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1 (JBE Vol. 23, No. 2, March 2018) (Regular Paper) 23 2, (JBE Vol. 23, No. 2, March 2018) ISSN (Online) ISSN (Print) - a), a) Enhanced Fast Luma Adjustment for High Dynamic Range Television Broadcasting Kyung Seok Oh a) and Yong-Goo Kim a) Taylor, 600~3,900 cd/m2. -,.., -,, Taylor, t-psnr 4.65dB. Abstract Highly non-linear electro-optical transfer function of the Perceptual Quantizer was approximated by a truncated Taylor series, resulting in a closed form solution for luma adjustment. This previous solution is fast and quite suitable for the hardware implementation of luma adjustment, but the approximation error becomes relatively large in the range of 600~3,900 cd/m2 linear light. In order to reduce such approximation error, we propose a new linear model, for which a correction is performed on the position and the slope of line based on the scope of approximation. In order to verify the approximation capability of the proposed linear model, a comparative study on the luma adjustment schemes was conducted using various high dynamic range test video sequences. Via the comparative study, we identified a significant performance enhancement over the previous fast luma adjustment scheme, where a 4.65dB of adjusted luma t-psnr gain was obtained for a test sequence having a large portion of saturated color pixels. Keyword : HDR TV, Perceptual Quantizer, HDR 10, Luma Adjustment, Chroma Subsampling a) (Dept. of Newmedia, Seoul Media Institute of Technology) Corresponding Author : (Yong-Goo, KIM) ygkim@smit.ac.kr Tel: ORCID: Manuscript received February 23, 2018; Revised March 14, 2018; Accepted March 14, Copyright 2016 Korean Institute of Broadcast and Media Engineers. All rights reserved. This is an Open-Access article distributed under the terms of the Creative Commons BY-NC-ND ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited and not altered.

2 1: - (Kyung Seok Oh et al.: Enhanced Fast Luma Adjustment for High Dynamic Range Television Broadcasting). -. [1], -,. -, ITU- R(International Telecommunication Union Radio communication sector) SG6(Study Group 6) HDR(High Dynamic Range) TV [2], 2014 SMPTE(Society of Motion Picture & Television Engineers) - [3]. DVB(Digital Video Broadcasting) CM-AVC(Commercial Module Advanced Video Coding) HDR, HDR, HDR 80 HDR, 2018 SDR(Standard Dynamic Range) TV HDR HDR TV. HDR, DECE(Digital Entertainment Content Ecosystems) 2015, HDR10, [4]. (PQ Perceptual Quantizer) [3] 4:2:0 (Non-Constant) YCbCr BT [5] 10-bit. BT.709 [6] YCbCr 8-bit 4:2:0 HDR, PQ - YCbCr - -. MPEG(Moving Picture Experts Group) [7-8], -. HDR10, J. Strom [9]. YCbCr - -(Sub-sampling) - (Y) 4:2:0 YCbCr 4:4:4., A. Norkin [10]. Taylor - 1,. [9] [10] HDR10 H.264 AVC(Advanced Video Coding) [11] / H.265 HEVC (High Efficiency Video Coding) [12] / / MPEG [13]. Taylor 1.,.. HDR,.,,.,

3 (JBE Vol. 23, No. 2, March 2018).. HDR [13] HDR -, [13] / 4:4:4 RGB ( ), - [2],, / DECE [4] (ST 2084, Y CbCr 4:2:0, 10-bit) -. ( ), ST 2084 [3] - OETF(Opto-Electrical Transfer Function) - R G B, OETF HVS(Human Visual System). BT.709 [6] BT.2020 [5] OETF -(Power Function),. m= , n= , c 1 = , c 2 = , c 3 = , X 0~1 R, G, B. - R G B - Y CbCr, [13] Fig. 1. Conventional Signal Conversion Process for HDR Video [13]

4 1: - (Kyung Seok Oh et al.: Enhanced Fast Luma Adjustment for High Dynamic Range Television Broadcasting), wx - -(color gamut). Y CbCr - Y Q,Cb Q,Cr Q, 10. E scale of f set, C(a, b, c) c a a, c b b, c, R(a) a (Rounding), (scale, offset) E Y ( D Y Q ) E Cb Cr (, D Cb Q Cr Q ) (876, 64) (896, 512). - 4:2:0 Y Q,Cb QS,Cr QS. HVS, - -(subsample). [13] - (4), [2] [5] Y (co-sited) -., x[n] Cb Q Cr Q, n -.,, 2 2., f 1 (0.5rad/sample 6dB ), f 0. f 1, f 0 MPEG - [14] -. -, - Y Q,Cb QS,Cr QS 4:2:0 / [13] Fig. 2. Characteristics of the Low-Pass Filters for Chroma Subsampling [13]

(JBE Vol. 23, No. 2, March 2018), - - -. 2. -, 1 - ( ). - / 10 bit 4:2:0-4:4:4.

