1、STD-BSI BS EN bL237-4-ENGL 1998 W Lb24bb b83420 904 W BRITISH STANDARD Broadcast video tape recorders - Methods of measurement Part 4. Analogue audio performance measurements The European Standard EN 612374 : 1997 has the status of a Britkh Standard ICs 33.160.40 NO COPYING WITHOUT BSI PERMISSION EX
2、CEPT AS PERMITTED BY COPYRIGHT LAW 3s EN OEC 61237-4 : 1997 51237-4 : 1998 STD-BSI BS EN bL237-4-ENGL 1778 W Lb24bb7 Ob83421 BLiO Standars Board and comes intn - present to the responsible intemational/European committee any enquiries on the interpretation, or proposals for change, and keep the UK i
3、nterests informed, - monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this subcommittee can be obtained on request to its secretary. Rom 1 January 1997, all IEC publications have the number 60000 added to the old number. Fo
4、r instance, IEC 27-1 has been renumbered as IEC 60027-1. For a period of time during the change over from one numbering system to the other, publications may contain identifiers from both systems. IEC 61237 comprises the following Parts: Part 1: Mechanical measurements Part 2 Electrical measurements
5、 of analogue composite video signais Part 3 Eldd measurements of dogue component signals Part 4 Analogue audio performance measurement Part 5 Electrical measurements of digital composite video signais and digital audio signais Part 6: Electrical measurements of digital component video signais and di
6、gital audio signais Cross-references Awntion is drawn to the fact that CEN and CENELEC Standards normally include an annex which iists nonnative references to intemational publications with their corresponding European publications. The British Standards which implement these intemationai or Europea
7、n publications may be found in the BSI Standards Catalogue under the section entitled International Standards Correspondence Index, or by using the Find facility of the BSI Standards Electronic Catalogue. Compliance with a British Standard does not of itself confer immunity from legal obligations. O
8、 BSI 1998 I I ISBN O 680 28891 9 STD.BS1 BS EN bL237-4-ENGL 1998 M lb24bb Ob83422 787 EUROPEAN STANDARD EN 61237-4 NORME EUROPENNE EUROPISCHE NORM November 1997 ICs 33.160.40 Descriptors: Electroecoustics, video recording, recording apparatus, magnetoscopes, radiocommunications, measurements, charac
9、teristics, acoustic signals, analog signals English version Broadcast video tape recorders - Methods of measurement Part 4: Analogue audio performance measurements (IEC 61 237-4: 1997) Magntoscopes de radiodiffusion Mthodes de mesure Meverfahren Partie 4: Mesure des caractristiques audio-analogiques
10、 fr analoge Tonsignale Videobandgerte fr den Rundfunk Teil 4: Messung der Leistungskennwerte (CE1 61 237-4:1997) (IEC 61 237-4: 1997) * * u, This European Standard was approved by CENELEC on 1997-1 0-01. CENELEC members are bound to comply with the CENKENELEC Internal Regulations which stipulate the
11、 conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists
12、 in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electro
13、technical committees of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comit Europen de Nor
14、malisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 1997 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61 237-4:1997 E STD.BSI BS EN bL237-4-ENG
15、L 1978 9 Lb24bbS b83423 b13 i Page 2 EN 61237-4 :1997 Foreword The text of document 1 OOB/93/FDIS, future edition 1 of IEC 61 237-4, prepared by SC 1008, Recording, of IEC TC 100, Audio, video and multimedia systems and equipment, was submitted to the IEC-CENELEC parallel vote and was approved by CE
16、NELEC as EN 61 237-4 on 1997-1 0-01. The following dates were fixed: - latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 1998-07-01 - latest date by which the national standards conflicting with the EN have to
17、 be withdrawn (dow) 1998-07-01 Annexes designated “normative“ are part of the body of the standard. Annexes designated “informative“ are given for information only. In this standard, annex ZA is normative and annexes A and B are informative. Annex ZA has been added by CENELEC. Endorsement notice The
18、 text of the International Standard IEC 61 237-4:1997 was approved by CENELEC as a European Standard without any modification. In the official version, for annex B, Bibliography, the following note has to be added for the standard indicated: IEC 60094-2 NOTE: Harmonized as EN 60094-2:1995 (not modif
19、ied). STD-BSI BS EN b1237-4-ENGL 1798 = Lb24bb9 Ob8342Li 55T W Page 3 EN 61237-4 :1997 CONTENTS Clause 1 General 1.1 Scope and objec! . 1.2 Normative references . 1.3 Definitions . 2 Manual and automatic measurements . 3 Procedure of measurement . 4 Environmental conditions 5 Measurements on analogu
