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ITC Handbook of Technical Standards for Television Programme
Production Issue 2.0-December 1996
I T C
HANDBOOK OF TECHNICAL STANDARDS
FOR
TELEVISION PROGRAMME PRODUCTION
PART A
ISSUE 2.0 - DECEMBER 1996
Standards and Technology, Engineering Division,Independent
Television Commission,
Kings Worthy Court, Kings Worthy, Winchester, Hants SO23 7QA
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ITC Handbook of Technical Standards for Television Programme
Production Issue 2.0 December 1996II
Independent Television Commission, 1992, 1993 and 1996.
All rights reserved. No reproduction, copy or transmission of
this publication may be made without thewritten permission of the
Independent Television Commission.
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ITC Handbook of Technical Standards for Television Programme
Production Issue 2.0 December 1996 III
HANDBOOK OF TECHNICAL STANDARDS
PART A: STUDIO CENTRES AND OUTSIDE BROADCAST FACILITIES
CONTENTS
CONTENTS III
INTRODUCTION VITechnical Performance Working Party Membership
VIPast Membership VI
SECTION 1 VIDEO CIRCUITS AND EQUIPMENT WITHIN THE SIGNAL PATH
11.1 PERFORMANCE FIGURES (COMPOSITE PATHS) 11.2 RECOMMENDED TEST
METHODS (COMPOSITE PATHS) 31.3 PERFORMANCE FIGURES (COMPONENT
PATHS) 81.4 RECOMMENDED TEST METHODS (COMPONENT PATHS) 9
SECTION 2 AUDIO CIRCUITS AND EQUIPMENT WITHIN THE SIGNAL PATH
132.1. PERFORMANCE FIGURES 132.2 RECOMMENDED TEST METHODS 15
SECTION 3 VIDEO TAPE RECORDERS 193.1. PERFORMANCE FIGURES
(COMPOSITE RECORDERS) 193.2. RECOMMENDED TEST METHODS (COMPOSITE
RECORDERS) 21VIDEO MEASUREMENTS 21AUDIO MEASUREMENTS 233.3
PERFORMANCE FIGURES (COMPONENT RECORDERS) 253.4 RECOMMENDED TEST
METHODS (COMPONENT RECORDERS) 26
SECTION 4 AUDIO RECORDERS 314.1. PERFORMANCE FIGURES 314.2.
RECOMMENDED TEST METHODS 32
SECTION 5 CAMERAS 355.1. PERFORMANCE FIGURES 355.2 RECOMMENDED
TEST METHODS 36
SECTION 6 TELECINES AND SOUND FOLLOWERS 436.1. PERFORMANCE
FIGURES 43VIDEO TOLERANCES 43AUDIO TOLERANCE 456.2 RECOMMENDED TEST
METHODS 46VIDEO MEASUREMENTS 46
SECTION 7 DISC REPRODUCERS 557.1. PERFORMANCE FIGURES 55
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Production Issue 2.0 December 1996IV
7.2 RECOMMENDED TEST METHODS 56
SECTION 8 WAVEFORMS 598.1 SOUND-IN-SYNCS 59
Fig 8.1 - Sound-in-Syncs Signal 598.2 VERTICAL BLANKING INTERVAL
59
SECTION 9 PEAK PROGRAMME METERS 639.1 PERFORMANCE FIGURES 639.2
RECOMMENDED TEST METHODS 64
SECTION 10 SATELLITE LINKS PATHS 6710.1 PERFORMANCE FIGURES
(Vision) 6710.2 RECOMMENDED TEST METHODS (Vision) 6910.3
PERFORMANCE FIGURES (Sound) 7410.4 RECOMMENDED TEST METHODS (Sound)
75
SECTION 11 DIGITAL VIDEO CIRCUITS AND EQUIPMENT 7711.1
RECOMMENDED CRITERIA 7711.2 RECOMMENDED TEST METHODS 81
SECTION 12 DIGITAL AUDIO CIRCUITS AND EQUIPMENT 8712.1
RECOMMENDED CRITERIA 8712.2 RECOMMENDED TEST METHODS 89
REFERENCE SECTION 93Ref. 1: Pulse and Bar test signals (ITU-R
BT.451-2) 93Ref. 2: Staircase test signal (ITU-R BT.451-2) 94Ref.
3: Differentiating and shaping network 94Ref. 4: Typical K-rating
graticule 95Ref. 5: 50 Hz Square-wave test signals (ITU-R BT.451-2)
96Ref. 6: Chrominance Pulse and Bar test signals 97Ref. 7:
Characteristics of Weighting Filters for video noise measurements
(ITU-R BT.567) 98Ref. 8: 100.0.100.0 Colour Bars (100%) 99Ref. 9:
Characteristics of Filters for audio noise measurements (ITU-R
BT.468-4) 100Ref. 10: Specification of Wow and Flutter meter (ITU-R
BT.409-2) 101Ref. 10: Specification of Wow and Flutter meter
(continued) 102Ref. 11: Specification of Rumble Meter to BS7063
103Ref. 12: Test Pattern for measurement of Telecine long-term
Streaking 104Ref. 13: Test patterns for measurement of Telecine
Flare 105Ref. 14: Measurement of Film frame steadiness 106Ref. 15:
List of Test Films and Tapes for Telecine 106Ref. 16: Test Patterns
for Camera Tests 107Ref. 16: Test Patterns for Camera Tests
(continued) 108Ref. 16: Test Patterns for Camera Tests (continued)
109Ref. 16: Test Patterns for Camera Tests (continued) 110Ref. 16:
Test Patterns for Camera Tests (continued) 111Ref. 17: Picture
Zones 112Ref. 18: 5-point Impairment scale 113Ref. 19: Crosstalk
and Phase Profiles 113Ref. 19: Crosstalk and Phase Profiles
(continued) 114Ref. 19: Crosstalk and Phase Profiles (continued)
115Ref. 19: Crosstalk and Phase Profiles (continued) 116Ref. 19:
Crosstalk and Phase Profiles (continued) 117Ref. 19: Crosstalk and
Phase Profiles (continued) 118Ref. 20: Delay Inequality Test
Signals 119Ref. 21: Non-linearity Test Sawtooth Signals 120
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Production Issue 2.0 December 1996 V
Ref. 22: Non-linearity Test Staircase Signals 121Ref. 23:
Typical Multiburst Test Signals 122Ref. 24: Colour Difference Noise
Filter 123Ref. 25: Vertical Synchronising and Blanking
waveformsError! Bookmark not defined. 124Ref. 26: Field interval
Blanking of the Colour Burst 125Ref. 27: Allocation of VBI Lines
125Ref. 28: Insertion Test Signals 126Ref. 29: Teletext Data
signals in the VBI 127Ref. 30: Widescreen signalling in Line 23
128Ref. 31: Status bits for Widescreen signalling 128Ref. 32: Ghost
Cancellation Reference signals 129Ref. 33: Parameters for GCR
signals 130Ref. 34: Analogue and Digital sync. And blanking timing
131Ref. 35: Timing reference signals 132Ref. 36: Audio channel
status 133Ref. 37: Ramp signal for Noise Measurement 134Ref. 38:
Colour Gamut in R, G, B and Y, Cr, Cb domains 134Ref. 39: Audio
Timing Reference 135Ref. 40: Noise in the presence of signal
135Ref. 41: DFIM performance profile 136Ref. 42: IMD and Harmonic
Distortion performance profile 136Ref. 43: Group Delay profile
137Ref. 44: 16:9 Telecine alignment test film 138
NOTES: 141
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ITC Handbook of Technical Standards for Television Programme
Production Issue 2.0 December 1996VI
INTRODUCTIONThis handbook contains performance figures for the
main elements of the video and audio equipmentand the signal paths
used in television programme production, and incorporates
recommended testprocedures for checking compliance with these
performance criteria. The main body of the ITCTechnical Performance
Code requires licensees to use reasonable endeavours to ensure
conformancewith these performance targets, stopping short of
requiring conformance as an absolute condition.However, the ITC may
at its discretion require conformance with specified targets if
tests havedemonstrated poor performance resulting in a less than
high standard of technical quality.
