1、TECHNICAL REPORT IECTR 62251 First edition 2003-05 Multimedia systems and equipment Quality assessment Audio-video communication systems Reference number IEC/TR 62251:2003(E)Publication numbering As from 1 January 1997 all IEC publications are issued with a designation in the 60000 series. For examp
2、le, IEC 34-1 is now referred to as IEC 60034-1. Consolidated editions The IEC is now publishing consolidated versions of its publications. For example, edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the base publication incorporating amendment 1 and the base publicati
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8、n 2003-05 Multimedia systems and equipment Quality assessment Audio-video communication systems PRICE CODE IEC 2003 Copyright - all rights reserved No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, w
9、ithout permission in writing from the publisher. International Electrotechnical Commission, 3, rue de Varemb, PO Box 131, CH-1211 Geneva 20, Switzerland Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmailiec.ch Web: www.iec.ch W For price, see current catalogue Commission Electrotec
10、hnique Internationale International Electrotechnical Commission 2 TR 62251 IEC:2003(E) CONTENTS FOREWORD 4 1 Scope 5 2 References 5 3 Terms and definitions 6 4 Configuration for quality assessment . 6 4.1 Input and output channels. 6 4.2 Points of input and output terminals 7 5 Video quality 8 5.1 I
11、ntroduction 8 5.2 End-to-end tone reproduction . 9 5.3 End-to-end colour reproduction11 5.4 End-to-end colour differences12 5.5 End-to-end peak-signal to noise ratio (PSNR)16 5.6 End-to-end objective assessment of video quality20 6 Audio quality.21 6.1 Perceived audio quality with full-reference sig
12、nals.21 6.2 Sampling rate and quantization resolution .23 6.3 Delay.24 7 Total quality24 7.1 Synchronization of audio and video (lip sync) 24 7.2 Scalability25 7.3 Overall quality .26 Annex A (informative) PSNRs defined in three-dimensional spaces applied to hypothetical deterioration over the refer
13、ence video sources 27 Annex B (informative) End-to-end objective assessment of video quality in spatial frequency domain31 Annex C (informative) PEAQ objective measurement method outline .36 Bibliography40 Figure 1 Model of audio-video communication systems . 7 Figure 2 Schematic diagram for quality
14、 assessment 7 Figure 3 The image of the grey steps defined in IEC 61146-1 9 Figure 4 An example plot of tone reproduction 10 Figure 5 The image of the colour reproduction chart defined in IEC 61146-111 Figure 6 Colour differences between reference and streamed video frames at 250 kbps and 30 fps.15
15、Figure 7 Examples of PSNR assessment19 Figure 8 Basic concept for making objective measurements.22 Figure 9 Representation of PEAQ model 22 Figure B.1 Assignment of the block numbers31 Figure B.2 Example of wavelet decomposition visualised .31TR 62251 IEC:2003(E) 3 Figure B.3 Trends of difference of
16、 coefficients of wavelet transform between reference and streamed video frames at 250 kbps and 30 fps .34 Figure C.1 Basic concept for making objective measurements .36 Figure C.2 Representation of PEAQ model.37 Figure C.3 FFT based ear model, PEAQ basic version.37 Figure C.4 Filter bank based ear m
17、odel, PEAQ advanced version 38 Table 1 An example of tone reproduction .10 Table 2 An example of colour reproduction.12 Table 3 Grand averages of colour differences 16 Table 4 Overall PNSRs averaged over the frames.20 Table 5 Test items and resulting DI and ODG values for the basic version .23 Table
18、 6 Test items and resulting DI and ODG values for the advanced version 23 Table A.1 Reference video sources available for objective assessment27 Table A.2 PSNRs in various colour spaces and the colour difference for SRC13 and SRC14 .28 Table A.3 PSNRs in various colour spaces and the colour differen
19、ce for SRC15 and SRC16 .28 Table A.4 PSNRs in various colour spaces and the colour difference for SRC17 and SRC18 .29 Table A.5 PSNRs in various colour spaces and the colour difference for SRC19 and SRC20 .29 Table A.6 PSNRs in various colour spaces and the colour difference for SRC21 and SRC22 .30
20、Table B.1 Summary of difference of coefficients of wavelet coefficients35 Table C.1 Model output variables, PEAQ basic version 38 Table C.2 Model output variables, PEAQ advanced version .39 4 TR 62251 IEC:2003(E) INTERNATIONAL ELECTROTECHNICAL COMMISSION _ MULTIMEDIA SYSTEMS AND EQUIPMENT QUALITY AS
21、SESSMENT AUDIO-VIDEO COMMUNICATION SYSTEMS FOREWORD 1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote international co-operation on
22、all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, the IEC publishes International Standards. Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may pa
23、rticipate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreem
24、ent between the two organizations. 2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested National Committees. 3) The do
25、cuments produced have the form of recommendations for international use and are published in the form of standards, technical specifications, technical reports or guides and they are accepted by the National Committees in that sense. 4) In order to promote international unification, IEC National Com
26、mittees undertake to apply IEC International Standards transparently to the maximum extent possible in their national and regional standards. Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter. 5) The IEC provides no m
27、arking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with one of its standards. 6) Attention is drawn to the possibility that some of the elements of this technical report may be the subject of patent rights. The IEC shall not be
28、 held responsible for identifying any or all such patent rights. The main task of IEC technical committees is to prepare International Standards. However, a technical committee may propose the publication of a technical report when it has collected data of a different kind from that which is normall
