SIST EN 61237-3:1999
(Main)Methods of measurement for broadcast video tape recorders -- Part 3: Electrical measurements for analogue component video signals
Methods of measurement for broadcast video tape recorders -- Part 3: Electrical measurements for analogue component 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 3: Elektrische Messungen für Videosignale mit analogen Komponenten
Méthodes de mesure pour les magnétoscopes de radiodiffusion -- Partie 3: Mesures électriques pour les signaux vidéo analogiques à composantes
Décrit les méthodes de mesure, les signaux et les procédures d'essai qui peuvent s'appliquer aux caractéristiques des appareils d'enregistrements de lecture vidéo, ces appareils étant principalement destinés à une utilisation professionnelle.
Methods of measurement for broadcast video tape recorders -- Part 3: Electrical measurements for analogue component video signals (IEC 61237-3:1995)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 61237-3:1999
01-april-1999
Methods of measurement for broadcast video tape recorders -- Part 3: Electrical
measurements for analogue component video signals (IEC 61237-3:1995)
Methods of measurement for broadcast video tape recorders -- Part 3: Electrical
measurements for analogue component video signals
Meßverfahren für Videobandgeräte für den Rundfunk -- Teil 3: Elektrische Messungen
für Videosignale mit analogen Komponenten
Méthodes de mesure pour les magnétoscopes de radiodiffusion -- Partie 3: Mesures
électriques pour les signaux vidéo analogiques à composantes
Ta slovenski standard je istoveten z: EN 61237-3:1995
ICS:
33.160.40 Video sistemi Video systems
SIST EN 61237-3:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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NORME CE1
IEC
INTERNATIONALE
1237-3
INTERNATIONAL
Première édition
STANDARD
First edition
1995-02
Méthodes de mesure pour les magnétoscopes
de radiodiffusion
Partie 3:
Mesures électriques pour les signaux vidéo
analogiques à composantes
Methods of measurement for broadcast
video tape recorders
Part 3:
Electrical measurements for analogue
component video signals
de reproduction réservés — Copyright — all rights reserved
© CEI 1995 Droits
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
any form or by any means, electronic or mechanical,
utilisée sous quelque forme que ce soit et par aucun pro-
including photocopying and microfilrh, without permission
cédé, électronique ou mécanique, y compris la photocopie et
in writing from the publisher.
les microfilms, sans l'accord écrit de l'éditeur.
Suisse
Bureau Central de la Commission Electrotechnique Inte rnationale 3, rue de Varembé Genève,
Commission Electrotechnique Internationale CODE PRIX
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E /V
PRICE COD
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voir catalogue en vigueur
Pour prix,
• •
For price, see current catalogue
---------------------- Page: 2 ----------------------
-3 -
1237-3 © IEC:1995
CONTENTS
Page
FOREWORD 5
Clause
9
1 Scope and object
2 Normative references 9
11
3 General
11
4 Test conditions
13 5 Measuring methods and test signals
13
5.1 Manual and automatic methods of measurement
13
5.2 Measurement of differences between adjacent tracks (fields/segments)
13 5.3 Procedure of measurement
15
5.4 Test signals
6 Measurement of characteristics 19
19
Luminance bar amplitude error
6.1
21 6.2 Synchronizing pulse amplitude error
23
6.3 Bar tilt
23
6.4 Pulse/bar ratio error
25 6.5 Pulse shape distortion
27 6.6 Amplitude/video-frequency characteristic
27 6.7 Chrominance-luminance gain inequality
29
6.8 Chrominance-luminance delay inequality
31
Line-time non-linearity 6.9
33 6.10 High-frequency non-linearity
33 6.11 High-frequency intermodulation
35
6.12 Crosstalk between channels
37 6.13 Luminance random noise
6.14 Chrominance random noise 39
39
6.15 Group delay
41
6.16 FM characteristic frequencies
43
6.17 Jitter
47
6.18 Velocity errors
47
6.19 Moiré
49
6.20 Noise reduction
6.21 Coder alignment 49
49
6.22 Power-supply interference
51
Figures
77
Annex A - Bibliography
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1237-3 © IEC:1995 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
METHODS OF MEASUREMENT FOR BROADCAST
VIDEO TAPE RECORDERS -
Part 3: Electrical measurements for analogue
component 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.
2) The formal decisions or agreements of the IEC on technical matters, prepared by technical committees on
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.