Developments in technology, for example resulting in the
introduction of a new VTR format or newcamera technology, during
the period of the licence might necessitate revision of this
handbook. TheITC intends to discuss such revisions with licensees,
as appropriate. Any revisions to existing Sections,or additional
Sections, will be considered by the Technical Performance Working
Party which consistsof a membership drawn from the ITC Engineering
Division and the licensees.
Technical Performance Working Party MembershipC Girdwood - ITC
(Chairman)
C Hunt - ITC (Secretary)
P Gray - Anglia Television
M Hughes - Carlton Television
R Hurley - Channel Four Television
R Soczywko - Granada Television
R White - Meridian Broadcasting
Past MembershipP Ballabon (London Weekend Television), I Dutton
(Tyne Tees Television), C Hibbert (CarltonTelevision), C Hunter
(Scottish Television), P Marshall (Channel Four Television), J
Nichol (TyneTees Television), R Pickles (Granada Television), J
Rogers (Yorkshire Television), T Ross (ScottishTelevision) and S
Waring (Thames Television).
The Technical Performance Working Party would like to thank the
many people and organisations fortheir help in the preparation of
the Handbook.
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Section 1: Video Circuits & Equipment within the signal path
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ITC Handbook of Technical Standards for Television Programme
Production Issue 2.0 December 1996 1
SECTION 1VIDEO CIRCUITS AND EQUIPMENT WITHIN THE SIGNAL PATH
1.1 PERFORMANCE FIGURES (COMPOSITE PATHS)
1.1.1 Definitions and Operational Practices
Direct PathFor purposes of measurement the direct path is
assumed to comprise the circuit from the agreedinterface with
British Telecom or Transmission Operators equipment, through the
Presentation andMaster Control switching and processing equipment
back to the agreed interface with British Telecomor Transmission
Operator's equipment.
The limits in brackets refer to the situation when a
synchroniser is included in the path.
Worst PathFor the purposes of measurement, the worst path is
assumed to comprise the following with allinterconnections carried
out using the normal equipment routes:-
(i) The source studio mixer(ii) A looped VTR path(iii) A second
studio mixer(iv) A second looped VTR path(v) The Presentation and
Master Control PathThe tolerance limits do not include degradations
due to signal sources such as cameras, telecines orvideo tape
recorders, as tolerances for these are separately specified.
The limits in brackets refer to the situation when digital video
effects are included in the path.
A measurement of the Worst Path parameters is normally only
necessary after the completion of a newinstallation or a major
re-installation.
Production PathFor the purposes of measurement the production
path will comprise that part of the system that starts atthe output
of originating equipment (camera or VTR) and that includes
assignment switching, mixingand effects equipment and ends at the
interface with a VTR or the Master Control Room. The pathmay be in
a studio centre or outside broadcast scanner.
The limits in brackets refer to the situation when digital video
effects are included in the path.
O.B. Link PathsOB link tolerances are related to an unspecified
number of point-to-point SHF links. Measurement ismade at the final
output of the link at which point connection to a permanent circuit
would be made.
DirectPath
WorstPath
ProductionPath
O.B. LinkPath
1.1.2 Signal Levels(a) Signal Level
Adjustment Error0.7V2%
0.7V2%
0.7V2%
0.7V2%
(b) Signal Level Gain Stability 2% 5% 2% 2%
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DirectPath
WorstPath
ProductionPath
O.B. LinkPath
1.1.3 Linear Waveform Distortion(a) 2T Pulse-to-Bar Ratio %
K
(1% K)1% K
(2% K)% K
(1% K)2% K
(b) 2T Pulse Response % K(1% K)
1% K(2% K)
% K(1% K)
2% K
(c) 2T Bar Response % K(1% K)
1% K(2% K)
% K(1% K)
2% K
(d) 50 Hz Square Wave Response % K(1% K)
1% K(2% K)
% K(1% K)
2% K
(e) Chrominance/Luminance GainInequality
3% 4% 3% 4%
(f) Chrominance/Luminance DelayInequality
20 ns 40 ns 20 ns 20 ns
1.1.4 Non-Linearity Distortion(a) Luminance Line Time
Non-Linearity 3% 5% 3% 5%(b) Differential Phase 2 5 2 5(c)
Burst/Chroma Phase 2 5 2 -(d) Differential Gain 3% 5% 3% 5%(e)
Transient Gain Change, Luminance 5%(f) Transient Gain Change,
Chrominance5%
(g) Transient Gain Change, Sync 5%(h) Chrominance / Luminance
Crosstalk - - - 3%1.1.5 Input/Output Impedance-Return Loss(a)
Luminance -30 dB -30 dB -30 dB -30 dB(b) Chrominance -30 dB -30 dB
-30 dB -30 dB(c) Low Frequency -30 dB -30 dB -30 dB -30 dB1.1.6 VLF
Response(a) First Overshoot - - - 20%(b) Second Overshoot - - -
8%1.1.7 Noise(a) Weighted Luminance (RMS) -64 dB
(-60 dB)*-58 dB -64 dB
(-60 dB)*-55 dB
(b) Weighted Chrominance (RMS) -58 dB -52 dB -58 dB -52 dB(c)
Total Low Frequency
Random and Periodic (p-p)-45 dB -45 dB -45 dB -40 dB
(d) Interchannel Crosstalk -55 dB -45 dB -52 dB -1.1.8
Modulation Derived Distortion
(Sound to Vision Crosstalk)
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Production Issue 2.0 December 1996 3
DirectPath
WorstPath
ProductionPath
O.B. LinkPath
(a) Sound Subcarrier Modulated - - - -52 dB(b) Sound Subcarrier
Unmodulated
(Level of Intermodulation productsbetween sound andchrominance
subcarriers)
- - - -57 dB
* The figure applies to 8-bit processors. If 9-bit processors
are used the figure should beimproved by 3-4 dB.
1.2 RECOMMENDED TEST METHODS (COMPOSITE PATHS)
1.2.1 Test ConditionsBefore commencing a measurement, all test
equipment should be checked for accuracy. Anyinaccuracies should be
corrected if possible, or noted and allowed for in the
measurement.
This section gives examples of test methods that use basic
techniques. These examples do not precludethe use of other valid
methods. The use of ITS type test signals is also not precluded but
the ITUwaveforms referred to in these notes are regarded as the
primary standard.
The signals specified below are applied to the path under test;
when vision mixers are included in thepath then the route should
include the shortest normally used path through each vision mixer
and anyprocessing amplifiers that are normally used. The processing
amplifiers should be set to the mode inwhich they are normally used
operationally.
1.2.2 Signal Levels
(a) Signal Level Adjustment ErrorThe test may be carried out
using a calibrated television waveform monitor.
The signal level adjustment error may be measured by using a 75
ohm generator of the 2T Pulse andBar test signal as shown in
Reference Section, Ref. 1. The generator should be adjusted so that
the baramplitude is 700 mV and the synchronising pulse amplitude is
300 mV. The sine-squared pulse isignored in this application. The
difference in amplitude of the bar centre at the output, expressed
as apercentage of 700 mV, is taken as the signal level adjustment
error.
(b) Signal Level Gain StabilityHaving completed the measurements
in 1.2.2 (a), no level adjustments should be made for a period
ofone hour. The measurements of 1.2.2 (a) should then be repeated
using the identical path and anychange recorded as the parameter
for this section.
