Guided BY: DR.K.r.RAO Submitted by: Lohith Subramanya 1000928742 A performance Comparison of Fractional-Pel interpolation filters in HEVC and H.264/avc Date of Submission: February 19th 2014 Guided BY: DR.K.r.RAO Submitted by: Lohith Subramanya 1000928742

OBJECTIVE The objective of this project is to compare and analyze the fractional-pel interpolation filters in HEVC [1] and H.264/AVC [17] based on their frequency responses, complexity, coding performance and performance gain. BD-PSNR [33] and BD-Bit Rate [33] are the metrics used for comparison.

INTRODUCTION The fractional-pel interpolation filters (6-tap FIR [24] and Average) adopted in H.264/AVC [17] improve motion compensation greatly. Similarly, the DCT - based fractional-pel interpolation filters (7-tap and 8-tap) are adopted in the HEVC [1] standard. This project involves the differences in performance between these two types of filters.

H.264 [7] It is an industry standard for video compression, the process of converting digital video into a format that takes up less capacity when it is stored or transmitted. The encoder converts video into a compressed format and the decoder converts compressed video back into an uncompressed format.

H.264 Block Diagram [23]

HEVC [1] High Efficiency Video Coding (HEVC) [1] is the current joint video coding standardization project of the ITU-T Video Coding Experts Group (VCEG) (ITU-T Q.6/SG 16) and ISO/IEC Moving Picture Experts Group (MPEG) (ISO/IEC JTC 1/SC 29/WG 11).

HEVC Block Diagram [6]

Why use Interpolation? Motion-compensated prediction (MCP) [8] is the key to the success of the modern video coding standards, as it removes the temporal redundancy in video signals and reduces the size of bitstreams significantly. With MCP, the pixels to be coded are predicted from the temporally neighboring ones, and only the prediction errors and the motion vectors (MV) [8] are transmitted.

Interpolation(Continued..) However, due to the finite sampling rate, the actual position of the prediction in the neighboring frames may be out of the sampling grid, where the intensity is unknown. So, the intensities of the positions in between the integer pixels, called sub-positions, must be interpolated and the resolution of MV [8] is increased accordingly.

N-Tap FIR Filter [27]

Magnitude Response of Half-Pel Interpolation Filters [10] Solid graph: DCTIF 8-Tap Filter Dashed graph: H.264/AVC Filter Dotted graph: DCTIF 6-Tap Filter

Filter Co-efficients for half-pel and quarter-pel pixels

Filter Weights of Pixels in HEVC

Plan of Action Step 1: Based on reference software HM13 [16] - To change the half-pel interpolation filter coefficients to the coefficients in H.264/AVC [17], and thus the fractional-pel pixels might get affected.   Step 2: Based on reference software HM13 [16] - To change the half-pel interpolation filter coefficients to the coefficients of DCTIF [10].

Plan of Action(Continued..) Step 3: In addition to the change in step 1, the interpolation methods of quarter-pel pixels in horizontal direction and in vertical direction are to be changed to those in H.264/AVC [17]. Thus the fractional-pel pixels might get affected again.   Step 4: Besides the changes in step 3, the interpolation methods of remaining four quarter-pel pixels in the diagonal direction are to be changed to those in H.264/AVC [17].

Representation of integer and fractional-pels [20]

The interpolation filters used in H  The interpolation filters used in H.264 [17] are 6 tap FIR filter for half-pel interpolation and the average filter for quarter-pel interpolation. Similarly, in HEVC [3], an 8-tap DCTIF is used for half-pel interpolation and a 7-tap DCTIF is used for quarter-pel interpolation. The comparison of the modified filter coefficients based on frequency response that are obtained from Steps 1-4 can be further assessed for the required parametric results mentioned in “A comparison of Fractional-Pel Interpolation Filters in HEVC and H.264/AVC” [10]

List of ACRONYMS AIF: Adaptive Interpolation Filter ALF: Adaptive Loop Filter APEC: Adaptive Prediction Error Coding AVC: Advanced Video Coding AQMS: Adaptive Quantization Matrix Selection CSVT: Circuits and Systems for Video Technology DCT: Discrete Cosine Transform DCTIF: Discrete Cosine Transform Interpolation Filter DMVD: Decoder-side Motion Vector Deviation DSP: Digital Signal Processing EMS: Extended Macro-block Size FIR: Finite Impulse Response HEVC: High Efficiency Video Coding IBDI: Internal Bit Depth Increasing ITU-T: International Telecommunication Union – Telecommunication Standardization Sector