ST 2084 EOTF (Electro-Optical Transfer Function). - /, - - -, -. 3. 3 RGB /, 1,000x1,000, 1,.

5 (JBE Vol. 23, No. 2, March 2018), , 1 - ( ). - / 10 bit 4:2:0-4:4:4. - -, -, (4) [b -1, b 0, b 1, b 2 ] = [-1, 9, 9, -1]/16 ( 0 1 ). - 4:4:4, - - (, 10 ), (5) -, (2) - -. ST 2084 EOTF (Electro-Optical Transfer Function). - /, - - -, RGB /, 1,000x1,000, 1,. x, y CIE(International Commission on Illumination) xy-, z. 3,,,, -(Color Gamut), - [9-10] RGB Fig. 3. Luminance Error in Linear RGB by Chroma Subsampling, 1 (/ ), , Y, Cb, Cr - -, Cb Cr - -. (5) 3,

6 1: - (Kyung Seok Oh et al.: Enhanced Fast Luma Adjustment for High Dynamic Range Television Broadcasting)., -, (7) - (8) -., a RCr, a GCb, a GCr, a BCb RGB -., R, G, B.. [9] J. Strom Y Q (11), 2~3. (5) ~ (11). [10], Taylor. (8) (10) EOTF Taylor. - (10) EOTF, ( (10) (1) ),, V ( ) V( ), X = R,G,B. (12) EOTF (11) (13)., R, G, B (9), (13) Y new 0, (15).. max,

7 (JBE Vol. 23, No. 2, March 2018), (11) (12) (15)., (12) Taylor ST 2084 EOTF,. 1. Taylor,, (),., ST 2084 EOTF, 4 3 (0.1~0.3, 0.7~0.9, 0.95~1.0) (12)., 0.1~ ~1.0 EOTF 0., 0.7~0.9 EOTF (16) Taylor, X. 0.7~ ~0.39, ST ~10,000cd/m2, 600~3,900cd/m2. - 2,000~4,000cd/m2, 0.7~0.9 HDR, Taylor Fig. 4. Approximation Error of the PQ-EOTF using Truncated Taylor Series Expansion

8 1: - (Kyung Seok Oh et al.: Enhanced Fast Luma Adjustment for High Dynamic Range Television Broadcasting), ST 2084 EOTF (Convex- ity). ( ), Taylor. (12).,,,. Taylor, 5. 5, 4 0.7~0.9, (12) Taylor (17)., Taylor. (, (0.7, V(0.7)), (0.9, V(0.9))),.,, Taylor., (17) X,.. 5. = [0.7, 0.9] Fig. 5. Illustration of the Proposed Linear Approximation when = [0.7, 0.9]

9 (JBE Vol. 23, No. 2, March 2018) (X = R, G, B ) (9) Y new, Y (20), Y new (9) R, G, B (11), (18) 0~1 r., (17) (11), (11) Y new (21)., F (22).., ( [9], [10]]., MPEG -/ -, BT.709 [6] - 6. MPEG 6. Fig. 6. Test Sequences used for the Comparative Study

10 1: - (Kyung Seok Oh et al.: Enhanced Fast Luma Adjustment for High Dynamic Range Television Broadcasting) 1. Table 1. Detailed Information on the Test Sequences Sequence Name Frames Gamut Characteristics FireEater2Clip4000r1_1920x1080p_25_hf_709_444_xxxxx.exr Market3Clip4000r2_1920x1080p_50_hf_709_444_xxxxx.exr Tibul2Clip4000r1_1920x1080p_30_hf_709_444_xxxxx.exr Ground_1440x1080_60_hf_709_xxx.exr PanoHD_1920x1080_60_hf_709_xxx.exr * xxxxx means the frame number of each exr file Saturated B and C, M(small) Saturated R(small), B, C, M, Y Saturated Black and White No Saturation Saturated B and C (small) 2. (: db) Table 2. Comparison Results for Each Luma Adjustment Schemes (unit: db) Test Sequence No Adj. (tpsnr-y) Interative Adj. [9] Fast Adj. [10] Proposed FireEater2 Market3 Tibul2 Ground PanoHD (0.4) (0.3) (0.7) (0.9) (0.6) Average BT.709, 1 /-, 3, BT ). BT BT.709 4,000cd/m2 16- [15] OpenEXR [16]. 1, -, () tpsnr(annex F [14] ) (, tpsnr-y), (No Adj.) (, tpsnr-y ). 2, 1.78dB, 1.18dB ( 2.96 db)., (18) r., 7 Tibul2 Market3 0~1., 0~1 ( )., 7 ( ), 1) BT.2020 (, BT.709 ), 8 (a) Ground -, 2 Ground.

