SIST EN 61237-2:1999

SLOVENSKI STANDARD
01-april-1999
Broadcast video tape recorders - Methods of measurement -- Part 2: Electrical
measurements of analogue composite video signals (IEC 61237-2:1995)
Broadcast video tape recorders - Methods of measurement -- Part 2: Electrical
measurements of analogue composite video signals
Meßverfahren für Videobandgeräte für den Rundfunk -- Teil 2: Elektrische Messungen
für analoge Composite-Videosignale
Magnétoscopes de radiodiffusion - Méthodes de mesure -- Partie 2: Mesures électriques
pour les signaux vidéo analogiques composites
Ta slovenski standard je istoveten z: EN 61237-2:1995
ICS:
33.160.40 Video sistemi Video systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEI
NORME
IEC
INTERNATIONALE
1237-2
INTERNATIONAL
Première édition
STANDARD
First edition
1995-05
Magnétoscopes de radiodiffusion —
Méthodes de mesure —
Partie 2:
Mesures électriques pour les signaux vidéo
analogiques composites
Broadcast video tape recorders —
Methods of measurement —
Part 2:
Electrical measurements of analogue
composite video signals
Copyright — all rights reserved
© CEI 1995 Droits de reproduction réservés —
No part of this publication may be reproduced or utilized in
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utilisée sous quelque forme que ce soit et par aucun pro-
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les microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher.
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- 3 -
1237-2 ©IEC:1995
CONTENTS
Page
FOREWORD 7
Clause
1 Scope and object
2 Normative references
13 3 General
4 Test conditions
5 Measuring methods and test signals
15 5.1 Manual and automatic measurements
5.2 Measurement of differences between adjacent tracks (fields/segments)
15 5.3 Procedure of measurement
5.4 Test signals
5.4.1 Introduction
5.4.2 Amplitudes and characteristics of test signals
5.4.3 Test signal arrangement
Measurements of characteristics 6
6.1 Amplitude of output signals in E-E mode and playback
6.1.1 Luminance bar amplitude error
19 6.1.2 Synchronizing pulse amplitude error
6.1.3 Burst amplitude error 21
6.2 Short and line time distortions 21
6.2.1 K2T factor 21
6.2.2 2T/bar ratio 23
6.2.3 Bar tilt
6.2.4 Base-line distortion 25
Chrominance-luminance gain inequality 27
6.3
delay inequality 29
Chrominance-luminance
6.4
6.5 Amplitude/frequency characteristics
6.5.1 Luminance
6.5.2 Chrominance
6.6 Non-linear distortions
6.6.1 Differential gain
6.6.2 Differential gain versus frequency
6.6.3 Differential phase
6.6.4 Group delay
cross-talk/intermodulation Chrominance-luminance
6.7
6.8 Luminance signal-to-noise ratio 39
signal-to-noise ratio 6.9 Chrominance
41 6.9.1 Measurement of PAL/NTSC colour video signals
SECAM colour video signals
6.9.2 Measurement of
- 5 -
1237-2 ©IEC:1995
Page
Clause
6.10 Field time distortions
6.10.1 Vertical tilt
6.11 Long time distortion 49
6.11.1 Signal bounce 49
6.11.2 Power supply interference
7 Special measurements
51 7.1 FM characteristic frequencies
7.2 Non-linear preemphasis
55 7.3 Noise coring
7.4 Moiré
7.5 Time base errors (measurements before time base error corrector)
7.5.1 Velocity errors
7.5.2 Phase step 59
7.5.3 Jitter 59
7.5.4 Time base errors after correction
7.6 Sc/H phase
Annexes
A - Test signals elements 69
B - 625-line systems
C - 525-line systems
D - Bibliography
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1237-2 © I EC:1995
INTERNATIONAL ELECTROTECHNICAL COMMISSION
BROADCAST VIDEO TAPE RECORDERS —
METHODS OF MEASUREMENT —
Part 2: Electrical measurements of analogue
composite video signals
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 cooperation 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.
The formal decisions or agreements of the IEC on technical matters, prepared by technical committees on
2)
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
They have the form of recommendations for international use published in the form of standards, technical
3)
reports or guides and they are accepted by the National Committees in that sense.
In order to promote international unification, IEC National Committees undertake to apply IEC International
4)
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.
International Standard IEC 1237-2 has been prepared by sub-committee 60B: Video
recording, of IEC technical committee 60: Recording.
IEC 698: Measuring methods for television tape machine, has been withdrawn from the
catalogue. However, this publication still applies, on the one hand, to materials specified
in IEC 347: Transverse track video recorders (second edition) which are not included in
the new draft and, on the other hand, to mechanical measurements on transverse track
video recorders (only).
The text of this standard is based on the following documents:
DIS Reports on voting
608(CO)159
60B(CO)171
60B(CO)159A
rt
Full information on the voting for the approval of this standard can be found in the repo
on voting indicated in the above table.

