1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T J.67 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2001) SERIES J: TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Circuits for analogue television transmission Test signals and measurement techniques for transmission circui
2、ts carrying MAC/packet signals ITU-T Recommendation J.67 (Formerly CCITT Recommendation) ITU-T J-SERIES RECOMMENDATIONS TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS General Recommendations J.1J.9 General specifications for analogue sound-programme transmission J.10J.19 Pe
3、rformance characteristics 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 tra
4、nsmission J.60J.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 transmis
5、sion J.100J.109 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 For further details, please r
6、efer to the list of ITU-T Recommendations. ITU-T J.67 (03/2001) i ITU-T Recommendation J.67 Test signals and measurement techniques for transmission circuits carrying MAC/packet signals Summary The purpose of this Recommendation is to give the tools of the transmission methodology of the MAC packet
7、family signals. This Recommendation is devoted to the traditional MAC packet signals (D/D2). This Recommendation begins with the definition of the test signals and the test lines that are the basis of the transmission methodology. Furthermore, the main quality measurement parameters are defined, as
8、well as the corresponding application methods. Source ITU-T Recommendation J.67 was revised by ITU-T Study Group 9 (2001-2004) and approved under the WTSA Resolution 1 procedure on 9 March 2001. ii ITU-T J.67 (03/2001) FOREWORD The International Telecommunication Union (ITU) is the United Nations sp
9、ecialized 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, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications o
10、n 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 turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid d
11、own 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. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunicatio
12、n administration and a recognized operating agency. 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 evidence, validity or
13、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, which may be required to
14、implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2001 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any mea
15、ns, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU. ITU-T J.67 (03/2001) iii CONTENTS Page 1 Scope. 1 2 Definition of the quality parameters of a MAC/packet signal 1 2.1 MAC signal. 1 2.1.1 Waveforms and line allocations 1 2.1.2 Quality paramet
16、ers. 1 2.2 Data signals. 3 2.2.1 Data signal waveform 3 2.2.2 Quality parameters for digital signals 3 3 Description of the test signals for MAC/packet systems 4 3.1 General remarks 4 3.2 Definition of elementary waveforms 5 3.2.1 Basic definitions 5 3.2.2 Transition. 5 3.2.3 Pulse. 5 3.2.4 Ramp 5 3
17、.2.5 Complex wobbulation 5 3.2.6 Modulated pulse 6 3.2.7 Burst. 6 3.3 Test signal description 6 3.3.1 Test signal No. 1 (see Figure A.1 and Table A.1). 6 3.3.2 Test signal No. 2 (see Figure A.2 and Table A.2). 7 3.3.3 Test signal No. 3 (see Figure A.3 and Table A.3). 7 3.3.4 Test signal No. 4 (natio
18、nal option) (see Figure A.4 and Table A.4) . 7 3.3.5 Test signal No. 5 (national option) (see Figure A.5 and Table A.5) . 7 3.3.6 Test signal No. 6 (national option) (see Figure A.6 and Table A.6) . 7 4 Measurement methods 7 4.1 General remarks 7 4.2 Measurements related to the vision signal 7 4.2.1
19、 Low-frequency noise . 7 4.2.2 High-frequency noise 8 4.2.3 Dynamic non-linearity. 8 4.2.4 Static non-linearity 8 4.2.5 Amplitude and phase/group delay frequency response . 8 4.3 Specific data signal measurements . 8 4.3.1 Bit-error ratio measurement. 8 4.3.2 Decoding margin measurement and equivale
20、nt impairment . 8 4.3.3 Analysis of eye diagrams. 9 iv ITU-T J.67 (03/2001) Page Annex A Test signal elements 9 ITU-T J.67 (03/2001) v Introduction A clear description of what is meant by the transmission circuit is essential for defining the measurement problem. The figure below shows a studio enco
21、der driving the transmission circuit, and a studio decoder driven by the transmission circuit. MAC is a multiplex of luminance, chrominance, and sound/data signals. The video inputs to the encoder are the luminance component and the two colour difference components. These are also present at the out
