document camera indocator; off(0)/on(1) bit 3 : Freeze picture release; off(0)/on(1) bit 4 : Source format; QCIF(0)/ CIF(1) bit 5 : Optional still image mode HI_RES; on(0)/off(1) bit 6 : Spare PEI(Extra Insertion Information for picture) : 1 bit; 0 setting PSPARE(Spare Information for picture) : 0/8/16... bits PEI= 1 ðp P; ITU-T future backward compatible addition Chosun Univ. Multimedia ASIC Lab. 12

7 GOB Layer GBSC (16) GN (4) GQUANT (5) GEI (1) GSPARE (0/8/16...) GEI (1) MB data (...) GOBt MB jxh GOBˆø8 á<ü GOBÀÀ: CIF(352x288) QCIF(176x144) A GOB of Y 88 pels/line A GOB of C B, C R 176 pels/line 24 lines/ GOB 48 lines/ GOB Chosun Univ. Multimedia ASIC Lab. 13 GOB Layer GOBXü MB,Ü(1 GOB = 33 MBs) MB,Ü EÀÀ( lines/ MB 16 pels/line MB of Y 8 8 MB of C B, C R GBSC(GOB Start Code) : 16 bits; GN(Group Number) : 4 bits GN=0: PSC; GN=13,14,15: reserved GQUANT(Quantization Info for GOB) : 5 bits; [1, 31] overridden by any subsequent MQUANT GEI(Extra Insertion Info for GOB) : 1 bit; 0 setting GSPARE(Spare Info for GOB) : 0/8/16... bits GEI= 1 ðp P; ITU-T future backword compatible addition Chosun Univ. Multimedia ASIC Lab. 14

8 Macroblock Layer MVD MBA MTYPE MQUANT (5) MBA stuffing MVD CBP Block data CBP MBA(Macroblock address) GOBXü MB üt VLC(Table 1 Ü) O,œ E¼8 MBA8 MBü 0; ˆð$Ô8 E MB,Üä $ è E MTYPE(Type Info fro MB) MBt ¹ ä Pü8 d80 <dh(table 2 Ü) MQUANT(Quantizer) : 5 bits; [1, 31] MTYPEà MQUANTP <dh ˆð MQUANT Ðððd P GOBtÀ PM Chosun Univ. Multimedia ASIC Lab. 15 Block Layer TCOEFF EOB MBXü,Ü; E ÀÀ Y(16x16) C B (8x8) C R (8x8) Chosun Univ. Multimedia ASIC Lab. 16

9 Block Layer TCOEFF(Transform Coefficients) INTRA ð L t P; œ8 MTYPE, CBPt Ô P Zig-zag scanning INTRA-coded DC: FLC(8 bits) INTRA-coded & INTER-coded AC: (Table 5Ü) 2-D Huffman Coding: [zero run, QC(i,j)]; sign bit: s ; positive(0)/negative(1) Remaining combination of [zero run, QC(i,j)] : 20 bits Escape(6) + Run(6) + Level(8): (Table 6,7 Ü) black: /white: not used level: , (REC Level 1024 coded ) Reconstruction level(rec): [-2048, 2047] : (Table 8 Ü) REC of INTRA DC: (Table 9 Ü) EOB(End of Block) ü ldm ø : 10 Chosun Univ. Multimedia ASIC Lab. 17 H.261 Transmission Coder Video Data Buffering Video Coding Delay Forward Error Correction Still Image Transmission Chosun Univ. Multimedia ASIC Lab. 18

10 Video Data Buffering H\`: HRDü 8Pt 0 ÀX $Üø¼8 átü è\h\`: 256kbits(CIF), 64 kbits(qcif) PSC and all other data,pspare,gspare,mba stuffing ; error corection framming bits, fill indicator(fi), fill bits/error correction parity infoà Hypothetical Reference Decoder(HRD) HRD ¼ ( : (B+256 kbits) Á HRD buffer occupancy (bit) B Ñ = ³ ± ìà tn +1 R (t)dt tn b n t n t n+1 d n+1 b n+1 óí + í+ + í óí ã á Ñ ó ãó Á Time (CIF interval) NOTE Time (t n +1 t n ) is an integer number of CIF p icture p eriods (1/29.97, 2/29.97, 3/29.97,...). Chosun Univ. Multimedia ASIC Lab. 19 Video Coding Delay è È $ÜÔä ÜÔü d : È È d e lip synchronization Codec delay measurement method: depend on implementation, picture format(cif/qcif) and data rate measuring points: B A video coder video decoder C input video sequence: more than 100 sec. typical moving scene consistent min coded picture rate: 7.5 Hz visible ID mark a): átü O t 97 ( Ô õ/õè dø X less than 10% stuffing encoder delay: A ü vidible ID dø B tà $@Äððd decoder delay: B ü vidible ID dø C tà $@Äððd Chosun Univ. Multimedia ASIC Lab. 20

11 Forward Error Correction BCH(511,493) forward error correction code General polynomial: g(x)=(x 9 +x 4 +1)(x 9 +x 6 +x 4 +x 3 +1) Error Correction Framing(ECF): Relock Time of ECF 3 ECF(24 bits) frame lock t ¼ ¼X ÜÔ8 ECF dø 34kbitsXt frame lockè Pȹüh Èh Chosun Univ. Multimedia ASIC Lab. 21 Still Image Transmission High quality image E:normal video resolutionü 4Ô progressive, hierarchical E ÈP: H.261ü 0dø, hí ua,øl E1hü Ä Õ QCIF--->CIF, CIF(352x288)--->4CIF(704x576) still image ¼m/¼eà 2:1 sub-samplingü è È E sub-sampling pattern: PTYPEü HI_RES= 0, TR= 000xx, xx= sub-images 0,1,2,3 Multipoint ÈP broadcasting of still image for this capability H.230 define MCV/Cancel-MCV TerminaltÀ MCUt MCV X è È broadcast¼h ü, Cancel-MCV X L d X *MCV: Multipoint Command Visualization-forcing MCU: Multipoint Control Unit Chosun Univ. Multimedia ASIC Lab. 22

12 Reference ITU-T Recommendation H.261, Video Codec for Audiovisual Services at px64 kbits, Mar, 1993 (KT), H.261}øe$Üø ÔÄ,À\ ýô ¼hX } 0 üh¹0, 1996 J.J.Hwang and B.R.Lee, Chapter 10. ITU-T Recomm. H261 Coder- Decoder of Digital Consumer Electronis Handbook, 1997 Andy C. Hung, PVRG-P64 CODEC 1.1, Nov. 17, 1993 Chosun Univ. Multimedia ASIC Lab H.263 Video Codec for Low Bitrate Communcations Chosun Univ. Multimedia ASIC Lab. 24