29、y published as an International Standard, for example “state of the art“. Technical reports do not necessarily have to be reviewed until the data they provide are considered to be no longer valid or useful by the maintenance team. IEC 62251, which is a Technical Report, has been prepared by IEC tech
30、nical committee 100: Audio, Video and Multimedia Systems and Equipment. The text of this technical report is based on the following documents: Enquiry draft Report on voting 100/561/DTR 100/662/RVC Full information on the voting for the approval of this technical report can be found in the report on
31、 voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.TR 62251 IEC:2003(E) 5 MULTIMEDIA SYSTEMS AND EQUIPMENT QUALITY ASSESSMENT AUDIO-VIDEO COMMUNICATION SYSTEMS 1 Scope This Technical Report specifies items to be measured by objec
32、tive methods, methods of measurement together with measuring conditions, processing of the measured data and presentation of acquired information for objective assessment of end-to-end quality of audio- video communication systems over digital networks. The measurements are supposed to be conducted
33、in a double-ended and a full reference. The systems are assumed to have electrical interface channels at the input and at the output of audio-video signals for objective assessment. The extension for systems that do not have such channels is left for further study. 2 Normative references The followi
34、ng referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies IEC 60268-4, Sound system equipment Part 4: Microphones IEC 6
35、0268-5, Sound system equipment Part 5: Loudspeakers IEC 61146-1:1994, Video cameras (PAL/SECAM/NTSC) Methods of measurement Part 1: Non-broadcast single-sensor cameras IEC 61146-2:1997, Video cameras (PAL/SECAM/NTSC) Methods of measurement Part 2: Two- and three-sensor professional cameras IEC 61966
36、-2-1:1999, Multimedia systems and equipment Colour measurement and management Part 1: Colour management Default RGB colour space sRGB Amendment 1 (2003) IEC 61966-2-1, Multimedia systems and equipment Colour measurement and management Part 2-1: Colour management Default RGB colour space sRGB IEC 619
37、66-3:2000, Multimedia systems and equipment Colour measurement and manage- ment Part 3: Equipment using cathode ray tubes IEC 61966-4:2000, Multimedia systems and equipment Colour measurement and manage- ment Part 4: Equipment using liquid crystal display panels IEC 61966-5:2000, Multimedia systems
38、and equipment Colour measurement and manage- ment Part 5: Equipment using plasma display panels IEC 61966-9:2000, Multimedia systems and equipment Colour measurement and manage- ment Part 9: Digital cameras 6 TR 62251 IEC:2003(E) CIE 15.2:1986, Colorimetry ITU-R BS.1387-1 :2001, Method for objective
39、 measurements of perceived audio quality ITU-R BT.601-5 :1995,Studio encoding parameters of digital television for standard 4:3 and wide-screen 16:9 aspect ratios ITU-T J.144 :2001, Objective perceptual video quality measurement techniques for digital cable television in the presence of a full refer
40、ence ITU-T P.931 :1998, Multimedia communications delay, synchronization and frame rate measurement 3 Terms and definitions In order to understand this Technical Report, the following terms and definitions apply. 3.1 audio-video communication system system that handles audio, video and optionally ot
41、her data streams in a synchronized way within users perception in order to transmit and/or exchange information, which is assumed to operate over a local- or wide-area digital network 3.2 DMOS difference between the source and processed Mean Opinion Scores (MOS) resulting from the subjective testing
42、 experiment conducted by the Video Quality Expert Group (VQEG) 3.3 PEAQ perceived evaluation of audio quality defined by ITU-R BS.1387-1 3.4 PSNR objective video quality metric defined by peak-signal to noise ratio, the noise being calculated from the source and processed video frames 3.5 VQR object
43、ive video quality rating reduced from any objective metric by being optimally correlated with the DMOS 4 Configuration for quality assessment 4.1 Input and output channels Audio signal and video signal in audio-video streams shall be captured at the input and at the output channel, respectively, of
44、the audio-video communication system as shown in Figure 1.TR 62251 IEC:2003(E) 7 Camera Input Video channel Output Microphone Audio channel Display Loudspeaker Encoder Decoder Decoder Encoder IEC 1468/03 Figure 1 Model of audio-video communication systems 4.2 Points of input and output terminals In
45、the spirit of the end-to-end quality assessment of audio-video communication systems, the points for acquisition of raw data should be as far as ultimate end points as possible. However, since the methods of measurement and characterization for equipment which incorporates input transducers such as
46、video cameras and microphones have already been standardized, such as in IEC 61146-1, IEC 61146-2, IEC 61966-9 and IEC 60268-4, and the methods of measurement and characterization of equipment which incorporates output transducers such as video signal displays and loudspeakers, as in IEC 61966-3, IE
47、C 61966-4, IEC 61966-5 and IEC 60268-5, they can be outwith the scope of the rage of the end-to-end. Figure 2 shows a schematic diagram for quality assessment under double-ended and full reference conditions. 1 2 3 4 4 5 IEC 1469/03 Key 1 Original audio or video reference. 2 Pre-conditioner: reduced
48、 dynamic range, frequency range for audio; reduced frame size and frame rate for video to fit to the quality assessment of the audio-video communication systems, if necessary. 3 Encoder for network streaming with a specified bit-rate in order to fit to the bandwidth of end-to-end network connection.
49、 4 Decoder and rendering for the received data to make them audible and visible. 4 Rendering for the preconditioned data to make them audible and visible, optional. 5 Data acquisition and calculation for quality assessment to provide information specified in this report. Figure 2 Schematic diagram for quality assessment 8 TR 62251 IEC:2003(E) 5
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