20、e audio baseband recording using bias . 5.1 Reproducing performance using calibration tape 5.2 Overall performance using reference tape Measurement on analogue audio recording using frequency modulation (FM audio) 6.1 Reproducing performance using calibration tape 6.2 Overall performance using refer
21、ence tape 7 Special measurements . 7.1 Measurements on FM carrier (unmodulated carrier and deviation) 7.2. Measurements on AGC (amplitude characteristic; attack time; hold time) . 7.3 Measurements on switchable noise reduction circuits . 7.4 Measurements on non-switchable noise reduction systems (in
22、 combination with a non-switchable AGC) 7.5 Polarity test . 6 Annexes A i3 Bibliography Method of measurement for magnetic tape flux . Page 4 4 4 5 6 6 6 6 6 9 12 12 14 16 16 16 16 19 20 21 24 ZA (normative) Normative references to international publications with their corresponding European publica
23、tions . 25 O BSI 1998 I page4 1 EN 61237-4 :1997 1 BROADCAST VIDEO TAPE RECORDERS - METHODS OF MEASUREMENT - Part 4: Analogue audio performance measurements 1 General 1.1 Scope and object This part of IEC 61237 describes methods of measurement and special test signals for the analogue audio part of
24、equipment mainly dedicated to recording reproduction of TV signals on magnetic tape on reels or in cassettes. The allowable tolerances for the rated values for acceptable performance are not given in this standard, but may be derived from the specifications for the related system .e. appropriate pub
25、lications, manufacturers specifications, etc. The necessary reference and calibration tapes are either mentioned in the specific IEC publication of the equipment under test or included in IEC 61105 and IEC 61295, respectively. The methods are applicable to acceptance tests, performance comparison an
26、d, as far as possible, to routine checks. To ensure that the results obtained at a specific time and at a specific place are comparable to other measurements, it is advisable to specify the test signal, measuring devices and types of tapes used together with results obtained. 1.2 Normative reference
27、s The following normative documents contain provisions which, through reference in this text, constitute provisions of this part of IEC 61237. At the time of publication, the editions indicated were valid. All normative documents are subject to revision and parties to agreements based on this part o
28、f IEC 61237 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IEC 60094-3: 1979, Magnetic tape sound recording and reproducing systems -
29、Part 3: Methods of measuring the characteristics of recording and reproducing equipment for sound on magnetic tape IEC 60268-1: 1985, Sound system equipment - Part 1: General IEC 60268-2: 1987, Sound system equipment - Part 2: Explanation of general terms and calculation methods IEC 60268-3: 1988, S
30、ound system equipment - Part 3: Amplifiers IEC 60268-8: 1973, Sound system equipment - Part 8: Automatic gain control devices - STD-BSI BS EN bL237-q-ENGL L77 W Lb24bb7 ObA342b 322 111 Page 5 EN 61237-4 :1997 IEC 60386: 1972, Method of measurement of speed fluctuations in sound recording and reprodu
31、cing equipment IEC 60602: 1980, Type 8 helical video recorders IEC 60651 : 1979, Sound level meters IEC 61041-1: 1990, Non-broadcast video tape recorders - Methods of measurement - Patt 1: General video (NTSC/PAL) and audio (longitudinal) characteristics IEC 61041-3: 1993, Non-broadcast video tape r
32、ecorders - Methods of measurement - Patt 3: Audio characteristics for FM recording IEC 61 105: 1991, Reference tapes for video tape recorder systems IEC 61 21 3: 1993, Analogue audio recording on video tape - Polarity of magnetization IEC 61 260: 1995, Electroacoustics - Octave-band and fractional-o
33、ctave-band filters IEC 61295: 1994, Calibration tapes for broadcast VTRs ITU-R Recommendation BS 468-4: 1990, Measurement of audio-frequency noise voltage level in sound broadcasting ITU-R 798-2: 1990, Simulated programme signals 1.3 Definitions For the purpose of this part of IEC 61237, the followi
34、ng definitions apply: 1.3.1 reference levei: Value of signal level defined in the relevant system IEC publication as remanent magnetic short-circuit flux level on the tape, for example 90f 5 nWb/m r.m.s. for 625-50 systems in IEC 60602. Method of measurement is given in annex A of this standard. 1.3
