SIST EN 61237-2:1999
(Main)Broadcast video tape recorders - Methods of measurement -- Part 2: Electrical measurements of analogue composite video signals
Broadcast video tape recorders - Methods of measurement -- Part 2: Electrical measurements of analogue composite video signals
Describes the methods of measurement, test signals and procedures which may apply to characteristics of video recording/playback machines mainly intended for professional use.
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
Décrit les méthodes de mesure, les signaux et les procédures d'essai qui peuvent s'appliquer aux caractéristiques des appareils d'enregistrement/de lecture vidéo, ces appareils étant principalement destinés à une utilisation professionnelle.
Broadcast video tape recorders - Methods of measurement -- Part 2: Electrical measurements of analogue composite video signals (IEC 61237-2:1995)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 61237-2:1999
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
SIST EN 61237-2:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
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
Aucune partie de cette publication ne peut étre reproduite ni
any form or by any means, electronic or mechanical,
utilisée sous quelque forme que ce soit et par aucun pro-
including photocopying and microfilm, without permission
cédé, électronique ou mécanique, y compris la photocopie et
les microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher.
Genève, Suisse
Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé
Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission
PRICE CODE
IEC McKayHapo,aHaa 3nelrrpoTexHH gecnaa HoMHCCHR
vigueur
Pour prix, voir catalogue en
• •
For price, see current cata logue
---------------------- Page: 2 ----------------------
- 3 -
1237-2 ©IEC:1995
CONTENTS
Page
FOREWORD 7
Clause
11
1 Scope and object
11
2 Normative references
13 3 General
13
4 Test conditions
15
5 Measuring methods and test signals
15 5.1 Manual and automatic measurements
15
5.2 Measurement of differences between adjacent tracks (fields/segments)
15 5.3 Procedure of measurement
17
5.4 Test signals
17
5.4.1 Introduction
17
5.4.2 Amplitudes and characteristics of test signals
17
5.4.3 Test signal arrangement
19
Measurements of characteristics 6
19
6.1 Amplitude of output signals in E-E mode and playback
19
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
25
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
31
6.5 Amplitude/frequency characteristics
31
6.5.1 Luminance
31
6.5.2 Chrominance
33
6.6 Non-linear distortions
33
6.6.1 Differential gain
33
6.6.2 Differential gain versus frequency
35
6.6.3 Differential phase
35
6.6.4 Group delay
37
cross-talk/intermodulation Chrominance-luminance
6.7
6.8 Luminance signal-to-noise ratio 39
41
signal-to-noise ratio 6.9 Chrominance
41 6.9.1 Measurement of PAL/NTSC colour video signals
43
SECAM colour video signals
6.9.2 Measurement of
---------------------- Page: 3 ----------------------
- 5 -
1237-2 ©IEC:1995
Page
Clause
47
6.10 Field time distortions
47
6.10.1 Vertical tilt
6.11 Long time distortion 49
6.11.1 Signal bounce 49
49
6.11.2 Power supply interference
51
7 Special measurements
51 7.1 FM characteristic frequencies
51
7.2 Non-linear preemphasis
55 7.3 Noise coring
55
7.4 Moiré
57
7.5 Time base errors (measurements before time base error corrector)
57
7.5.1 Velocity errors
7.5.2 Phase step 59
7.5.3 Jitter 59
61
7.5.4 Time base errors after correction
61
7.6 Sc/H phase
Annexes
A - Test signals elements 69
87
B - 625-line systems
105
C - 525-line systems
119
D - Bibliography
---------------------- Page: 4 ----------------------
- 7 -
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.
---------------------- Page: 5 ----------------------
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
---------------------- Page: 6 ----------------------
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
---------------------- Page: 7 ----------------------
- 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
---------------------- Page: 8 ----------------------
- 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.
---------------------- Page: 9 ----------------------
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.
---------------------- Page: 10 ----------------------
1237-2 © IEC:1995 - 19 -
Measurements of characteristics
6
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.
---------------------- Page: 11 ----------------------
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
---------------------- Page: 12 ----------------------
- 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.
---------------------- Page: 13 ----------------------
- 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,
11
Calculate the error from the expression
c)
(%)
100
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
3
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
(%)
100
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.
---------------------- Page: 14 ----------------------
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 (%)
100
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.
---------------------- Page: 15 ----------------------
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: (%)
100
V1,2
U5 — 0,8 U
1 '2 (%)
- for 525-line systems:
100
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
---------------------- Page: 16 ----------------------
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
0
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.
---------------------- Page: 17 ----------------------
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 indic
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.