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

2. EE-5359 : Final Project Presentation
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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3. HEVC Encoder Block Diagram [1]
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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. 
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5. 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 [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.
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8. Example of block boundary with blocking artifact [11]
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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.
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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.
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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.
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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
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13. Sample Processing in SAO
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).
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.
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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.
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1. Bus.qcif
INTRA
TIME (Sec)
bitrate (KbPS)
PSNR(dB)
DB On
52.368
633.2
DB Off
52.071
633.1
encoder_intra_main.cfg with DB off and DB ON for bus.qcif ( QP=32 ) and 10 frames
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Low Delay
TIME (Sec)
bitrate (KbPS)
PSNR(dB)
DB On
213.24
DB Off
120.47
212.96
encoder_lowdelay_main.cfg with Default and DB ON for bus.qcif ( QP=32 ) and 10 frames
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2.BQSquare_416x240_60.yuv
INTRA
TIME (Sec)
Bitrate (KbPS)
PSNR(dB)
QP=32
QP=20
DB ON
DB OFF
encoder_intra_main.cfg with DB OFF and DB ON for BQSquare.yuv ( QP=32 and QP=20) and 10 frames
TIME measurement for BQSquare.yuv test sequence in encoder_intra_main.cfg with DB Off and DB ON and 10 frames
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Bitrate measurement for BQSquare.yuv test sequence in encoder_intra_main.cfg with DB Off and DB ON and 10 frames
PSNR measurement for BQSquare.yuv test sequence in encoder_intra_main.cfg with DB Off and DB ON and 10 frames
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LOW DELAY
TIME (Sec)
Bitrate (KbPS)
PSNR(dB)
QP=32
QP=20
DB ON
DB OFF
encoder_lowdelay_main.cfg with DB OFF and DB ON for BQSquare.yuv ( QP=32 and QP=20) and 10 frames
TIME measurement for BQSquare.yuv test sequence in encoder_lowdelay_main.cfg with DB Off and DB ON and 10 frames
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Bitrate measurement for BQSquare.yuv test sequence in encoder_lowdelay_main.cfg with DB Off and DB ON and 10 frames
PSNR measurement for BQSquare.yuv test sequence in encoder_lowdelay_main.cfg with DB Off and DB ON and 10 frames
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3.BasketballDrill_832x480_50.yuv
INTRA
TIME (Sec)
Bitrate (KbPS)
PSNR(dB)
QP=32
QP=20
DB ON
DB OFF
encoder_intra_main.cfg with DB OFF and DB ON for BasketballDrill.yuv ( QP=32 and QP=20) and 10 frames
TIME measurement for BasketballDrill.yuv test sequence in encoder_intra_main.cfg with DB Off and DB ON and 10 frames
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Bitrate measurement for BasketballDrill.yuv test sequence in encoder_intra_main.cfg with DB Off and DB ON and 10 frames
PSNR measurement for BasketballDrill.yuv test sequence in encoder_intra_main.cfg with DB Off and DB ON and 10 frames
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LOW DELAY
TIME (Sec)
Bitrate (KbPS)
PSNR(dB)
QP=32
QP=20
DB ON
1111.8
DB OFF
1089.8
encoder_lowdelay_main.cfg with DB OFF and DB ON for BasketballDrill.yuv ( QP=32 and QP=20) and 10 frames
TIME measurement for BasketballDrill.yuv test sequence in encoder_lowdelay_main.cfg with DB Off and DB ON and 10 frames
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EE-5359 : Final Project Presentation

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Bitrate measurement for BasketballDrill.yuv test sequence in encoder_lowdelay_main.cfg with DB Off and DB ON and 10 frames
PSNR measurement for BasketballDrill.yuv test sequence in encoder_lowdelay_main.cfg with DB Off and DB ON and 10 frames
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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.
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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
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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 – 1668, Dec [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 , Aug [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 [4] K.R. Rao, D. N. Kim and J. J. Hwang, “Video Coding standards”, pp , Springer [5] “High Efficiency Video Coding HEVC / H.265” article Available Vcodex website
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[6] “Next generation video compression – Ericsson Review The Communications Journal” Available website: compression_ _c
[7] L. Zhao et al, “Fast mode decision algorithm for intra prediction in HEVC”, Conference Article no , IEEE Visual Communications and Image Processing, 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 , 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
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[11] A. Norkin et al, “HEVC Deblocking Filter”, IEEE Transactions on Circuits and Systems for Video Technology, Vol. 22, No. 12, pp , Dec
[12]W. Shen et al , “A high-throughput VLSI architecture for deblocking filter in HEVC” ,“IEEE International Symposium on Circuits and Systems (ISCAS)” , pp , 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 , 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 , 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
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[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
[17] ITU-T: "H.265 : High efficiency video coding", April 2013.To access it, go to
[18] HEVC Reference Software HM
[19] E .Ozcan et al , “A high performance deblocking filter hardware for High Efficiency Video Coding” , rd International Conference on Field Programmable Logic and Applications , pp 1-4 , Sept.2013.
[20] Required test sequence
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[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 , 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 , Dec
[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 , Dec. 2013
[24] IEEE Journal of Selected Topics in Signal Processing, vol. 7, pp , Dec
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