1、 International Telecommunication Union ITU-T J.243 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2006) SERIES J: CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Measurement of the quality of service Requirements for operational monitoring in televisi
2、on programme transmission chains ITU-T Recommendation J.243 ITU-T Rec. J.243 (11/2006) i ITU-T Recommendation J.243 Requirements for operational monitoring in television programme transmission chains Summary In digital television programme transmission, more effective monitoring methods than the con
3、ventional methods that rely on human operators are needed. This Recommendation categorizes operational monitoring issues in television programme transmission chains and describes the requirements. Monitoring is classified into “status monitoring“ and “quality monitoring“, and their relevant issues a
4、re described. Based on this, user requirements for operational monitoring appropriate for digital transmission are described from the viewpoint of operators. Source ITU-T Recommendation J.243 was approved on 29 November 2006 by ITU-T Study Group 9 (2005-2008) under the ITU-T Recommendation A.8 proce
5、dure. ii ITU-T Rec. J.243 (11/2006) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical,
6、 operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in tu
7、rn, 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 technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOT
8、E In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e
9、.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not s
10、uggest that compliance with the Recommendation is required of any party. INTELLECTUAL 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 e
11、vidence, validity or applicability of claimed Intellectual Property Rights, 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, whic
12、h may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2007 All rights reserved. No part of this publication ma
13、y be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. J.243 (11/2006) iii CONTENTS Page 1 Scope 1 2 References. 1 2.1 Normative references 1 2.2 Informative references 1 3 Types of monitoring. 1 3.1 Status monitoring (test of physical signal conformance to
14、 standards and specifications). 2 3.2 Quality monitoring (assessment of perceptual quality for service contents). 2 4 Issues in operational monitoring. 2 4.1 Issues in status monitoring . 2 4.2 Issues in quality monitoring . 3 5 User requirements for operational monitoring . 3 5.1 Common requirement
15、s for status and quality monitoring 3 5.2 Requirements for status monitoring . 4 5.3 Requirements for quality monitoring . 4 5.4 Requirements for monitoring equipment 5 iv ITU-T Rec. J.243 (11/2006) Introduction Digital compression coding technologies have enabled the widespread growth of high-quali
16、ty multi- channel audiovisual services. Audiovisual signals after digital coding process have characteristics different from those of conventional analog signals, e.g., the perceptual quality depends on the content and the characteristics of the original signal, and the degradation due to digital co
17、mpression coding and transmission errors often occurs locally. In addition, digitalization has made systems more advanced and complex, and new services such as data broadcasting have emerged. Therefore, it has become difficult to manage the quality by conventional methods for monitoring analog syste
18、ms or subjective evaluation, and a new monitoring method is needed. This Recommendation describes user requirements for operational monitoring for digital television programme transmission chains based on quality monitoring/assessment technologies in broadcasting stations and communication carriers.
19、 ITU-T Rec. J.243 (11/2006) 1 ITU-T Recommendation J.243 Requirements for operational monitoring in television programme transmission chains 1 Scope This Recommendation describes user requirements for operational monitoring in digital television programme transmission chains. Monitoring issues are f
20、irst categorized into status monitoring and quality monitoring, and the requirements are itemized in each category. 2 References 2.1 Normative references None. 2.2 Informative references J.143 ITU-T Recommendation J.143 (2000), User requirements for objective perceptual video quality measurements in
21、 digital cable television. J.148 ITU-T Recommendation J.148 (2003), Requirements for an objective perceptual multimedia quality model. BS.1387 ITU-R Recommendation BS.1387-1 (2001), Method for objective measurements of perceived audio quality. BT.1204 ITU-R Recommendation BT.1204 (1995), Measuring m
22、ethods for digital video equipment with analogue input/output. BT.1683 ITU-R Recommendation BT.1683 (2004), Objective perceptual video quality measurement techniques for standard definition digital broadcast television in the presence of a full reference. BT.1720 ITU-R Recommendation BT.1720 (2005),
23、 Quality of service ranking and measurement methods for digital video broadcasting services delivered over broadband Internet protocol networks. 3 Types of monitoring Operational monitoring means to monitor whether the object is in the desired operational status or conforms to the standard or specif
24、ication. In this Recommendation, operational monitoring especially means in-service objective monitoring operation by equipment, not by human operators. It is categorized into status monitoring of physical signal levels and perceptual quality monitoring of audiovisual contents. Signals to be monitor
25、ed are categorized into the following three: Baseband signal (SDI, analog video and audio signals, etc.); Coded bit-stream (MPEG2-TS signals, etc.); Modulated signal (RF signals, etc.). 2 ITU-T Rec. J.243 (11/2006) 3.1 Status monitoring (test of physical signal conformance to standards and specifica
26、tions) Status monitoring means to monitor whether signals conform to certain standards or specifications, which means judgment by some physical quantity of in-service signals including the status of equipment and transmission links. Equipment and networks necessary for digital television transmissio
27、n are also monitored as to whether they are functioning appropriately. Applications of status monitoring include contribution such as transmission by communication networks, live relay and news gathering, production and post-production and master in a broadcasting station, and primary/secondary dist
28、ribution and emission (see Figure 1). Figure 1/J.243 Basic processes in a television programme transmission chain 3.2 Quality monitoring (assessment of perceptual quality for service contents) Quality monitoring means to monitor whether the perceptual quality of contents such as video, audio, data,
