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Introduction to

Introduction to. Shape Coding. Outline. Introduction Shape Coding Approaches Block-based methods CAE, Modified MMR, … .. Contour-based methods Chain code, BBSC (baseline-based) , … .. Vertex-based binary shape coding Conclusions. Introduction. Why shape coding? Binary Alpha Plane

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Introduction to

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  1. Introduction to Shape Coding

  2. Outline • Introduction • Shape Coding Approaches • Block-based methods • CAE, Modified MMR, ….. • Contour-based methods • Chain code, BBSC (baseline-based) , ….. • Vertex-based binary shape coding • Conclusions

  3. Introduction • Why shape coding? • Binary Alpha Plane • describes the shape of one VOP Akiyo QCIF format (176 x 144)

  4. Introduction • Shape coding modes • Intra mode ( I VOPs) • Inter mode ( P, B VOPs) • Lossy coding • Progressive (scalable encode)

  5. CAE method (1) • Context-based Arithmetic Encoding • Intra mode BAB : Binary Alpha Block Size : 16 x 16 pixels

  6. CAE method (2) • Binary arithmetic encoding using the context of the neighboring pixels • A template of ten pixels is used to predict the current pixel

  7. CAE method (3) • Inter mode

  8. CAE method (4) • InterCAE

  9. CAE method (5) • Lossy coding Conversion Ratio (CR) : ¼, ½ or 1

  10. CAE method (6)

  11. Contour_based method (1) • Chain code

  12. Contour_based method (2) • DCC (differential chain code) • encode the differential between two consecutive directional links • DCC with Huffman Coding • Characteristics of one contour

  13. Contour_based method (3) • EBDCC

  14. Contour_based method (4) Starting point Turning points

  15. Contour_based method (5) • The decoder should know • The starting point of tracing • Locations of turning points • Sequences (one bit per step)

  16. Contour_based method (6) • Compression results for intra coding

  17. Contour_based method (7) • Lossy coding • Reduce the number of TPs ! • The slope between two neighboring TPs is compared with • Hori_TH : viewed as a horizontal line • Vert_TH : viewed as a vertical line

  18. Contour_based method (8) 563 bits / per VOP 497 bits / per VOP

  19. TPs Seq. (1/2) Contour_based method (9) • Scalable shape representation • TPs are important information! Seq. (additional) Local TPs & seq.

  20. Contour_based method (10) H : 9 V : 7 H’ : 5 V’ : 4 

  21. Conclusions • Block-based method • High coding efficiency • Suitable for hardware implementation • Irregular boundary effect & blocking effect • Contour-based method • Smaller blocking effect on the reconstructed shape • Suitable for specific application where semantic shape features are utilized • Hardware optimization

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