ICIP 2006, Atlanta, GA
 

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Paper Detail

Paper:MP-P3.2
Session:Transcoding
Time:Monday, October 9, 14:20 - 17:00
Presentation: Poster
Topic: Image & Video Coding: Transcoding
Title: LOW-COMPLEXITY TRANSCODING OF INTER CODED VIDEO FRAMES FROM H.264 TO H.263
Authors: Jens Bialkowski; University of Erlangen-Nuremberg 
 Marcus Barkowsky; University of Erlangen-Nuremberg 
 Florian Leschka; University of Erlangen-Nuremberg 
 AndrĂ© Kaup; University of Erlangen-Nuremberg 
Abstract: The presented work addresses the reduction of computational complexity for transcoding of interframes from H.264 to H.263 baseline profiles maintaining the quality of a full search approach. This scenario aims to achieve fast backward compatibility for interoperability inbetween new and existing video coding platforms, e.g. between DVB-H and UMTS. By exploiting side information of the H.264 input bitstream the encoding complexity of the motion estimation is strongly reduced. Due to the possibilty to divide a macroblock (MB) into partitions with different motion vectors (MV), one single MV has to be selected for H.263. It will be shown, that this vector is suboptimal for all sequences, even if all existing MVs of a MB of H.264 are compared as candidate. Also motion vector refinment with a fixed 1/2-pel refinement window as used by transcoders throughout the literature is not sufficient for scenes with fast movement. We propose an algorithm for selecting a suitable vector candidate from the input bitstream and this MV is then refined using an adaptive window. Using this technique, the complexity is still low at nearly optimum rate-distortion results compared to an exhaustive full-search approach.