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  1. Block Artifacts Reduction using Two HEVC Encoder methods EE5359 Multimedia Processing Interim Presentation SPRING 2015ADVISOR: Dr.K.R.Rao BY: BHARGAV VELLALAM SRIKANTESWAR Email-bhargav.vellalamsrikanteswa@mavs.uta.edu UTA ID – 1001048654 Submission date – 21st April 2015 EE5359 Multimedia Processing

  2. Acronyms • 3D - Three Dimension • AVC - Advanced Video Coding • AMVP - Advanced motion vector prediction • CTU - Coding Tree • CU - Coding Unit • CABAC - Context Adaptive Binary Arithmetic Coding • DCT- Discrete Cosine Transform • FPS – Frames Per Second • GOP - Group Of Pictures • HD - High Definition EE5359 Multimedia Processing

  3. Acronyms • HEVC - High Efficiency Video Coding • ISO - International Organization for Standardization • MPEG - Moving Pictures Experts Group • MSE - Mean Square Error • MV - Motion Vector • POC - Phase-Only Correlation • PB – Prediction Block • PU - Prediction Unit • QP - Quantization Parameter EE5359 Multimedia Processing

  4. Acronyms • RD – Rate Distortion • SAO - Sample Adaptive Offset • SSIM – Structural Similarity Index Metrics • TB - Transform Block • TU- Transform Unit • VCEG - Video Coding Experts Group EE5359 Multimedia Processing

  5. Overview • Introduction to HEVC • About Block Artifacts • Proposed Implementation • Comparison metrics • Profile used and testing platform • Configuration of HM 16.4 • Test sequences • Results • Conclusion and Future work • References EE5359 Multimedia Processing

  6. Introduction to HEVC • HEVC is the latest video coding standard jointly presented by ITU-T Video Coding Experts Group and the ISO/IEC Moving Picture Experts Group[1]. • The best performance improvement of HEVC over H.264 is ~50% bit rate reduction for equal perceptual video quality[1]. • The growing popularity of HD video, and the emergence of beyond-HD formats (e.g.4kx2k or 8kx4k resolution) are creating even stronger needs for coding efficiency superior to H.264/MPEG-4 [4] AVC's capabilities[4]. EE5359 Multimedia Processing

  7. HEVC Over Previous Standards Figure 1: Comparison of bit rates in HEVC over previous standards[14] EE5359 Multimedia Processing

  8. HEVC Encoder Figure 2: Block diagram of HEVC Encoder[9] EE5359 Multimedia Processing

  9. Steps Involved in Encoding • Partitioning each picture into multiple units • Predicting each unit using inter or intra prediction, and subtracting the prediction from the unit • Transforming and quantizing the residual (the difference between the original picture unit and the prediction) • Entropy encoding transform output, prediction information, mode information and headers[17] EE5359 Multimedia Processing

  10. HEVC Decoder Figure 3: HEVC Decoder[10] EE5359 Multimedia Processing

  11. Steps Involved in Decoding • Entropy decoding and extracting the elements of the coded sequence • Rescaling and inverting the transform stage • Predicting each unit and adding the prediction to the output of the inverse transform • Reconstructing a decoded video image [17] EE5359 Multimedia Processing

  12. Block Artifacts • A distortion that appears in compressed video material as abnormally large pixel blocks[6]. • Occurs when the encoder cannot keep up with the allocated bandwidth[6]. • Visible with fast motion sequences or quick scene changes[6]. EE5359 Multimedia Processing

  13. Continued.. Figure 4 : example showing macro blocks in a image[15] EE5359 Multimedia Processing

  14. Continued.. • In a coding scheme that uses block-based prediction and transform coding, discontinuities can occur in the reconstructed signal at the block boundaries [17]. • Visible discontinuities at the block boundaries are blocking artifacts [17]. EE5359 Multimedia Processing

  15. Continued.. Figure 5 : Block boundary with blocking artifact[17] EE5359 Multimedia Processing

  16. Implementation • The HEVC de-blocking filter significantly improves the subjective quality of coded video sequences at lower bitrates[6]. • Reference software encoder may produce visible block artifacts on some sequences with content that shows chaotic motion, such as water or fire[6]. EE5359 Multimedia Processing

  17. Continued.. • Analyzed the reasons for blocking artifacts in various sequences • Two simple encoder-side methods are implemented that improve the subjective quality. • 0 to 1% increase in bit rate. EE5359 Multimedia Processing

  18. Deblocking strength adaptation order • In order to attenuate block artifacts in a picture with higher depth, HEVC can be configured to signal the deblocking filter offsets at the slice/picture level. • Higher offsets are sent for the frames, which are at higher depth in the coding hierarchy. • The proposed approach relaxes the deblocking decisions thresholds and clipping values for the pictures at higher depth [6]. EE5359 Multimedia Processing

  19. Reducing Intra block size • When the rate-distortion optimization chooses 32 × 32 intra-predicted CUs at higher depth, the prediction is often coarse . • It might be difficult to conceal a blocking artifact by just applying the deblocking filtering • By limiting the maximum TU size to 16 × 16 samples for coding of intra CUs in inter-predicted slices . • This will restrict the maximum intra-predicted block size and will increase the bit rate [6]. EE5359 Multimedia Processing

