Direct Access Video Streaming Scheme Supporting Effective Error Concealment Chun-Ming Huang, Kai-Chao Yang and Jia-Shung Wang

Outline Introduction Hierarchical Coding Scheme Center-weighted Hierarchical Coding Scheme Proximity Approximation Questions in the Hierarchical Structure Modified Sequential Coding Scheme Decoder Error Concealment Error Concealment in Hierarchical Coding Structure Error Concealment in Modified Sequential Coding Structure Conclusion and Future Work

Introduction VCR Operation  Stop-Resume, Pause-Resume, Slow motion, Jump, Fast Forward Scan, Back Forward Scan Group of Pictures (GOPs) IBBPBBPBBP I PPP GOP

Introduction General sequential video coding system the average number of frames to be transmitted for randomly accessing an arbitrary frame time … I P P P P

Hierarchical Coding Scheme I PPPPPP GOP time Improve the efficiency of random access operation. (n -> lg n)

Center-weighted Hierarchical Coding Scheme

Center-weighted Hierarchical Coding Scheme e.g x2 Cost : Cost : 10 Cost : 8 x

Proximity Approximation Human visual system is normally not very sensitive to minor change of scenes in the temporal domain. (e.g. 0, 3, 6 vs. 0, 4, 6) Cost : 6 x3

Questions in the Hierarchical Structure More overhead while sequential playing The necessity of backward playback? Fast forward speed x3, x5, x7, … are quite similar to x2, x4, x6, … time Initial delay & Large buffer

Modified Sequential Coding Scheme Add redundant links to sequential coding system x2x4 time

Decoder Error Concealment Recovery of Texture Information Syntax-Based Repair Recovery of Motion Vectors  Set to zero  Use the corresponding MVs in the previous frame  Use the average MVs from spatially adjacent MBs  Use the median MVs from spatially adjacent MBs  Re-estimate the MVs

Error Concealment in Hierarchical Coding Structure

Error Concealment in Hierarchical Coding Structure Add redundant links into the hierarchical tree Each damaged leaf node can be recovered via interpolation approach. Each damaged internal node can be reconstructed through its son or the redundant link. ※ Either the redundant link or original link must survive

Error Concealment in Modified Sequential Coding Structure XXXX

Conclusion and Future Work The proposed video streaming schemes support direct access and error concealment. Future Work  Reduce the buffer size.  Reduce the number of the redundant links.  Reduce the initial waiting time in the hierarchical coding structure.