3) They have the form of recommendations for international use 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.
International Standard IEC 1237-3 has been prepared by sub-committee 60B: Video
recording, of IEC technical committee 60: Recording.
The former IEC 698: Measuring methods for television tape machines, will not be
withdrawn because it contains the two transverse track video recorders (IEC 347), which
will not be included in the new draft. IEC 698 is valid for mechanical measurements on
transverse track video recorders only.
The text of this standard is based on the following documents:
Report on voting
DIS
60B(CO)160
60B(CO)172
60B(CO)160A
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.
rts, under the general title Methods of measurement
IEC 1237 consists of the following pa
for broadcast video tape recorders:
Part 1: Mechanical measurements
Part 2: Electrical measurements of analogue composite video signals
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1237-3 © I EC:1995
Part 3: Electrical measurements of analogue component video signals
Part 4: Measurements of audio performance
Part 5: Electrical measurements of digital composite video signals and digital audio
sigals
Part 6: Electrical measurements of digital component video signals and digital audio
signals
Annex A is for information only.
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1237-3 © IEC:1995 –9–
METHODS OF MEASUREMENT FOR BROADCAST
VIDEO TAPE RECORDERS -
Part 3: Electrical measurements for analogue
component video signals
1 Scope and object
This part of IEC 1237 describes the test signals and measurement methods for equipment
mainly dedicated to record/playback of analogue component TV signals on magnetic tape
on reels or in cassettes. It may also be applied for measuring methods for general use in
television production and transmission. The allowable tolerances for the rated values for
ormance are not given in this standard, but may be derived from appropriate
acceptable pe rf
system specifications, 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 1105 (reference tapes) and
IEC technical report 1295 (calibration tapes) [1]*.
rformance comparisons and, as far as
The methods are applicable to acceptance tests, pe
possible, to routine checks.
The principal object of this document 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 hereafter
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
indicated were valid. All standards are subject to revision, and parties to agreements
based on this part of IEC 1237 are encouraged to investigate the possibility of applying
the most recent editions of the standards indicated below. Members of IEC and ISO
maintain registers of currently valid International Standards.
Measuring methods for television tape machines
IEC 698: 1981,
Helical-scan video tape cassette system using 12,65 mm (0,5 in) magnetic
IEC 961: 1989,
tape on type L
* Figures in square brackets refer to annex A, Bibliography.
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1237-3 ©IEC:1995 - 11 -
I EC 1105: 1991, Reference tapes for video tape recorder systems
ITU-R Recommendation 471-1: 1990, Nomenclature and description of colour bar signals
(Vol. XI-1)
ITU-R Recommendation 567-3: 1990, Transmission performance of television circuits
designed for use in international connections (Vol. XII)
ITU-R Recommendation 601-2: 1990, Encoding parameters of digital television for studios
(Vol. XI-1)
ITU-R Recommendation 656: 1986, Interfaces for digital component video signals in 525-line
and 625-line television systems (Vol. XI-1)
3 General
To ensure 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 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 5.1 and 5.2), they may
give results which differ from those obtained or calculated with full-field test signals.
Therefore is necessary to additionally specify the measuring method:
it
- 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:
Temperature (20 ± 1) °C
Relative humidity (50 ± 2) %
Air pressure 106 kPa
86 kPa to
Conditioning before testing 24 h
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1237-3 ©IEC:1995 - 13 -
5 Measuring methods and test signals
5.1 Manual and automatic methods of measurement
If automatic measuring apparatus is designed to give reliable results under the special
conditions of television tape playback as e.g. drop-out, jitter, noise, time-base errors,
suppression of vertical blanking interval or insufficient head-to-tape contact, a significant
improvement in measurement speed, accuracy and comparability of results can be
achieved.
Therefore preference was given to measurement 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 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.
Since two or more heads are used for record and playback of the video information to and
from the tracks, it is desirable to restrict the measurement to segments or tracks 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 [2].
5.3 Procedure of measurement
The measurements shall be carried out by measuring the playback signal after recording
rformance,
on the same machine (best-case configuration). Before testing the overall pe
the playback channel shall be measured by means of a calibration tape (see clause 1).
rformance of a video recording system
In certain particular cases, if the multigeneration pe
is measured, the measurements shall be carried out by measuring the playback signal
after 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.
