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MPEG-4 Video

Explore the advanced technology behind MPEG-4 video coding standards. Learn about motion and texture coding, scalable and sprite coding, error resilience, applications like digital terrestrial TV, interactive video games, and more. Discover existing coding standards like MPEG-1, MPEG-2, H.261, H.263, JPEG, and JBIG, as well as functionalities such as content-based manipulation, object-based coding, and flexible access editing. Benefit from low-complexity, robust error resilience, and object-based hyperlink manipulation. Dive into video object definitions, coding structures, decoding, texture tools, and motion compensation techniques.

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MPEG-4 Video

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  1. MPEG-4 Video Xuemin Chen and Bob Eifrig Advanced Technology Department Instructor: L. J. Wang, Dept. of Information Technology, National Pingtung Institue of Commerce X. Chen, B. Eifrig

  2. Outline • Introduction to MPEG-4 video • Basic definition and concepts • Motion and texture coding for video • Scalable coding • Shape coding • Sprite coding • Still texture coding • Error-resilience X. Chen, B. Eifrig

  3. Video Applications • MPEG-2 • BSS(broadcast satellite service) • CATV(cable TV) • DTTB(digital terrestrial TV b’cast) • EC(Electronic Cinema) • HTT(Home TV Thratre) • IPC(video phone...) • MMM(multimedia mailing) • NDB(network database svc, e.g. VOD) • RVS(remote video surveillance) • SSM(serial storage media e.g. digital VTR) • MPEG-4 • IMM(internet multimedia) • IVG(interactive video game • IPC(video phone...) • ISM • MMM • NDB • RVS • WMM(wireless multimedia X. Chen, B. Eifrig

  4. MPEG-4 video applications X. Chen, B. Eifrig

  5. Requirements on Functionalities • Content-based manipulation and bitstream eidting • Object-based coding (e.g. Chroma-keying) • View of contents of video in different resolutions, refresh rates, and quality. • Transmission of video over error-prone environments (e.g. wireless communication networks) • Coding “Sprite” for game applications, and more ... X. Chen, B. Eifrig

  6. Existing Coding Standards • MPEG-1 (Progressive, frame-based,bit rate ~1.5 mbps...) • MPEG-2 (MPEG-1 + frame-based Interlaced coding, frame-based scalabilities, error resilience, fixed frame rate, ITU-R 601 resolution, bit rate ~ 4 mbps ...) • H.261 (CIF and QIF resolution, frame-based, No B-frame, No quant matrix, bit rate ~ px64 kbps...) • H.263 (H.261+ PB-frame, OBMC, bit rate > 10kbps ...) X. Chen, B. Eifrig

  7. Existing Coding Standards • JPEG (frame-based, limited scalabilities,...) • JBIG (frame-based, still binary image only...) MPEG-4 Functionalities • Syntax and techniques to support content-based manipulation and bitstream editing without the need of transcoding . X. Chen, B. Eifrig

  8. MPEG-4 Functionalities • Flexible in the level of access, editing and manipulation are performed in arbitrary-shape video object with fine granularity in contents, spatial resolution, temporal resolution, quality and complexity. • Video object-based scalability. • More powerful error-resilience tools • Scalable still texture coding tools X. Chen, B. Eifrig

  9. Benefits • Low-complexity, reduced memory and bandwidth requirement, low-delay and no quality loss; • Object-baed hyper-link, manipulation and editing • Address video game applications • More robust in error-prone environments X. Chen, B. Eifrig

  10. Definitions • Video Object Definition and Format VO3 VOP VO2 ...... ... VOP VO1 • Video Object(VO) and • Video Object Plane(VOP) 3 2 ...... 1 (1) YUV 4:2:0 (8-bit). (2) Segmentation Masks. (3) Alpha Plane X. Chen, B. Eifrig

  11. Example X. Chen, B. Eifrig

  12. Video Coding Structure • Video Syntax Hierarchy • Visual Object Sequence(VOS) • Video Object(VO) • Video Object Layer (VOL) or Texture Object Layer (TOL) • Group of Video Object Plane (GOV) • Video Object Plane (VOP) • Special Case--Single Rectangular VO Case • VOS “=“ VO <==> Video Sequence • VOL or TOL <==> Sequence Scalable Extension • GOV <==> GOP • VOP <==> Frame X. Chen, B. Eifrig

  13. Video Syntax Hierarchy X. Chen, B. Eifrig

  14. Basic Visual Decoding + Scaleable coding Sprite coding Error resilience coding X. Chen, B. Eifrig

  15. Video Decoding X. Chen, B. Eifrig

  16. Texture Coding Tools • Hybrid DCT coding tools similarities to MPEG-2 • 4:2:0 chroma format (4:2:2 & 4:4:4 are not part of MPEG-4) • I, P & B pictures (VOPs) • DCT • Quantization • 16x16 prediction • field prediction & frame/field DCT interlace • MPEG-4 visual texture coding is about 10-20% more efficientthan MPEG-2 • Comparing bits at 4 Mbps for 601-size interlaced videoat constant quantizer; frame structure; N=15, M=3 X. Chen, B. Eifrig

  17. New Hybrid DCT Texture Coding Tools • Unrestricted Motion Compensation • Overlapped block motion compensation • Median based motion vector predictors in P-VOPs • Intra MBs • AC/DC prediction • non-linear DC quantization • multiple scan paths • MPEG-2 or H.263 quantization • 8x8 mode in P-VOPs • Direct mode in B-VOPs • 3D (run, level, last) VLC • MV round toward half-pel • Variable picture rate • Limited quantizer change X. Chen, B. Eifrig