1237-2 © IEC:1995 - 9 -
IEC 1237 consists of the following parts, under the general title - Methods of measure-
ment for broadcast video tape recorders:
Part 1: Mechanical measurements
Part 2: Electrical measurements of analogue composite video signals
Part 3: Electrical measurements of analogue component video signals
Part 4: Measurement of audio performance - analogue
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
only.
Annexes A, B, C and D are for information

1237-2 ©IEC:1995 - 11 -
BROADCAST VIDEO TAPE RECORDERS —
METHODS OF MEASUREMENT —
Part 2: Electrical measurements of analogue
composite video signals
1 Scope and object
This part of IEC 1237 describes the test signals and measuring methods for equipments
mainly dedicated to record/playback analogue composite 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 equipment under test or included in IEC 1105 (reference tapes) and
IEC 1295 (calibration tapes).
The principal object of this standard is to describe the methods of measurement, test
signals and procedures which may apply to characteristics of video recording/playback
machines mainly intended for professional use. The measuring methods described here-
after do not directly concern home equipment and it would appear that some will be
difficult to apply to them.
2 Normative references
The following normative documents contain provisions which, through reference in this
text, constitute provisions of this part of IEC 1237. At the time of publication, the editions
rties to agree-
indicated were valid. All normative documents are subject to revision, and pa
ments based on this pa rt of IEC 1237 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 244-10: 1986, Methods of measurement for radio transmitters - Part 10: Methods of
rtion test signals
measurements for television transmitters and transposers employing inse
IEC 756: 1991, Non-broadcast video tape recorders - Time base stability
IEC 883: 1987, Measuring method for chrominance signal-to-random noise ratio for video
tape recorders
- 13 -
1237-2 © I EC :1995
Non-broadcast video tape recorders - Methods of measurement -
IEC 1041-1: 1990,
Part 1: General video (NTSC/PAL) and audio (longitudinal) characteristics
Non-broadcast video tape recorders - Methods of measurements -
IEC 1041-2: 1994,
Part 2: Video characteristics chrominance
Nomenclature and description of colour bar signals
CCIR Recommendation 471-1: 1990,
(Vol. XI-1)
Transmission performance of television circuits
CCIR Recommendation 567-3: 1990,
XII)
designed for use in international connections (Vol.
3 General
This standard deals with the application of measuring methods designed for general use
television production and transmission as well as special measurement techniques for
television tape machines.
The methods are applicable to acceptance tests, performance comparisons and, as far as
possible, to routine checks. To insure that the results obtained at a specific time at a
specific place are comparable to other measurements it is advisable to specify the test
signals, measuring devices and types of tapes used together with the results obtained.
Since measurements of television tape machines on the basis of a single test-line per field
may not be fully representative of the full-field performance (see 5.2 and 5.3), they may
give results which differ from those obtained or calculated with full-field test signals. There-
fore it is necessary to additionally specify the measuring method i.e.
- single line measurement (line number);
block measurement (start-line, step-by-step line(s), number of steps);
-
- full-field measurement.
Additionally it should be stated if the selection of lines coincides with a single
record/playback head only.
4 Test conditions
If not otherwise stated all measurements shall be carried out at the following atmospheric
conditions.
(20 ± 1) °C
Temperature
(50 ± 2) %
Relative humidity
86 kPa to 106 kPa
Air pressure
24 h
Conditioning before testing
- 15 -
1237-2 © IEC:1995
methods and test signals
5 Measuring
5.1 Manual and automatic measurements
If an automatic measuring device is designed to give reliable results under the special
conditions of television tape recording/playback as e.g. 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 auto-
matic 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 measurement 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.
Measurement of differences between adjacent tracks (fields/segments)
5.2
All currently standardized recording formats make use of segmented recording techniques.
The length of the segments (tracks) varies between approximately 16 lines and one field
where the latter is often termed "non segmented recording" which only indicates that there
is no cut within the field.
two or more heads are used for record and playback of the video information to and
Since
from the tracks it is desirable to restrict the measurement to segments related to a specific
head. This requires a special signal arrangement which provides identical information to
the heads or segments in turn.
A suitable arrangement for most formats is to repeat a packet of up to 16 different signals
of a duration of one line within a field and to make the signals identical in both fields.
5.3 Procedure of measurement
The measurements shall be carried out by measuring the playback signal after recording
on the same equipment (best-case configuration).
cases, if the multigeneration-performance of a video recording system
In ce rtain particular
by measuring the playback signal af-
is measured, the measurements shall be carried out
ter recording on a different machine (worst-case configuration).
If the television tape machine under test is equipped with external controls, e.g. tracking
control, gain control, etc. these controls shall be set to their preset or mid-position for all
measurements.
1237-2 ©IEC:1995 - 17 -
5.4 Test signals
5.4.1 introduction
A representative range of test signals is shown in annexes B and C (figures B.1 to B.6
and C.1 to C.7). For ease of reference they are indicated by roman numerals. The test
signals elements are defined in annex A.
The terms concerning the components and values of a composite colour video signal are
given after figure A.3.
5.4.2 Amplitudes and characteristics of test signals
The peak-to-peak amplitude of a monochrome composite video signal, e.g. from sync tip
to white level, shall be
Vp-p
1,0
The nominal value of the luminance component and the amplitude of the synchronizing
pulses differs between the television systems as shown in table 1.
The nominal value of the luminance component is regarded as 100 %.
Table 1 - Nominal signal amplitudes for 625-line and 525-line standard
625-line 525-line
standards standards
700mV=100% 714 mV = 100 % IRE
Luminance(Y)
—286 mV
Sync —300 mV
All other test signal amplitudes may be expressed as a percentage of the nominal value of
the luminance component.
Unless otherwise stated the characteristics of the synchronising signal and the character-
signal shall be in accordance with the CCIR television standard
istics of the chrominance
relevant to the television tape equipment under test.
5.4.3 Test signal arrangement
For manual or automatic measurement under identical conditions, the active field period
shall contain a specific picture test signal for measurement of the video characteristics.
However, particularly in case of automatic measurements, a signal arrangement as
mentioned in 5.2 may be used. This supports simultaneous measurements of different
parameters and renders reliable results by averaging values obtained from the specific
picture test signal of successive packets within a field. Unless otherwise stated the
specific picture test signal shall be identical in each horizontal line of the active field
period, e.g. regarding amplitude, frequency, phase, timing, etc.