List of ACRONYMS(Continued..) JCT-VC: Joint Collaborative Team on Video Coding JPEG: Joint Photographic Experts Group KLT: Karhunen - Loeve Transform LTS: Larger Transform Size MCP: Motion Compensated Prediction MPEG: Moving Picture Experts Group MV: Motion Vectors RDO: Rate Distortion Optimization SOC: System On Chip SVN: Sub-Version VCEG: Video Coding Experts Group VCIP: Visual Communications and Image Processing

References Fraunhofer Heinrich Hertz Institute - http://hevc.hhi.fraunhofer.de/ Open Patents and Standards Platform - http://www.iplytics.com/en/tag/hevc/ Telco Group (Russian) - Integrators and equipment suppliers in the market of cable, satellite and terrestrial television - http://telcogroup.ru/files/materials-pdf/High_Efficiency_Video_Coding_H265.pdf Overview of HEVC - http://iphome.hhi.de/wiegand/assets/pdfs/2012_12_IEEE-HEVC-Overview.pdf Extremetech Blog: http://www.extremetech.com/computing/162027-h-265-benchmarked-does-the-next-generation-video-codec-live-up-to-expectations Altera Technologies: http://www.altera.com/technology/system-design/articles/2013/tv-studio-system.html I.Richardson, “ Real time implementation of H.264 Video Coding”, 2008 IEEE International SOC Conference, PP: 390, Sept. 2008 H.265 Blog http://www.h265.net/2010/07/adaptive-interpolation-filter-for-video-coding.html

CNET Blog http://news. cnet H.Lv, et al, “ A comparison of fractional-pel interpolation in HEVC and H.264/AVC”, 2012 IEEE Conference on Visual Communications and Image Processing (VCIP), PP: 1-6, Nov 2012 G.J.Sullivan, et al, “ Overview of the HEVC Standard”, 2012 IEEE Transactions on Circuits and Systems for Video Technology(CSVT), Vol: 22, No: 12, PP: 1649-1668, Sept 2012 B.Lee, et al, “Performance Comparison of various interpolation methods for color filter arrays”, 2001 IEEE Symposium on Industrial Electronics, Vol: 1, PP: 232-236, Jun 2001 V.Yu and J.Ostermann, “Locally Adaptive Non-Separable Interpolation Filter for H.264/AVC”, 2006 IEEE International Conference on Image Processing, PP: 33-36, Oct 2006 Video Test Sequences: http://trace.eas.asu.edu/yuv/ Tortoise SVN Downloadable Software Link: http://tortoisesvn.net/downloads.html

HM 13 Software Link: https://hevc. hhi. fraunhofer H.264 Advanced Video Coding Blog https://www.vcodex.com/h264.html G.J.Sullivan, et al, “ Standardized Extensions of HEVC”, 2013 IEEE Journal of Selected Topics in Signal Processing, Vol : 7, No: 6, PP: 1001-1016, Dec. 2013 K.R.Rao, D.N.Kim and J.J.Hwang, “Video coding standards”, Springer Publications, Jan. 2014: http://www.springer.com/physics/book/978-94-007-6741-6 SPIE Digital Library: http://electronicimaging.spiedigitallibrary.org/article.aspx?articleid=1730243 Karhunen-Loeve Transform: http://en.wikipedia.org/wiki/Karhunen%E2%80%93Lo%C3%A8ve_theorem Sharp 8Kx4K TV: http://www.sound-news.net/index.php/the-novosti/hifi-av-novosti/item/552-sharp-8kx4k-tv

23. Institute of Computer and Communication Engineering: http://research.ncku.edu.tw/re/articles/e/20071102/2.html FIR Filter: http://en.wikipedia.org/wiki/Finite_impulse_response JCT-VC Document Management System: http://phenix.int-evry.fr/jct/ T.Wiegand, et al, “Overview of the H.264/AVC Video Coding Standard”, 2003 IEEE Transactions on Circuits and Systems for Video Technology, Vol: 13, No: 7, PP: 560-576, July 2003 Iowegian International DSP Site: http://www.dspguru.com/dsp/faqs/fir/basics N-Tap FIR Filter: http://www.analog.com/static/imported-files/seminars_webcasts/MixedSignal_Sect6.pdf I.Richardson, “ The H.264 Advanced Video Compression Standard”, Wiley Publications, Aug. 2010: http://www.wiley.com/WileyCDA/WileyTitle/productCd-0470516925.html HM 13 Software Reference Manual: http://mpeg.chiariglione.org/standards/mpeg-h/high-efficiency-video-coding/high-efficiency-video-coding-hevc-encoder-description JPEG: http://www.jpeg.org/ JM 18.6 Software Repository: http://iphome.hhi.de/suehring/tml/download/ BD-PSNR and BD-BR: http://www.mathworks.com/matlabcentral/fileexchange/27798-bjontegaard-metric/content/bjontegaard.m