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1237-3 © IEC:1995 - 15 -
5.4 Test signals
5.4.1
Introduction
A representative range of test signals is shown in figures 1 to 10. For ease of reference,
they are indicated by roman numerals. Other test signals not shown in the figures are
collected in 5.4.2.
All signals are defined as a luminance and two colour-difference signals. In practice, these
signals are generally represented by the symbols Y, B-Y, R-Y, but in the following a short
CR) has been used:
form of the notation adopted by the ITU-R (E' Y, E'C8 and E'
Y,CB and CR
These components are defined in terms of the primary signals R, G and B by:
= 0,564 (B-Y), CR = 0,713 (R-Y)
Y = 0,587 • G + 0,299 • R + 0,114 • B, CB
It should be noted that some of the test signals will produce "illegal" values of R, G, B or
composite if dematrixed and/or coded.
Amplitudes and bandwidth of test signals
5.4.2
The amplitude of the signals is given in per cent of full-picture amplitude of the luminance
and/or chrominance signals. The nominal full amplitude shall be identical but may differ
between systems. The preferred levels given in table 1 are those defined by the common
EBU/SMPTE Standard (EBU N10, SMPTE 253) ([3] and [4]). They are in use in all 625-line
countries. In 525-line countries several other luminance and sync levels as well as colour
difference offset levels can be found. In those cases the signals delivered to and received
from the system under test should comply with the individual machine setting.
Table 1 - Nominal signal amplitudes for 625-line and 525-line standards
525-line standards
625-line standards
mV %
mV %
714 100 or IRE
Luminance (Y) 700 100
±350 ±50 ±350 ±50 or IRE
Colour difference (C B, C R)
–300 42,8
Sync –300 42,8
The luminance bandwidth of analogue component VTRs is often higher than the nominal
SECAM signals. It is usually as
luminance bandwidths of composite coded NTSC, PAL or
high as specified for the digital studio standard (ITU-R Recommendation 601-2 and 656),
Especially the NTSC-composite band
which is 5,75 MHz for Y and 2,8 MHz for CB , CR .
limit of 4,2 MHz does not exist. This has been taken into consideration in the specification
of the test signals, e.g. rise times, pulse widths and multiburst frequencies.
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17 –
–
1237-3 © I EC:1995
In order to further reduce the differences between 525- and 625-line systems measurements,
the test signals are identical for both systems as far as possible. This allows for identical
test procedures also in those cases, where the signals are converted into the digital
component format or converted from 525 to 625 lines or vice versa.
5.4.3 Characteristics of test signals
The luminance signal Y shall include sync pulses and line and field blanking in accordance
with the CCIR television standard relevant to the television tape machine under test.
shall include line and field blanking in
The two colour-difference signals CB and CR
accordance with the ITU-R television standard relevant to the television tape machine
under test. Neither of them shall include sync pulses.
) shall be simultaneous in real time and carry time-
All three signals (Y, C B and CR
coincident picture information.
5.4.4 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.
5.4.5 Description of test signals Ito XI
Test signal I, shown in figure 1, is the 100/0/100/0 colour-bar signal as defined in ITU-R
Recommendation 471. It is used for measuring absolute levels, level differences and
timing differences between channels.
Test signal Il, shown in figure 2, is a five-riser staircase used for static non-linearity
measurements. If digital signal processing is involved, test signal Ill is recommended in
order to suppress the influence of quantization errors from the measurement.
Test signal III, shown in figure 3, is a line-repetitive sawtooth of full amplitude. It is
recommended for non-linearity and noise measurements in equipment where digital signal
processing is included.
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1237-3 © IEC:1995 –19 –
Test signal IV, shown in figure 4, is a multiburst signal. The amplitude is 60 % of full amplitude
to reduce the influence of linear and non-linear pre-emphasis circuits. It is used for
frequency response and crosstalk measurements.
Test signal V, shown in figure 5, is a line-rate sweep signal which can be used as an
alternative to test signal IV. A field rate sweep is also possible and preferable for more
accurate measurement.
Test signal VI, shown in figure 6, contains a 25 µs bar signal and a 2T-pulse in the
luminance channel. For the signal in the colour-difference channels the recommended rise
time and pulse width is 5T with the exception of system L, MODE I (IEC 961) where only
8T-signals can be handled without severe distortion. No complete arrangement of signal
elements is given in order to allow different combinations of elements. The amplitudes of
the elements shall be 100 %. For more stringent tests, negative pulses may be used.
