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1、 TECHNICAL REPORT T1.TR.75-2001 Technical Report on Objective Perceptual Video Quality Measurement Using a JND-Based Full Reference Technique Prepared by T1A1.1 Working Group on Multimedia Communications Coding and Performance Problem Solvers to the Telecommunications Industry A Word from ATIS and C

2、ommittee T1 Established in February 1984, Committee T1 develops technical standards, reports and requirements regarding interoperability of telecommunications networks at interfaces with end-user systems, carriers, information and enhanced-service providers, and customer premises equipment (CPE). Co

3、mmittee T1 is sponsored by ATIS and is accredited by ANSI. NOTE - The users attention is called to the possibility that implementation of this Technical Report may require use of an invention covered by patent rights. By publication of this Technical Report, no position is taken with respect to the

4、validity of this claim or of any patent rights in conjunction therewith. The patent holder has, however, filed a statement of willingness to grant a license under these rights on reasonable and nondiscriminatory terms and conditions to applicants desiring to obtain such a license. Details may be obt

5、ained from the publisher. T1.TR.75-2001 Published by Alliance for Telecommunications Industry Solutions 1200 G Street, NW, Suite 500 Washington, DC 20005 Committee T1 is sponsored by the Alliance for Telecommunications Industry Solutions (ATIS) and accredited by the American National Standards Insti

6、tute (ANSI). Copyright 2002 by Alliance for Telecommunications Industry Solutions All rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. For information contact ATIS at 202

7、.628.6380. ATIS is online at . Printed in the United States of America. T1.TR.75-2001 Technical Report Objective Perceptual Video Quality Measurement Using a JND-Based Full Reference Technique Alliance for Telecommunications Industry Solutions Approved October 2001 Abstract There is an urgent indust

8、ry need for documentation of video quality metrics (VQM). To meet that need T1A1 has developed a series of Technical Reports specifying accuracy and cross calibration of video quality metrics (T1.TR.72-2001), normalization algorithms useful in implementing FR methods (T1.TR.73-2001), and VQM algorit

9、hms that are suitable for application in design, manufacturing, installation and servicing of video transmission systems incorporating compression techniques. PSNR is defined in T1.TR.74-2001. This Technical Report specifies a JND-based VQM utilizing the full reference technique. T1.TR.75-2001 Forew

10、ord Over the past ten years, the transmission of video using digital compression methods has progressed from limited video conferencing applications to widespread use in applications from high definition television to personal desktop computer communications. During this period there have been conti

11、nuing efforts by laboratories and standards organizations to develop objective measurement methods to be used for quality of service (QoS) testing. In the mid 1990s a series of three standards - T1.801.01-1995 (R2001), T1.801.02-1996 (R2001), and T1.801.03-1996 - were issued by T1 providing backgrou

12、nd information and an extensive list of parametric calculations to be used in video performance assessment. While those standards have not led to the development of commercially available measurement instruments they have provided the basis for further research as well as the commonly used definitio

13、n of peak signal to noise ratio (PSNR). As part of the industry-wide effort to develop video QoS measurements, three methodological approaches have been defined. Full Reference (FR) - A method applicable when the full reference video signal is available. This is a double-ended method and is the subj

14、ect of this Technical Report. Reduced Reference (RR) - A method applicable when only reduced video reference information is available. This is also a double-ended method. No Reference (NR) - A method applicable when no reference video signal or information is available. This is a single-ended method

15、. It is generally believed that the FR method will provide the most accurate measurement results while the RR and NR methods will be more convenient for QoS monitoring. To address the validation and comparison of video quality metrics, the Video Quality Experts Group (VQEG) was formed in 1997 as an

16、informal subgroup of the ITU-T and ITU-R. VQEG members are experts from various backgrounds and affiliations, including participants from several internationally recognized organizations working in video quality assessment. Over a two-year period VQEG designed and implemented extensive subjective an

17、d objective test plans to evaluate a number of perceptually based proponent algorithms for the FR method including the commonly used definition of peak signal to noise ratio (PSNR) as specified in T1.801.03. Analysis of the Phase 1 VQEG tests determined that none of the nine proponent models statist

18、ically out-performed any of the others nor were they statistically better than PSNR. In addition, none of the models were deemed good enough to be recommended to the ITU at that time There is an urgent industry need for documentation of video quality metrics (VQM). To meet that need T1A1 has develop