1237-2 © IEC:1995 - 19 -
Measurements of characteristics
6.1 Amplitudes of output signals in E-E mode and playback
6.1.1
Luminance bar amplitude error
Introduction
The luminance bar amplitude error is the difference between the actual luminance bar
amplitude and its nominal value, expressed as a percentage of the nominal value.
The sign of the error is positive if the bar amplitude is greater than the nominal value.
Measurement procedure
Select test signal I (figure B.1) for 625-line systems or test signal V (figure C.1) for
a)
525-line systems.
1 and b2, and record this value U1 2
b) Measure the difference in level between point b
in millivolts.
c) Calculate the error from the expression:
(%)
100 U^ '2 Uo
U0
where Uo is the nominal value of the luminance bar amplitude.
6.1.2 Synchronizing pulse amplitude error
Introduction
The synchronizing pulse amplitude error is the difference between the actual amplitude of
the synchronizing pulse and its nominal value, expressed as a percentage of the nominal
value.
The sign of the error is positive if the synchronizing pulses are larger than the nominal
value.
Measurement procedure
C.1)
Select test signal I (figure B.1) for 625-line systems or test signal V (figure for
a)
525-line systems.
Measure the difference in level between points b8 and b9, and record this value U8 9
b)
in millivolts.
If a manual method of measurement is used, calculate the error from the formula:
c)
U89— Uso
So = 100 (%)
Us0
is the nominal value of the synchronizing pulse amplitude at the output given
where Us0
in table 1.
1237-2 ©IEC:1995 - 21 -
6.1.3
Burst amplitude error
Introduction
The burst amplitude error is the difference between the actual amplitude of the burst and
its nominal value, expressed as a percentage of the nominal value.
The signal of the error is positive if the actual burst amplitude is larger than the nominal
value.
Measurement procedure
Select test signal I (figure B.1) for 625-line systems or test signal V (figure C.1) for
a)
525-line systems.
b) Measure the burst amplitude and record this value Ub in millivolts.
c) Calculate the error from the expression
Ubo
100 Ub — (%)
Ub0
where Ubo is the nominal value of the burst amplitude.
6.2 Short and line time distortions
6.2.1 K2T
factor
Introduction
2T pulse shape distortion relates to the departure of the 2T pulse from its ideal shape. The
performance with respect to this type of distortion is normally given in terms of a rating
factor, K, for which numerical limits are assigned in the equipment specification. It is
measured by means of an appropriate graticule for the relevant television standard and
equipment specification.
IEC 212/95
NOTES
1 Values result from a specific analogue Thomson-filter. By using digitally generated signals better
values can be achieved.
2 The half-amplitude duration shall be:
— 200 ns ± 3 % for 625-line systems;
— 250 ns ± 3 % for 525-line systems.
Figure 1 - Shape of the standardized 2 T pulse