29、and characters conforms to a certain quality level, which depends on the applications intended by the providers. This Recommendation concerns monitoring of in-service contents by objective assessment instead of subjective assessment. The monitored points are those where subjective or objective quali
30、ty assessment by operators is possible. Applications of quality monitoring include broadcasting reception in addition to those for status monitoring (see Figure 1). It is important to include monitoring of the received signal because clock jitters and CRC errors are accumulated at each stage and som
31、etimes lead to degradation of final quality, even if each process in a transmission chain conforms to the standard. 4 Issues in operational monitoring 4.1 Issues in status monitoring 1) There are different causes of signal degradation, such as transmission errors, unlocked clock, improper original s
32、ignals, and malfunctioning of transmission links and equipment. It is difficult to identify the cause only by monitoring video and audio signals. 2) Errors may occur in video and audio signals even if the signals conform to standards and equipment is functioning normally. The causes of digital error
33、s are in general more difficult to identify than those of analog errors. For example, even if each piece of equipment conforms to its specification, clock jitters and CRC errors may accumulate at each process. 3) Black signals or silent signals may lead to false alarms by automatic monitoring equipm
34、ent even though they are intentional. ITU-T Rec. J.243 (11/2006) 3 4.2 Issues in quality monitoring 1) In digital audiovisual systems, very complex processing such as content-adaptive processing, switching between different operational modes, and change of bit rates is performed. In addition, the op
35、erational status of an encoder frequently changes. Therefore, the cause of degradation is very complicated. 2) The quality of digitally encoded video and audio signals depends on the characteristics and contents of the original signal, and tends to degrade locally. In addition, the degradation pecul
36、iar to digital coding such as blockiness is very different from analog degradation. Therefore, the conventional quality criteria for analog signals are not necessarily appropriate for judging the quality of digitally coded audiovisual signals. 3) In digital television transmission, various levels of
37、 quality of services can be provided in the same channel, according to bit rates and contents. Quality criteria may differ depending on services. 4) Quality management is not easy for format converters (e.g., up-converters, down- converters, frame rate converters, and aspect ratio converters) since
38、the input and output formats are different. 5) There may be problems in synchronizing video processing and audio processing. 6) Reception quality may be dependent on receivers due to different performance behaviours especially in the case of transmission errors. 5 User requirements for operational m
39、onitoring 5.1 Common requirements for status and quality monitoring In digital television transmission, bandwidth is very effectively used by compression coding of audiovisual contents, which is different from analog systems. Digital transmission has increased the number of channels and made various
40、 services possible. On the other hand, the transmission system has become so complex that the limited number of operators can no longer adequately monitor digital transmission equipment. The common requirements for status and quality monitoring, which are essential for reducing the operational burde
41、n and realizing advanced and flexible digital television transmission services, are as follows: 1) Capability of in-service monitoring; 2) Applicability to the video formats in use such as SDTV and HDTV; 3) Applicability to the numbers of audio channels in use; 4) Applicability to the coding bit rat
42、es in use, irrespective of variable bit rate (VBR) or constant bit rate (CBR); 5) Applicability to the transmission bit rates in use; 6) Applicability to the coding parameters and tools (e.g., profile/level, picture structure, range of motion vectors) in use; 7) Applicability to different signal pro
43、cessing such as compression coding, standards conversion and aspect ratio conversion; 8) Applicability to different sources of degradation (e.g., compression ratio and transmission error rate); 9) Applicability to different program contents; 10) Applicability to the system configurations in use; 11)
44、 Traceability of the causes of malfunction, failure and degradation; 4 ITU-T Rec. J.243 (11/2006) 12) Availability of precise information for switching to a reserve system from the monitoring result. 5.2 Requirements for status monitoring In digital television transmission chains, even if the monito
45、red signal conforms to its specification and each piece of equipment is functioning normally, errors sometimes occur in a later stage of the chain. It is highly desired to adapt to complex digital transmission systems and to support operators by the precise detection of errors and malfunctions of eq
46、uipment. The user requirements for status monitoring are as follows: 1) Ability to judge whether the signal, including RF characteristics and syntax, conforms to its specification; 2) Ability to detect any errors in the signal; 3) Ability to monitor the functioning status of equipment including malf
47、unctions; 4) Ability to detect errors and malfunctions precisely in a short time (preferably in real-time); 5) Ability to monitor each component and equipment in the whole transmission chain; 6) Ability to check auxiliary data (e.g., data broadcasting contents, closed captions and EPG); 7) Applicabi
48、lity to bit-streams (e.g., MPEG Transport Stream) and RF signals, in addition to baseband video and audio signals; 8) Ability to detect errors which cannot be detected by humans (e.g., occasional bit error); 9) Ability to automatically scan auxiliary data (e.g., data broadcasting contents and closed
49、 captions) to see whether they are as intended. 5.3 Requirements for quality monitoring For quality management of digital transmission, conventional subjective quality assessment methods and waveform-based measurement methods are not sufficient. A novel assessment method based on systematic monitoring of quality is needed. As digital transmission mainly uses a signal form of bit-streams such as MPEG-TS instead of conventional baseband signals, there are fewer monitoring points which human operators can subjectively assess. In addition, there is an issue of relative dela
