1. Conference title 1 A WYNER-ZIV TO H.264 VIDEO TRANSCODER José Luis Martínez, Pedro Cuenca, Gerardo Fernández-Escribano, Francisco José Quiles and Hari Kalva February 27, 2009 Barcelona, Spain

2. RTCTCM 2009 2 OVERVIEW 1.Introduction/Motivation 2.H.264 and WZ Video Coding Paradigms 3.Proposed WZ/H.264 Video Transcoder 4.Results 5.Conclusion

3. RTCTCM 2009 3 OVERVIEW 1.Introduction/Motivation 2.H.264 and WZ Video Coding Paradigms 3.Proposed WZ/H.264 Video Transcoder 4.Results 5.Conclusion

4. RTCTCM 2009 4 Introduction/Motivation (I) TRANSCODER Requirements: Low complexity devices. Low complexity encoding / decoding algorithm Battery consumptions Low cost Solution adopted: Traditional video coding with low complexity tool Low complexity profiles (baseline, etc…) Rate-Distortion loss

5. RTCTCM 2009 5 Introduction/Motivation (II) What is video transcoding? The process of converting video encoded sequence from format A to format B. The conversion process can affect one or more of the coding parameters, such as frame rate, bitrate, resolution, quality, error resilience, etc. When is it necessary? Mismatch in video capabilities and resources at the sender and the receiver –Resource mismatch, e.g. sender has CIF and the receiver requires QCIF resolution), bandwidth, computing resources, battery life, etc. –Format mismatch, e.g. sender has MPEG-2 video and the receiver requires H.264 video Then we need transcoding How to transcode? –Decode video A and then encode to video B How to transcode efficiently? –Complexity reduction is the key problem –Manage quality vs. complexity tradeoffs Video Transcoder

6. RTCTCM 2009 6 OVERVIEW 1.Introduction/Motivation 2.H.264 and WZ Video Coding Paradigms 3.Proposed WZ/H.264 Video Transcoder 4.Results 5.Conclusion

7. RTCTCM 2009 7 H.264 Video Coding Paradigm H.264 is becoming popular, why? The H.264/AVC standard achieves much higher coding efficiency than the H.263, MPEG-2, and MPEG-4 standards, due to its improved inter and intra prediction modes at the expense of higher computation complexity. Therefore, H.264/AVC is a strong candidate for a wide range of applications in the near future. The complexity reduction techniques for the ME and MC for transcoders based on H.264 is the key for developing fast real-time systems. Number of Profiles: - Baseline, Main, Extended, and FRExt. Motion compensation minimum block size: - From 16x16 to 4x4 (frame/field) Motion vector accuracy: - Quarter-pixel Transform: - 4x4 DCT integer approximation Reference frames: - Up to 16 reference frames Built-in deblocking filter: - Yes Intra prediction: - Yes H.264

8. RTCTCM 2009 8 WZ Video Coding Paradigm Low-complexity encoding makes possible more complex decoding Side Information: Estimation of X´ i available at the decoder. What we use to correct errors / mistakes in communications? –ERROR CORRECTIONS CODES –Coset codes, Turbo codes, LDPC, … –Turbo Trellis Codes Modulation (TTCM)

9. RTCTCM 2009 9 Emerging Challenges Applications (from down-link to up-link) Wireless digital video cameras Multimedia mobile phones and PDAs Low-power video sensors and surveillance cameras Wireless video teleconferencing systems Requirements Light and flexible distribution codec complexity Robustness to packet/frame losses High compression efficiency Low latency Target Inter coding efficiency Intra coding complexity (encoder) Intra coding robustness

10. RTCTCM 2009 10 OVERVIEW 1.Introduction/Motivation 2.H.264 and WZ Video Coding Paradigms 3.Proposed WZ/H.264 Video Transcoder 4.Results 5.Conclusion

