Coding of Videophone Sequences using an Anatomical Model of a Human Person

1. Coding of Videophone Sequences using an Anatomical Model of a Human Person Markus Kampmann

2. Overview • Introduction • Adaptation of a 3D face model • Generation of a 3D wireframe of head and shoulders • Estimation of 3D motion of head and shoulders • Analysis and synthesis of facial expressions • Parameter coding • Experimental results • Summary

3. Introduction • Videophone sequence: 12 Mbit/s (CIF, 10 Hz frame rate, PCM) • Transmission channel: 8 - 128 kbit/s (ISDN,mobile) => Video coding necessary

4. Introduction: Model-based coding

5. Introduction Problems: • Adaptation of a 3D face model • Generation of a 3D wireframe of head and shoulders • Estimation of 3D motion of head and shoulders • Analysis and synthesis of facial expressions • Parameter coding

6. Introduction Problems: • Adaptation of a 3D face model • Generation of a 3D wireframe of head and shoulders • Estimation of 3D motion of head and shoulders • Analysis and synthesis of facial expressions • Parameter coding

7. Adaptation of a 3D face model Two steps: 1. Estimation of 2D facial features in the image plane 2. Adaptation of the 3D face model using the estimated facial features

8. Adaptation of a 3D face model

9. Chin/cheek contour Parametric model of contours 8 unknown parameters MAP estimator probability of the occurrence of contours at a certain position conditional probability between contour position and image gradient Adaptation of a 3D facemodel

10. Eyebrows Original image Segmentation eyebrows darker than surrounding skin Seperation between hair and eyebrows Adaptation of a 3D facemodel

11. Nose features Nostrils darker than surrounding skin typical shape Sides of the nose typical shape image gradient Adaptation of a 3D facemodel

12. Adaptation of a 3D face model • Adaptation of size, position, shape and initial mimic

13. Introduction Problems: • Adaptation of a 3D face model • Generation of a 3D wireframe of head and shoulders • Estimation of 3D motion of head and shoulders • Analysis and synthesis of facial expressions • Parameter coding

14. Generation of a 3D wireframe of head/shoulders

15. Generation of a 3D wireframe of head/shoulders

16. Introduction Problems: • Adaptation of a 3D face model • Generation of a 3D wireframe of head and shoulders • Estimation of 3D motion of head and shoulders • Analysis and synthesis of facial expressions • Parameter coding

17. Estimation of 3D motion of head/shoulders

18. Estimation of 3D motion of head/shoulders Three steps: 1. Estimation of rotation and translation parameters of the shoulders (6 parameters) 2. Compensation of shoulders and head motion using the estimated motion parameters of the shoulders 3. Estimation of head rotation around the neck joint (3 parameters)

19. Introduction Problems: • Adaptation of a 3D face model • Generation of a 3D wireframe of head and shoulders • Estimation of 3D motion of head and shoulders • Analysis and synthesis of facial expressions • Parameter coding

20. Synthesis of facial expressions • Each muscle: 1 parameter describing contraction

21. Synthesis of facial expressions • Additional mimic parameters: • jaw rotation • rotation of eyelids • translation of iris

22. Analysis of facial expressions • 27 mimic parameter • Maximum likelihood estimator • measured value: temporal luminance difference at observation points • conditional probability between measured value and the mimic parameters (motion parameters) • Multistage estimation

23. Introduction Problems: • Adaptation of a 3D face model • Generation of a 3D wireframe of head and shoulders • Estimation of 3D motion of head and shoulders • Analysis and synthesis of facial expressions • Parameter coding

24. Parameter coding => 10 Hz frame frate: 6 kbit/s Motion, mimic PCM 200 bit/frame Polygon/spline approximation 200 bit/frame 2D person silhouette Uncovered background DCT 200 bit/frame

25. Experimental results

26. Experimental results

27. Experimental results 3D wireframe over original sequence

28. Experimental results 3D face model over original sequence

29. Experimental results 3D wireframe in side-view

30. Experimental results 3D wireframe over 3D face model over original sequence original sequence

31. Experimental results block-based, 22 kbit/s model-based, 6 kbit/s

32. Experimental results original, 12 Mbit/s model-based, 6 kbit/s Compression ratio: 2000 : 1

33. Summary • Video coder based on an anatomical model of a human person • Coding of videophone sequences (CIF, 10 Hz) at 6 kbit/s • Algorithms not restricted to video coding