1. FHTW
Wavelet Based Video Compression Using Long Term Memory Motion-Compensated Prediction and Context-based Adaptive Arithmetic Coding
D.Marpe, H.L.Cycon, Th.Wiegand
FHTW Berlin
(University of Applied Sciences)
Heinrich Hertz Institut Berlin
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

2. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Outline
Introduction
Wavelet-Based Transform Coding
Video Coding
Experimental Results
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

3. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Introduction
Very Low Bit Video Codecs (< 64 kbit/s):
MPEG-4 (ISO standard)
H261/H263 (++) (ITU-T standard)
H26L: about to be defined, (TML8/9 exists)
DVC wavelet based codec proposed for new MPEG-4
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

4. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
DVC Codec
DVC is a new very low bit rate hybrid video coding scheme based on
wavelet coding (DWT)
effective entropy coding (PACC+AAC)
Overlapped Block Motion Compensation (OBMC)
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

5. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Transform Coding
Image
Rec.Image
compressed
bit stream
lossless
decorelation
lossy quantizer
lossless entropy
coder
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

6. Discrete Wavelet Transform
For DWT we use a new one-parametric family of biorthogonal filters defined by Petukhov, with:
More degrees of freedom in the design than for commonly used biorthogonal FIR-filters
Better performance than most frequently used biorthogonal 9/7-(FBI)-filter
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

7. Biorthogonal Wavelet-Filters
Optimal choice of parameters
(obtained by numerical simulations):
Analysis
Filter
Synthesis
filter
I-Frame a = 8
P-Frame a = 25
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

8. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Quantizer
scalar quantizer (replaces the continuous gray value function by step functions)
uniform (equal bin sizes) with extended dead zone
controls compression ratio
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

9. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Entropy Coder
Precoder (PACC)
binary adaptive arithmetic coding
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

10. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Precoding (PACC)
Partitioning of quantized coefficients into 3 subsources: significance map, magnitude map and sign map
Aggregation of zero quantized coefficients into „zerotrees“ or run length coding
Conditional Coding of elements of each subsource using appropriately designed models
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

11. Precoder encoding quantized data
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

12. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Conditional Coding
significance maps use templates depending on scale and orientation of a band
magnitude maps use estimations of the significance or their 8-neighborhood
sign maps use contexts build of 2 preceding signs with respect to the orientation of a given band
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

13. Context Templates for CC
Significance CC
using orientation & scale
Magnitude CC
using 8-Ngbhd
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

14. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Transform Coder
DWT Q
Arithmetic
Coder
Pre
Bit
Stream
Video
Input
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

15. Video MC Prediction Coding
DWT Q
Arithmetic
Coder
Pre
Bit
Stream
IDWT IQ +
Reference
Frame Buffer
OBMC
BME -
Video
Input
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

16. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
DVC Coding Scheme
DWT Q
Arithmetic
Coder
Pre
Bit
Stream
IDWT IQ +
Reference
Frame Buffer
OBMC
BME -
Video
Input
Inter/intra
frame
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

17. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Motion Model
Block Motion Estimation with different block sizes and macro block modes
motion search by 1/4 pel accuracy
OBMC using cosine shaped weight functions w = w1w2
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

18. Macro block partition modes
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

19. Overlapped Block Matchingw1 w2
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

20. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Summary of Methods
3-level dyadic decomposition DWT
(biorthogonal filter pairs)
uniform quantization with central widened deadzone
sophisticated entropy coder (PACC + binary adaptive arithmetic coder)
sophisticated motion model (H26L)
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

21. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Experimental Results
DVC codec outperforms optimized MPEG-4 codec by PSNR gains between 1 and 3 dB
DVC shows comparable results to H26L TML8 (tops H26L in some cases by 0.5 dB)
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

22. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Test Conditions
MPEG-4 coder:
1/4-pel motion vector accuracy
search range 32 pels
2 B frames (IBBPBBP...)
global MC
DVC coder
1/4-pel motion vector accuracy
search range 32 pels
No B frames!
5 reference pictures
arithmetic coding
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

23. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
DVC vs MPEG4 Fm Frame 22
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

24. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

25. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

26. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Conclusions
Wavelet video codecs are still in business!
(for still images: JPEG 2000)
DVC very low bit coder outperforms MPEG-4 (ASP)
DVC has comparable results to H26L (TML8)
presented as proposal for new MPEG4, Sidney 2001 (ranks 3rd after H26L w/o B frames)
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

27. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Future Work
implementing B-frames
real-time version of a very low bit rate codec DVC
optimizing motion estimation process w.r.t. (OBMC)
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand

28. Waveletprojekt /HHI ,Cycon/Marpe/Wiegand
Visual Demo ?
Waveletprojekt /HHI ,Cycon/Marpe/Wiegand