Giá trị của phương pháp đánh giá khách quan sử dụng PSNR có thể chuyển đổi tương đương sang điểm MOS của đánh giá chủ quan
Bảng 18 Chuyển đổi giá trị PSNR sang MOS
STT PSNR(dB) MOS 1 >37 5 Rất tốt 2 31÷37 4 Tốt 3 25÷31 3 Trung bình 4 20÷25 2 xấu 5 <20 1 Rất xấu
C.4 Các tham số đối với MobileTV
STT Các tham số EDGE TV 3G TV Mobile HDTV
1. Băng thông cho một kênh
56Kbps 100Kbps 256Kbps
2. Độ phân giải QCIF(176*144) QCIF(176*144) QVGA(320*240)
3. Video Codec H263 MPEG4 MPEG4/H264
4. Audio Codec AMR AMR hoặc AAC AMR hoặc AAC
5. Tốc độ hình/giây 5-7 6,5-15 >15
6. Phương thức truyền thông tin
Streaming Streaming Streaming
C.5 Đánh giá độ lệch hình và tiếng
Độ lệch tiếng không được nhanh hơn hình 15ms hoặc không chậm hơn 45ms theo ATSC IS191, Bởi cảm nhận của người xem nhạy cảm với trễ tiếng hơn là nhanh. Chất
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lượng tiếng đánh giá theo độ lệch hình và tiếng biểu diễn bằng MOS như Hình 52
0 10 20 30 40 50 60 -200 -150 -100 -50 0 50 100 150 200
Audio lags video ---ms--- Audio leads video
Q u alit y s co re ( 0- 50 )
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TÀI LIỆU THAM KHẢO
[1] http://www.chiariglione.org/mpeg/
[2] ITU-R BT.500-13 Methodology for the subjective assessment of the qualityof television pictures
[3] ITU-T P.910 - Subjective video quality assessment methods for multimedia applications.
[4] ITU-R BT.1788 - Methodology for the subjective assessment of video quality in multimedia applications.
[5] ITU – T J.247 - Objective perceptual multimedia video quality measurement in the presence of a full reference
[6] VQEG Final Report of HDTV Phase I Validation Test (2010), “Video Quality Experts Group: report on the validation of video quality models for high definition
video content”, Video Quality Experts Group (VQEG),
http://www.its.bldrdoc.gov/vqeg/projects/hdtv
[7] Making a ‘Completely Blind’ Image Quality Analyzer, Anish Mittal, Rajiv Soundararajan and Alan C. Bovik, Fellow, IEEE.
[8] A metric for continuous quality evaluation of compressed video with severe distortion, Masry, M., Hemami, S., Signal Processing: Image Communication 2004 [9] Comparing Subjective Image Quality Measurement Methods for the Creation of Public Databases, Judith Redi,Hantao Liub, Hani lers, Rodolfo Zuninoa, and Ingrid Heynderickxb,University of Genoa, DIBE, Via Opera Pia 11a, Genova, Italy 16145 Delft University of Technology, Mekelweg 4, Delft, The Netherlands 2628 CD Philips Research Laboratories, Prof. Holstlaan 4, Eindhoven, The Netherlands 5656 AA
[10] D. L. Ruderman, “The statistics of natural images,” Network Computation in Neural Syst., vol. 5, no. 4, pp. 517–548, 1994.
[11] A. Mittal, A. K. Moorthy, and A. C. Bovik, “No-reference image quality assessment in the spatial domain,” IEEE Trans. Image Process, 2012.
[12] ITU-T Recommendation J.144-2004, Objective Perceptual Video Quality Measurement Techniques for Digital Cable Television in the presence of a Full Reference.
[13] A. K. Moorthy and A. C. Bovik, “Statistics of natural image distortions,” in IEEE Int. Conf. Acoust. Speech Sig. Process., pp. 962–965.