- 23 -
1237-2 © I EC:1995
Measurement procedure for a manual method of measurement
Select test signal I (figure B.1) for 625-line systems or test signal V (figure C.1) for
a)
525-line systems.
b) Employ the oscilloscope graticule shown in figure 2 and adjust the oscilloscope
so that:
- the sweep velocity corresponds to the time scale of the graticule;
blanking level coincides with the horizontal axis through level reference
-
point "0 %" of the graticule;
the peak of the 2T pulse falls on the horizontal line through level reference
-
point "100 %";
the half-amplitude points of the 2T pulse are symmetrically disposed about the
-
vertical axis through time reference point "0".
c) State whether the waveform is within the specified K-rating tolerance, or state the
measured K-rating factor.
100%
90%
50%
30%
0%
I I II I it ^ I
ill I ti
0 2T 4T 6T 8T 10T 12T
8T 6T 4T 2T
All rating limits
IEC 2I3/9S
2% inner, 4% outer
Figure 2 - Example of oscilloscope graticule for the measurement
of 2 T pulse shape distortion
6.2.2 2T/bar ratio
Introduction
The 2T sine-squared pulse/bar ratio error is the difference between the amplitude of the
2) of the test signals I (figure B.1)
2T pulse (section B 1 ) and the luminance bar (section B
or V (figure C.1), expressed as a percentage of the luminance bar amplitude. The
11 and the level at
amplitude of the 2T pulse is the difference between the level at point b
reference point b7.
- 25 -
1237-2 © I EC:1995
The sign of the error is positive if the amplitude of the 2T pulse is greater than the
luminance bar amplitude.
Some measuring equipment may indicate the 2T pulse/bar ratio itself, rather than the
error.
Measurement procedure
Select test signal I (figure B.1) for 625-line systems or test V (figure C.1) for
a)
525-line systems.
U7,11 , between points b and 137.
b) Measure the amplitude of the 2T pulse,
Calculate the error from the expression
c)
(%)
U
1,2
6.2.3 Bar tilt
Introduction
The luminance bar tilt is the difference between the level of the luminance bar (section 62)
of the test signals I (figure B.1) or V (figure C.1) 1 µs after the half-amplitude
at point b
4, 1 µs before the nominal half-amplitude
point of its leading edge, and the level at point b
point of its trailing edge, expressed as a percentage of the luminance amplitude.
4 is higher than
The sign of the bar tilt is positive if the level of the luminance bar at point b
the level at point b3.
Measurement procedure
Select test signal I (figure B.1) for 625-line systems or test signal V (figure C.1) for
a)
525-line systems.
and b4.
Measure the difference in level, U3,4 , between points b3
b)
c) Calculate the bar tilt from the expression:
U3,4
(%)
U1,2
6.2.4 Base-line distortion
Introduction
b7 of the test
Base-line distortion is expressed as the difference between the level at point
signals I (figure B.1) or V (figure C.1), 1 µs after the half-amplitude point of the trailing
2), and the level at reference point b1 , expressed as a
edge of the luminance bar (section B
percentage of the luminance bar amplitude.
7 is higher than the
The sign of the base-line distortion is positive if the level at point b
level at point b1.
The measurements are made with the bandwidth of the video signal limited by the network
described in figure 3 or by an equivalent technique.

1237-2 © IEC:1995
- 27 -
L1 = 2,948
^YYY1.
L3 = 5,767 L4 = 5,664
HH
Cl = 147,7
L2 = 0,5752
C3 = 141,6 C4 = 1057
75 Q ---
-•--- 75 S2
C5 = 310,5
C2 = 4044
T T
T
o o
IEC 214195
NOTES
1 foo is the frequency of the first zero of the output/input transfer function.
2 Inductances are given in µH, capacitances in pF.
3 For further details see MacDiarmid and Phillips, Proc. IEE, Vol 105B, 440.
=
Figure 3 - Thomson filter diagram (foo 3,3 MHz)
Measurement procedure
a) Select test signal I (figure B.1) for 625-line systems or test signal V (figure C.1) for
525-line systems.
b) Measure the difference in level, between points b 1 and
U17 b7.
c) Calculate the distortion from the expression:
V1,7 (%)
U1,2
6.3 Chrominance-luminance gain inequality

