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Reducing/Eliminating visual artifacts in HEVC by Deblocking filter final report

Reducing/Eliminating visual artifacts in HEVC by Deblocking filter final report. Submitted By: Harshal Shah Under the guidance of Dr. K. R. Rao. HEVC Overview [2]. HEVC–Most recent standard in video compression technology. Also known as H.265.

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Reducing/Eliminating visual artifacts in HEVC by Deblocking filter final report

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  1. Reducing/Eliminating visual artifacts in HEVC by Deblocking filter final report Submitted By: Harshal Shah Under the guidance of Dr. K. R. Rao

  2. HEVC Overview [2] • HEVC–Most recent standard in video compression technology. Also known as H.265. • Provides around 50% bit-rate reduction while maintaining the same subjective video quality relative to its predecessor H.264 • Developed by the ISO and ITU-T EE-5359 : Final Project Presentation

  3. HEVC Encoder Block Diagram [1] EE-5359 : Final Project Presentation

  4. Each picture is split into block-shaped regions, with the exact block  partitioning being conveyed to the decoder. • The first picture of a video sequence  (and the first picture at each clean random access point into a video sequence) is  coded using only intrapicture prediction • For all remaining pictures of a sequence or between random access points, interpicture temporally predictive coding modes are typically used for most blocks. • The encoding process for interpicture prediction consists of choosing motion data comprising the selected reference picture and motion vector (MV) to be applied for predicting the samples of each block. EE-5359 : Final Project Presentation

  5. HEVC Decoder Block Diagram [1] EE-5359 : Final Project Presentation

  6. Why HEVC ? • To ensure the highest level of compression efficiency, and support for parallel processing, some parts of HEVC have been significantly modified compared with previous generations of hybrid block-based codecs. [3] • For most of the previous MPEG-x and H.26x codecs, the largest entity that could be independently encoded was a macro block (16 × 16 pixels) [10]. For HEVC, the picture is split into coding-tree units (CTUs) with a maximum size of 64 × 64 pixels. [3] EE-5359 : Final Project Presentation

  7. Blocking Artifacts [10] • Discontinuities can occur in the reconstructed signal at the block boundaries. Visible discontinuities at the block boundaries are blocking artifacts. • Degrades the quality of video and image • Most annoying artifacts in video and image compression coding. EE-5359 : Final Project Presentation

  8. Example of block boundary with blocking artifact [11] EE-5359 : Final Project Presentation

  9. Deblocking filter [12] • Detects artifacts at the coded block boundaries and attenuates them by applying a selected filter. • The deblocking filter in HEVC has been designed to improve the subjective quality while reducing the complexity. • The HEVC deblocking filter is less complex as compared to the H.264/AVC deblocking filter, while still having the capability to improve the subjective and objective quality. EE-5359 : Final Project Presentation

  10. Processing flow of deblocking filter [13] • Firstly, the decision should be made that whether the current boundary is a boundary of CU, PU or TU. If not, the filtering processing should be not applied to the current boundary. • Boundary strength (BS) reflects how strong the filtering is needed for the boundary. • Threshold values β and tc which are used for filter on/off decision, strong/weak filter selection. EE-5359 : Final Project Presentation

  11. Sample Adaptive Offset (SAO) in HEVC : • SAO is a process that modifies the decoded samples by conditionally adding an offset value to each sample after the application of the deblocking filter, based on values in look-up tables transmitted by the encoder. • The key idea of SAO is to reduce sample distortion by first classifying reconstructed samples into different categories, obtaining an offset for each category, and then adding the offset to each sample of the category. EE-5359 : Final Project Presentation

  12. Block Diagram of Deblocking filter • As shown in Fig. 1, SAO is located after DF and also belongs to in-loop filtering. • The concept of SAO is to reduce mean sample distortion of a region by first classifying the region samples into multiple categories with a selected classifier, obtaining an offset for each category, and then adding the offset to each sample of the category, where the classifier index and the offsets of the region are coded in the bit stream EE-5359 : Final Project Presentation

  13. Sample Processing in SAO • SAO may use different offsets sample by sample in a region depending on the sample classification, and SAO parameters are adapted from region to region. • Two SAO types that can satisfy the requirements of low complexity are adopted in HEVC: edge offset (EO) and band offset (BO). For EO, the sample classification is based on comparison between current samples and neighboring samples. For BO, the sample classification is based on sample values. • Figure is of Four 1-D directional patterns for EO sample classification: horizontal (EO class = 0), vertical (EO class = 1), 135° diagonal (EO class = 2), and 45° diagonal (EO class = 3). EE-5359 : Final Project Presentation

