EN 61237-4:1997
(Main)Broadcast video tape recorders - Methods of measurement - Part 4: Analogue audio performance measurements
Broadcast video tape recorders - Methods of measurement - Part 4: Analogue audio performance measurements
Describes methods of measurement and special test signals for the analogue audio part of equipment mainly dedicated to recording reproduction of TV signals on mangetic tape on reels or in cassettes. Is applicable to acceptance tests, performance comparison and, as far as possible, to routine checks.
Videobandgeräte für den Rundfunk - Meßverfahren - Teil 4: Messung der Leistungskennwerte für analoge Tonsignale
Magnétoscopes de radiodiffusion - Méthodes de mesure - Partie 4: Mesure des caractéristiques audio-analogiques
Décrit les méthodes de mesure et les signaux d'essai particuliers pour la partie audio-analoguique du matériel principalement dédiée à la lecture d'enregistrement de signaux de télévision sur bande magnétique en bobine ou en cassette. S'applique aux essais d'acceptation, aux comparaisons de performances, et autant que possible aux esais de routine.
Broadcast video tape recorders - Methods of measurement -- Part 4: Analogue audio performance measurements (IEC 61237-4:1997)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-april-1999
Broadcast video tape recorders - Methods of measurement -- Part 4: Analogue
audio performance measurements (IEC 61237-4:1997)
Broadcast video tape recorders - Methods of measurement -- Part 4: Analogue audio
performance measurements
Videobandgeräte für den Rundfunk - Meßverfahren -- Teil 4: Messung der
Leistungskennwerte für analoge Tonsignale
Magnétoscopes de radiodiffusion - Méthodes de mesure -- Partie 4: Mesure des
caractéristiques audio-analogiques
Ta slovenski standard je istoveten z: EN 61237-4:1997
ICS:
33.160.40 Video sistemi Video systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
NORME
CEI
INTERNATIONALE
IEC
61237-4
INTERNATIONAL
Première édition
STANDARD
First edition
1997-10
Magnétoscopes de radiodiffusion –
Méthodes de mesure –
Partie 4:
Mesure des caractéristiques audio-analogiques
Broadcast video tape recorders –
Methods of measurement –
Part 4:
Analogue audio performance measurements
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61237-4 © IEC:1997 – 3 –
CONTENTS
Page
FOREWORD . 5
Clause
1 General. 7
1.1 Scope and object . 7
1.2 Normative references. 7
1.3 Definitions . 9
2 Manual and automatic measurements . 11
3 Procedure of measurement. 11
4 Environmental conditions . 11
5 Measurements on analogue audio baseband recording using bias. 11
5.1 Reproducing performance using calibration tape . 11
5.2 Overall performance using reference tape. 17
6 Measurement on analogue audio recording using frequency modulation (FM audio) . 23
6.1 Reproducing performance using calibration tape . 23
6.2 Overall performance using reference tape. 27
7 Special measurements . 31
7.1 Measurements on FM carrier (unmodulated carrier and deviation) . 31
7.2. Measurements on AGC (amplitude characteristic; attack time; hold time) . 31
7.3 Measurements on switchable noise reduction circuits. 31
7.4 Measurements on non-switchable noise reduction systems (in combination with
a non-switchable AGC) . 37
7.5 Polarity test . 39
Annexes
A Method of measurement for magnetic tape flux . 41
B Bibliography. 47
61237-4 © IEC:1997 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
BROADCAST VIDEO TAPE RECORDERS –
METHODS OF MEASUREMENT –
Part 4: Analogue audio performance measurements
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61237-4 has been prepared by subcommittee 100B: Recording, of
IEC technical committee 100: Audio, video and multimedia systems and equipment.
The text of this standard is based on the following documents:
FDIS Report on voting
100B/93/FDIS 100B/111/RVD
Full information on the voting for the approval of this standard can be found in the report of
voting indicated in the above table.
IEC 61237 consists of the following parts, under the general title Broadcast video tape
recorders – Methods of measurement:
Part 1: Mechanical measurements
Part 2: Electrical measurements of analogue composite video signals
Part 3: Electrical measurements of analogue component video signals
Part 4: Analogue audio performance measurement
Part 5: Electrical measurements of digital composite video signals and digital audio signals
Part 6: Electrical measurements of digital component video signals and digital audio signals
Annexes A and B are for information only.
61237-4 © IEC:1997 – 7 –
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 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 i.e. appropriate
publications, 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 and, 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 references
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 of IEC 61237 are encouraged to investigate the possibility of applying the most
recent editions of the normative documents indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
IEC 60094-3: 1979, Magnetic tape sound recording and reproducing systems – 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, Sound system equipment – Part 3: Amplifiers
IEC 60268-8: 1973, Sound system equipment – Part 8: Automatic gain control devices
61237-4 © IEC:1997 – 9 –
IEC 60386: 1972, Method of measurement of speed fluctuations in sound recording and
reproducing equipment
IEC 60602: 1980, Type B helical video recorders
IEC 60651: 1979, Sound level meters
IEC 61041-1: 1990, Non-broadcast video tape recorders – Methods of measurement – Part 1:
General video (NTSC/PAL) and audio (longitudinal) characteristics
IEC 61041-3: 1993, Non-broadcast video tape recorders – Methods of measurement – Part 3:
Audio characteristics for FM recording
IEC 61105: 1991, Reference tapes for video tape recorder systems
IEC 61213: 1993, Analogue audio recording on video tape – Polarity of magnetization
IEC 61260: 1995, Electroacoustics – Octave-band and fractional-octave-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 following definitions apply:
1.3.1 reference level: Value of signal level defined in the relevant system IEC publication as
remanent magnetic short-circuit flux level on the tape, for example 90 ± 5 nWb/m r.m.s. for
625-50 systems in IEC 60602. Method of measurement is given in annex A of this standard.
1.3.2 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 different 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 channel 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 (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 tape interchange, detailed explanation is given in IEC 61213.
61237-4 © IEC:1997 – 11 –
2 Manual and automatic measurements
If an automatic measuring device is designed to give reliable results under the special
conditions of television tape recording/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 carried 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, although 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 on
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 the 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 by means
of a calibration tape (see 1.1). Attention shall be paid to the manufacturer's manual and
instructions respectively.
4 Environmental conditions
If not otherwise stated, all measurements shall be carried out at the following atmospheric
conditions:
temperature (20 ± 2) °C;
relative humidity (50 ± 2) %;
air pressure 86 kPa to 106 kPa;
conditioning before testing 24 h.
5 Measurement on analogue audio baseband reco
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