Introduction
Chrominance-luminance gain inequality is the difference between the peak-to-peak
amplitude of the
chrominance signal in section G 1 or G2 (or in section G) of the test
signal IV (figure B.4) or VI (figure C.2) and the amplitude of a reference luminance signal,
expressed as a percentage of this amplitude.
The sign of the gain inequality is positive if the amplitude of the chrominance signal is
greater than that of the luminance bar.
Measurement procedure
a) Select test signal IV (figure B.4) for 625-line systems or test signal VI (figure C.2)
for 525-line systems.
b)
Measure the peak-to-peak amplitude U5 of the chrominance signal in section G1
or
G2 for 625-line systems, or in section G for 525-line systems, at the time defined by
point b5.
1237-2 ©IEC:1995 - 29 -
c) Measure the amplitude of the luminance bar as previously described.
U12
d) Calculate the gain inequality from the expressions:
U
5 — V1,2
- for 625-line systems: (%)
V1,2
U5 — 0,8 U
1 '2 (%)
- for 525-line systems:
0,8 U1,2
6.4 Chrominance-luminance delay inequality
Introduction
Chrominance
-luminance delay inequality is the time difference, in nanoseconds, between
the luminance and the chrominance component of the composite 20T pulse (or the
composite 10T
pulse for system I) of the test signal I (figure B.1) or the composite 12,5T
pulse of the test signal V (figure C.1).
The sign of the delay inequality is positive if the axis of symmetry of the chrominance
component lags behind the axis of symmetry of the luminance component.
Measurement procedure
a) Select test signal I (figure B.1) for 625-line systems or test signal V (figure C.1) for
525-line systems.
b) Mesure
the time difference between the luminance pa rt of the pulse and the enve-
lope of the chrominance part of the pulse in nanoseconds.
Method using a nomogram
The chrominance-luminance gain inequality and chrominance-luminance
delay inequality
may also be determined by measuring the amplitudes Ua and Ub of the composite
Umax,
20 T-pulse (see figure 4) and by using the appropriate nomogram (see e.g. (ROSMAN),
(SIOCOS), (MALLON and WILLIAMS)).
NOTE — In this case, if -luminance
chrominance cross-talk is present, this will affect the results of the
measurements, as it will not be possible to discriminate between cross-talk and delay inequality on the
shape of the waveform and base-line of the T pulse.
1FAC 215195
Figure 4 - Chrominance-luminance delay inequality

1237-2 © IEC:1995 - 31 -
6.5 Amplitude/frequency characteristics
6.5.1 Luminance
Introduction
The amplitude/video frequency characteristic is determined by measuring the ratio
between (1) the peak-to-peak amplitude of each sine-wave signal at the different video
of the test signal II (figure B.2) or VI (figure C.2) and (2) the
frequencies in section C2
Il
1 when test signal
peak-to-peak amplitude of the reference luminance signal in section C
is used, or half the peak-to-peak amplitude when test signal VI is used.
of test signals I (figure B.1) or V (figure C.1)
B2
Alternatively, the luminance bar in section
U1,2.
may be taken as the reference luminance signal
Measurement procedure
Select test signal II (figure B.2) for 625-line systems or test signal VI (figure C.2) for
a)
525-line systems.
between the mid-duration points of the
C1
b) Measure the peak-to-peak amplitude U
reference luminance in section C1.
at the mid-duration point of each sine-
UC2
c) Measure the peak-to-peak amplitude
for each frequency up to the highest in accordance with the
wave signal in section C2
television standard concerned.
For each frequency of the sine-wave signal, calculate the ratio
d)
- for 625-line systems:
tic
(dB)
(dB) or 20 log
20 log
0,6
/./C`
U1,2
- for 525-line systems:
2U
2U
C2
(dB)
(dB) 20 log 0
20 log C2 or
U1,2
UC1
e) Tabulate the ratios as a function of video frequency.
6.5.2 Chrominance
Introduction
chrominance information may be
The amplitude/frequency characteristics of modulated
e envelopes
determined by comparing the amplitudes of the colour carrier signals in the sin
in test signal IX (figure B.5) for 625-line systems, where the values of B1
of F1 to F4
are equal to those in test signal I (figure B.1) and the half-amplitude durations
and B2
are 4,0 µs, 2,0 µs, 1,2 ils and 0,6 µs.
of F1 to F4
This method however needs further investigations.
For 525-line systems, use the test signal VII indicated in figure C.3.

1237-2 ©IEC:1995 - 33 -
6.6 Non-linear distortions
6.6.1 Differential gain
Introduction
Differential gain is defined as the maximum change in amplitude of the chrominance
sub-carrier signal relative to the amplitude of this signal at blanking level, resulting from a
change in amplitude of the associated luminance signal.
chrominance
The measurements are made at the differing luminance levels of the
of test signals Ill (figure B.3) or V (figure C.1) disregarding the
staircase in section D2
highest level, unless this is specifically required, e.g. as in system I.
A band-pass filter is used to separate the chrominance sub-carrier signal from the
luminance signal.
Measurement procedure
a) Select test signal Ill (figure B.3) for 625-line systems or test signal V (figure C.1)
for 525-line systems.
b) Measure the peak-to-peak amplitude of the chrominance sub-carrier at the differing
luminance levels, including the sub-carrier at blanking level at the point b1O.
c) x and -y from the formula:
Calculate the values of
Amin - A
Amax - o O
A
x = 100 (%) and -y = 100 (%)
AO
Ao
min are the largest and the smallest peak-to-peak amplitudes of the
where A and A
max
chrominance sub-carrier measured in item b) above, and A 0 is the peak-to-peak ampli-
tude at blanking level.
x and -y. The peak-to-peak value
d) The differential gain is given by both the values of
of differential gain is given by x + y.
6.6.2 Differential gain versus frequency
Introduction
In video recording systems using usual low frequency carrier FM-modulation or "colour-
under" processing, "differential gain" indicated in clause 6.6.1 does not indicate non-linear
distortion precisely because of the influence of the characteristics in the FM domain or
separation recording of chrominance signal.
In such cases it is advisable to use different superposed carrier frequency as modulation
on the staircase in test signals Ill (figure B.3) or V (figure C.1). Superposed carrier
frequencies can be e.g. 1,0 MHz, 2,0 MHz, 3,0 MHz.
The measuring procedure is the same as indicated in 6.6.1.