Test signal VII, shown in figure 7, is a multi-pulse signal suitable for group-delay
measurements at six discrete frequencies.
Test signal VIII, shown in figure 8, is the bow-tie signal composed of a 500 kHz sinusoid
on a 50 % pedestal in the luminance channel and a 502 kHz sinusoid in the colour-
difference channels phased to produce cancellation at the mid-point of the active line
when either colour-difference signal is subtracted from the luminance signal.
Test signal IX, shown in figure 9, is a noise-coring test waveform used to measure the
frequency dependent amount of loss of picture detail due to noise suppression.
Test signal X, shown in figure 10, is a three-level HF-signal on a pedestal used for HF
signal non-linearity and HF signal intermodulation measurement, which are likely to occur
in systems with restricted FM bandwidth.
NOTE – The width of the pulses from currently available test equipment may differ between 525- and
625-signals due to widespread current practice from prior NTSC, PAL or SECAM composite measurement
techniques. This should be avoided however for future component measurements.
5.4.6 Other test signals
For measurements in 6.12 and 6.16 variations of test signals IV or V and constant-level
component signals are required. They are described in tables 2 and 3.
6 Measurement of characteristics
Luminance bar amplitude error
6.1
6.1.1 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.
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1237-3 © IEC:1995 - 21 -
The sign of the error is positive if the bar amplitude is greater than the nominal value.
6.1.2 Measurement procedure
a) Select test signal I.
b) Measure the difference in level between points bt and b2 , and record this value U1,2
in millivolts.
c) Calculate the error from the expression:
100 1 Ut ' 2 – Un (%)
Un
where Un is the nominal value of the luminance bar amplitude given in table 1.
NOTE — The level of the colour-difference signals can be measured in the same way as described for the
luminance channel using test signal I. It is however better to define these levels relative to the luminance
bar as defined in 6.7.
6.2 Synchronizing pulse amplitude error
6.2.1
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.
The sync pulse amplitude can only be measured on the luminance signal because the
colour-difference signals contain no such signal at the EBU/SMPTE inte rface. The
measurement of sync pulses added to waveforms internal to some television tape
machines is not subject to this measurement.
6.2.2 Measurement procedure
a) Select test signal I or any other suitable test signal containing syncs.
Measure the difference in level between points b8 and b9, and record this value U8,9
b)
in millivolts.
c) Calculate the error from the formula:
U89 – Uso
So = 100 (%)
Us0
where Us0 is the nominal value of the synchronizing pulse amplitude.
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1237-3 © IEC:1995
6.3 Bar tilt
6.3.1
Introduction
The bar tilt shall be measured in the luminance and the two colour-difference channels.
The luminance bar tilt is the difference between the level of the luminance bar (test signal
VI, section B2) at point A, 1 ps after the half-amplitude point of its leading edge, and the
level at point C, 1 µs before the nominal half-amplitude point of its trailing edge,
expressed as a percentage of the luminance bar amplitude.
The colour-difference bar tilt is measured in the same way, except that the sampling
points are located 3 p.s from the leading and trailing edges.
The sign of the bar tilt is positive if the level of the bar at point C is higher than the level at
point A.
6.3.2 Measurement procedure
a) Select test signal VI.
between points C and A and UB - UE
b) Measure the difference in level, Uc - UA
between points B and E.
Calculate the bar tilt from the expression:
c)
Uc- UA
or IRE)
100 (%
UE
UB-
6.4 Pulse/bar ratio error
6.4.1 Introduction
The pulse/bar ratio error shall be measured in the luminance and the two colour-difference
channels.
Luminance:
The 2T sine-squared pulse/bar ratio error is the difference between the amplitudes of the
2T pulse (section B1) and the luminance bar (section B2) of test signal VI, expressed as a
percentage of the luminance bar amplitude. The amplitude of the 2T pulse is the difference
between the level at point D and the mean level at reference points E before and after the
pulse.
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.
Chrominance:
The 5T sine-squared pulse/bar ratio error is defined in the same way as above, using the
colour-difference waveforms instead. The pulse width of 500 ns (5T • 100 ns) corresponds
well to 4T . 125 ns, a pulse width which is in use for 525/60-line analogue component
VTRs.
