1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T J.147TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2002) SERIES J: CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Measurement of the quality of service Objective picture quality measurement method by use
2、of in-service test signals ITU-T Recommendation J.147 ITU-T J-SERIES RECOMMENDATIONS CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS General Recommendations J.1J.9 General specifications for analogue sound-programme transmission J.10J.19 Performance charac
3、teristics of analogue sound-programme circuits J.20J.29 Equipment and lines used for analogue sound-programme circuits J.30J.39 Digital encoders for analogue sound-programme signals J.40J.49 Digital transmission of sound-programme signals J.50J.59 Circuits for analogue television transmission J.60J.
4、69 Analogue television transmission over metallic lines and interconnection with radio-relay links J.70J.79 Digital transmission of television signals J.80J.89 Ancillary digital services for television transmission J.90J.99 Operational requirements and methods for television transmission J.100J.109
5、Interactive systems for digital television distribution J.110J.129 Transport of MPEG-2 signals on packetised networks J.130J.139 Measurement of the quality of service J.140J.149 Digital television distribution through local subscriber networks J.150J.159 IPCablecom J.160J.179 Miscellaneous J.180J.19
6、9 Application for Interactive Digital Television J.200J.209 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. J.147 (07/2002) i ITU-T Recommendation J.147 Objective picture quality measurement method by use of in-service test signals Summary This Recommendation prese
7、nts an objective picture quality measurement method by use of in-service test signals in a digital television network. This method is separated into three procedures: a) test signal generation at the transmission side using the invisible marker method; b) test signal detection at measurement points;
8、 and c) picture quality measurement using the result of test signal detection. A practical implementation is described in Appendix I, whilst the parameters for generating in-service test signals and the performance of this method are described in Appendices II and III, respectively. Source ITU-T Rec
9、ommendation J.147 was prepared by ITU-T Study Group 9 (2001-2004) and approved under the WTSA Resolution 1 procedure on 29 July 2002. ii ITU-T Rec. J.147 (07/2002) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. Th
10、e ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standa
11、rdization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information
12、technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INT
13、ELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights,
14、whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors ar
15、e cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2002 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. J.147 (07/
16、2002) iii CONTENTS Page 1 Scope 1 2 References. 1 2.1 Normative references 1 2.2 Informative references 1 3 Terms, definitions and acronyms 1 4 User requirements. 2 5 Recommended framework 2 Appendix I Description of implementation method . 3 I.1 Marker embedding 3 I.2 Marker detection. 5 I.3 Pictur
17、e quality measurement from the result of marker detection . 6 Appendix II Parameters for generating in-service test signals . 6 II.1 Marker intensity 6 II.2 Embedded bit 6 II.3 The number of embedded bits in a block . 6 II.4 Blocksize 7 II.5 PN sequences 7 II.6 Orthogonal transform and manipulation
18、of its coefficients 7 II.7 How to estimate picture quality from FDR 7 Appendix III Performance evaluation. 7 III.1 Experiment conditions 7 III.2 Experiment Result 8 III.2.1 Estimation accuracy 9 III.2.2 Degradation of the original picture caused by marker embedding. 9 iv ITU-T Rec. J.147 (07/2002) I
19、ntroduction The Reduced Reference (RR) and No Reference (NR) methods, which are currently being studied by an independent body, are expected to be covered in a future Recommendation for an objective measurement method of perceived picture quality that does not require reference pictures. This Recomm
20、endation recommends a different framework from RR or NR for measuring picture quality without reference pictures by use of in-service test signals. In-service test signals are embedded into the active picture area of television signals by using the invisible marker method. Television signals with te
21、st signals are transmitted to the receiver side and the test signals are detected from the received pictures. Degradation of the test signals is measured to estimate picture quality degradation. This framework does not require an additional circuit for reference information because the reference inf
22、ormation is already embedded into the transmitted pictures. It may be possible to apply this method also to audio signals to ensure that the correct audio and video is matched within a multichannel environment, to ensure that audio and video are properly synchronized, and to measure any asynchronies
23、, which are beyond the scope of this Recommendation. ITU-T Rec. J.147 (07/2002) 1 ITU-T Recommendation J.147 Objective picture quality measurement method by use of in-service test signals 1 Scope This Recommendation presents an objective picture quality measurement framework that works as an automat
24、ic quality monitoring system in a digital television network by use of in-service test signals. In-service test signals are applied for applications such as video transmission between different two locations. This method is applicable for either compressed or uncompressed transmission; however, this
25、 method is practical especially when lossy compression is applied in the transmission chain, because compression degradation masks degradation caused by test signals themselves. When PSNR is to be estimated by the method, it is a good idea to adapt the intensity of the test signals to the compressio
26、n bit rate (see Appendix III). This method is applicable, for example, to transmission between studios and to broadcasting to end receivers. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this R
27、ecommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other re
28、ferences listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. 2.1 Normative references ITU-T Recommendation J.143 (2000), User requ
29、irements for objective perceptual video quality measurements in digital cable television. 2.2 Informative references ITU-T Recommendation J.144 (2001), Objective perceptual video quality measurement techniques for digital cable television in the presence of a full reference. ITU-R Recommendation BT.