1.2.3 Linear Waveform Distortion
(a) 2T Pulse-to-Bar RatioThe test signal should be the 2T Pulse
and Bar Waveform as specified in Reference Section Ref. 1.
The pulse-to-bar K-rating is defined as:
%1004
xP
PBK =
Where B and P are the amplitudes of the bar and pulse
respectively.
Therefore, in practice, to make the measurement, the pulse will
be taken as reference.
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Set the pulse amplitude to be 100% on the centre scale of an
appropriate graticule (Reference SectionRef. 4) and divide by four
the percentage difference in amplitude between the pulse and the
barmeasured at its mid-point, to obtain the K-rating.
When the waveform is subject to line tilt or an extended
distortion along the leading edge at the top ofthe bar, the
amplitude of the bar must be measured at its midpoint after first
setting the blanking levelmid-way between two successive bars to
0%.
b) 2T Pulse ResponseThe test signal should be the 2T Pulse and
Bar Waveform as specified in Reference Section, Ref. 1.Measurement
may be made using a graticule such as that shown in Reference
Section, Ref. 4.
The vertical gain is adjusted to make the pulse amplitude 100%
and then the vertical shift moved tobring the blanking level onto
the base line at 30%. The horizontal gain is advanced and the
horizontalshift adjusted to make the waveform touch the H.A.D.
markers on the 80% line. With normal gain thegraticule markers are
2% K and 4% K. For 1% K and 2% K the calibrated vertical gain is
advanced by2. For limits of % K and 1% K the pulse amplitude is
first set to 80% and the calibrated verticalgain then advanced by
5.
If it is desired to measure the K rating exactly, the variable
vertical gains should be adjusted until theworst pulse overshoot
just touches the inner limits. The calibrated gain is then returned
to normal andthe amplitude of the pulse measured (P%) then
%200gainCalibratedxP
K =
This is illustrated in the following table:-
Pulse Amplitude 5 Gain100 0.4% K80 0.5% K67 0.6% K
57.5 0.7% K50 0.8% K
(c) 2T Bar ResponseThe test signal should be the 2T Pulse and
Bar waveform as specified in Reference Section, Ref. 1.
The horizontal timebase of the oscilloscope is adjusted so that
the half amplitude points of the barreach the outer limits marked
on a graticule such as that shown in Reference Section, Ref. 4.
Ignoring the first and last 2.5% (0.625 ms) of the bar, the
deviation from its mid-point, expressed as apercentage of its
amplitude at that point, is the K rating of the bar. It must be
emphasised thatmeasurements are made using only half the bar, the
worst half being quoted as the result. It is wrong tomeasure the
whole bar and divide by two to obtain the K rating.
(d) 50 Hz Square Wave ResponseThe test signal should be the 50
Hz square wave test signal as specified in Reference Section, Ref.
5.
With the horizontal scan at field rate the 50 Hz signal is
adjusted as in 1.2.3. (c). For a stationarydisplay the signal must
contain field synchronising pulses. Again, ignoring the first and
last 2.5%(250 ms) the percentage deviation of the worst half
divided by 2 is the K rating of the bar. (It may benoted that for
the same deviation on the display a 4% K figure for the bar
response looks the same as a2% K for 50 Hz).
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(e) Chrominance/Luminance Gain InequalityThe measurement is best
made using the 2Tc non-composite waveform (Reference Section, Ref.
6b).The 50% luminance pedestal is used to calibrate the vertical
gain of the oscilloscope. The chrominanceamplitude is then measured
directly.
NOTE: The use of the composite 2Tc waveform with a gain and
delay test set will produce anerroneous result in the presence of
chrominance/luminance crosstalk.
(f) Chrominance/Luminance Delay InequalityThe measurement is
made using a 2Tc composite Pulse-and-Bar signal (Reference Section,
Ref. 6a)and a delay measuring test set where available.
The output of the test set is viewed on an oscilloscope and the
test set adjusted to cancel any pathchrominance/luminance delay
inequality. If a test set is not available then the level of
distortion should beestimated by examining the sinusoidal
distortions at the bottom of the 2Tc composite pulse on awaveform
monitor or oscilloscope. The method is described in Part B,
Guidelines.
1.2.4 Non-Linearity Distortion
(a) Luminance Line Time Non-LinearityThe test signal consists of
a 5-step staircase (Reference Section, Ref. 2 occupying one line in
everyfour, followed by three lines of black or white. Measurements
are made with three lines of white (baron) and with three lines of
black (bar off) and the worst result quoted.
It should be noted that the staircase with added sub-carrier
waveform is used to conform with C.C.I.R.recommended practice.
At the receiving end the test signal is passed through a
suitable differentiating network (ReferenceSection, Ref. 3) and
amplifier and displayed on an oscilloscope. The result is a train
of five pulses.Non-linearity is measured as the difference in
amplitude between the largest and the smallestexpressed as a
percentage of the largest.
i.e. %100max
minmax xE
EE
(b) Differential PhaseThe test signal should be a 5 step
staircase with added subcarrier (Reference Section, Ref. 2).
The differential phase may be measured by using a vectorscope in
the line-time mode. The six sectionsof subcarrier are compared for
their phase relationships taking the blanking level section as
areference. The differential phase is defined as the largest
departure in phase from that reference.Measurements are made with
the white bar on and with the white bar off and the worst
measurement isquoted.
(c) Burst/Chroma PhaseBurst/Chroma Phase errors may be measured
as follows. Display the output of a colour bar generatordirectly on
a vectorscope and after aligning the burst on the graticule,
carefully measure the phasedisplacement (if any) of the BLUE bar.
Apply the colour bar signal to the equipment or path under testand
display the output signal on the vectorscope. After aligning the
burst on its graticule, measureagain the BLUE bar phase
displacement. Phase measurement minus the phase displacement of
theoriginal signal indicates the burst/chroma distortion due to the
equipment or path under test.
(d) Differential GainThe test signal should be a 5 step
staircase with added subcarrier (Reference Section, Ref. 2.)
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The differential gain may be measured by using a vectorscope in
the line time mode. The six sectionsof subcarrier are compared for
their amplitude relationship and taking the blanking level section
as areference, the differential gain is defined as the largest
departure in amplitude from that reference.Measurements are made
with the white bar on and with the white bar off and the worst
measurement isquoted.
NOTE ON TRANSIENT DISTORTION APPLICABLE TO SUB-SECTIONS (e), (f)
& (g)BELOWThe transient gain change due to a change of APL is
defined as the maximum transient departure in theamplitude of each
component from that which existed before the change in APL,
expressed as apercentage of the original amplitude. Separate
measurements are made on the five step staircase withadded
subcarrier (Reference Section, Ref. 2), with the APL changed from
low (intervening lines atblanking level) to high (intervening lines
at white level) and from high to low.
(e) Transient Gain Change, Luminance (see note above)At the
receiving end the test signal is passed through a suitable
differentiating network (ReferenceSection, Ref. 2), amplified and
displayed on an oscilloscope (some commercial filters with
amplifiersoverload at normal signal level and require some 10 dB
reduction of input signal level).
The oscilloscope should be synchronised by an external source
and the black level clamp or dc restorershould be switched off.
Movement of the base line of the waveform when the APL is
changedindicates overload or some other non-standard measuring
condition.
Set up the oscilloscope to make the amplitude of each of the
spikes corresponding to the steps in turnequal to 100% with
intervening lines at black. Measure the maximum transient departure
from 100%of each of the spike amplitudes when the APL is switched
from low to high and vice-versa.
The largest departure from 100% is taken as the result and it
should be noted whether the change ispredominantly on only one
spike and if so, on which spike.