22、put of the decoder. The measurement methods described in this Recommendation are for automatic measurements of the transmission circuit between the MAC encoder and the MAC decoder. T0909620-00YCRCBYCRCBMACencoderMACdecoderTransmission circuitSound/data in Sound/data outFigure Intro./J.67 Transmissio
23、n of MAC signalsITU-T J.67 (03/2001) 1 ITU-T Recommendation J.671Test signals and measurement techniques for transmission circuits carrying MAC/packet signals 1 Scope The purpose of this Recommendation is to give the tools of the transmission methodology of the MAC packet family signals. Thus, MAC/p
24、acket signals, whose quality parameters are defined in clause 2 should be measured using the test signals defined in clause 3 and Annex A, and measured using the methods defined in clause 4. 2 Definition of the quality parameters of a MAC/packet signal 2.1 MAC signal 2.1.1 Waveforms and line allocat
25、ions The MAC analogue waveform is directly derived from the standard 4:2:2 sampling ratio used for digital television (ITU-R BT.601). MAC coding produces a sequential transmission of a chrominance signal, compressed in a 3:1 ratio, and the luminance signal, compressed in a 3:2 ratio. Given the sampl
26、ing frequencies defined for the digital television standard (13.5 MHz for luminance and 6.75 MHz for chrominance), the consequent MAC sampling frequency is 20.25 MHz. The resulting nominal bandwidth required for the coded MAC signal is 8.4 MHz. After decompression the luminance bandwidth is 5.6 MHz.
27、 It is important to note that, even though the MAC signal is derived through a sampling process, the resulting signal has an analogue form for transmission. A remarkable feature of the MAC coding system is that there is no absolute limit for the bandwidth. This characteristic can be used to broadcas
28、t the MAC signal in a narrow-band channel. 2.1.2 Quality parameters 2.1.2.1 Nominal signal amplitude The nominal amplitude of a MAC signal is 1 V. It is defined as the difference between the white level and the black level of the reference signal of line 624. 2.1.2.2 Distortions 2.1.2.2.1 Gain/frequ
29、ency response The gain/frequency characteristic of the circuit is defined as the variation in gain between the input and the output of the circuit over the frequency band extending from the field repetition frequency to the nominal cut-off frequency of the MAC signal, relative to the gain at a suita
30、ble reference frequency. 2.1.2.2.2 Phase distortion The phase-frequency distortion is defined as the difference in degrees relative to a linear phase characteristic over a frequency band extending from, ideally, 0 Hz to a defined upper frequency. _ 1Formely ITU-R CMTT.772. 2 ITU-T J.67 (03/2001) 2.1
31、.2.2.3 Group-delay distortion The group-delay distortion, expressed in ns, is defined by the difference between the group delay for each measured frequency and the group delay for a given reference frequency. 2.1.2.2.4 Long-time waveform distortion If a test signal, simulating a sudden change of the
32、 luminance from a black level to a white level or vice versa, is applied to the input of a circuit, a long-time waveform distortion is present if the variations of the clamp level (medium grey) of the output signal do not precisely follow those of the clamp level of the input signal. This failure ma
33、y be either in exponential form, or more frequently in the form of damped very low frequency oscillations. 2.1.2.2.5 Field-time waveform distortion If a square-wave signal with a period of the same order as one field and of nominal luminance amplitude is applied to the input of the circuit, the fiel
34、d-time waveform distortion is defined as the change in shape of the square wave at the output. A period at the beginning and end of the square wave, equivalent to the duration of a few lines, is excluded from the measurement. 2.1.2.2.6 Line-time waveform distortion If a square-wave signal with a per
35、iod of the same order as one line and of nominal luminance amplitude is applied to the input of the circuit, the line-time waveform distortion is defined as the change in shape of the square wave at the output. A period at the beginning and end of the square wave, equivalent to a few picture element
