1、STD*ETSI ETS 300 712-ENGL 1997 3900855 0157950 393 EISI ETS 300 732 January 1997 Source : EBU/CENELEC/ETS I JTC Reference: DWJTC-GCR ICs: 33.020 Key words: Broadcasting, analogue, TV European Broadcasting Union Union Europenne de Radio-Tlvision Television systems; Enhanced 625-line PAUSECAM televisi
2、on; Ghost Cancellation Reference (GCR) signals ETSI European Telecommunications Standards Institute ETSI Secretariat Postal address: F-O6921 Sophia Antipolis CEDEX - FRANCE Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE X.4: c=fr, a=atlas, p=etsi, s=secretariat - Inter
3、net: secretariatOetsi.fr Tel.: +33 4 92 94 42 O0 - Fax: +33 4 93 65 47 16 Copyright Notification: No pari may be reproduced except as authorized by written permission. The copyright and the foregoing restriction extend to reproduction in all media. O European Telecommunications Standards Institute 1
4、997. O European Broadcasting Union 1997. All rights reserved. STD-ETSI ETS 300 732-ENGL L777 3q00855 0157951 28T Page 2 ETS 300 732: January 1997 Whilst every care has been taken in the preparation and publication of this document, errors in content, typographical or otherwise, may occur. If you hav
5、e comments concerning its accuracy, please write to “ETSI Editing and Committee Support Dept.“ at the address shown on the title page. Contents Foreword . 5 1 Scope 7 2 Normative reference 7 3 Abbreviations . 7 4 Ghost Cancellation Reference (GCR) signal 7 4.1 GCR waveform 7 4.1.1 GCR amplitude 7 4.
6、1.2 GCR pedestal 7 GCR polarity and transmission sequence . 9 4.2 4.3 Location of the GCR signal 8 Annex A (normative): Derivation of the GCR waveform 11 A.l Defining equations . 11 Annex 6 (informative): GCR generation and transmission . 12 6.1 General 12 8.2 Tolerances of the GCR signal . 12 B.3 A
7、nnex C (informative): Transparency of digital codecs to the GCR 13 Operation of ghost cancellers . 14 C.l Cancellation range and response time 14 C.2 Ghost cancellation and Motion Adaptive Colour Plus (MACP) 14 Historyy. . 15 STD*ETSI ETS 300 732-ENGL 1997 3vOCI855 CIL57753 052 Page 4 ETS 300 732: J
8、anuary 1997 Blank page STD-ETSI ETS 3UU 732-ENGL 1777 D 3400855 0157754 T77 D Page 5 ETS 300 732: January 1997 Foreword This European Telecommunication Standard (ETS) has been produced by the Joint Technical Committee (JTC) of the European Broadcasting Union (EBU), Comit Europen de Normalisation ELE
9、Ctrotechnique (CENELEC) and the European Telecommunications Standards Institute (ETSI). NO * TE: The SPf boc res Pro ord Pro in t ? EBWETSI JTC was established in 1990 to Co-ordinate the drafting of ETSs in the !cific field of broadcasting and related fields. Since 1995 the JTC became a tripartite i
10、y by including in the Memorandum of Understanding also CENELEC, which is ponsible for the standardization of radio and television receivers. The EBU is a Ifessional association of broadcasting organizations whose work includes the co- lination of its Members activities in the technical, legal, progr
11、amme-making and igramme-exchange domains. The EBU has Active Members in about 60 countries he European Broadcasting Area; its headquarters is in Geneva *. European Broadcasting Union Case Postale 67 CH-1218 GRAND SACONNEX (Geneva) Switzerland Tel: +41 22 717 21 11 Fax: +41 22 717 24 81 Transposition
12、 dates Date of adoption 20 December 1996 Date of latest announcement of this ETS (doa): 30 April 1997 Date of latest publication of new National Standard or endorsement of this ETS (dop/e): 31 October 1997 Date of withdrawal of any conflicting National Standard (dow): 31 October 1997 1 Page 6 ETS 30
13、0 732: January 1997 Blank page STD-ETSI ETS 300 732-ENGL 1997 m 3400855 OL5795b BbL m Page 7 ETS 300 732: January 1997 1 Scope This European Telecommunication Standard (ETS) is applicable to 625-line PAUSECAM systems B, G, H, I, L, D and K broadcast on the VHF / UHF terrestrial networks, including t
14、heir distribution on cable networks. It specifies reference signals that may be inserted into the vertical blanking interval of the baseband video signal prior to transmission, and the way of incorporating these reference signals into the television system. These reference signals are intended for u
15、se by appropriately equipped television receivers to reduce or eliminate the effects of multi-path reception on displayed pictures and, in addition, to improve the eye-height of received teletext data so as to reduce the likelihood of errors in teletext decoding. This ETS specifies the waveform inse
16、rted into the baseband video signal, at the point of insertion. 2 Normative reference This ETS incorporates by dated and undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For da
17、ted references, subsequent amendments to or revisions of any of these publications apply to this ETS only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. t11 ITU-R Recommendation BT.470: “Television Systems“. 3 Abbre