(f) Transient Gain Change, Chrominance (See note above)Set up
the oscilloscope using the chrominance filter and measure the
maximum transient departurefrom 100% of the peak-to-peak subcarrier
amplitude on the third step, when the APL is switched fromlow to
high and vice-versa.
(g) Transient Gain Change, Sync (See note above)Using the
differentiating network, amplifier and oscilloscope as in (e)
above, set the oscilloscope sothat the amplitude of the positive
spike corresponding to the trailing edge of sync equals 100%
withintervening lines at black.
Measure the maximum transient departure from 100% of the spike
amplitude when the APL isswitched from low to high and
vice-versa.
(h) Chrominance to Luminance CrosstalkThe 2Tc pulse and bar
waveform (Reference Section, Ref. 6b) should be used for the test.
Thecrosstalk, which manifests itself as a change in the mean level
of the pedestal during transmission ofthe chrominance component,
should be expressed as a percentage of the picture level, as
determinedby the measurement described in Para 1.2.2. (a),
(nominally 700 mV).
1.2.5 Input/Output Impedance - Return Loss
(a)(b)(c) Return LossThe measuring point for this test is the
same interface as defined in Section 1.1.1. Direct Path.
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The test is first carried out using a 2T pulse-and-bar waveform
in conjunction with a return loss bridgewhich should first be
calibrated using two very closely matched, 75 0.1% ohm
resistors.
In addition, the same leads should be used for calibration and
measurement and the reference path leadshould be identical to the
main path connection. With one return loss bridge presently
available, acalibration distortion of -40 dB is provided; if this
bridge is used the output is displayed on anoscilloscope and
adjusted to give a reference display (5 divisions for example). The
bridge is thenrearranged to include the circuit under test and the
unbalance output measured. The return loss is thencalculated by
linear interpolation. For large mismatches a 10 dB switch is
incorporated in the bridge toallow calibration at -30 dB. When
measuring output impedance the input signal should be removedand
the input terminated. For very small return loss measurements an
external trigger to theoscilloscope is often necessary.
The test should be repeated using the 2Tc pulse-and-bar and the
50 Hz waveforms. These results arerespectively recorded as the (a)
Luminance, (b) Chrominance and (c) Low Frequency parameters.
1.2.6 V.L.F. ResponseThe signal used should switch all lines to
black and white. The switching should occur at a sufficientlyslow
rate to allow the waveform to settle before the following
transition. The 1st and 2nd overshoots ofblanking level variation
are measured (Fig. 1.1) and expressed as a percentage of standard
picture level(700 mV peak-to-peak).
It should be noted that the dc change ("c" in Fig. 1.1) is not
measured since it is a function only of thetest signal.
Both the black to white and the white to black transitions are
measured and the worst result quoted.
A dc-coupled oscilloscope with a very slow timebase may be used
for these measurements.Alternatively, if only a television waveform
monitor is available, a line rate display should be usedwith the Y
amplifier switched to dc coupled and the dc restorer switched
off.
Fig. 1.1
1.2.7 NoiseMeasurement is made using a 10% lift signal. Care
should be taken that the noise of the generatedsignal is not
significant. When measurements are made on paths containing digital
processingequipment the 10% lift signal may be adjusted slightly to
minimise the effects of quantisation noise ora ramp waveform may be
used.
(a) Weighted LuminanceMeasurement is made in the band 10 kHz
(7.5 kHz) - 5.0 MHz using RMS detection. Thecharacteristic of the
luminance weighting filter is shown in Reference Section, Ref.
7.
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(b) Weighted ChrominanceMeasurement is made in the band 3.5 MHz
- 5.5 MHz as defined only by the characteristic of theweighting
filter as shown in Reference Section, Ref. 7 and using RMS
detection.
(c) Total L.F. Random and PeriodicMeasurement is made
peak-to-peak in the band 40 Hz - 10 kHz (7.5 kHz).
(d) Interchannel CrosstalkOne channel is selected as the one to
be measured as the receiver of crosstalk interference. Thischannel
is fed with a blanking and sync waveform.
Another channel that is considered to be the nearest
electrically adjacent channel is used as the hostilechannel. This
is fed with Colour Bars (Reference Section, Ref. 8).
The signal-to-crosstalk ratio is defined as the ratio, expressed
in decibels, of the normal peak-to-peakamplitude of the picture
signal to the peak-to-peak amplitude of the crosstalk waveform.
1.2.8 Modulation Derived Distortion (Sound to Vision
Crosstalk)
a) Sound Subcarrier ModulatedMeasured with whole-time 5-step
staircase, without chrominance sub-carrier, into the vision
channeland +8 dBu at 1 kHz into the sound channel. The crosstalk
should be measured unweighted, peak-to-peak, in the frequency band
40 Hz to 10 kHz (7.5 kHz) using a noise measuring set. The result
isexpressed with reference to standard picture level (700 mV
p-p).
(b) Sound Subcarrier UnmodulatedMeasured with whole time 5-step
staircase, with chrominance subcarrier, into the vision channel
andno sound modulation. The crosstalk should be measured luminance
weighted, peak-to-peak in thefrequency band 40 Hz to 5.0 MHz, using
a noise measuring set. The result is expressed with referenceto
standard picture level (700 mV p-p).
N.B. Other methods of measurement using spectrum analysis are
acceptable.
1.3 PERFORMANCE FIGURES (COMPONENT PATHS)This section gives the
performance figures for production component paths (excluding
digital effectsequipment).
A Company may reserve the right to test all three component
channels to the luminance channelperformance. This may be necessary
in ensuring good chroma-keying signals where a wide bandwidthin the
colour difference channels is required. In this case the linear
waveform distortions should bemeasured using the 2T Pulse and Bar
signal and the noise performance should be the same as in
theluminance channel.
1.3.2 Signal Levels
(a) Signal LevelAdjustment Error
0.7 V 2%
(b) Signal Level Gain Stability 2%1.3.3 Linear Waveform
Distortions (2T Pulse and Bar in Luminance
and 5T Pulse and Bar in Colour Difference Channels)(a)
Pulse-to-Bar Ratio 0.5% K(b) Pulse Response 0.5% K
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(c) Bar Response 0.5% K(d) 50 Hz Square Wave Response 0.5%
K1.3.4 Delay Inequality between all Component Channels
Timing difference 10 ns1.3.5 Non-Linear Waveform Distortion(a)
Amplitude Non-Linearity 3%(b) Component Crosstalk -50 dB1.3.6
Noise(a) Weighted Luminance (RMS) -64 dB (-60 dB)*(b) Colour
Difference (RMS) - 1.6 MHz low pass filter -64 dB(c) Total Low
Frequency in Luminance Channel (p-p) -45 dB(d) Total Low Frequency
in Colour Diff. channels (p-p) -43 dB* The figure applies to 8-bit
processors. If 9-bit processors are used the figure
should be improved by 3-4 dB.
1.4 RECOMMENDED TEST METHODS (COMPONENT PATHS)
1.4.1 Test ConditionsThe analogue component signals (Y, Pr and
Pb) will be related to the colour separation signals (R, Gand B) by
the following matrix equations:
Y 0.299 0.587 0.114 RPb = -0.169 -0.331 0.500 . GPr 0.500 -0.419
-0.081 B
The colour separation signals have normal peak amplitudes of 700
mV. Synchronising signals may beadded to or kept separate from the
luminance component.
The following methods are relevant when component paths are
being measured and it may beconvenient to use a waveform monitor
capable of displaying the three components simultaneously:
1.4.2 Signal Levels
(a) Signal Level Adjustment ErrorThe test may be carried out
using a calibrated television waveform monitor and suitable
graticule.