1237-2 ©IEC:1995 - 35 -
6.6.3 Differential phase
introduction
Differential phase is defined as the maximum change in phase of the chrominance
sub-carrier signal relative to the phase of this signal at blanking level, resulting from the
change in amplitude of the associated luminance signal.
The measurements are made at the differing luminance levels of the chrominance
staircase in section
D2 of test signals Ill (figure B.3) and V (figure C.1) disregarding the
highest level, unless this is specifically required, e.g. as in system I.
A band-pass filter is used to separate the chrominance sub-carrier signal from the
luminance signal.
Measurement procedure
a) Select test signal Ill (figure B.3) for 625-line systems and test signal V (figure C.1)
for 525-line systems.
b) Measure the phase difference, 4, between the chrominance sub-carrier at the
differing luminance levels and the chrominance sub-carrier at blanking level at the
point b10.
c) The differential phase, expressed in degrees, is given by both the maximum positive
phase difference Abp, and maximum negative phase difference Acpn.
The peak-to-peak value of differential phase is given by App + Acpn.
clY 116/93
a) Chrominance staircase b) Display of the measurement waveform
Figure 5 - Measurement of differential phase
6.6.4 Group delay
Test equipment specifically designed for the measurement of group delay in video tape
recorders is now available. Alternatively, a new waveform, the multipulse, has been
devised which allows group delay to be measured over a range of frequencies within the
video pass band. The waveform is shown in figure B.6 and consists of five 20T pulses
modulated by a range of frequencies. The assessment of group delay may be obtained by
a similar method to that used with the chrominance pulse (see 6.3 and 6.4).

- 37 -
1237-2 ©IEC:1995
Method using sin x/x pulse signal
The sin x/x test signal (figure C.5 test signal VIII A for 625-line and test signal VIII B for
525-line systems) which is generated by a digital synthesizer and a measuring instrument
operating on software base are used in this method.
The playback sin x/x signal from the VTR under test is applied to the measuring instru-
ormance A/D converter is acquired into the
rf
ment and after being digitized by a high pe
memory with a sampling rate sufficiently high, such as four times subcarrier frequency.
Sampled data of the test signals with positive and negative polarity are averaged and
Fourier coefficients are computed according to equations (6.6.4-1) and (6.6.4-2)
IC
ak = (6.6.4-1)
f (x) cos kx dx
Tr
J
-rz
a
bk
(6.6.4-2)
f (x) sin kx dx
TG
-a
where k = 0, 1, 2, 3 .
Group delay is computed by differentiating the phase term series as shown in equation
(6.6.4-3)
— tan- 1
tan-1
[b
] [b
k-1 /ak-1 }
k+1 /ak+1 (6.6.4-3)
Fk 2 X (ilk
where
(^k n fk;
= 2
are the frequencies in Fourier series;
fk
k= 0,1,2,3.
Amplitude response is also computed at the same time by using equation (6.6.4-4).
2 + bk2
(6.6.4-4)
^
Ak = 1 ak
The calculation results are shown as a curve (average value at the frequency range of
400 kHz to 600 kHz is used as reference).
NOTE — Attention should be drawn of the amplitude of input test signal not to be clipped by white clip
circuit in the modulator.
luminance cross-talk/Intermodulation
6.7 Chrominance-
Introduction
cross-talk relates to the change in amplitude of the luminance
-luminance
Chrominance
chrominance signal.
signal as a function of the amplitude of the associated

