1、INTERNATIONAL TELECOMMUN CATION UN ION ITU-T TELECOMMUNICATION STAN DA RD I ZATI ON S ECTO R OF ITU J.64 (ex CMTT.569) (05/86) TELEVISION AND SOUND TRANSMISSION DEFINITIONS OF PARAMETERS FOR SIMPLIFIED AUTOMATIC MEASUREMENT OF TELEVISION INSERTION TEST SIGNALS ITU-T Recommendation J.64 (Formerly Rec
2、ommendation ITU-R CMTT.569) FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standa
3、rdizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. ITU-T Recommendation 5.64 (formerly
4、Recommendation ITU-R CMTT.569) was elaborated by the former ITU-R Study Group CMTT. See Note 1 below. NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standar
5、dization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector (ITU-R). Conforming to a joint decision by the World Telecommunication Standardization Conference (Helsinki, March 1993) and the Radioc
6、ommunication Assembly (Geneva, November 1993), the ITU-R Study Group CMTT was transferred to ITU-T as Study Group 9, except for the satellite news gathering (SNG) study area which was transferred to ITU-R Study Group 4. 2 In this Recommendation, the expression “Administration” is used for concisenes
7、s to indicate both a telecommunication administration and a recognized operating agency. O ITU 1990 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, without permission in writin
8、g from the ITU. Recommendation J.64l) DEFINITIONS OF PARAMETERS FOR SIMPLIFIED AUTOMATIC MEASUREMENT OF TELEVISION INSERTION TEST SIGNALS (1978; revised in 1982 and 1986) The CCIR, CONSIDERING (a) that Recommendation 567 is the basic reference which defines the parameters which are to be measured an
9、d the test signal elements and measuring methods which are to be used, in order to determine the performance of a television transmission circuit; (6) that Reports 628 and 411 describe various techniques for automatic measurement and monitoring of the performance of television chains which make use
10、of insertion test signals; (e) that operational measurements are commonly carried out using insertion test signals which are defined in Recommendation 473; (4 that Report 314 describes the allocation of lines in the field-blanking interval for special purposes; (e) that, although automatic measuring
11、 equipment exists that can make measurements in accordance with Recommendation 567, simplified automatic measuring equipment also exists that requires modifications of the measurement methods and definitions; (J3 that such simplified automatic measurement of insertion test signals suits the requirem
12、ents of operational staffs and makes the analysis of measurement results easier, UNANIMOUSLY RECOMMENDS, that, when simplified automatic measuring equipment is used to make measurements of an insertion test signal, and when a normalized form of presentation of the results is desired, the definitions
13、 used in quantifying the parameters of that signal should be those which are given in Annex I. ANNEX I 1. Introduction will depend upon the type of plant in use and the policy of the administrations. The need for each of the measurements described in this Recommendation (and possibly other measureme
14、nts) The test signals specified are those shown in Recommendation 473. The definitions assume that the performance of the measuring equipment employed is such that any harmonic components of the incoming signal, occurring above the nominal video band, will not give rise to measurement errors which e
15、xceed the specified accuracy of that equipment. The definitions also assume instrumentation that will substantially eliminate the effects of any noise present on the incoming signal from the measurement of any test signal parameter. The magnitude of distortions exhibited by signals which have passed
16、 through a non-linear transmission circuit tend to vary with average picture level. Therefore it may be desirable also, to measure automatically the value of Average Picture Level (APL) associated with any particular magnitude of distortion or error. Formerly Recommendation lTU-R CMTT.569. Recommend
17、ation 5.64 (05/86) 1 2. Definitions 2.1 Luminance bar amplitude The luminance bar amplitude is defined as the difference between the level corresponding to the mid-point of the bar (element B2) and the level corresponding to a point immediately following the composite pulse (element F). These points
18、 are shown as b2 and bl respectively in Figs. 1 and 2. It is to be expressed as a percentage of the nominal bar amplitude (0.7 V for 625-line signals, 0.714 V for 525-line signals). 2.2 Luminance bar amplitude error The luminance bar amplitude error is defined as the difference between the actual lu