The insertion gain may be measured by using a 75 ohm generator
of the 2T and 5T Pulse and Bar testsignals as shown in the
Reference Section, Ref. 1. The 2T signal is fed to the Luminance
Channel andthe 5T to the Colour Difference channels when required.
The generator should be adjusted so that thebar amplitude is 700 mV
in both cases and the synchronising pulse amplitude is 300 mV in
theluminance channel. The difference in amplitude of the bar centre
at the output, expressed as apercentage of 700 mV, is taken as the
signal level adjustment error.
(b) Signal Level Gain StabilityHaving completed the measurements
in 1.3.2 (a), no level adjustments should be made for a period
ofone hour. The measurements should be repeated using the same
channels and any change recorded asthe parameter for this
section.
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1.4.3 Linear Waveform DistortionsLinear waveform distortions (a)
to (c) are measured using the 2T Pulse and Bar test signal in the
Y(luminance) channel and the 5T Pulse and Bar test signal in the Pr
and Pb (colour difference) channels.The waveforms are shown in the
Reference Section, Ref. 1.
(a) Pulse-to-Bar RatioThe pulse-to-bar K rating is defined
as:
%1004
xP
PBK =
where B and P are the amplitudes of the bar and pulse
respectively.
In practice, the pulse will be taken as the reference during
measurement.
Set the pulse amplitude to be 100% on the centre scale of an
appropriate graticule (Reference Section,Ref. 4) and divide by four
the percentage difference in amplitude between the pulse and the
barmeasured at its mid-point, to obtain the K rating.
When the waveform is subject to line tilt or an extended
distortion along the leading edge at the top ofthe bar, the
amplitude of the bar must be measured at its mid-point after first
setting the reference level(blanking for Y) mid-way between two
successive bars to 0%.
(b) Pulse ResponseMeasurement may be made using a graticule such
as that shown in the Reference Section, Ref. 4.
The vertical gain is adjusted to make the pulse amplitude 100%
and then the vertical shift moved tobring the reference level
(blanking for Y) onto the baseline at 30%. The horizontal gain is
advancedand the horizontal shift adjusted to make the waveform
touch the H.A.D. markers on the 80% line.With normal gain the
graticule markers are 2% K and 4% K. For 1% K and 2% K the
calibratedvertical gain is increased by x2. For 0.5% K and 1% K the
pulse amplitude is first set to 80% and thecalibrated vertical gain
is increased to x5.
If it is desired to measure the K rating exactly, the variable
vertical gains should be adjusted until theworst pulse overshoot
just touches the inner limits. The calibration gain is then
returned to normal andthe amplitude of the pulse measured (P%)
then
%200GainCalibratedxP
K =
This is illustrated in the following table:
Pulse Amplitude 5 Gain100 0.4% K80 0.5% K67 0.6% K
57.5 0.7% K50 0.8% K
(c) Bar ResponseThe horizontal timebase of the waveform monitor
or oscilloscope is adjusted so that the half amplitudepoints of the
bar reach the outer limits marked on a graticule such as that shown
in the ReferenceSection, Ref. 4.
Ignoring the first and last 2.5% (0.625ms) of the bar, the
deviation from its mid-point, expressed as apercentage of its
amplitude at that point, is the K rating of the bar. It must be
emphasised that
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measurements are made using only half the bar, the worst half
being quoted as the result. It is wrong tomeasure the whole bar and
divide by two to obtain the K rating.
(d) 50 Hz Square Wave ResponseThe test signals are the 50 Hz
square waves shown in the Reference Section, Ref. 5. The 0V to700
mV signal is used in the Y channel and the -350 mV to +350 mV
signal is used in the Pr and Pbchannels.
With the horizontal scan at field rate the 50 Hz signal is
adjusted to coincide with the appropriate barmarkings on the
graticule. For a stationary display the signal must contain field
synchronising pulses(Y) or the waveform monitor must be externally
triggered from the same synchronising pulses (Pr andPb). Ignoring
the first and last 2.5% (250 ms) of the bar, the percentage
deviation of the worst halfdivided by two is the K rating of the
bar. (It may be noted that for the same deviation on the display
a4% K figure for the bar response looks the same as a 2% K figure
for 50 Hz).
1.4.4 Delay InequalityThe test signal consists of sinusoids as
shown in the Reference Section, Ref. 20 where the frequency ofthe
sinusoid applied to the luminance channel is 500 kHz and that to
the colour difference channels is502 kHz. When these signals are
subtracted a null appears half way along active line time giving
theappearance of a "bowtie". A timing difference in the paths gives
rise to a positional displacement ofthe null by 1ms for about 4ns
of timing error. Markers on some of the picture lines enable a
directreading of any timing errors to be made. The method is not
well suited for showing timing differenceswhich are not constant
throughout the line time.
In this situation, or when there is noise or the sinewaves are
distorted, a dual channel oscilloscope withdelayed timebase and
writing speed in the order of 20 ns per division should compare the
coincidenceof rising or falling slopes of the sinewaves shown in
the Reference Section, Ref . 20.
The delaying timebase should be triggered from the rising edge
of the luminance pedestal so that Prand Pb can be compared with Y.
High gain should be used in the vertical amplifiers to give a
steepslope to the edges being measured and the oscilloscope delay
time multiplier control used to inspectthe full line period. The
worst error should be quoted.
The tracking of the oscilloscope input amplifier controls can be
checked using the staircase at the startof the waveform, the step
amplitudes being designed to match the 5, 10 and 20 mV per
divisionsequence of many general purpose instruments.
When this method is used, it is also beneficial if some lines of
the test signals are left unmodulated togive a line through the
sinewave crossings, aiding the vertical positioning of the traces
at highmagnifications.
If a high speed oscilloscope is not available, an estimate can
be made using matched and calibratedswitchable delays in both
oscilloscope inputs (to account for insertion delay) and adjusted
for a visualtiming null. Again this should be checked across the
line period.
1.4.5 Non-Linear Waveform Distortion
(a) Amplitude Non-LinearityThe waveforms used are ramp signals
shown as typical examples in the Reference Section, Ref. 21.
Inorder that the system may be tested under a wide range of APL,
the signal should consist of 6 lines oframp in every 24, with the
intervening lines at black or white. Measurements are made with 18
lines ofwhite (bar on) and then 18 lines of black (bar off) and the
worst result quoted.
To make the measurement, the output of the appropriate component
channel is differentiated by asuitable network as in the Reference
Section, Ref. 3 and the mid-point of the resultant signal level
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made to occupy 100% on an oscilloscope. The error is then the
peak-to-peak percentage deviation overthe duration of the
differentiated ramp.
If the significant noise is present, making the assessment of
non-linearity difficult and the rampwaveforms have been inspected
to ensure that there are no quantisation errors, then
staircasewaveforms similar to those shown in the Reference Section,
Ref. 22 may be used. The signal shouldconsist of 6 lines of
staircase in every 24 with the intervening lines at black and
white. Measurementsare made with 18 lines of white (bar on) and
then with 18 lines of black (bar off) and the worst
resultquoted.
At the receiving end the test signal is passed through the
differentiating network and displayed on anoscilloscope to show a
train of five pulses. Non-linearity is given by the difference in
amplitude betweenthe largest and smallest pulse expressed as a
percentage of the largest.
i.e. %100max
minmax xE
EE
(b) Component CrosstalkTwo of the component channels are
energised with the multiburst test signals shown in the
ReferenceSection, Ref. 23 and the crosstalk into the "dormant"
third component is measured peak-to-peak. Theresult is expressed in
dB relative to 700 mV
NOTE: Some waveform monitors may have insufficient gain to
achieve 100% amplitude when aline rate ramp such as that shown in
Reference 21 is differentiated. In cases such as these,the ramp
signals provided as `valid' waveforms from Component Test Signal
Generatorsmay be used, as the shorter duration of these ramps give
a larger amplitude pedestal whendifferentiated. Alternatively, the
line rate signal may be used as for the case when noise
ispresent.
