FAST MODE DECISION ALGORITHM FOR INTRA PREDICTION IN HEVC

Lanka Naga Venkata Sai Surya Teja

Student ID 1000916473

Mail ID nvssurya.lanka@mavs.uta.edu

Date 03/02/2014

UNDER THE GUIDANCE OF

Dr. K. R. Rao

PROPOSAL

• To improve the coding efficiency of intra frame coding, up to 34 intra prediction modes are defined in High Efficiency Video Coding (HEVC) [1]

• The best mode among these pre-defined intra prediction modes is selected by rate-distortion optimization (RDO) for each block

• This project proposes a new method to reduce the candidates in RDO process, as it will be time-consuming if all directions are tested in the RDO process when compared with the default method of intra prediction in HM 13.0.

• Also analysis of PSNR, BD- PSNR, SSIM, BD- Bitrate can be done by comparing with the default encoding scheme in HM 13.0 [5].

INTRODUCTION

• HEVC standard [2] provides a highly flexible hierarchy of unit representation which consists of three block concepts: coding unit (CU), prediction unit (PU), and transform unit (TU).

• This separation of the block structure is helpful for each unit of optimization.

• CU is a macroblock-like unit of region splitting which is always square and its size can be from 8x8 luma samples up to the largest coding units (LCUs).

• The PU is used only for the CU which is the leaf node in the Quadtree structure and the size of two PUs are 2Nx2N and NxN.

• The third block concept transform unit size cannot exceed that of the CU.

BLOCK DIAGRAM OF HEVC ENCODER[15]

BLOCK DIAGRAM OF H.264 ENCODER[20]

BLOCK DIAGRAM OF HEVC DECODER[15]

• Since encoder needs to exhaust all the combinations of CU, PU and TU to find the optimal solutions, it is very time-consuming

• The encoder will not tolerate it if all the directions are employed in the rate-distortion optimization process

• To reduce the computational complexity of the encoder, a fast intra mode decision [4] was adopted in HM13.0 [5]

CODING TREE ALGORITHM

(c) (d)

OVERVIEW OF INTRA PREDICTION

• In H.264, intra prediction [6][7][8][9] is based on spatial extrapolation of samples from previously decoded image blocks, followed by integer discrete cosine transform (DCT) [10] based coding

• HEVC utilizes the same principle, but further extends it to efficiently represent wider range of textural and structural information in images

• HEVC contains several elements improving the efficiency of intra prediction over earlier solutions

HEVC INTRA PREDICTION MODES [7]

H.264 INTRA PREDICTION MODES[21]

METHOD PROPOSED FOR FAST MODE DECISON ALGORITHM FOR INTRA

PREDICTION• The fast intra prediction consists of three steps:

1. Hadamard Transformed Coefficients Of Residual Signal[13]

2. Progressive Mode Search[13]

3. Early RDOQ Termination[13]

• Combining the three steps, fast mode decision algorithm can be performed in intra prediction

• The unified intra in HM1.0 first determines the first N best candidate modes selected by a rough mode decision (RMD) process where all modes are tested by minimum absolute sum of Hadamard Transformed coefficients of residual signal and the mode bits in the rough mode decision

• Instead of the total intra prediction modes decision, the RD optimization is only applied to the N best candidate modes selected by the rough mode decision where all modes are compared in this decision

• However, computation load of the encoder is still very high. On the other side, the intra prediction modes are always correlated among the neighbors which are not considered in HM13.0

• Therefore, there is still some space for further reducing the encoder complexity

TEST SEQUENCES

• [1] BQSquare_416x240_60

• [2] BQMall_ 832x480_60

• [3] KristenAndSara_1280x720_60

ACRONYMS• BD- Bitrate - Bjøntegaard Delta Bitrate• BD- PSNR - Bjøntegaard Delta Peak Signal-to-Noise Ratio• CU - Coding Unit• DCT - Discrete Cosine Transform• DST - Discrete Sine Transform• HEVC - High Efficiency Video Coding• JCT- VC- Joint Collaborative Team on Video Coding• LCU - Largest Coding Unit• MPM - Most Probable Mode• PSNR - Peak Signal-to-Noise Ratio• PU - Prediction Unit• RDOQ - Rate Distortion Optimization Quantization• RDO - Rate- Distortion Optimization• RMD - Rough Mode Decision• SSIM - Structural Similarity Index• TU - Transform Unit

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. 1649 – 1668, Dec 2012.