19、minance bar amplitude and the nominal value expressed as a percentage of the nominal value (0.7 V for 625-line signals, 0.714 V for 525-line signals). 2.3 Bar tilt The luminance bar tilt is defined as the difference between the level of the luminance bar one microsecond after the half amplitude poin
20、t of its leading edge (point b3 in Figs. 1 and 2), and the level one microsecond before the half amplitude point of its trailing edge, (point b4 in Figs. 1 and 2) expressed as a percentage of the luminance bar amplitude. The sign of the difference is positive if b4 is higher than b3. Note. - The par
21、ameter bar tilt as defined above is a unique measurement by automatic devices of a specific form of line time waveform distortion, i.e. the difference in the level of the line bar at two specific reference points. This measurement is different to the measurements of line time waveform distortion des
22、cribed in Recommendation 567 (3 C.3.5.1.3 and Annex III to Part C, 3 2.1) where the maximum difference in level at any point between defined reference points is measured. 2.4 Base-line distortion The base-line distortion is defined as the difference between the levels of the signal at point b7, whic
23、h is located after the mid-amplitude point of the trailing edge of the bar (element B2) at a distance of 400 ns for 625-line systems and 500 ns for 525-line systems (see Figs. 1 and 2), and at a reference point bl located before the beginning of the staircase in line 17 (see also Figs. 1 and 2). The
24、 base-line distortion is expressed as a percentage of the luminance bar amplitude. It is to be measured after the bandwidth of the signal has been limited (see Note). The sign of the difference is positive if the signal level at point b7 is higher than the level of reference point bl. Note. - Limita
25、tion may be achieved by the use of a network, the design of which is based on “Solution 3” Thomson, 19521, having its first zero at 3.3 MHz, or by an equivalent technique. 2.5 2Tpulse/bar ratio error The 2T sine-squared pulsehar ratio error is defined as the difference between the amplitudes of the
26、2T pulse (element Bi) and the luminance bar (element B2), expressed as a percentage of the luminance bar amplitude. The peak amplitude of the 2T pulse is referred to a reference point bl (see Note) (Figs. 1 and 2) before the first riser of the staircase. The sign of the difference is positive if the
27、 2T pulse amplitude is greater than the luminance bar amplitude. Note. - To avoid error due to line tilt, it may be preferable to use a reference point exclusively for the measurement of 2T pulsebar ratio error, which is defined to be the linear mean level of the insertion test signal during the per
28、iods: 2 to 1 ps before, and 1 to 2 ps after the 2 Tpulse. 2.6 2Tpulse shape distortion This definition requires further study. 2.7 Chrominance-luminance gain inequality The chrominance-luminance gain inequality is defined as the difference between the peak-to-peak amplitude of the chrominance compon
29、ent of the element G, GI, G2 and the amplitude of the luminance bar (element B2) expressed as a percentage of the luminance bar amplitude. The sign of the difference is positive if the amplitude of the chrominance component is greater than that of the luminance bar. Note that in the 525-line case th
30、e nominal amplitude of element G is 80 IRE units. This factor must be taken into account when normalizing results. If for any reason signal elements G, G1 or G2 are not available, the measurement can be made with the chrominance component of element F. 2 Recommendation 5.64 (0986) 2.8 Chrominance-lu
31、minance delay inequality The chrominance-luminance delay inequality is defined as the time difference (expressed in ns) between the luminance and the chrominance component of the composite pulse (element F). This difference is positive, if the symmetry axis of the demodulated chrominance component l
32、ags behind the symmetry axis of the luminance component. 2.9 Luminance non-linearity The luminance non-linearity is to be measured with the staircase signal in line 17 (element D1 for 625-lines, 02 for 525-lines). It is defined as the difference between the largest and the smallest step amplitudes,
33、expressed as a percentage of the amplitude of the largest step. As the sign of the difference is not significant it is taken to be positive. 2.10 Differential gain Differential gain is determined by evaluating the amplitude modulation of the colour sub-cmier superimposed on the staircase in element
34、D2. Recommendation 567 defines differential gain in terms of two parameters +x and -y which represent the maximum (peak) differences in amplitude between the sub-cmier on the treads of the received test signal and the sub-cmier on its blanking level, expressed as a percentage of the latter. In the c