1.4.6 NoiseMeasurement is made using a 10% lift signal. Care
should be taken that the noise of the generatedsignal is not
significant. When measurements are made on paths containing digital
processingequipment the 10% lift signal may be adjusted slightly to
minimise the effects of quantisation noise.
(a) Weighted LuminanceMeasurement is made on the Y channel in
the band 10 kHz (7.5 kHz) - 5.0 MHz using RMSdetection. The
characteristic of the luminance weighting filter is shown in the
Reference Section,Ref. 7.
(b) Colour Difference NoiseMeasurement is made on the Pr and Pb
channels in the band 10 kHz -1.6 MHz using RMS detection.The Colour
Difference filter having the characteristic shown in the Reference
Section, Ref. 24 shouldbe used. Note that this network has a 6 dB
insertion loss and therefore the measured figure should becorrected
accordingly.
(c) Total Low Frequency Noise in Luminance ChannelMeasurement is
made unweighted in the band 40 Hz - 10 kHz (7.5 kHz) using
peak-to-peak detection.
(d) Total Low Frequency Noise in Colour Difference
ChannelsMeasured the same as in the Luminance Channel.
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SECTION 2AUDIO CIRCUITS AND EQUIPMENT WITHIN THE SIGNAL PATH
2.1. PERFORMANCE FIGURES
2.1.1 Definitions and Operational Practices
Direct PathFor purposes of measurement the direct path is
assumed to comprise the circuit from the agreedinterface with
British Telecom or Transmission Operator's equipment, through the
Presentation andMaster Control switching and processing equipment
back to the agreed interface with British Telecomor Transmission
Operator's equipment.
Worst PathFor the purposes of measurement, the worst path is
assumed to comprise the following, with allinterconnections carried
out using the normal equipment routes:-(i) A studio mixer
(ii) A looped VTR path
(iii) A second studio mixer
(iv) A second looped VTR path
(v) The presentation and Master Control Path.
The input signal may either be an assigned source or commence at
a studio wall box at a microphoneinput.
The tolerance limits do not include degradations due to signal
sources such as tape recorders, astolerances for these are
separately specified.
A measurement of the Worst Path parameters is normally only
necessary after the completion of a newinstallation or a major
re-installation.
Production PathFor the purposes of measurement the production
path will comprise that part of the system that starts atthe output
of originating equipment (microphone, disc reproducer, ATR or VTR
etc). and that includesassignment switching and mixing and ends at
the interface with recording equipment or the MasterControl Room.
The path may be in a studio centre or outside broadcast
scanner.
O.B. Link PathsO.B. Link tolerances are related to an
unspecified number of point-to-point SHF links. Measurement ismade
at the final output of the link at which point connection to a
permanent circuit would be made.
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DirectPath
WorstPath
ProductionPath
O.B. LinkPath
2.1.2 Output Signal Level(a) Output signal level at agreed
interface after line-up0 dBm
0.25 dB0 dBm
0.5 dB0 dBm
0.25 dB0 dBm
0.25 dB(b) Gain Stability, variation of
insertion gain during one hour0.25 dB 0.5 dB 0.25 dB 0.25 dB
2.1.3 Amplitude/Frequency Response(a) 40 Hz-15 kHz +1 dB +1 dB
+1 dB +0.5 dB
w.r.t.1 kHz -2 dB -3 dB -2 dB -3.0 dB(b) 125 Hz-10 kHz +1 dB +1
dB +1 dB +0.5 dB
w.r.t.1 kHz -1 dB -2 dB -1 dB -2.0 dB2.1.4 Total Harmonic
Distortion(a) 1 kHz at -10 dBu 0.5% 0.5% 0.5% 1.0%(b) 1 kHz at +8
dBu 0.5% 1.0% 0.5% 1.0%(c) 80 Hz at -10 dBu 0.5% 0.5% 0.5% 1.0%(d)
80 Hz at +8 dBu 0.5% 2.0% 1.0% 1.0%(e) Input Overload - - 17 dB
-2.1.5 Signal/Noise Ratio(a) 0 dBu input(i) Weighted, Random Peak
60 dB 56 dB 60 dB 42 dB(ii) Unweighted, Random Peak - - 63 dB 47
dB(b) -50 dBu input(i) Weighted,Random Peak - 53 dB 56 dB -(ii)
Unweighted,Random Peak - - 60 dB -(c) Interchannel Crosstalk,
Weighted, Peak53 dB 53 dB 53 dB -
2.1.6 Modulation Derived Distortion(a) Vision to Sound
Crosstalk,
Weighted- - - 45 dB
DUAL CHANNEL SOUND PATHS ONLY2.1.7 Level Difference Between A
and B Channels(a) 40 Hz-15 kHz 1.0 dB 1.5 dB 1.0 dB 1.0 dB(b) 125
Hz-10 kHz 0.5 dB 1.0 dB 0.5 dB 0.5 dB2.1.8 Crosstalk Between A and
B Channels(a) 40 Hz -35 dB -26 dB -35 dB -35 dB(b) 40 Hz-315 Hz -6
dB/
octave-6 dB/octave
-6 dB/octave
-6 dB/octave
(c) 315 Hz-6.3 kHz -53 dB -44 dB -53 dB -53 dB(d) 6.3 kHz-15 kHz
+6 dB/
octave+6 dB/octave
+6 dB/octave
+6 dB/octave
(e) 15 kHz -45 dB -36 dB -45 dB -45 dB
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DirectPath
WorstPath
ProductionPath
O.B. LinkPath
Profiles are shown in Reference Section, Ref. 19 (a) and Ref. 19
(b)2.1.9 Phase Difference Between A and B Channels(a) 40 Hz 20 30
20 20(b) 40 Hz-200 Hz Oblique
SegmentObliqueSegment
ObliqueSegment
ObliqueSegment
(c) 200 Hz-4 kHz 10 15 10 10(d) 4 kHz-15 kHz Oblique
SegmentObliqueSegment
ObliqueSegment
ObliqueSegment
(e) 15 kHz 20 30 20 20Profiles are shown in Reference Section,
Ref. 19(f) and Ref. 19 (g)
2.2 RECOMMENDED TEST METHODS
2.2.1 Test ConditionsNormally signal levels are measured as
voltages irrespective of impedance and are quoted in decibelswith
reference to O dBu, where O dBu corresponds to 0.775 volts, RMS.
This definition of signal levelapplies throughout this Han dBook of
Technical Standards for equipment measurements but does notapply to
line measurements or where it is separately defined.
2.2.2 Output Signal LevelThe measurements may be made at any
overall gain setting. The PPMs, which are used to control
theprogramme output levels of each mixer, will be used as the
indicating meters.
With the input level set constant at -50 dBu for microphone
level inputs, or O dBu for line level inputs,the greatest change
occurring in one hour in the output is defined as the gain
stability.
2.2.3 Amplitude/Frequency ResponseThis measurement may be made
at any gain setting up to the maximum available; the output
levelshould be O dBu approximately on each output when the
measurement is made.
Tests should be made at the following frequencies and the
measurements should be referenced to thelevel at 1 kHz.
40 Hz, 60 Hz, 125 Hz, 250 Hz, 500 Hz,
1 kHz, 2 kHz, 4 kHz, 6 kHz, 8 kHz,
10 kHz, 12 kHz, 15 kHz,Additional tests should be made to ensure
that the overall response falls off smoothly outside thisfrequency
band.