18、viations For the purposes of this ETS, the following abbreviations apply: GCR Ghost Cancellation Reference MACP Motion Adaptive Colour Plus PAL Phased Alternate Line SECAM Sequentielle Couleur Avec Mmoire (French colour-TV system) 4 Ghost Cancellation Reference (GCR) signal 4.1 GCR waveform The GCR
19、waveform shall be derived according to the formula given in annex A. The GCR waveform shall be placed on a pedestal of amplitude V1, as indicated in figure 1, using the parameters listed in table 1. 4.1.1 GCR amplitude The maximum peak-to-peak amplitude of the GCR signal at the point of insertion in
20、to the television signal shall be: 700 mV + O / - 70 mV. NOTE: The maximum peak-to-peak amplitude of the GCR signal is reached only at the high frequency end of its energy spectrum. The amplitude of the GCR shall have a frame-to-frame consistency within 5 mV peak-to-peak. 4.1.2 GCR pedestal The pede
21、stal amplitude with respect to black level shall be the mean of the nominal values V2 and V3: (v2 + v3) v1 = mV. 2 NOTE: The nominal pedestal amplitude equates to 350 mV. STD-ETSI ETS 300 732-ENGL 1777 3400855 0157757 7T8 Page 8 ETS 300 732: January 1997 The rise and fall times of the pedestal shall
22、 be: 300 the mean value of V3 shall be within +O/- 35 mV of its nominal value. The duration of the GCR, T3, arising from application of the formula in annex A, is nominally 23,23 ps. The first peak of the GCR, arising from application of the formula given in annex A, and from the value specified abo
23、ve for T4, occurs at nominally 15,8 f 0,2 ps. The parameters T1, T2, T3, T4, and T5 shall have a frame-to-frame timing consistency within I 15 ns (Le., within 30 ns peak-to-peak). Guidelines on tolerances in the distribution path are given in annex B, Values of VI, V2 and V3 are given with respect t
24、o black level. 4.3 GCR polarity and transmission sequence On alternate frames, the polarity of the GCR waveform shall be inverted prior to its placement on the pedestal, forming positive-going GCR “line A“ as shown in figure 2, and negative-going GCR “line B as shown in figure 3. Transmissions of GC
25、R line A and GCR line B shall alternate, following either one of the two alternative sequences shown in table 2. Frame GCR (sequence 1) 1 line A 2 line B 3 line A A line B 700 - GCR (sequence 2) line B line A line B line A Amplihide (mv) 0- -300 - 700 Ampliiude (mv) O -300 NOTE: There is no absolute
26、 relationship between the polarity of the GCR transmission sequence and the 8-field sequence of PAL, and no absolute relationship with the sequence of colour reference signals of SECAM. Figure 2: Line A (positive going) GCR signal u 7 I I I I I I I I Time ml O 10 20 30 40 50 60 70 Figure 3: Line B (
27、negative going) GCR signal STD-ETSI ETS 300 732-ENGL 1997 3400855 01579b 292 Page 11 ETS 300 732: January 1997 Annex A (normative): A.l Defining equations Numerical values of the reference signal as a function of time shall be derived according to the following formula: Derivation of the GCR wavefor
28、m R C O cos(h2) + jsin(h2) W(o)edo + cos(h2) - jsin(h2) W(w)edo -R 211 53 lo6 rad si 0.91 21 1 O6 rad s- where W(o) is the window function defined as follows: and where the constants A, b, c, Q and QI are given in table A.1. Table A.l: Parameter values for GCR waveform equations Parameter I Value A
29、0.30358 1 O-6 V s I b I 0,2829 s2 rad- I Q I 2x 5,O lo6 rad sm1 STDqETSI ETS 300 732-ENGL 1777 D 3LiOO855 OL577bL L27 Page 12 ETS 300 732: January 1997 Annex B (informative): GCR generation and transmission 6.1 General To act as an effective reference signal, the GCR contains high energy across the
30、whole range of video frequencies over which equalization is sought. The parameters of the GCR given in annex A are chosen such as to result in a nominally flat energy spectrum up to almost 5 MHz, as illustrated in figure B.l, with a very low level of energy beyond 5,2 MHz. The signal may therefore b
31、e included in any European PAUSECAM 625-line terrestrial transmission channel. 1- 018- 016- Magnitude 014- 0,2- 0- WMd 1 2 3 4 5 6 Frequency MHz Figure B.l: Magnitude of the energy spectrum of the GCR signal The energy spectrum shown in figure 5.1, and the idealized GCR waveforms illustrated in figu
32、res 2 and 3 at the point of insertion into the baseband television signal, will subsequently be modified according to any distortions and echoes present in the distribution and transmission paths. B.2 Tolerances of the GCR signal Based on experience of ghost cancellation with the PAL system, to allo
33、w effective operation of a ghost canceller the amplitude and timing parameter values of the GCR should be maintained throughout the distribution path to a frame-to-frame consistency within 5 mV (peak-to-peak) amplitude and 5 ns (r.m.s.) time jitter respectively. Assuming that jitter is distributed i