  14. Proposed Work • Study and implementation of Deblocking filters to reduce the visual artifacts in HEVC. • study the working and performance analysis of deblocking filter algorithm in HEVC and compare it with H.264. • Implementing it on HM13.0 reference software. EE-5359 : Final Project Presentation

  15. 1. Bus.qcif encoder_intra_main.cfgwith DB off andDB ON for bus.qcif ( QP=32 ) and 10 frames EE-5359 : Final Project Presentation

  16. EE-5359 : Final Project Presentation

  17. encoder_lowdelay_main.cfgwith Default andDB ON for bus.qcif ( QP=32 ) and 10 frames EE-5359 : Final Project Presentation

  18. EE-5359 : Final Project Presentation

  19. 2.BQSquare_416x240_60.yuv encoder_intra_main.cfgwith DB OFF andDB ON for BQSquare.yuv ( QP=32 and QP=20) and 10 frames TIME measurement for BQSquare.yuv test sequence inencoder_intra_main.cfgwithDB Off andDBON and 10 frames EE-5359 : Final Project Presentation

  20. Bitrate measurement for BQSquare.yuv test sequence inencoder_intra_main.cfgwithDB Off andDBON and 10 frames PSNR measurement for BQSquare.yuv test sequence inencoder_intra_main.cfgwithDB Off andDBON and 10 frames EE-5359 : Final Project Presentation

  21. encoder_lowdelay_main.cfgwith DB OFF andDB ON for BQSquare.yuv ( QP=32 and QP=20) and 10 frames TIME measurement for BQSquare.yuv test sequence inencoder_lowdelay_main.cfgwithDB Off andDBON and 10 frames EE-5359 : Final Project Presentation

  22. Bitrate measurement for BQSquare.yuv test sequence inencoder_lowdelay_main.cfgwithDB Off andDBON and 10 frames PSNRmeasurement for BQSquare.yuv test sequence inencoder_lowdelay_main.cfgwithDB Off andDBON and 10 frames EE-5359 : Final Project Presentation

  23. 3.BasketballDrill_832x480_50.yuv encoder_intra_main.cfgwith DB OFF andDB ON for BasketballDrill.yuv ( QP=32 and QP=20) and 10 frames TIMEmeasurement for BasketballDrill.yuv test sequence inencoder_intra_main.cfgwithDB Off andDBON and 10 frames EE-5359 : Final Project Presentation

  24. Bitratemeasurement for BasketballDrill.yuv test sequence inencoder_intra_main.cfgwithDB Off andDBON and 10 frames PSNRmeasurement for BasketballDrill.yuv test sequence inencoder_intra_main.cfgwithDB Off andDBON and 10 frames EE-5359 : Final Project Presentation

  25. encoder_lowdelay_main.cfgwith DB OFF andDB ON for BasketballDrill.yuv ( QP=32 and QP=20) and 10 frames TIMEmeasurement for BasketballDrill.yuv test sequence inencoder_lowdelay_main.cfgwithDB Off andDBON and 10 frames EE-5359 : Final Project Presentation

  26. Bitratemeasurement for BasketballDrill.yuv test sequence inencoder_lowdelay_main.cfgwithDB Off andDBON and 10 frames PSNRmeasurement for BasketballDrill.yuv test sequence inencoder_lowdelay_main.cfgwithDB Off andDBON and 10 frames EE-5359 : Final Project Presentation

  27. CONCLUSION • So from the results shown in the figure there is significant change in encoding time, PSNR and bitrate when deblcoking filter is on/off. • Hence, the benefits of applying the deblocking filter is that it will help remove the blocking artifacts from the reconstructed image. The performance can also be improved by including the Quantization Parameter (QP) effect on the deblocking filter parameters. EE-5359 : Final Project Presentation

  28. List of ACRONYMS • CU: Coding unit. • CABAC: Context adaptive binary arithmetic coding • CTUs: Coding tree units. • DSPs : Digital signal processors • FDCT: Fast discrete cosine transform. HDTV: High definition television • HEVC: High Efficiency Video Coding. • ITU: International Telecommunication Union • ITU-TITU Telecommunication Standardization Sector • JVT - VT: Joint collaborative team on video coding • MSE: Mean square error. • MPEG: Moving picture experts group. PU: Prediction unit • PSNR: Peak signal to noise ratio. • QVGA: Quarter Video Graphics Array. • QCIF: Quarter common intermediate format. • QP: Quantization parameter • VCEG: Video Coding Experts Group EE-5359 : Final Project Presentation