  20. Comparison Metrics • PSNR – Peak Signal to Noise Ratio • Computational time • BD- Bit rate • BD - PSNR EE5359 Multimedia Processing

  21. Profile used and testing platform • The HM 16.4 main profile [8] , This profile allows for a bit depth of 8-bits per sample with 4:2:0 chroma sampling, which is the most common type of video used with consumer devices. • TESTING PLATFORM Processor : Intel(R) core(TM) i5-4200,2.30 GHz Memory : 6 GB Operating system : 64 bit windows 8 EE5359 Multimedia Processing

  22. Configuration of HM 16.4 • The project is implemented in Random Access configuration of HM 16.4 • Profile : main • IntraPeriod : 1 # Period of I-Frame ( -1 = only first) • GOPSize : 8 # GOP Size (number of B slice = GOPSize-1) • QP : 32 # Quantization parameter(0-51) • FastSearch 1 # 0:Full search 1:TZ search • SearchRange : 64 # (0: Search range is a Full frame) EE5359 Multimedia Processing

  23. Test Sequences The following test sequences are used for analyzing the project [11] EE5359 Multimedia Processing

  24. Test Sequences Figure 6: RaceHorses_416x240_30.yuv [11] Figure 7: ParkScene_1920x1080_24.yuv [11] Figure 8: Kimono_1920x1080_24.yuv [11] EE5359 Multimedia Processing

  25. Test Sequences Figure 10: BasketballDrill_832x480_50.yuv [11 Figure 9: football30_cif_90.yuv [11] EE5359 Multimedia Processing

  26. Results Figure 12: ParkScene_1920x1080_24.yuv with reduction of block artifacts Figure 11: ParkScene_1920x1080_24.yuv Without reduction of block artifacts Figure 11 and Figure 12 are encoded sequences for a QP of 42 without and with reduction of block artifacts respectively. EE5359 Multimedia Processing

  27. Results EE5359 Multimedia Processing

  28. Results Figure 13 : RD- Plot for RaceHorses_416x240_30.yuv EE5359 Multimedia Processing

  29. Results Figure 14 : QP vs PSNR comparison plot for RaceHorses_416x240_30.yuv EE5359 Multimedia Processing

  30. Results Figure 15 : QP vs Encoding time comparison Plot for RaceHorses_416x240_30.yuv EE5359 Multimedia Processing

  31. Results EE5359 Multimedia Processing

  32. Results Figure 16 : RD- Plot for ParkScene_1920x1080_24.yuv EE5359 Multimedia Processing

  33. Results Figure 17: QP vs PSNR comparison Plot for ParkScene_1920x1080_24.yuv EE5359 Multimedia Processing

  34. Results Figure 18: QP vs Encoding time comparison Plot for ParkScene_1920x1080_24.yuv EE5359 Multimedia Processing

  35. Results EE5359 Multimedia Processing

  36. Results Figure 19: RD-Plot for Kimono_1920x1080_24.yuv EE5359 Multimedia Processing

  37. Results Figure 20: QP vs PSNR comparison plot for Kimono_1920x1080_24.yuv EE5359 Multimedia Processing

  38. Results Figure 21: QP vs Encoding time comparison plot for Kimono_1920x1080_24.yuv EE5359 Multimedia Processing

  39. Results EE5359 Multimedia Processing

  40. Results Figure 22: RD-Plot for football30_cif_90.yuv EE5359 Multimedia Processing

  41. Results Figure 23: QP vs PSNR comparison plot for football30_cif_90.yuv EE5359 Multimedia Processing

  42. Results Figure 24: QP vs Encoding time comparison Plot for football30_cif_90.yuv EE5359 Multimedia Processing

  43. Results EE5359 Multimedia Processing

  44. Results Figure 25: RD-Plot for BasketballDrill_832x480_50.yuv EE5359 Multimedia Processing

  45. Results Figure 26: QP vs PSNR comparison plot for BasketballDrill_832x480_50.yuv EE5359 Multimedia Processing

  46. Results Figure 27: QP vs Encoding time comparison Plot for BasketballDrill_832x480_50.yuv EE5359 Multimedia Processing

  47. Results EE5359 Multimedia Processing

  48. Results Figure 28: BD-PSNR Comparison with and without blocking artifacts EE5359 Multimedia Processing

  49. Results Figure 29: %BD-Bit rate comparison with and without blocking artifacts EE5359 Multimedia Processing

  50. Conclusion and Future Work • RD plots infer that after the blocking artifacts are reduced in a sequence , PSNR increases where as Bit rate also increases. This is a drawback. • As the Quantization Parameter is increased the encoding time decreases. • BD-Bit rate plot indicates that there is 0.578%increase in average BD-bit rate with reduction of blocking artifacts. • BD-PSNR indicates that there is an average of 1.67dBincrease in BD-PSNR with reduction of blocking artifacts. • Future work has to be done to decrease the bit rate and encoding time. EE5359 Multimedia Processing