It should be noted that, as this test is a measurement of the
variation of gain of the equipment withfrequency, corrections
should be made for any variations in the input level with
frequency.
2.2.4 Total Harmonic Distortion(i) For microphone channels, -50
dBu input with normal balance attenuator, channel, group and
main fader settings to achieve O dBu output.
(ii) For line level channels, O dBu input with normal balance
attenuator, channel, group and mainfader settings to achieve O dBu
output.
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The input signal level is varied to give an output level of
first -10 dBu and then +8 dBu w.r.t. line-up.At each level tests
are made at 80 Hz and 1 kHz.
For microphone inputs only, additional tests of input overload
capability at 80 Hz and 1 kHz are made.The input signal level is
slowly increased and the channel fader adjusted to keep the output
level at+8 dBu (ie peak signal level) until the onset of evident
distortion (for the purposes of this measurementthis is defined at
3%). The increase in input signal level above normal peak input
level, -42 dBu, is theinput overload capability.
2.2.5 Signal/Noise RatioThe noise levels are measured using a
test set incorporating a standard PPM (to BS 6840), and a lownoise
amplifier with calibrated variable gain. The 'unweighted' bandwidth
is constrained in accordancewith ITU-R BT.468-4, shown in Reference
Section, Ref. 9(a) and the 'weighted' frequency response
isdetermined by the ITU network as defined in ITU-R BT.468-4 shown
in Reference Section, Ref. 9(b).
1 kHz tone at the appropriate level is fed to the path under
test and the gain of the test set is adjusted sothat the PPM gives
a scale reading of '4' (i.e. O dBu). The input signal is then
replaced by a termination(as defined below) and the gain of the
test set is re-adjusted so that the PPM again peaks to the
scalereading of '4'. The signal/noise ratio is the difference
between settings of test set gain. Themeasurements are made both
weighted and unweighted.
(a) Line Level Path (O dBu)The input should be terminated in
600ohms.
(b) Microphone Input (-50 dBu)Balance attenuator, channel, group
and main faders should be set as for normal operation. The
inputshould be terminated in 200 ohms directly at the injection
point.
(c) CrosstalkThe interfering signal, consisting of a 7 kHz tone,
is fed to an adjacent input of each sound desk andswitching matrix
in the path under test. The interfering path is lined up, using
separate group andoutput faders where this is possible without
mixing with the path under test. Desk inputs may be atmicrophone
level (-50 dBu) or line level (O dBu). When the interfering path
has been lined up theinput level is raised by 8 dB. The input of
the path under test is terminated and the peak, weightedoutput
level of the path under test is then measured on a noise meter. A
bandpass filter may be neededto separate the crosstalking tone from
random noise.
2.2.6 Modulation Derived Distortion (Vision to Sound
Crosstalk)Measured as noise (Para 2.2.5), with vision channel
modulated by 100% amplitude, 100% saturatedcolour bars.
DUAL CHANNEL SOUND PATHS ONLY
2.2.7 Level Difference Between A and B ChannelsFor any signal
path one of four possible input conditions will be applicable.
(i) Microphone inputs to stereophonic channel - stereophonic
circuits throughout.(ii) Microphone input to monophonic channel -
stereophonic signals derived in a 'pan-pot'.(iii) Line inputs to
stereophonic channel - stereophonic circuits throughout.(iv) Line
input to monophonic channel - stereophonic signals derived in a
'pan-pot'.
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With stereophonic input channels, test signals (initially at 1
kHz) from a common source should beinjected into both channel
inputs, the channels being lined up in the normal way. The output
levelsfrom the A and B chains should be measured at frequencies
between 40 Hz and 15 kHz and thedifferences calculated.
2.2.8 Crosstalk Between A and B ChannelsA test signal at 1 kHz
from a common source should be injected into both channel inputs,
the channelsbeing lined up in the normal way.
In the case of stereophonic channels, the test signal should
then be injected into the input of the Achannel, the input of the B
channel being terminated in 200 ohms for microphone inputs and 600
ohmsfor line inputs. The levels of the signals on the A and B
outputs should be measured and the difference(i.e. crosstalk)
calculated. The inputs should then be reversed and the measurements
taken again toascertain the crosstalk under this configuration.
In the case of monophonic input channels test signals should be
injected and the channel routing selectorswitched so that the
signal is fed to only one output. The levels of the wanted signal
on this output and theunwanted signal on the other should be
measured and the difference (i.e. crosstalk) calculated. Thechannel
routing selector should then be switched so that the input is fed
to the other output and themeasurements taken again to ascertain
the crosstalk under this configuration.
Measurements should be made at frequencies between 40 Hz and 15
kHz. Profiles for Crosstalkperformance are shown in Reference
Section, Ref. 19 (a) and Ref. 19 (b)
2.2.9 Phase Difference Between A and B ChannelsFor any signal
path, one of the four input conditions described in Section 3.2.7
above will beapplicable.
With stereophonic input channels, test signals (initially at 1
kHz) from a common source should beinjected into both channel
inputs, the channels being lined up in the normal way. The phase
differencebetween the outputs of the A and B chains should be
measured and the tests repeated at frequenciesbetween 40 Hz and 15
kHz.
In the case of monophonic input channels, a test signal
(initially at 1 kHz) should be injected into thechannel input, the
channel being lined up in the normal way. The test may be made with
the 'pan-pot'set in any position. The phase difference between the
outputs of the A and B chains should bemeasured and the tests
repeated at frequencies between 40 Hz and 15 kHz. Profiles for
Phaseperformance are shown in Reference Section, Ref. 19 (f) and
Ref. 19 (g).
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SECTION 3VIDEO TAPE RECORDERS
3.1. PERFORMANCE FIGURES (COMPOSITE RECORDERS)
3.1.1 Definitions and Operational PracticesTolerances listed for
video tape recorders refer to a single recording and replay not
necessarily on thesame machine.
The tolerances are based on full field measurements and the most
common and straightforwardmethods of measurement are given in 3.2.
Where alternative methods, giving more accurate results,
areavailable these are mentioned in the appropriate paragraph.
The tolerances given below apply to both quadruplex and helical
recorders, which lay down PALtracks. They may also apply to
component recorders if these are tested in the PAL domain
usingsuitable codec pairs.NOTE: The use of VTRs not fully meeting
this specification should be the subject of discussion
with the ITC where the subjective quality of the recordings
justifies this.