  29. 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] P.Topiwala et al , “Performance comparison of JPEG2000 and H.264/AVC high profile intra-frame coding on HD video sequences”, SPIE int‘l symposium, digital image processing, vol. 6312, no.8, pp. 63120-63135, Aug. 2006. [3] Q.Cai, et al, “Lossy and lossless intra coding performance evaluation: HEVC, H.264/AVC, JPEG 2000 and JPEG LS”. Published in signal and information processing association annual summit and conference, vol.9, no.12, pp.1-9, Dec.2012. [4] K.R. Rao, D. N. Kim and J. J. Hwang, “Video Coding standards”, pp. 125-158, Springer 2013. [5] “High Efficiency Video Coding HEVC / H.265” article Available Vcodex website http://www.vcodex.com/h265.html EE-5359 : Final Project Presentation

  30. [6] “Next generation video compression – Ericsson Review The Communications Journal” Available website: http://www.ericsson.com/news/130424-next-generation-video-compression_244129228_c [7] L. Zhao et al, “Fast mode decision algorithm for intra prediction in HEVC”, Conference Article no.6115979, IEEE Visual Communications and Image Processing, 6-9 Nov. 2011 [8]JCT-VC, “WD1: Working Draft 1 of High-Efficiency Video Coding”, JCTVC-C403, JCT-VC Meeting, Guangzhou, October 2010. [9] G.J. Sullivan et al, “Standardized Extensions of High Efficiency Video Coding (HEVC)”, IEEE Journal on Selected Topics in signal Processing, vol. 7, pp. 1001-1016, December 2013. [10]W.Y. Wei, "Deblocking Algorithms in Video and Image Compression Coding." Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC EE-5359 : Final Project Presentation

  31. [11] A. Norkin et al, “HEVC Deblocking Filter”, IEEE Transactions on Circuits and Systems for Video Technology, Vol. 22, No. 12, pp. 1746-1754, Dec. 2012. [12]W. Shen et al , “A high-throughput VLSI architecture for deblocking filter in HEVC” ,“IEEE International Symposium on Circuits and Systems (ISCAS)” , pp 673-676 , May 2013 [13] W. Shen et al, “A 64 Cycles/MB, Luma- Chroma Parallelized H.264/AVC Deblocking Filter for 4Kx2K Applications” , “IEEE International Symposium on Circuits and Systems (ISCAS)”,  vol.E95-C, no.4, pp.441- 446, April 2012. [14] K.Xu ,  “A Five-Stage Pipeline, 204 Cycles/MB, Single-Port SRAM-Based Deblocking Filter for H.264/AVC,”, IEEE Transactions on Circuits and Systems for Video Technology , vol.18, no.3, pp.363-374, March 2008. [15] P. List et al , “Adaptive deblocking filter,” IEEE Trans. Circuits Syst. Video Technol., vol. 13, no. 7, pp. 614–619, July 2003 EE-5359 : Final Project Presentation

  32. [16] C.-M. Fu et al , “Sample adaptive offset in the HEVC standard,” IEEE Transactions on Circuits and Systems for Video Technology., vol. 22, no. 12, pp. 1755–1764, Dec. 2012. [17] ITU-T: "H.265 : High efficiency video coding", April 2013.To access it, go to http://www.itu.int/rec/T-REC-H.265-201304-I/en [18] HEVC Reference Software HM13.0. https://hevc.hhi.fraunhofer.de/svn/svn_HEVCSoftware/tags/HM-13.0rc1/ [19] E .Ozcan et al , “A high performance deblocking filter hardware for High Efficiency Video Coding” , 2013 23rd International Conference on Field Programmable Logic and Applications , pp 1-4 , Sept.2013. [20] Required test sequence http://media.xiph.org/video/derf/ EE-5359 : Final Project Presentation

  33. [21]F. Pescador et al, “Complexity analysis of an HEVC decoder based on a digital signal processor”, IEEE Trans. on Consumer Electronics. vol. 59, no. 2, pp. 391-399, May 2013. [22] Special issue on emerging research and standards in next generation video coding, IEEE Trans. on Circuits and Systems for Video Technology, vol. 22, pp. 1646-1909, Dec. 2012. [23] Special issue on emerging research and standards in next generation video coding, IEEE Trans. on Circuits and Systems for Video Technology, vol. 23, pp. 2009-2142, Dec. 2013 [24] IEEE Journal of Selected Topics in Signal Processing, vol. 7, pp. 931-1151, Dec. 2013. EE-5359 : Final Project Presentation

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