19、ed a series of Technical Reports specifying accuracy and cross calibration of video quality metrics (T1.TR.72-2001), normalization algorithms useful in implementing FR methods (T1.TR.73-2001), and VQM algorithms that are suitable for application in design, manufacturing, installation and servicing o

20、f video transmission systems incorporating compression techniques. PSNR is defined in Technical Report T1.TR.74-2001. This Technical Report specifies the JND-based VQM closely related to one of the proponent methods included in the VQEG tests. Suggestions for improving this technical report are welc

21、ome and should be sent to the Alliance for Telecommunications Industry Solutions - Committee T1 Secretariat, 1200 G Street N.W., Suite 500, Washington, D.C. 20005. At the time this report was completed, the following were the contributors: ii T1.TR.75-2001 Name Affiliation Ahmad Ansari SBC Michael H

22、. Brill Sarnoff Corporation Greg Cermak Verizon Phil Corriveau CRC Pierre Costa SBC David Fibush Tektronix John Grigg Qwest Jeffrey Lubin Sarnoff Corporation Harley Myler University of Central Florida John Pearson Sarnoff Corporation Debra Phillips SBC Margaret Pinson NTIA Dick Streeter CBS Stephen

23、Voran NTIA A. B. Watson NASA Ames Research Center Alexander Woerner Rohde luminance and color gain changes; luminance and color DC level changes; and component or luminance to color channel-to-channel delay offset. Because these changes could produce changes in perceived picture quality, they shall

24、be reported as part of test results. It is necessary to separate these changes from the PQR calculation for two reasons. The main reason is to provide the most accurate PQR value. Second, such normalization corresponds closely with typical system operation for the gain and DC level parameters where

25、appropriate adjustments are generally available and routinely made. Small values of picture shift, horizontally or vertically, are generally not considered to change perceived picture quality. However, their presence is a picture error and will produce significant problems in multi-generation applic

26、ations. Temporal alignment must be perfect so each processed field/frame is compared with the equivalent reference. Processed video is normalized on a field-by-field basis by measurement of calibrated test signals embedded in the reference sequence. Only time-invariant static changes in the video ar

27、e removed, dynamic changes due to the compression and decompression processes are measured as part of the PQR calculation. Normalization of the processed video prior to PQR calculations shall meet the tolerances shown in Table 1. PQR values based on normalization not meeting the tolerances of Table

28、1 will have less accuracy than specified in 1.3.3. Table 1 - Normalization parameters and tolerance Parameter Normalization Tolerance Luminance level 0.008856L*= 903.3YYn forYYn0.008856(7) u*=13 L*( u u n) (8) v*= 13L*( v v n) (9)Here, 20 T1.TR.75-2001 u =4X(X + 15Y + 3Z)(10) v =9Y( X +15Y + 3Z)(11)

29、 u n=4Xn(Xn+15Yn+ 3Zn)(12) v n=9Yn( Xn+15Yn+ 3Zn)(13)Note that the coordinate L* does not enter the luminance computation. L* is used only in computing the chroma coordinates u* and v*.8Consequently, out of the above quantities, only u* and v* images are saved for further processing. 5.2 Luma Proces

30、sing See Figure 11. In this clause, input test and reference field images are denoted by Ikand Irefk(k = 0, 1, 2, 3). Pixel values in Ikand Irefkare denoted by Ik(i,j) and Irefk(i,j), respectively. They start out as Y tri-stimulus values computed in Front End Processing. Only the fields Ikare discus

31、sed in the following. Irefkprocessing is identical. k=3 denotes the most recent field in a 4-field sequence. Clauses 5.2.1 to 5.2.6 below describe full-height processing. Clause 5.2.7 discusses the modifications required for half-height processing. 5.2.1 Luma Compression The first step of the luma m

32、odel is a non-linearity comprising a decelerating power function offset by a constant. Let the relative-luminance array from the latest field be Y3(i,j), where 3 denotes the latest field. Then _ 8The luminance channel L*from CIELUV is not used in luma processing, but instead is replaced by a visual non-linearity for which the vision model has been calibrated over a range of luminance values. L* is used in chroma processing, however. to create a chroma metric that is approximately uniform and familiar to display engineers. 21