08김현휘_ok.hwp

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1 (Regular Paper) 21 3, (JBE Vol. 21, No. 3, May 2016) ISSN (Online) ISSN (Print) a), a) An Audio Coding Technique Employing the Inter-channel Phase Difference Skip Hyun-Hwi Kim a) and Rin-Chul Kim a) / (USAC) MPEG (IPD). IPD.. IPD, IPD 0. 38%, MUSHRA. Abstract This paper deals with an efficient method for skipping inter-channel phase differences (IPD) in the MPEG surround of the unified speech and audio coding (USAC). Based on the psycho-acoustic sensitivity on the IPD, we estimate a threshold on IPD, below which we can not notice degradation in spatial cue. We propose an IPD skip method, in which any IPDs within the threshold are set to zero and are not transmitted. The proposed IPD skip method gives about 38% savings in terms of bit amount for IPD. Nevertheless, in the MUSHRA test, the proposed method does not show any noticeable degradation in the decoded audio quality. Keyword : MPEG Surround(MPS), Unified speech and audio coding(usac), Inter-channel phase difference(ipd), Overall phase difference(opd) a) (Dept. of ECE, Univ. of Seoul) Corresponding Author : (Rin-Chul Kim) rin@uos.ac.kr Tel: ORCID: Manuscript received September 4, 2015; Revised May 4, 2016; Accepted May 23, MPEG (MPS : MPEG Surround) [1] (SAC : spatial audio coding) / (USAC : unified speech and audio coding) [2]. MPS

2 (JBE Vol. 21, No. 3, May 2016) (CLD : inter-channel level difference), (ICC : inter-channel correlation), (IPD : inter-channel phase difference), (OPD : overall phase difference). IPD (ITD : inter-channel time difference) ITD SAC (BCC : binaural cue coding) [3]. MPS MPS [4]. CLD.,,, CLD (1). log CLD ICC. ICC bsphasecoding = 0 IPD, bsphasecoding = 1 IPD. IPD ICC (2). ICC , 0, 1. ICC. IPD OPD, 0. IPD ICC (3).

3 CLD IPD [5].,. 2. ICC 0 1. IPD. 0, 1. ICC IPD OPD. (2) (3) 8. IPD. IPD (4). Coarse Fine, 8, 16. IPD. OPD. OPD,. OPD (5). OPD..,,,,,, (6), (7), (8), (9). arccos arctan tan,,, (10).,, CLD ICC. 1. cos sin cos sin

4 (JBE Vol. 21, No. 3, May 2016),, IPD ITD (11). 1. Fig. 1. Up-mixing representation without phase IPD OPD. OPD, OPD IPD. ITD ITD. IPD 0 0 ± IPD. IPD. IPD 4, MPEG USAC. 1. Table 1. Test samples 3. IPD ITD,. ITD IPD IPD [6]. ITD 0.6ms 1.66kHz. ITD ITD.. IPD ITD. IPD,

5 1.5kHz IPD 2. 3,,.. 2 IPD. Music_ ±IPD. IPD ITD.., 2(a). 2(b). 2(c).,, IPD, 2. IPD Table 2. Sustainability of IPD Parameters

6 (JBE Vol. 21, No. 3, May 2016). 2(d). ITD IPD IPD. IPD, OPD. 4. ICC. 2.. (). (). (). (). Fig. 2. Perception of time difference in actual listening environment. () Time difference of single parameter band. () Time difference of series parameter bands with non-sustained IPD parameters. () Time difference of series parameter bands with sustained IPD parameters. () Case of increasing time difference with series parameter bands

7 , 225Hz 125, 715Hz 50 ITD [7][8]. 1 ICC ITD. 2~4 1, 5~ ± IPD Fine -/4, / , ITD. IPD,. ITD ITD. IPD 0.. IPD 0 IPD USAC IPD bsphasemode 0 IPD 0. IPD 3. Fig. 3. Phase alteration terms

8 (JBE Vol. 21, No. 3, May 2016). IPD. 2. -/4, /4 IPD. IPD IPD 0 ITD. IPD IPD. ITD. 3. IPD IPD 0. 1, /. 4. 4(a) 4(b). 4(c). 3 bsphasemode 0. bsphasemode 0 IPD. IPD IPD Coarse 38, Fine 48 1., IPD Fine Coarse. USAC IPD 4. Fig. 4. Proposed bit stream structure

9 3. Table 3. Bit efficiency IPD 0. louis_raquin_15, HarryPotter 0 HarryPotter. es01, twinkle_ff51, SpeechOverMusic_1, 4. twinkle_ff ±IPD. Arirang_speech, te15, Music_1, 3. 38% 24kbps 1.39%. MUSHRA [9], IPD 3, 6 Sennheiser HD louis_raquin_15, Harry- Potter USAC IPD 0 0. SpeechOverMusic_1, Music_1 SpeechOverMusic_4, Music_3. SpeechOverMusic_4, twinkle_ff51.

10 (JBE Vol. 21, No. 3, May 2016) 5. MUSHRA Fig. 5. MUSHRA test result USAC IPD 0, 0. es01 0. Arirang_ speech, te15, Music_3. Arirang_speech, Music_3 0...,. MUSHRA.. (References) [1] ISO/IEC : Information technology MPEG audio technologies Part 1 : MPEG Surround, [2] ISO/IEC : Information technology MPEG audio technologies Part 3 : Unified speech and audio coding, [3] C. Faller and F. Baumgarte, Binaural cue coding part I : psychoacoustic fundamentals and design principles, IEEE Trans. On Speech and Audio Proc., vol. 11, no. 6, pp , [4] J. Breebaart, G. Hotho, J. Koppens, E. Schuijers, W. Oomen, and S. van de Par, Background, concept, and architecture for recent MPEG surround standard on multichannel audio compression, J. Audio Eng. Soc. Vol. 55, no. 5, pp , [5] J. Kim, E. Oh, and J. Robilliard, Enhanced stereo coding with phase parameters for MPEG unified speech and audio coding, AES 127th Convention, paper no. 7875, [6] J. Breebaart, S. van de Par, A. Kohlrausch, and E. Schuijers, Parametric coding of stereo audio, EURASIP J. Appl. Signal Process., vol. 9, pp , [7] B. Rakerd and W. Hartmann, Localization of sound in room. V. Binaural coherence and human sensitivity to interaural time differences in noise, J. Acoust. Soc. Am. Vol. 128, no. 5, pp , [8] McFadden D., Jeffress L. A., and Lakey J. R, Differences in interaural phase and level in detection and lateralization : 1000 and 2000 Hz, J. Acoust. Soc. Am. 52, , [9] ITU-R BS , Method for the subjective assessment of intermediate sound quality(mushra), 2011.

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