1. Comparative study of Intra Frame Coding efficiency in HEVC and VP9
EE5359 Multimedia Processing Interim Report
Under the guidance of
Dr.K.R.Rao
University of Texas at Arlington
Dept. of Electrical Engineering :
By: Shwetha Chandrakant Kodpadi
Spring 2014

2. Contents Objective General Compression Dataflow HEVC Coding Standard
Google VP9
Intra Prediction Modes in HEVC and VP9
Performance Metrics
Test sequences and Implementation
Implementation Results
Conclusions
Acronyms and abbreviations
References

3. Objective
This project aims at studying and comparing intra frame coding efficiency between video coding technologies HEVC and VP9.
Overview of different coding tools in HEVC and VP9 such as Prediction, Transforms, Entropy Coding and Post-processing
Detailed analysis and implementation of HEVC and VP9 Intra Frame coding [1][3] and compare the performances by using various performance metrics.
PSNR, MSE, BD-PSNR and BD-BR [14] are used as comparison metrics.

4. General compression dataflow
Both HEVC and VP9 video compression standards are hybrid block-based codecs relying on spatial transformations [9]. General compression data flow of hybrid block-based encoders is illustrated in Figure 1.
Figure 1: Hybrid block-based codec dataflow [9]

5. General compression dataflow (Continued..)
The input video frame is initially partitioned into blocks of the same size called macroblocks
A macroblock is subpartitioned into smaller blocks to perform prediction (intra and inter predictions)
The aim of the prediction process is to reduce data redundancy and therefore, not store excessive information in coded bitstream
Intra-prediction works within a current video frame and is based upon the compressed and decoded data available for the block being predicted
Predicted frame is subtracted from the original data to get residuals which are subjected to transforms such as forward discrete Fourier transform and discrete cosine transform [22]
The transform coefficients are further quantized and subjected to Entropy Coding which makes it possible to get compressed bit-stream.

6. High Efficiency Video Coding
High Efficiency Video Coding (HEVC) is the latest Video Coding format [4].
It challenges the state-of-the-art H.264/AVC [21] Video Coding standard which is in current use in the industry by being able to reduce the bit rate by 50%, retaining the same video quality [4].
Also HEVC supports increased use of parallel processing architectures [1].

7. Figure 2: Encoder block diagram for HEVC [4]

8. Figure 3: Decoder block diagram for HEVC [17]

9. VP9
VP9 is an open and royalty free video compression standard being developed by Google [2][3].
One of the goals for VP9 is to reduce the bit rate by 50% compared to VP8 while having the same video quality [7]
VP9 expands techniques used in AVC and VP8 and is very likely to replace H.264/AVC at least in the YouTube video service [9].

10. Figure 4: Encoder block diagram for VP9 [19]

11. Figure 5: Decoder block diagram for VP9 [19]

12. HEVC and VP9 Coding Tools
Macroblock concept and Prediction block sizes
Prediction Modes (Intra and Inter)
Transform and Quantization
Entropy Coding
Post Processing

13. Intra Prediction modes in HEVC
HEVC has 35 luma intra prediction modes (Figure 6)
Intra prediction can be done at different block sizes, ranging from 4 X 4 to 64 X 64 (whatever size the PU has) (Figure 7)
HEVC also includes a planar and DC intra prediction modes
Figure 6: Modes and directional orientations
for intra picture prediction for HEVC [1]
Figure 7: Luma intra prediction modes for different PU sizes in HEVC [8]

14. VP9 techniques Recursive variable block size
support (64x64 to 4x4, square
and rectangular)
Finer motion vector precision
(16th-pel) and adaptive motion
filters (sharp, lowpass, regular) Figure 8: Example partitioning of a 64x64
Super-block
Multi-level past and future reference (alt-ref) frames
larger dct transforms (32x32,16x16, 8x8, 4x4) and adst transforms (16x16, 8x8, 4x4)

15. Intra Prediction modes in VP9
There are total of ten intra-prediction modes in VP9 [9]: DC, True Motion (TM), and eight angular modes (H, V, D207, D153, D135, D117, D63 and D45 on Figure 8)
Figure 9: VP9 angular intra-prediction modes [9]

16. Performance Metrics Criteria to evaluate the compression quality
Two types of quality measures
Objective quality measure- PSNR, MSE
Structural quality measure- SSIM [10]
MSE and PSNR for a NxM pixel image are defined as
where O is the original image and R is the reconstructed image. M and N are the width and height of an image and ‘L’ is the maximum pixel value in the NxM pixel image.

