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Study and Optimization of the Deblocking Filter in H.265 and its Advantages over H.264

Study and Optimization of the Deblocking Filter in H.265 and its Advantages over H.264. By: Valay Shah. Unde r the guidance of: Dr. K. R. Rao. HEVC Overview. HEVC – a buzz word in compression standards Also known as H.265 50% bit rate reduction compared to H.264 (same picture quality)

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Study and Optimization of the Deblocking Filter in H.265 and its Advantages over H.264

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  1. Study and Optimization of the Deblocking Filter in H.265 and its Advantages over H.264 By: Valay Shah Under the guidance of: Dr. K. R. Rao

  2. HEVC Overview • HEVC – a buzz word in compression standards • Also known as H.265 • 50% bit rate reduction compared to H.264 (same picture quality) • Price – more complex video coding algorithm with computationally more expensive tools[2] • HEVC test codec – HM (HEVC test Model) EE-5359 : Project Proposal Presentation

  3. What’s Different? • Picture partitioning • A Coding Tree Block (CTB) of upto 64×64 spatial dimension in HEVC against 16×16 Macro-Block (MB) in H.264 • Minimum size of Coding Unit (CU) in HEVC is 8×8 versus 4×4 in H.264 • In-loop deblocking filtering • Sample Adaptive Offset (SAO) filtering • Challenges: • HEVC takes more time (approx. 40%) and hence more power consumption [2] EE-5359 : Project Proposal Presentation

  4. Deblocking Filter (DBF) • Focusing on – Deblocking filter to reduce the processing time • In-loop deblocking filtering in HEVC: • Similar to H.264, operated within inter-prediction loop • Simplified design in regard to its decision making, hence makes it viable for parallel processing • In HEVC the processing order of the deblocking filter is [1]: • Horizontal filtering for vertical edges for the entire picture first • Followed by vertical filtering for horizontal edges EE-5359 : Project Proposal Presentation

  5. Parallel Deblocking • Salient Features [2]: • - Larger deblocking removes data dependency between the edges in one direction (H.264 uses 4×4 deblocking filter size versus 8×8 used by HEVC) • - Hence, the vertical and horizontal filtering could be parallelized fully EE-5359 : Project Proposal Presentation

  6. HEVC DBF Procedure[2] • Advantages: • Allows parallel deblocking • Disadvantages: • Increases the processing time since some data needs to be re-fetched EE-5359 : Project Proposal Presentation

  7. Modified DBF Procedure[2] • The principle of performing vertical filtering first followed by the horizontal filtering is kept intact • The difference lies in selection of the blocks as shown in the figure on left EE-5359 : Project Proposal Presentation

  8. Proposed Work • Try to implement modified architecture in HEVC software code to get the performance enhancement • Implement a low complexity offsets perceptual optimization for deblocking filtering [3] • Optimize the skipping mode technique in order to decrease edge processing thereby reducing the power consumption • Compare the HEVC performance with H.264 EE-5359 : Project Proposal Presentation

  9. Expected Results EE-5359 : Project Proposal Presentation

  10. References [1] G. J. Sullivan et al, “Overview of the High Efficiency Video Coding (HEVC) Standard”, IEEE Transactions on Circuits and Systems for Video Technology, vol. 22, no. 12, pp. 1649-1668, Dec. 2012. [2] M. Li et al, “De-blocking Filter Design for HEVC and H.264/AVC/AVC”, PCM 2012, LNCS 7674, pp. 273–284, 2012. [3] M. Naccari et al, “Low Complexity Deblocking Filter Perceptual Optimization For The HEVC Codec”, 18th IEEE International Conference on Image Processing, pp. 737-740, 2011. [4] 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. [5] A. J. Honrubia, J. L. Martínez and P. Cuenca, “HEVC: A Review, Trends and Challenges”, Instituto de Investigación en Informática de Albacete, Spain. [6] T. Wiegand et al, “High Efficiency Video Coding (HEVC) Standarization”, IEEE Transactions on Circuits and Systems for Video Technology, Dec. 2010. [7] C. Man-Yau and S. Wan-Chi, “Computationally-Scalable Motion Estimation Algorithm for H.264/AVC Video Coding”, IEEE Transactions on Consumer Electronics, vol. 56, pp. 895-903, 2010. EE-5359 : Project Proposal Presentation