– 39 –
1237-2 © IEC:1995
l or G2 of test
Chrominance -luminance cross-talk is measured by using section a
signal IV, (figure B.4), or section G of test signal VI (figure C.2). It is defined as the differ-
5 and the luminance amplitude at point
ence between the luminance amplitude at point b
B2 of test
expressed as a percentage of the amplitude of the luminance bar in section
b6,
signal I (figure B.1) or V (figure C.1).
is greater than
The sign of the cross-talk is positive if the luminance amplitude at point b
the luminance amplitude at point b6.
Measurement procedure
Select test signal IV (figure B.4) for 625-line systems or test signal VI (figure C.2)
a)
for 525-line systems.
of the luminance signal at the points b 5 and b6.
Determine the difference in level U5,6
b)
-luminance cross-talk from the expression:
c) Calculate the chrominance
U5,6
(%)
U1,2
6.8 Luminance signal-to-noise ratio
Introduction
The signal-to-noise ratio for continuous random noise is defined as the ratio, expressed in
decibels, of the nominal peak-to-peak amplitude of the picture luminance signal to the
RMS amplitude of the noise measured under the following conditions:
the noise is passed through a specified bandpass filter to delineate the effective
–
frequency range and also, where appropriate, through a specified weighting network or
equivalent;
the measurement is made with an instrument having, in terms of power, an effective
–
time constant or integrating time of one second.
a) Unweighted
The nominal frequency range is 200 kHz to 5 MHz.
Weighted (CCIR Recommendation 567-3)
b)
The nominal frequency range is 200 kHz to 5 MHz. The weighting network response
is shown in figure 6. It has a weighting effect of 8,6 dB for flat random noise
and 12,4 dB for triangular random noise
For a video tape recorder the signal to noise ratio may vary at different signal levels of lift
due to limitations in the FM domain. A measurement should be made at a luminance level
of 50 %, but most organizations make additional measurements between 10 % and 90 %
lift.
Where the VTR incorporates a digital time base corrector it is preferable to measure the
noise before time base correction as the measurement after time base correction could be
affected by quantizing errors. Alternatively a ramp or sawtooth waveform can be used.
The 200 kHz high pass filter incorporated in the noise measuring equipment eliminates the
low frequency content from the sawtooth signal.
NOTE – Many noise measuring instruments in use incorporate a colour sub-carrier notch filter. A measure-
ment should be taken with the notch filter in, and out, of circuit. A significant difference between the
readings can indicate a residual sub-carrier component in the measured waveform.

1237-2 © IEC:1995 -41 -
Unified weighting network for random noise
Network configuration
1EaC 217195
Figure 6 - Network diagram
Insertion loss A
rr
1 +Lt1 +â) cot]
A = 10 log dB
rr
1 +La wi^
at high frequencies: A. - 20 log (1 + a)
where
T = 245 ns; a = 4,5 (Aœ ->14,8 dB)
6.9 Chrominance signal-to-noise ratio
Introduction
When reproducing colour pictures on a video tape recorder, impairments in colour may oc-
cur, caused partly by the recording method (conversion of the sub-carrier) and partly by
the equipment (tape, tape recorder).
6.9.1 Measurement of PAL/NTSC colour video signals
IEC 883 describes a technique for measuring the impairment of a TV-picture due to
random noise in a colour signal. It should be realized that other mechanisms can be
present which introduce impairments that appear to be caused by random noise, but are
not measured by this technique. This method is suitable for PAL and NTSC colour video
signals.
1237-2 ©IEC:1995 - 43 -
Other techniques are necessary for measuring parameters such as moiré, time base error
and cross-colour.
The values which result from this measurement method make it possible to compare
different video tape recorders, recording systems and video tapes for the random noise
characteristics.
6.9.2 Measurement of SECAM colour video signals
NOTE – The same technique is used in IEC 1041-2 for non broadcast VTRs.
The circuit arrangement shall be as shown in figure 7.
The test signal shall be a full field blue or red signal corresponding to the blue or red pa
rt
of the 100/0/75/0 colour bars defined in the CCIR Recommendation 471-1.
The measurement of the chrominance signal to noise ratio is made as explained
hereunder:
a) Put the switch SW1 in position 1 in order to measure the demodulator noise level at
the output, with the red signal (R-Y) and with the blue signal (B-Y).
- The noise level (r.m.s.) will be taken as NRO from the (R-Y) output and NBO
from the (B-Y) output.
b) Put the SW1 in position 2 and record the red signal on one tape section and then
the blue signal on another one.
During playback of both sections, make the respective measurements at the (R-Y)
c)
and (B-Y) outputs;
- The noise level (r.m.s.) is taken as NR1 and NB1 respectively.
- The peak to peak signal level is taken as VR1 and VB1 respectively.
d) The chrominance signal to noise ratio of the VTR under test is given as follows:
VR1
S/N in dB = 20 log
(R-Y)
1NR12 - NR02
VB1
in dB = 20 log S/N
(B Y)
^NB1 2 - NB02
e) The results of measurement shall be stated in unweighted values of the S/N
obtained at the (R-Y) and (B-Y) output.