34、n a gaussian fashion, the above timing guideline equates, for measurement purposes, to a frame-to-frame consistency of i 15 ns (Le., within 30 ns peak-to-peak) with respect to the absolute value of O,. Frame-to-frame jitter greater than the above values is likely to result in reduced performance of
35、ghost cancellers, particularly under severe echo conditions. t STD-ETSI ETS 300 732-ENGL I997 Ii00855 OL577b2 Ob5 = Page 13 ETS 300 732: January 1997 8.3 Transparency of digital codecs to the GCR .Where it is required to distribute a television signal containing the GCR via a digital contributionldi
36、stribution circuit (for example, at 34 Mbis or 14 Mbis), particular attention should be given to the design of the codec interface if it is required to ensure effective transparency of the GCR signals. In practice, it is likely to be cost effective to re-insert the GCR signals at the output of the c
37、odec. It might also be necessary to ensure that processing (for example, comb filtering) carried out by a codec PAUSECAM interface does not result in the generation of spurious signals on lines 317, 318 and 319 at the codec output, arising from the presence of a GCR at the codec input. STD*ETSI ETS
38、300 732-ENGL 1777 3400855 0357763 TTL W Page 14 ETS 300 732: January 1997 Annex C (informative): Operation of ghost cancellers C.l Cancellation range and response time To allow detection of echoes, the GCR signal shall be both preceded and followed by a period of time within which the television sig
39、nal contains no time-varying information. The parameters of the GCR signal have been chosen so as to allow the detection and cancellation of multiple echoes with delays up to approximately 40 ps, without regard as to the content of the following line, 31 9. NOTE: Detection and cancellation of echoes
40、 of longer durations than nominally 40 ps is theoretically possible, but account would have to be taken of the likely presence of time-varying information on line 31 9 (for example, teletext) which could be expected to lead to increased complexity for the canceller and longer cancellation times. In
41、practical reception situations, the great majority of echoes can be expected to fall well within the above target cancellation range of delays of up to nominally 40 jts. Detection and cancellation of pre-echoes is possible, and this depends on the canceller algorithm and is not constrained by the GC
42、R itself. Similarly, the number of echoes that may be cancelled depends on the design of the canceller. In the case of PAL, for echoes with long delays which fall beyond the start of the colour synchronizing burst on line 319 (greater than approximately 33,4 ps), it is necessary for an echo cancelle
43、r to take account of the presence of the colour burst. The cancellation range can be maximized by extracting the received GCR signals using a four-frame (or multiple thereof) running average in the following manner: This has the effect of eliminating static information, such as sync pulses, together
44、 with the colour synchronizing burst on line 31 9, thereby maximizing the cancellation range. A consequence of using a running average of extracted GCR signals in this way is to increase the signal- to-noise ratio of the extracted GCR information. However, the greater the number of GCR signals used
45、to form the running average, the slower the response time is likely to be in equalizing time-varying ghosting. Depending on the cancellation algorithm, It can be expected that practical ghost cancellers could establish equalization within a few seconds (perhaps within under one second) of first bein
46、g presented with a signal containing echoes. C.2 Ghost cancellation and Motion Adaptive Colour Plus (MACP) Correct operation of the Motion Adaptive Colour Plus process (as used by the PALplus system - see note) relies on the fact that points separated by 312 lines within a frame have a precise phase
47、 relationship. In order to avoid disturbing this relationship, any changes to the equalization of the signal applied by a ghost canceller located in either the transmission or reception chain should be made during the period of lines 624 to 22. NOTE: The operation of the PALplus system and of Motion
48、 Adaptive Colour Plus (MACP) is described in working draft prETS 300 731 on “Television systems; Enhanced 625-line Phased Alternate Line (PAL) television; PALplus“. STDaETSI ETS 300 732-ENGL 1777 3400855 01579b4 738 Page 15 ETS 300 732: January 1997 May 1996 October 1996 January 1997 History Public Enquiry PE 106: 1996-05-20 to 1996-09-1 3 Vote V 113: 1996-1 0-21 to 1996-12-1 3 First Edition ISBN 2-7437-1248-1 Dpt lgal : Janvier 1997