35、.2 crosstalk attenuation or track separation: In multi-channel equipment, signals in one channel can break through into another channel in an attenuated and distorted form. Particularly when two adjacent tracks are used or two adjacent channels in the same head stack are operated simultaneously in d
36、ifferent modes for example record and reproduction, impairments can arise. To make matters worse, beside these audio tracks additional longitudinal tracks are present on a video tape for example control track and time and control code track. The influence of a signal in one channel to another channe
37、l can be described in terms of crosstalk attenuation or track separation. 1.3.3 polarity of the audio signal: An audio signal is deemed to be positive when it results in an increase in the acoustic pressure on the microphone diaphragm, and thus in the displacement of the diaphragm towards the rear (
38、see IEC 60268-2). 1.3.4 conservation of polarity on magnetic tapes: To obtain an optimal audio reproduction it is necessary to make sure that a backward movement of the microphone diaphragm leads to a forward direction of the loudspeaker diaphragm. This should be preserved either during recording or
39、 tape interchange, detailed explanation is given in IEC 61213. STD-BSI BS EN bL237-4-ENGL 1778 Ip Lb2LibbS 0b83Li27 2b W Page 6 EN 61237-4 :1997 2 Manual and automatic measurements If an automatic measuring device is designed to give reliable results under the special conditions of television tape r
40、ecording/reproducing as for example drop-out, jitter, time-base errors, head switching or partly insufficient head-to-tape contact, a significant improvement in measuring speed, accuracy and comparability of results can be achieved. Therefore preference was given to measuring methods which can be ca
41、rried out by automatic measuring equipment or which are suitable for automatic measuring techniques. Except where a distinction is made in particular clauses between manual and automatic methods of measurement, the measuring procedures given in this standard are valid for both methods. However, alth
42、ough in the case of automatic measurements the procedure is carried out automatically by the test signal analyzer, the various steps are described as if they were performed manually. 3 Procedure of measurement The measurements shall be carried out by measuring the reproduced signal after recording o
43、n the same machine (best case configuration). In certain particular cases, if the multigeneration-performance of a TV signal recording system is measured, the measurements shall be carried out by measuring the reproduced signal after recording on a different machine (worst case configuration). If th
44、e television tape machine under test is equipped with external controls for example tracking control, gain control, etc. these controls shall be set to their preset and mid-position respectively for all measurements. Before testing the overall performance, the reproducing channel shall be measured b
45、y means of a calibration tape (see 1.1). Attention shall be paid to the manufacturers manual and instructions respectively. 4 Environmental conditlonr If not otherwise stated, all measurements shall be carried out at the following atmospheric conditions: temperature (20 f 2) “C; relative humidity ai
46、r pressure conditioning before testing 24 h. (50 f 2) %; 86 kPa to 106 kPa; 5 Measurement on analogue audlo baseband recording using bias 5.1 Reproducing performance using calibration tape An audio calibration tape according to IEC 61295 or recommended by the manufacturer of the equipment under test
47、 shall be used for measuring the performance of the reproducing chain of each channel. - STD-BSI BS EN b1237-4-ENGL 1998 U Lb24bb9 Ob83428 1T5 = Page 7 EN 61237-4 :1997 If adjustable reproduction gain controls are provided on the equipment, they shall be adjusted to give the reference output level w
48、hen reproducing the reference recording level. If adjustable reproduction-equalization controls are provided, they shall be adjusted to give the closest approximation to the specified reproducing characteristic when reproducing the frequency response section of the specified calibration tape. 5.1.1
49、Head adjustment The 10 kHz tone recorded on the calibration tape is reproduced and the azimuth angle of the audio heads shall be adjusted for minimum phase error. The phase difference expressed in degrees between the particular audio tracks shall be reported. 5.1.2 Reference output lev81 The reference level section (1 kHz) of the calibration tape is reproduced and the obtained output level LIRef expressed in decibels shall be reported. 5.1.3 Maximum programme level The maximum output level at 3 %* harmonic distortion (see 5.1.5) shall be