[2] JCT-VC, “WD1: Working Draft 1 of High-Efficiency Video Coding”, JCTVC-C403, JCT-VC Meeting, Guangzhou, October 2010.

[3] Coding tree structure - https://www.google.com/search?q=coding+tree+structure+in+hevc

[4] Y. Piao et al, “Encoder improvement of unified intra prediction,” JCTVC-C207, Guangzhou, October 2010.

[5] Software for HEVC - https://hevc.hhi.fraunhofer.de/svn/svn_HEVCSoftware

[6] T.L. Silva et al, ”HEVC intra coding acceleration based on tree inter-level mode correlation”, SPA 2013 Sep.2013, Poznan, Poland

[7] H. Zhang and Z. Ma, ”Fast intra prediction for high efficiency video coding ”, Pacific Rim Conf. on Multimedia, PCM2012, Singapore, Dec. 2012.

[8] M. Zhang et al, ”An adaptive fast intra mode decision in HEVC ”, IEEE ICIP 2012, pp.221-224, Orlando, FL, Sept.- Oct. 2012.

[9] Y. Kim et al, “A fast intra-prediction method in HEVC using rate-distortion estimation based on Hadamard transform”, ETRI Journal, vol.35, #2, pp.270-280, Apr. 2013.

[10 ]A. Saxena and F. Fernanades, “Mode dependent DCT/DST for intra prediction in block based image/video coding”, IEEE ICIP, pp. 1685-1688, Sept. 2011.

[11] M. Khan et al, “An adaptive complexity reduction scheme with fast prediction unit decision for HEVC Intra encoding”, IEEE ICIP, pp. 1578-1582, Sept. 2013.

[12] P. Mehta, “Complexity reduction for intra mode selection in HEVC using OpenMP”, course website: http://www-ee.uta.edu/Dip/Courses/EE5359/ Section: previous projects, Sub section: Projects (Spring 2014).

[13] S. Vasudevan, “Fast intra prediction and fast residual quadtree encoding implementation in HEVC”, course website: http://www-ee.uta.edu/Dip/Courses/EE5359/ Section: previous projects, Sub section: Projects (Spring 2014).

[14] K.R.Rao , D. N. Kim and J.J. Hwang ,” Video coding standards: AVS China, H.264/MPEG-4 Part10, HEVC, VP6, DIRAC and VC-1"´, Springer, 2014.

[15] G.Sullivan et al, “Standard Extensions of the High Efficiency Video Coding (HEVC) Standard” Journal of Special Topics in Signal Processing, vol.7, No. 6, pp. 1001-1016, Dec 2013.

[16] Test Sequences: ftp://ftp.kw.bbc.co.uk/hevc/hm-11.0-anchors/testsequences/

[17] F. Bossen et al, "HM Software Manual", JCT-VC of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, AHG chairs, January 2014

[18] 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. 2013 available on http://phenix.it-sudparis.eu/jct/doc_end_user/current_document.php?id=7243

[19] JVT Draft ITU-T recommendation and final draft international standard of joint video specification (ITU-T Rec. H.264-ISO/IEC 14496-10 AVC), March 2003, JVT-G050 available on http://ip.hhi.de/imagecom_G1/assets/pdfs/JVT-G050.pdf

• [20] I.E.G. Richardson, “The H.264 advanced video compression standard”, 2nd Edition, Hoboken, NJ, Wiley, 2010.

• [21] Intra Prediction Modes of H.264 -https://www.google.com/search?q=intra+prediction+modes+h.264