  11. References-contd. [8] R. Jianfeng, N. Kehtarnavaz, and M. Budagavi, “Computationally Efficient Mode Selection in H.264/AVC Video Coding, IEEE Transactions on Consumer Electronics, vol. 54, pp. 877-886, 2008. [9] Dr. K. R. Rao, “High Efficiency Video Coding”, Chapter 5 – soon to be published. [10] P. List et al, “Adaptive deblocking filter”, IEEE Transactions on Circuits and Systems for Video Technology, vol. 13, pp. 614-619, 2003. [11] K. Xu and C. S. Choy, “A Five-Stage Pipeline, 204 Cycles/MB, Single-Port SRAM-Based Deblocking Filter for H.264/AVC”, IEEE Transactions on Circuits and Systems, vol. 18(3), pp. 363–374, 2008. [12] F. Tobajas et al, “An Efficient Double-Filter Hardware Architecture for H.264/AVC De-blocking Filtering”, IEEE Transactions on Consumer Electronics, Vol. 54(1), Feb. 2008. [13] Y. C. Lin et al, “A Two-Result-Per-Cycle De-Blocking Filter Architecture for QFHD H.264/AVC Decoder”, IEEE Transactions on VLSI Systems, vol. 17(6), June 2009. [14] D. Zhou et al, “A 48 Cycles/MB H.264/AVC De-blocking Filter Architecture for Ultra High Definition Applications”, IEICE Transactions Fundamentals E92-A (12), Dec. 2009. [15] JM software download for H.264/AVC: http://iphome.hhi.de/suehring/tml/ [16] HM codec download for H.265: https://hevc.hhi.fraunhofer.de/svn/svn_HEVCSoftware/branches/ EE-5359 : Project Proposal Presentation

  12. Implementation Steps • Enable/Disable Deblocking Filter • LoopFilterDisable parameter – under Deblock Filter – alone would not do the job of disabling the deblocking filter • Have to use combination of following deblocking filter parameters: • DeblockingFilterControlPresent • LoopFilterDisable • LoopFilterBetaOffset_div2 • LoopFilterTcOffset_div2 EE-5359 : Project Proposal Presentation

  13. Results – Total Encoding Time Total time taken in sec for encoding where columns in yellow (i.e.: 2, 4, 6 & 8) denotes results where deblocking filter was disabled whereas columns in green (i.e.: 3, 5, 7 & 9) denotes results where the deblocking filter was enabled and its parameters were optimized. EE-5359 : Project Proposal Presentation

  14. Results – Bit-Rate Bit-rate in kbps for encoding where columns in yellow (i.e.: 2, 4, 6 & 8) denotes results where deblocking filter was disabled whereas columns in green (i.e.: 3, 5, 7 & 9) denotes results where the deblocking filter was enabled and its parameters were optimized. EE-5359 : Project Proposal Presentation

  15. Results – PSNR PSNR in dB of the encoded image where columns in yellow (i.e.: 2, 4, 6 & 8) denotes results where deblocking filter was disabled whereas columns in green (i.e.: 3, 5, 7 & 9) denotes results where the deblocking filter was enabled and its parameters were optimized. EE-5359 : Project Proposal Presentation

  16. Conclusions • It is apparent from the results that the bit-rate have increased by optimizing the deblocking filter parameters. • Hence, there are two benefits of applying the deblockingfilter: • (i) it will help remove the blocking artifacts from the reconstructed image and • (ii) it will help increase the bit-rate of the signal EE-5359 : Project Proposal Presentation

  17. Next Steps • To include the Quantization Parameter (QP) to see how does it affect the performance since it affects Beta and tC (deblocking parameters) • To vary all the deblocking parameters to get the best results in terms of PSNR, total encoding time and bit-rate EE-5359 : Project Proposal Presentation

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