  18. Unrestricted Motion Compensation • Reference block can be partially outside the picture(more generally partially outside object) • Convex image is constant extended • 2 or 4 point average defines pixel for non-convex case X. Chen, B. Eifrig

  19. Overlapped Block Motion Compensation • Applied on 8x8 block basis • Weighted average of 5 predictionblocks formed by MVs from • Current block • left, right, top neighbor blocks • Current is used for bottom neighbor • MV=0 if neighbor is intra Top weigh Bottom weight Current block Left Right X. Chen, B. Eifrig

  20. MV Predictors for P-VOPs PMV[MV] = median(MV1, MV2, MV3) X. Chen, B. Eifrig

  21. Intra DC prediction (Graham’s Rule) X. Chen, B. Eifrig

  22. Intra AC Prediction Controlled by a flag at macroblock layer Use Graham’s Rule to determine the pre- diction direction: (horizonal vs. vertical) X. Chen, B. Eifrig

  23. H.263 (~ MPEG-1) Quantization X. Chen, B. Eifrig

  24. Multiple Scanning Paths Alternate horizontal Alternate vertical Zigzag X. Chen, B. Eifrig

  25. Direct Mode in B-VOPs (No intra-MB in B-VOPs !) • only mode that allows 8x8 in B-VOPs • Progressive X. Chen, B. Eifrig

  26. Interlaced Direct Mode X. Chen, B. Eifrig

  27. 3D Variable Length Coding X. Chen, B. Eifrig

  28. Dquant VLCs & MV division • Dquant VLCs P-VOPs B-VOPs • MV division tables (from chroma & fld->frm prediction) X. Chen, B. Eifrig

  29. Generalized Scalability • Block diagram • Spatial scalability X. Chen, B. Eifrig

  30. Temporal Scalability Type 1 with I & P-VOPs Type 1 with B-VOPs X. Chen, B. Eifrig

  31. Enhancement Types X. Chen, B. Eifrig

  32. Shape Coding • Binary alpha shape • Gray-level alpha shape • Temporal Scalability + Shape coding • Interlaced tools + shape coding • Sprite + shape coding • Spatial scalability + shape coding X. Chen, B. Eifrig

  33. Binary Shape Sequences • Binary alpha block(bab) • 7 types of BABs I-VOP P-,B-VOP time X. Chen, B. Eifrig

  34. Binary Shape Decoding X. Chen, B. Eifrig

  35. Context-based Arithmetic Coding • Arithmetic coding bypasses the idea of replacing an input symbol with a specific code. It replaces a stream of input symbols with a single floating-point output number. • A context number is computed based on a template. • The context number is used to access the probability table • Using the accessed probability value, the next bits of binary_aruthmetic_code are decoded to give the pixel value. ? ? X. Chen, B. Eifrig

  36. Some details on arithmetic coding LPS,MPS (Less Probable Symbol) Interval A Context Probability table (P(0)) A LPS Interval : A*PLSP arithmetic code(ac) MPS Interval : A*(1-PLSP) 0 X. Chen, B. Eifrig

  37. Sprite Coding • A sprite is an image composed of pixels belong to a video object that are visible throughout an entire video segment. • Basic sprite coding • low-latency sprite coding • scalable sprite coding X. Chen, B. Eifrig

  38. Example of Sprite Coding • Coding background of a video conference room (much large than a single frame of video • coded as the I-VOP • sprite pieces use INTRA quant • update pieces use INTER quant • shape information is sent in the VOL as part of I-VOP • Shape and texture coding • Warping X. Chen, B. Eifrig

  39. Sprite Decoding Process X. Chen, B. Eifrig

  40. Warping and Sample Reconstruction • Any pixel (i,j) inside the VOP “warping position” ( F(i,j), G(i,j)), (Fc(i,j),Gc(i,j)) are computed on a basis of no_of_sprite_warping_point. • Reconstructed sample values are computed from sample values at the location (F(i,j),G(i,j)), (Fc(i,j),Gc(i,j)). X. Chen, B. Eifrig

  41. Still Texture Coding • Applications • internet images • medical images • Requirements • Scaleable (e.g. 4kx4k------ 64x64) • Support lossless, almost lossless, and lossy • Support arbitrary shape • and more... X. Chen, B. Eifrig

  42. Still Texture Coding • Wavelet-based texture coding • DWT and subband decomposition • quantization of the wavelet coefficients • coding the LL band (PCM coding) • zero-tree scanning of higher order bands • entropy coding X. Chen, B. Eifrig

  43. Still Texture Coding X. Chen, B. Eifrig

  44. Error Resilience • Applications : Wireless communication networks, e.g. GSM and CDMA. • physical (layer) channel ------ logical channels, e.g. signaling channels, data channels, and speech channel, etc. Each logical channel often uses different error protection. Inside the speech channel, data are partioned into classes. Different class uses different protection. • video channel in the future. • Requirements • Resyn. • Data Partitioning • etc.. X. Chen, B. Eifrig

  45. Error Resilience Coding • Resynchronization • video packet approach (similar to GOB in H.263) : the length of the video packets are not based on the number of MBs, but the bits contained in the packet. • Data recovery • Reversible VLC • Error concealment • Data Partitioning X X motion marker Resync marker texture info. MVs ....... X. Chen, B. Eifrig

  46. THE END • It is only with understanding of our history, our neighbors, and our prospects for the future that we can alter and appreciate our own times and circumstances. X. Chen, B. Eifrig

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