Reducing/Eliminating visual artifacts in HEVC by Deblocking filter

1. Reducing/Eliminating visual artifacts in HEVC by Deblocking filter 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 : Project Proposal Presentation

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

4. HEVC Decoder Block Diagram [1] EE-5359 : Project Proposal Presentation

5. 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 : Project Proposal Presentation

6. Blocking Artifacts [4] • 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 : Project Proposal Presentation

7. Example of block boundary with blocking artifact [4] EE-5359 : Project Proposal Presentation

8. Deblocking filter [5] • 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 : Project Proposal Presentation

9. Processing flow of deblocking filter [6] • 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 : Project Proposal Presentation

10. 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. EE-5359 : Project Proposal Presentation

11. 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] “Next generation video compression – Ericsson Review The Communications Journal” http://www.ericsson.com/res/thecompany/docs/publications/ericsson_review/2013/er-hevc-h265.pdf [4] Wei, Wei-Yi. "Deblocking Algorithms in Video and Image Compression Coding." Graduate Institute of Communication Engineering National Taiwan University, Taipei, Taiwan, ROC. [5] 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. [6] W.Shen et al , “A high-throughput VLSI architecture for deblocking filter in HEVC” “Circuits and Systems (ISCAS), 2013 IEEE International Symposium on” , pp 673-676 , May 2013 EE-5359 : Project Proposal Presentation