11. RTCTCM 2009 11 Proposed WZ/H.264 Transcoder TRANSCODER

12. RTCTCM 2009 12 1st Step: Reducing the Motion Estimation

13. RTCTCM 2009 13 2nd Step: Reducing the Inter Prediction Inter frame coding of H.264, seven different block division modes (16x16, 16x8, 8x16, 8x8, 8x4, 4x8 and 4x4) H.264 adopts the spatial domain intra prediction in the block sizes 16x16 and 4x4, which include four and nine directional predictions. For each of these partions, the motion estimation is carried out

14. RTCTCM 2009 14 Background What is data mining? Algorithms and techniques that allow computers to learn A decision tree is made by mapping the observations about a set of data in a tree made of arcs and nodes The goal is to reduce macroblock mode search in H.264 to a classification problem The decision trees use the information from the incoming WZ video Sum of Absolute Differences values (SAD), Motion Vectors (MVs) length and the amount of pixels that have to be reconstructed The coding mode of the corresponding MBs in H.264 is also saved for training purposes Decision Trees Data Mining Tools WZ Decoder H.264 Encoder Video Sequence SAD, MVs length and the amount of pixels H.264 MB Coding Modes Pixel data

15. RTCTCM 2009 15 Background The decision tree for MB mode classification was made using the WEKA WEKA is a collection of machine learning algorithms for data mining tasks. The algorithms can be applied directly to a dataset It is open source software ARFF files are used to prepare the data sets for training

16. RTCTCM 2009 16 Background

17. RTCTCM 2009 17 OVERVIEW 1.Introduction/Motivation 2.H.264 and WZ Video Coding Paradigms 3.Proposed WZ/H.264 Video Transcoder 4.Results 5.Conclusion

18. RTCTCM 2009 18 Proposed Transcoder 1.Reduced Motion Estimation based on the Dynamic Search Windows 2.Reduced the Inter Prediction based on the decision trees algorithm

19. RTCTCM 2009 19 RESULTS Training Sequence: 10 QCIF frames flower garden Tested Sequences: Akiyo, Coastguard, Container, Hall Monitor and Mother Simulation conditions  The transcoder was implemented using the H.264/AVC reference software (JM13.2)  QP values 28, 32, 36 and 40 were use for testing. IWZ GOP format was transcoded as IP  The approach is compared with a cascade WZ to H.264 transcoder

20. RTCTCM 2009 20 RESULTS SequenceFormat∆PSNR (dB)∆Bitrate (%)∆Time (%) AkiyoQCIF-0,0040,1095,23 CoastguardQCIF-0,0360,9594,99 ContainerQCIF-0,0010,0396,00 Hall MonitorQCIF-0,0060,1495,43 MotherQCIF-0,0050,1495,32 MeanQCIF-0.0110.2795.39 G. Bjontegaard, Calculation of average PSNR differences between RD-Curves. Presented at the 13th VCEG-M33 Meeting, Austin, TX, April 2001 RD differences

21. RTCTCM 2009 21 OVERVIEW 1.Introduction/Motivation 2.H.264 and Video Coding Paradigms 3.Proposed WZ/H.264 Video Transcoder 4.Results 5.Conclusion

22. RTCTCM 2009 22 Conclusions We propose a WZ to H.264 video transcoder as a solution for mobile-to- mobile video communications. Transcoders based on data mining techniques for exploiting the WZ encoding correlation. The H.264 Motion Estimation done in H.264 can be reduced by using the incoming side information motion vectors The proposed solution eliminates the requirements of complex WZ decoders and H.264 encoders in the end-user devices. These first approach results show an extremely close RD performance with an 95% of complexity reduction.

23. RTCTCM 2009 23 Collaborations Internationals Florida Atlantic University. Florida, USA Dr Hari Kalva University of Surrey. Centre for Communication System Research (CCSR). United Kingdom Dr. W.A.C. Fernando Nationals Universidad Miguel Hernandez. Elche Dr. Manuel Perez Malumbres

24. Conference title 24 Gracias!!!

25. RTCTCM 2009 25 RESULTS WZ encoding time