17. Performance Metrics(Continued..)
Bjøntegaard-Delta Bit-Rate and peak signal-to-noise ratio Measurements
The Bjøntegaard delta peak signal-to-noise ratio (dB) [14][20] and the
Bjøntegaard delta bit-rate (%) will be used compare performance of
HEVC and VP9 Codecs.
As rate-distortion (R-D) performance assessment [14], Bjøntegaard-Delta bit-rate measurement method is used for calculating average bit-rate differences between R-D curves for the same objective quality (e.g., for the same PSNR-YUV values), where negative BD-BR values Indicate actual bit-rate savings.
Encoding time is used to compare the implementation complexity

18. Implementation
For comparison purposes open-source implementations of the reviewed codecs will be used. HEVC compression efficiency will be measured with the HM Test Model [12].
Evaluation of VP9 compression performance will be carried out with the VPX encoder from The WebM Project [13].
Since HEVC has more Intra Prediction modes and few other features better than VP9, both the codecs are configured to establish a fair comparison.

19. Implementation(Continued..)
The test video sequence set that will be used for the comparison are; BlowingBubbles, BasketballDrill, FourPeople, Kimono1 [9].
Sequence
Resolution, Pixels
Frame-rate, Hz
Number of Frames
RaceHorses
416x240 30
500
BasketballDrill
832x480 50
Kimono1
1920x1080 24
240
PeopleOnStreet
2560x1600
150

20. Implementation(Continued..)
Figures 10, 11, 12 and 13 are frames of the test sequences RaceHorses, BasketballDrill, Kimono1 and PeopleOnStreet, respectively.
Figure 11: BasketballDrill (832x480)
Figure 10: RaceHorses (416x240)
Figure 12: Kimono (1920x1080)
Figure 13: PeopleOnStreet (2560x1600)

21. Implementation results
RaceHorses_416x240_30.yuv (AI mode)
HEVC
VP9 QP
PSNR(dB)
Bitrate(Kbit/s)
Encoding Time(s) 22
63.726
41.143
52.426 27
57.084
40.191
50185 32
48.975
36.230
42.470 37
41.869
35.913
40.828
BasketballDrill_832x480_50.yuv (AI mode)
HEVC
VP9 QP
PSNR(dB)
Bitrate(Kbit/s)
Encoding Time(s) 22 27
39.553 32
38.224 37
35.831  

22. Implementation results(continued..)
Kimono1_1920x1080_24.yuv (AI mode)
HEVC
VP9 QP
PSNR(dB)
Bitrate(Kbit/s)
Encoding Time(s) 22
43.164 27
42.053 32
40.955 37
39.868
PeopleOnStreet_2560x1600_30_crop.yuv (AI mode)
HEVC
VP9 QP
PSNR(dB)
Bitrate(Kbit/s)
Encoding Time(s) 22
43.219 27
40.387 32
38.794 37
36.611

23. Implementation results(continued..)

24. Implementation results(continued..)

25. Implementation results(continued..)

26. Implementation results(continued..)

27. Implementation results(continued..)

28. Implementation results(continued..)

29. Conclusions
HEVC provides better compression rates than VP9, but VP9 is patent-free and can be used without licensing expenses.
For Intra frame coding, HEVC gives 13% more bitrate savings than VP9. And the encoding time taken by VP9 is marginally less than HEVC.

30. List of Acronyms ADST - Asymmetric Discrete Sine Transform
AVC – Advanced Video Coding
BD-BR- Bjøntegaard-Delta Bit-Rate Measurements
BD-PSNR - Bjøntegaard-Delta Peak signal to noise ratio
CU- Coding unit
CTU- Coding tree unit
DBF- Deblocking Filter
DFT – Discrete Fourier Transform
DCT – Discrete Cosine Transform
DST – Discrete Sine Transform
DPB - Decoded Picture Buffer
DC – Direct Current
HD- High definition
HEVC-High Efficiency Video Coding
ITU-T - International Telecommunication Union (Telecommunication Standardization Sector)
JPEG - Joint photographic experts group
JCT-VC- Joint collaborative team on video coding
MSE-Mean square error
MPEG-Moving picture experts group
NGOV- Next Geneneration Open Video
PU- Prediction unit
PSNR-Peak signal to noise ratio
PU – Prediction Unit
RD – Rate Distortion
SAO - Sample Adaptive Offset
SSIM- Structural similarity index
TM- True Motion
TU-Transform units
VCEG – Video Coding Experts Group