1237-2
© IEC:1995 - 45 -
SECAM
test signal
SW1
generator
VTR
Select full-field
to be tested
red or blue
test signals
t 0,5 dB
Sync.
Demodulator
(R–Y) 1(B–Y)
SW2
\
Frequency
200 500 1 000 2 000 kHz
400 kHz
Low pass filter
± 0,5 dB
fc = 500 kHz
Loss 4
in dB
Noise meter
Oscilloscope
High pass filter
fc = 100 Hz
10Hz 100 Hz 1 kHz
IEC 2I8/95
Figure 7 - The circuit arrangement

1237-2 © IEC:1995 - 47 -
6.10 Field time distortions
6.10.1 Vertical tilt
Introduction
The vertical tilt is defined as the difference between the signal levels of the white part of
the ve rtical bar signal approximately 250 ps after the rising edge (point «v» in figure 8)
and approximately 250 µs before its falling edge (point «r» in figure 8).
This is the sum of the magnitudes "av 1 " and av2».
The ve rtical tilt shall be reported in percent of the ve rtical rectangular signal magnitude
level difference between the points "m" and "s" in figure 8.
The vertical tilt is positive if the signal level "r" is larger than the level "v". The diagram,
figure 8, shows a negative ve rtical tilt.
Measurement procedure
a) Select test signal "A" (annex A).
b) Measure the level according to figure 8.
c) Calculate the value of the ve rtical tilt using the expression:
100 (%)
((m
- s)
250 µs ♦250 µs
100 %
t — 50%
0%
— 5 ms 5 ms
•
-,. 20 ms
IEC 219/56
Figure 8 - Vertical tilt definition

1237-2 ©IEC:1995 - 49 -
6.11 Long time distortion
6.11.1
Signal bounce
video test signal, simulating a sudden change from a low average picture level to a
If a
high one or a high average picture level to a low one, is applied to the input of a circuit,
long-time waveform distortion is present if the blanking level of the output signal does not
accurately follow that of the input. This failure may be either in exponential form or, more
frequently, in the form of damped very low-frequency oscillations.
!k]C 220195
Figure 9 - Effect of signal bounce on the synchronising pulses -
clamped display
(The lower trace shows the variation of sync-pulse amplitude)
The extent of the crushing of the synchronising signal which can occur is well illustrated in
icient clamp has been employed to eliminate the actual signal
figure 9 where a very eff
excursion, so revealing extremely clearly the changes with time of the synchronising pulse
amplitude. The maximum reduction in this instance turns out to be as much as 64 %.
Since such crushing can also be accompanied by waveform distortion due, amongst other
things, to interference with the negative feedback characteristic of signal-handling
equipment as active circuit elements are driven to the extremes of their ranges, the effect
on synchronisation, not to mention the sound channel when sound-in-syncs is present, can
be imagined. The standard test signal for this purpose is a white bar on each line for a
duration of 2 s, followed by syncs only for exactly the same period of time, this sequence
being repeated periodically so as to produce the equivalent of a square wave variation of
the APL.
6.11.2 Power supply interference
Introduction
This parameter is defined as the peak to peak value of the fluctuations of the video
blanking level measured by an oscilloscope. The frequency-range of interest is
approximately between 10 Hz and 2 kHz.
The result may be reported in percentage of the peak white level or sometimes in dB (hum
ratio). The test signal for this measurement shall be a black signal to avoid a possible line
base distortion.
1237-2 © IEC:1995 -51 -
7 Special measurements
7.1 FM characteristic frequencies
Introduction
FM characteristic frequencies are specified in the standard and correspond respectively
to:
a) sync tip;
blanking level;
b)
c) peak white.
The measurements are taken with a spectrum analyser at the output of the FM modulator.
The frequencies corresponding to blanking level and peak white are measured on a zero
pedestal field and on a 100 % pedestal field respectively.
Measurement procedure
a) Select signal A (figures A.1 and A.2 in annex A).
b) Measure the characteristic frequencies corresponding to the sync tip, blanking level
and peak white according to the relevant specification at the output of the
FM-modulator (during recording) or during playback at the input of FM-limiter (also
applicable to calibration tapes).
The tolerances shall not exceed the indicated values.
Alternative method using calibrated variable oscillator
The measurement consists of mixing the output signal of a calibrated variable sinusoidal
oscillator with the output of the FM modulator.
If the levels of the two signals are in a suitable ratio, beat patterns produced by the inter-
action of the modulated video signal and the oscillator signal will appear on the
demodulated video signal at the demodulator output in E-E mode.
The input test signal shall be a 100 % flat field signal and the frequency corresponding to
sync tip, blanking level and peak white are measured as zero beats on the E-E demodu-
lated video signal respectively, by tuning the calibrated variable oscillator frequency.
7.2 Non-linear preemphasis
Introduction
In some recording systems a non linear preemphasis is applied to improve the
...