36、s, is excluded from the measurement. 2.1.2.2.7 Short-time waveform distortion If a short pulse (or a rapid step-function) of nominal luminance amplitude and defined shape is applied to the input of the circuit, the short-time waveform distortion is defined as the departure of the output pulse (or st
37、ep) from its original shape. 2.1.2.2.8 Distortions due to echoes This distortion is that caused by the superposition of the direct signal in the RF paths and an attenuated version of that signal delayed in time and shifted in phase relative to the direct signal. 2.1.2.2.9 Low frequency non-linear di
38、stortion For a particular value of average picture level, the low frequency non-linear distortion is defined as the departure from proportionality between the amplitude of the input signal and the output signal, when the input signal is shifted from the black level to the white level within the dura
39、tion of a line period. 2.1.2.3 Noise 2.1.2.3.1 Continuous random noise The signal-to-noise ratio for continuous random noise is defined as the ratio, expressed in decibels, of the nominal amplitude of the luminance signal (1 V) to the r.m.s. amplitude of the noise measured after band limiting. A sig
40、nal-to-weighted-noise ratio is defined as a ratio, expressed in decibels, of the nominal amplitude of the luminance signal, to the r.m.s. amplitude of the noise measured after band limiting and weighting with a specified network. One possibility is that wideband random noise should be measured in a
41、bandwidth of 8.4 MHz using a constant impedance noise-weighting network with a time constant of 90 ns. Such a network is based partly on the assumption that with the trend towards larger picture displays and with the improved picture quality available from the MAC/packet television standard, future
42、subjective tests ITU-T J.67 (03/2001) 3 will more commonly employ a viewing distance of four times the picture height, rather than six times, as at present. The second possibility uses the existing unified weighting network, scaled according to the 3:2 compression ratio, as a common weighting networ
43、k for all MAC systems. This filter gives the same results as would be obtained from a signal in decompressed form with the unified weighting filter described in ITU-T J.612. It also takes account of the noise carried in the more-compressed colour-difference signals. The possibly greater noise sensit
44、ivity due to the higher bandwidth HD-MAC signals when these use the same networks that are designed for present-day MAC signals is also considered. The definition of this network and its amplitude/frequency response are given in Figure 1. 2.1.2.3.2 Low frequency noise The signal-to-noise ratio for l
45、ow frequency noise is defined as the ratio, expressed in decibels, of the nominal amplitude of the luminance signal (1 V) to the mean square value of the noise. 2.1.2.3.3 Interference The signal-to-interference ratio is defined as the ratio, expressed in decibels, of the nominal amplitude of the lum
46、inance signal (1 V) to the peak-to-peak amplitude of the interfering signal. 2.2 Data signals 2.2.1 Data signal waveform The data signals have very different characteristics within the family of MAC systems. They are defined in the former CCIR special publication “Specifications of Transmission Syst
47、ems for the Broadcasting-Satellite Service“. 2.2.2 Quality parameters for digital signals 2.2.2.1 Bit-error ratio The bit-error ratio (BER) is defined as the ratio of the number of detected bit errors to the number of transmitted bits over a given period of time. 2.2.2.2 Eye diagram The eye diagram
48、is defined as the superposition of all the configurations of the data signals. 2.2.2.3 Equivalent impairment The data signal quality is evaluated by adding a Gaussian noise signal to the received signal and plotting the bit-error ratio versus the noise level. For a given bit-error ratio, the differe
49、nce in dB between the measured noise level and the theoretical level produces, by definition, the “equivalent impairment“. 2.2.2.4 Decoding margin Another method to evaluate the data signal quality by adding a Gaussian noise is to measure the level of added noise to obtain a given bit-error ratio. This is, by definition, the “decoding margin“. _ 2Formerly ITU-R CMTT.567. 4 ITU-T J.67 (03/2001) 012345670481216T0902420-94aZRZaRZCZL000021=dB11111log1022+=aaAZ0Z0Z0LR1R2Z0CInsertionlossA(dB)Frequency (MHz)whe
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