35、ase of a monotonic characteristic, either x or y will be zero. x and y can be found from the expressions below: y=looz-l Amin where: Ao : amplitude of the received sub-cmier on the blanking level tread of element D2. A, : highest value of sub-cmier on any tread. Amin : lowest value of sub-cmier on a
36、ny tread. Two alternative methods of expressing the results are acceptable for automatic measurement. These are: (a) “peak differential gain”, which is defined by either +x or -y, depending upon which of these parameters has the larger magnitude. (b) “peak-to-peak differential gain”, which is define
37、d as x + y. used then is: Note. - For the measurement of peak-to-peak differential gain some administrations use A, rather than AO. The formula Results obtained by this method will differ only slightly from those defined above if the magnitude of the distortion is not excessive. 2.1 1 Differential p
38、hase Differential phase is determined by evaluating the phase modulation of the colour sub-cmier superimposed on the staircase in element D2: (Fig. 5: 625-lines; Fig. 2: 525-lines). Recommendation 567 defines differential phase in terms of two parameters +x and -y which represent the maximum (peak)
39、differences in phase between the sub-cmier on the treads of the received test signal and the sub-carrier on its blanking level, expressed in degrees difference from the latter. In the case of a monotonic characteristic either x or y will be zero. x and y can be found from the expressions below: Reco
40、mmendation 5.64 (05/86) 3 where: o : phase of sub-cmier on the blanking level tread of element D2. maw : highest value of sub-cmier phase on any tread. min : lowest value of sub-cmier phase on any tread. Two alternative methods of expressing the results are acceptable for automatic measurement. Thes
41、e are: (a) “peak differential phase”, which is defined by either +x or -y depending upon which of these parameters has the larger magnitude. (b) “peak-to-peak differential phase”, which is defined as x + y. 2.12 Chrominance-luminance intermodulation The chrominance-luminance intermodulation is measu
42、red on element G, G1 or G2, after suppressing the incoming colour sub-carrier. It is defined as the difference between the luminance amplitude in element GI, or in the last section of element G or G2 (b5 in Figs. 3 and 4) and the amplitude of the succeeding section (66 in Figs. 3 and 4) in which the
43、 test signal has no sub-cmier, expressed as a percentage of the amplitude of the luminance bar (element 4). The sign of the difference is positive if the luminance amplitude b5 is greater than the luminance amplitude of the succeeding section b6. Note. - Some administrations use element F instead of
44、 G, G1 or G2 for measurement of this parameter. In this case measurement of the amplitude of the luminance component of the composite pulse (element F) is made after suppressing the incoming colour sub-carrier. The result will be given by the difference between the composite pulse luminance amplitud
45、e and half the luminance bar amplitude, expressed as a percentage of the luminance bar amplitude. The sign of the difference is positive if the amplitude of the composite pulse component is greater than half the luminance bar amplitude. In some cases the result may differ from that given by the pref
46、erred method, since the signal element F is not so well suited as element G to the measurement of this distortion. 2.13 Two-level chrominance amplitude non-linearity This parameter is to be measured with element G or G2. Its value, expressed in per cent, and with a sign, is defined by: (” - _ 5v1) x
47、 100for 625-line signals where VI and V3 are respectively the peak-to-peak amplitudes of the first and last sections of element G or G2. 2.14 Two-level chrominance phase non-linearity This parameter is to be measured with element G or G2. Its value, expressed in degrees, and with a sign, is defined
48、by: where 3 and I are respectively the phases of the last and first sections of element G or G2. 2.15 Signal-to-random noise ratio 2.15.1 Signal-to-unweighted random noise ratio The signal-to-unweighted random noise ratio is defined as the ratio of the amplitude of the luminance bar (element 4) to t
49、he r.m.s. value of the noise measured on a specified line, or part of this line, (line 22, or optionally both lines 22 and 335, in the case of 625-line signals). It is to be given in dB. The noise bandwidth is assumed to be limited by the low pass filter defined in Recommendation 567 Annex II to Part C. Lower frequency limiting shall be done by a 200 kHz high pass filter with a slope of 20 dB per decade (see Note). To suppress any periodic noise at sub-cmier frequency, a notch filter should be used (see Note). For 625-line signals, the amplitude/frequency response of the filter sho
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