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1237-3 © IEC:1995 - 25 -
6.4.2
Measurement procedure
a) Select test signal VI.
b) Measure the amplitude of the 2T pulse, Up - UE between points D and E of the
pulse, and the amplitude of the bar UB - UE between points B and E of the bar.
c) Calculate the error from the expression:
00 (Up -UE)- (Us
-UE)
(% or IRE)
10
U8- UE
6.5 Pulse shape distortion
6.5.1 Introduction
The pulse shape distortion shall be measured on the 2T pulse in the luminance channel
and the 5T pulse in the colour-difference channel.
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. An example is shown in figure 11.
The 5T pulse distortion is measured using the same graticule and an appropriate sweep
velocity of the scope (0,5 ps/div. instead of 0,2 ps/div.).
6.5.2 Measurement procedure for a manual method of measurement
a) Select test signal VI section B1.
b) Employ the oscilloscope graticule shown in figure 11 or equivalent 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 or 5T pulse falls on the horizontal line through level reference
point "100 %";
- the half-amplitude points of the 2T or 5T 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.
6.5.3 Measurement procedure for an automatic method of measurement
This subclause is still under consideration because at the present time the results of
automatic methods of measurement do not correspond sufficiently with those obtained by
manual methods. Additionally, the results differ between equipment of different manufacturers,
mainly because the automatic adjustments according to 6.5.2 b) are violated by the
algorithm used in some of these instruments.
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1237-3 © I EC:1995
Amplitude/video-frequency characteristic
6.6
Introduction
6.6.1
The amplitude/video-frequency characteristic shall be measured in the luminance and the
two colour-difference channels.
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
frequencies of the test signal IV and (2) the peak-to-peak amplitude of the reference
luminance signal of the test signal.
Alternatively, 60 % of the luminance bar of test signals I and 60 % of the colour-difference
signal amplitude of the colour-difference part of test signal I may be taken as the
reference signal.
6.6.2 Measurement procedure
Select test signal IV.
a)
between the mid-duration points of
UA — UB
b) Measure the peak-to-peak amplitude
the reference luminance signal.
U0 — Up at the mid-duration point of each
Measure the peak-to-peak amplitude
c)
sine-wave signal for each frequency up to the highest in accordance with the television
tape machine standard.
For each frequency of the sine-wave signal, calculate the ratio in dB or %:
d)
(dB) or
(dB) or 20 log 0 6 ^^ — U^ )
20 log U° — Up
b2— b1
A B
(Uc-Up)- 0,6
(Uc -Up)- (UA -UB
) (Ub2—Ub1)
100 or 100 (%)
(%)
UA UB 0,6 Ub1)
—
(Ub2—
luminance gain inequality
6.7 Chrominance-
6.7.1 Introduction
ion gain in the
rt
Chrominance-luminance gain inequality is produced by different inse
luminance channel and the two colour-difference channels. It shall be measured separately
for the two colour-difference channels.
The playback channel must be checked first by means of a calibration tape (see clause 1)
ormance is checked by record and playback of
rf
carrying the test signal I, before the overall pe
the same test signal.
6.7.2 Measurement procedure
Select test signal I from the calibration tape or the tape recorded on the machine
a)
under test.
1 2 between points b 1 and b2 and
Measure the luminance signal amplitude U
b)
and b6
and U5 6 between points and b4 or b5
chrominance signal amplitudes U3,4
the
b3
respectively.
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1237-3 ©IEC:1995 - 29 -
c) Calculation of results
Calculate the chrominance luminance gain inequality of the CB and CR channels from
the expressions:
U5,6 - U1,2
%
CB/Y = 100 CR/Y = 100
U1 ,2 U1,2
Separate values for the playback measurements and the overall measurements are
required and shall be stated properly.
6.8 Chrominance-luminance delay inequality
6.8.1 Introduction
The chrominance
-luminance delay inequality is the mean value of the time difference of
the two colour-difference signals C B and CR with respect to the luminance signal,
measured at the centre of the active line. The transition from green to magenta of the
colour-bar test signal (test signal I) is used for the measurement.
The measurement shall be made for the playback channel by means of a calibration tape
(see clause 1) as well as for the overall performance.
6.8.2 Measurement procedure
a) Select test signal I from the calibration tape or the tape recorded on the machine
under test.
b) slopes of the green-magenta transition on a
Display the luminance and the C B or CR
dual-trace oscilloscope or a special measurement instrument. The gain of the channels
should be such that the transitions have equal amplitude.
...
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