31. References
[1] G.J. Sullivan et al, “Overview of the high efficiency video coding (HEVC) standard”, IEEE Trans. circuits and systems for video technology, vol. 22, no.12, pp – 1668, Dec 2012.
[2] D. Grois et al, “Performance Comparison of H.265/MPEG-HEVC, VP9, and H.264/MPEG-AVC Encoders” 30th Picture Coding Symposium 2013 (PCS 2013), San José, CA, USA, Dec 8-11, 2013
[3] D. Mukherjee et al, “The latest open-source video codec VP9–An overview and preliminary results”, Google Inc., United States
[4] G.J. Sullivan et al, "Standardized Extensions of High Efficiency Video Coding (HEVC)", IEEE Journal of Selected Topics in Signal Processing, vol.7, no.6, pp , Dec. 2013
[5]Article on HEVC -
[6] Q. Cai et al, “Lossy and lossless intra coding performance evaluation: HEVC, H.264/AVC, JPEG 2000 and JPEG LS”, Signal & Information Processing Association Annual Summit and Conference (APSIPA ASC), 2012 Asia-Pacific, vol.9, no.12, pp.1-9, Dec 2012.
[7] "VP-Next Overview and Progress Update" (PDF). WebM Project (Google). Retrieved Available on :
[8]M.T. Pourazad et al, “HEVC:The new gold standard for video compression”, IEEE consumer electronics magazine ,vol.1, no.7, pp.36-46, July 2012.

32. References(Continued..)
[9] M.P. Sharabayko et al, "Intra Compression Efficiency in VP9 and HEVC" Applied Mathematical Sciences, Vol. 7, no. 137, pp.6803 – 6824, Hikari Ltd, 2013
[10] Z. Wang et al, “Image quality assessment: From error visibility to structural similarity,” IEEE Trans. on Image Processing, vol. 13, no. 4, pp , Apr
[11] H. Jain, “Comparative performance analysis of HEVC and H.264 Intra frame coding and JPEG2000”, EE5359, UTA, spring 2013.
[12] HM Reference Software-
[13] Chromium® open-source browser project, VP9 source code, Online:
[14] G. Bjøntegaard, “Calculation of average PSNR differences between RD-curves”, ITU-T Q.6/SG16 VCEG 13th Meeting, Document VCEG-M33, Austin, USA, Apr
[15] S. Jeong et al., High efficiency video coding for entertainment quality. ETRI J. vol.33, pp.145–154, 2011.
[16] JVT Draft ITU-T recommendation and final draft international standard of joint video specification (ITU-T Rec. H.264-ISO/IEC AVC), March 2003, JVT-G050-

33. References(Continued..)
[17] White paper on PSNR-NI -
[18] HEVC tutorial by I.E.G. Richardson:
[19] J. Padia, “Complexity reduction for VP6 to H.264 transcoder using motion vector reuse,” M.S. Thesis, EE Dept., UTA, Arlington, TX, Available on :
[20] G. Bjøntegaard , “Improvements of the BD-PSNR model” ITU-T SG16 Q.6, Doc. VCEG-AI11, Berlin, Germany, July 16-18, 2008
[21] T. Wiegand et al, “Overview of the H.264/AVC Video Coding Standard”, IEEE Transactions on Circuits and Systems for Video Technology, Vol. 13, No. 7, pp , Jul
[22] N. Ahmed , T. Natarajan, K.R. Rao, “Discrete Cosine Transform”, IEEE Transactions on Computers, Vol. C-23, pp , Jan
[23] I.E.G. Richardson, “The H.264 advanced video compression standard”, 2nd Edition, Hoboken, NJ, Wiley, 2010.
[24] I.E.G. Richardson, “Video Codec Design: Developing Image and Video Compression Systems”, Wiley, 2002.
[25] K.R. Rao, D.N. Kim and J.J. Hwang, “Video Coding Standards: AVS China, H.264/MPEG-4 Part 10, HEVC, VP6, DIRAC and VC-1”, Springer, 2014.
[26] B. Bross et al, “High Efficiency Video Coding (HEVC) Text Specification Draft 10”, Document JCTVC-L1003, ITU-T/ISO/IEC Joint Collaborative Team on Video Coding (JCT-VC), Mar available on

34. Thank You