[14] K. Sharifi and A. Leon-Garcia, “Estimation of shape parameter for generalized Gaussian distributions in subband decompositions of video,” IEEE Trans. Circ. Syst. Video Technol., vol. 5, no. 1, pp. 52–56, 1995.
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[15] Final Report from the Video Quality Experts Group on the validation of objective models of video quality assessment, VQEG 2000
[16] Z. Wang, A. C. Bovik and B. L. Evans, Blind measurement of blocking artifacts in images, Proc. IEEE Int. Conf. Image Proc., vol. 3, pp. 981-984, Sept. 2000.
[17] P. Gastaldo, S. Rovetta and R. Zunino, Objective assessment of MPEG-video quality: a neural-network approach, in Proc. IJCNN, vol. 2, pp. 1432-1437, 2001. [18] M. Knee, A robust, efficient and accurate single-ended picture quality measure for MPEG-2, available at http://www-ext.crc.ca/vqeg/frames.html, 2001.
[19] J. E. Caviedes, A. Drouot, A. Gesnot, and L. Rouvellou, Impairment metrics for digital video and their role in objective quality assessment,Proc. SPIE, vol. 4067, pp. 791-800, 2000.
[20] H. R. Sheikh, M. F. Sabir, and A. C. Bovik, “A statistical evaluation of recent full reference image quality assessment algorithms,” IEEE Trans Image Process, vol. 15, no. 11, pp. 3440–3451, 2006. [21] http://planet.com.vn/hotro/kienthuc/dichvumang/camera/Mpegvideo1 [22] http://www.vnpt.com.vn/ [23] http://vietteltelecom.vn/ [24] www.fpt.vn/ [25] www.vtc.com.vn/ [26] http://www.opticom.de [27] http://www.psytechnics.com [28] http://www.telchemy.com/vqmonsavm.html [29] http://www.telchemy.com/reference/draft-clark-avt-rtcpxr-video-01.pdf
[30] Stephen Wolf and Margaret H. Pinson, Low bandwidth reduced reference video quality monitoring system, Institute for Telecommunication Sciences (ITS), NTIA. [31] Hervé Benoit, “Digital Television- Satellite, Cable, Terrestrial, IPTV, Mobile TV in the DVB Framework - Third Edition”, Elsevier Focal Press, 2008
[32] [b-ITU-T G.114] Recommendation ITU-T G.114 (2003), One-way transmission time.
[33] [b-ITU-T H.261] Recommendation ITU-T H.261 (1993), Video codec for audiovisual services at p × 64 kbit/s.
[34] [b-ITU-T P.920] Recommendation ITU-T P.920 (1996), Interactive test methods for audiovisual communications.
[35] [b-ITU-T Handbook] ITU-T Handbook (1993), Handbook on Telephonometry, ITU, Geneva.
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[36] [b-ITU-R BT.812] Recommendation ITU-R BT.812 (1992), Subjective assessment of the quality of alphanumeric and graphic pictures in Teletext and similar services.
[37] [b-ITU-R BT.815-1] Recommendation ITU-R BT.815-1 (1994), Specification of a signal for measurement of the contrast ratio of displays.
[38] [b-CCIR Report 1213] CCIR Report 1213 (1990), Test pictures and sequences for subjective assessments of digital codecs, Annex to Volume XI, Part 1.
[39] [b-Gonzalez] Gonzalez, R.C. and Wintz, P. (1987), Digital Image Processing, 2nd Edition, Addison-Wesley Publishing Co., Reading, Massachusetts.
[40] [b-RACE] RACE Industrial Consortium Project 1018 HIVITS, WP B5, Picture Quality Measurement, 1988.
[41] [b-Snellen] Snellen Eye Chart.
[42] [b-Beck] Pseudo Isochromatic Plates (1940), engraved and printed by The Beck Engraving Co., Inc., Philadelphia and New York, United States.
[43] [b-Kirk] Kirk, R.E. (1982), Experimental Design – Procedures for the Behavioural Sciences, 2nd Edition, Brooks/Cole Publishing Co., California.