30、656-4 (1998), Interfaces for digital component video signals in 525-line and 625-line television systems operating at the 4:2:2 level of Recommendation ITU-R BT.601 (Part A). 3 Terms, definitions and acronyms This Recommendation uses the following abbreviations: DEC Decoder ENC Encoder FDR False Det
31、ection Rate PSNR Peak Signal-to-Noise Ratio WHT Walsh-Hadamard Transform XOR Exclusive OR 2 ITU-T Rec. J.147 (07/2002) 4 User requirements User requirements for perceptual measurement methods of picture quality are given in ITU-T Rec. J.143. 5 Recommended framework Configuration of the assumed trans
32、mission chain is shown in Figure 1. Figure 1 shows cascading connections of the transmission equipment (ENC and DEC). Either the compressed or uncompressed transmission can be applied for each single connection. A combination of compressed and uncompressed transmission connections can also be applie
33、d. J.147F01ENC DEC ENC DEC ENC DEC OutputInputInvisible markerembeddingMarkerdetectorMarkerdetectorMarkerdetector nPicture qualityCentral monitoring room QoS management of entire network Detection of impairment at each link point etc.Picture quality Picture qualityFigure 1/J.147 Configuration of tra
34、nsmission chain In-service test signals are embedded into input pictures and are detected at each link point of the cascading connection. Objective picture quality assessment score at each measurement point are transmitted to the central monitoring room via a dedicated circuit for remote monitoring
35、which is separately constructed from video transmission. Since the picture quality of each link point can be monitored at the central monitoring room, network operators can recognize at which point the picture quality degradation (i.e. transmission trouble) has occurred. In order to monitor picture
36、quality by this configuration, the following items are required: embedding in-service test signal into source pictures; test signals detection from received pictures; picture quality assessment from the result of marker detection. Appendix I describes a practical implementation. ITU-T Rec. J.147 (07
37、/2002) 3 Appendix I Description of implementation method1I.1 Marker embedding Invisible markers are embedded into the active picture area of the video signal. Ancillary data of the video signal (e.g. ITU-R Rec. BT.656-4) should be transmitted transparently. Marker embedding is performed at each pixe
38、l block. The selection of which and how many blocks the marker is embedded into is arbitrary. However, it is recommended to embed the markers into all the blocks in a frame/field when the measurement of an entire frame/field degradation is required. The procedure for marker embedding is shown in Fig
39、ure I.1. xB(n) denotes the input signal separated into pixel blocks. First, the spectrum of the signal xB(n) is spread by multiplying a PN sequence and then transform coefficients XSSs are derived by orthogonal transform. Invisible markers are embedded by choosing arbitrary frequency component siand
40、 manipulating those amplitude component Aiaccording to embedded bit embedded bitiand marker intensity Mi. The relationship between Ai, embedded bitiand Mi is shown in Tables I.1 and I.2. J.147F02SpreadspectrumOrthogonaltransformInverseorthogonal transformSpreadspectrumQuantizationembedded bitiMS = S
41、iS SiAi= XssSiAi= XssSixB(n) xB(n)Figure I.1/J.147 Marker embedding Table I.1/J.147 Relationship between Ai, embedded bitiand Mi embedded biti= 0 embedded biti= 1 MmiAMm+ 0. On the other hand, if Aimay be negative, the application of Table I.2 is recommended. J.147F031int(A / M )5M543213M MM3M 5M234
42、5AFigure I.2/J.147 Definition of int(x) J.147F041round(A / M )543212345AM29 M25 M21M21M25M29Figure I.3/J.147 Definition of round(x) ITU-T Rec. J.147 (07/2002) 5 When more than one markers are embedded, i.e. Nm 1, a different value of the embedded bitiand Mican be applied for each component i. After
43、manipulating the transform coefficient by the above procedures, inverse orthogonal transform and inverse spread spectrum are applied and spatial domain signal xB(n) is finally derived. I.2 Marker detection Invisible markers are detected at the receiver side and each link point of the transmission ch
44、ain (see Figure I.4). In the detection side, either of the following formulae are applied to iA to detect an embedded bit: 1)/int(0)/int(=iiiibit detectedoddMAbit detectedevenMAif Table I.1 is applied for embedding 1)/(round0)/(round=iiiibit detectedoddMAbit detectedevenMAif Table I.2 is applied for
45、 embedding where iA denotes the amplitude components of the signal of the received picture after spread spectrum. After detecting the binary information detected bitifrom the received picture, the embedded bitiand detected bitiare compared. When these two bits are different, i.e.: XOR (embedded biti
46、, detected biti) = 1 where XOR (a,b) denotes exclusive-OR between binary symbol a and b, the block is assumed to be falsely detected. False detection expresses that the transform coefficient iA has been changed more than the marker intensity Miand it implies that both the marker signal and video sig
47、nal are degraded by transmission. Thus, the degradation of the video signal can be detected based on the result of detection of the marker signals. In order to compare embedded and detected bits, the si, Mi, embedded biti and the information which block the marker is embedded should be shared betwee
48、n the transmission side and each link point. Furthermore, the PN sequence used for the spread spectrum should be common to all the measurement points. J.147F05SpreadspectrumOrthogonaltransformXORdetected bitembedded bitxB(n)TRUE/FALSEorAi = Xsssi2modroundMiA2modintMiAFigure I.4/J.147 Marker detectio
49、n 6 ITU-T Rec. J.147 (07/2002) I.3 Picture quality measurement from the result of marker detection Picture quality measurement of each frame/field is performed based on the result of marker detection. An arbitrary method can be applied to evaluate picture quality. In this clause, one example that uses the FDR (False Detection Rate) of the markers as a simple index for marker degradation is shown. FDR is defined in the following equation: frameain block
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