Reducing/Eliminating visual artifacts in HEVC by Deblocking

filter

By:Harshal Shah

Under the guidance of: Dr. K. R. Rao

EE-5359 : Project Proposal Presentation 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

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HEVC Encoder Block Diagram [1]

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HEVC Decoder Block Diagram [1]

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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]

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Blocking Artifacts [4]

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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 imageMost annoying artifacts in video and image

compression coding.

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Example of block boundary with blocking artifact [4]

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Deblocking filter [5]

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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.

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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.

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Proposed Work

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• 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.

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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

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