11 (JBE Vol. 23, No. 2, March 2018). 2, 4.65dB(PanoHD ),., 2 Ground,, /. / Market3, 14.26dB( [10] ) 16.53dB( [9] ), Ground / ( 2 No Adj., 49.64dB, ),. /, 8 Ground Market3 -. CIE-xy +,. 7. Fig. 7. Test Sequences used for the Comparative Study 8. Ground Market3 - Fig. 8. Plots of Pixel Positions in Color Gamut for the Test Sequences Ground and Market3

, Market3 Blue, Cyan, Magenta Yellow. / [7-10],., ( 9 ). (, ) - ( 10 ), -.

12 1: - (Kyung Seok Oh et al.: Enhanced Fast Luma Adjustment for High Dynamic Range Television Broadcasting), 1 -, Ground - (- )., Market3 Blue, Cyan, Magenta Yellow. / [7-10],., ( 9 ). (, ) - ( 10 ), -., 8 - Ground Market3 Cb(Chrominance blue) , Ground Market3, - 9. Ground Market3 Cb Fig. 9. Cb Images for the Test Sequence Ground and Market3 10. Ground Market3 Cb Fig. 10. Cb Images for the Test Sequence Ground and Market3

13 (JBE Vol. 23, No. 2, March 2018), , 10 Ground Market Cb Q - -, Market3.,, 2,,.. Taylor EOTF,. EOTF,.,, (References) [1] Peter G. J. Barten, Contrast sensitivity of the human eye and its effects on image quality, SPIE Press, [2] ITU-R, Image parameter vlaues for high dynamic range television for use in production and international programme exchange, Rec. ITU-R BT.2100, [3] SMPTE, High dyamic range electro-optical transfer function of mastering reference displays, ST 2084, [4] DECE, Common file format & media formats specification, Version 2.1, [5] ITU-R, Parameter values for ultra-high definition television systems for production and international programme exchange, Rec. ITU-R BT , [6] ITU-R, Parameter values for the HDTV standards for production and international programme exchange, Rec. ITU-R BT.709-6, [7] J. Stessen, R. Nijland, R. Brondjik, R. Grois, Chromaticity based color signals for wide color gamut and high dynamic range, ISO/IEC doc. m35065, France, [8] J. Strom, Investigation of HDR color subsampling, ISO/IEC doc. m35841, Switzerland, [9] J. Strom, J. Samuelsson, and K. Dovstam, Luma adjustment for high dynamic range video, in Proc. of IEEE Data Compression Conf. (DCC), Snowbird, USA, pp , [10] A. Norkin, Fast algorithm for HDR video pre-processing, in Proc. of IEEE Data Compression Conf. (DCC), Snowbird, USA, pp , [11] ITU-T, Advanced video coding for generic audiovisual services, Rec. ITU-T H.264, [12] ITU-T, High efficiency video coding, Rec. ITU-T H.265, [13] ISO/IEC, Conversion and coding practices for HDR/WCG Y CbCr 4:2:0 video with PQ transfer characteristics, ISO/IEC doc. N16505, [14] ISO/IEC, Call for Evidence (CfE) for HDR and WCG Video Coding, ISO/IEC doc. N15083, [15] IEEE, IEEE Standard for Floating-Point Arithmetic, IEEE , [16] F. Kainz, R. Borgart, P. Stanczyk, and P. Hillman, Technical Introduction to OpenEXR, Lucas Digital Ltd. LLC., 2013, com.

14 1: - (Kyung Seok Oh et al.: Enhanced Fast Luma Adjustment for High Dynamic Range Television Broadcasting) : : ~ 2007 : () / ~ 2017 : () / ~ : () / ~ : - ORCID : - :,, : : : ~ 2006 : / ~ : SMIT - ORCID : - :,,, -

(JBE Vol. 21, No. 1, January 2016) (Regular Paper) 21 1, (JBE Vol. 21, No. 1, January 2016) ISSN 228

(JBE Vol. 21, No. 1, January 2016) (Regular Paper) 21 1, (JBE Vol. 21, No. 1, January 2016) ISSN 228 (JBE Vol. 1, No. 1, January 016) (Regular Paper) 1 1, 016 1 (JBE Vol. 1, No. 1, January 016) http://dx.doi.org/10.5909/jbe.016.1.1.60 ISSN 87-9137 (Online) ISSN 16-7953 (Print) a), a) An Efficient Method