VIDEO TOLERANCES3.1.2 Output Signal Level(a) Adjustment Error
2.0%(b) Gain Stability (over 1 hour) 2.0%3.1.3 Linear Waveform
Distortion(a) 2T Pulse-to-Bar Ratio 1.5% K(b) 2T Pulse Response
1.5% K(c) 2T Bar Response 1.5% K(d) 50 Hz Square Wave Response 1.5%
K(e) Chrominance/Luminance Gain Inequality 3%(f)
Chrominance/Luminance Delay Inequality 20 ns3.1.4 Non-Linearity
Distortion(a) Luminance Line Time Non-Linearity 4%(b) Differential
Phase 5(c) Differential Gain 5%3.1.5 Noise(a) Weighted Luminance
(RMS) -52 dB(b) Weighted Chrominance (RMS) -46 dB(c) Total Low
Frequency Random and Periodic (p-p) -46 dB(d) Moire and Chrominance
Modulation Noise -25 dB
AUDIO TOLERANCES3.1.6 Output Signal Level(a) Signal level at
output after line-up 1.0 dB(b) Gain Stability 0.5 dB
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3.1.7 Amplitude/Frequency Response(a) 40 Hz - 15 kHz w.r.t 1 kHz
2.0 dB(b) 125 Hz - 10 kHz w.r.t. 1 kHz 1.0 dB3.1.8 Total Harmonic
Distortion(a) 1 kHz at +8 dBu 2.5%(b) 80 Hz at +8 dBu 2.5%3.1.9
Signal/Noise Ratio(a) Weighted, Random, Peak 42 dB(b) Unweighted,
Random, Peak 46 dB3.1.10 Interchannel Crosstalk(a) 40 Hz -45 dB(b)
40 Hz - 125 Hz oblique segment(c) 125 Hz - 10 kHz -55 dB(d) 10 kHz
- 15 kHz oblique segment(e) 15 kHz -45 dB(f) 15 kHz - 80 kHz -35
dBA profile is shown in Reference Section, Ref. 19 (c)3.1.11 Wow
and Flutter 0.1%
DUAL CHANNEL SOUND RECORDING3.1.12 Level Difference Between A
and B Channels(a) 40 Hz - 15 kHz 2.0 dB(b) 125 Hz - 10 kHz 1.0
dB3.1.13 Crosstalk Between A and B Channels(a) 40 Hz -20 dB(b) 40
Hz - 125 Hz oblique segment(c) 125 Hz - 10 kHz -40 dB(d) 10 kHz -
15 kHz oblique segment(e) 15 kHz -30 dBA profile is shown in
Reference Section, Ref. 19 (d)3.1.14 Phase Difference Between A and
B Channelsaverage:(a) 40 Hz 30(b) 40 Hz - 200 Hz oblique segment(c)
200 Hz - 4 kHz 15(d) 4 kHz - 15 kHz oblique segment(e) 15 kHz
30
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peak:(a) 40 Hz - 15 kHz 40(b) 200 Hz - 4 kHz 20A profile is
shown in Reference Section 2, Ref. 19 (h)
3.2. RECOMMENDED TEST METHODS (COMPOSITE RECORDERS)
VIDEO MEASUREMENTS
3.2.2 Output Signal Level
(a) Signal Level Adjustment ErrorA recording is made of the 2T
Pulse and Bar signal shown in the Reference Section, Ref. 1.
afteradjustment of the bar amplitude to 700 mV at the generator
output. The tape is replayed and theamplitude of the bar centre at
the output of the VTR, expressed as a percentage of 700 mV, is
taken asthe signal level adjustment error.
(b) Gain StabilityThe greatest change occurring in the output
level over a period of 1 hour, using the same recording.
3.2.3 Linear Distortion
(a) 2T Pulse-to-Bar RatioThe signal should be the 2T
Pulse-and-Bar waveform as shown in Reference Section, Ref. 1.
The K rating of the pulse-to-bar ratio is defined as:-
%1004
xP
PBK =
Where B and P are the amplitudes of the bar and pulse
respectively.
Set the pulse amplitude to be 100% on the centre scale of an
appropriate graticule (Reference Section,Ref. 4) and divide by four
the percentage difference in amplitude between the pulse and the
barmeasured at its mid-point, to obtain the K rating.
When the waveform is subject to line tilt or an extended
distortion of the leading edge at the top of thebar, the amplitude
of the bar must be measured at its mid-point after first setting
the blanking levelmid-way between two successive bars to 0%.
(b) 2T Pulse ResponseThe test signal should be the 2T
Pulse-and-Bar waveform as shown in Reference Section, Ref.
1.Measurement may be made using a graticule such as that shown in
Reference Section, Ref. 4
If this graticule is used, the vertical gain of the oscilloscope
is adjusted to make the pulse amplitude100% and then the vertical
shift moved to bring the banking level onto the base line at 30%.
Thehorizontal gain is advanced and the horizontal shift adjusted to
make the waveform touch the H.A.Dmarkers on the 80% line. With
normal gain the graticule markers are 2% K and 4% K. For 1% K and2%
K the calibrated vertical gain is advanced by x2. For limits of % K
and 1% K the pulse amplitudeis first set to 80% and the calibrated
vertical gain then advanced by x5.
c) 2T Bar ResponseThe test signal should be the 2T Pulse-and-Bar
waveform as shown in Reference Section, Ref. 1.
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The horizontal timebase of the oscilloscope is adjusted so that
the half amplitude points of the barreach the outer limits marked
on a graticule such as that shown in Reference Section, Ref. 4.
Ignoring the first and last 2.5% (0.625ms) of the bar, the
deviation from its mid-point, expressed as apercentage of its
amplitude at that point, is the K rating of the bar. Measurements
are made using onlyhalf the bar, the worse half being quoted as the
result. It is incorrect to measure the whole bar tilt anddivide by
two to obtain the K rating.
(d) 50 Hz Square Wave ResponseThe test signal should be the 50
Hz square wave test signal as shown in Reference Section, Ref. 5,
butwith added field synchronising pulses.
With the horizontal scan at field rate the 50 Hz signal is
adjusted as in 3.2.3(c). For a stationary displaythe signal must
contain field synchronising pulses. Again, ignoring the first and
last 2.5% (250 ms), thepercentage deviation of the worse half
divided by 2 is the K rating of the bar. (It may be noted that
forthe same deviation on the display a 4% K figure for the bar
response looks the same as 2% K for50 Hz).
(e)(f) Chrominance/Luminance Gain and delay InequalityThe
measurements are made using a 2Tc composite Pulse-and-Bar signal
(Reference Section, Ref. 6a)with the output of the recorder under
test fed to a Gain and Delay test set where available. The outputof
the test set is viewed on an oscilloscope and the test set is
adjusted to make the envelope of thechrominance pulse flat along
the baseline. If a test set is not available then the level of
distortionshould be estimated
By examining the sinusoidal distortions at the bottom of the 2Tc
composite pulse on a waveformmonitor or oscilloscope. The method is
described in Part B.
It should be noted that if Chrominance/Luminance crosstalk is
present the above method forgain inequality will produce an
erroneous result. The measurement is best made using the 2Tc
non-composite waveform (Reference Section, Ref. 6b). The 50%
luminance pedestal is used to calibratethe vertical gain of the
oscilloscope and the chrominance amplitude is measured
directly.
3.2.4 Non-Linearity Distortion
(a) Luminance Line Time Non-LinearityThe test signal consists of
a 5-step staircase (Reference Section, Ref. 2) occupying one line
in everyfour, followed by three lines of black or white.
Measurements are made with three lines of white (baron) and with
three lines of black (bar off) and the worst result quoted.
The output signal is passed through a suitable differentiating
network (Reference Section, Ref. 3),amplified and displayed on an
oscilloscope. The result is a train of five pulses. Non-linearity
ismeasured as the difference in amplitude between the largest and
the smallest expressed as a percentageof the largest.
i.e. %100max
minmax xE
EE
(b) Differential PhaseThe test signal should be a 5 step
staircase with added subcarrier (Reference Section, Ref. 2)
The differential phase may be measured by using a vectorscope in
the line-time mode. The six sectionsof subcarrier are compared for
their phase relationships taking the blanking level section as
areference. The differential phase is defined as the largest
departure in phase form that reference.Measurements are made with
the white bar on and with the white bar off and the worst
measurement isquoted.
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(c) Differential GainThe test signal should be a 5 step
staircase with added subcarrier (Reference Section, Ref. 2)
The differential gain may be measured by using a vectorscope in
the line-time mode. The six sectionsof subcarrier are compared for
their amplitude relationships and taking the blanking level section
as areference, the differential gain is defined as the largest
departure in amplitude from that of thereference expressed as a
percentage. Measurements are made with the white bar on and with
the whitebar off and the worst measurement is taken as the
result.
The measurements in paragraph 3.2.4 (a) and (b) are difficult to
make accurately on a VTR due to thepresence of noise, moire and
jitter. More accurate measurements can be made using a suitable
non-linearity test set, preferably one which integrates the
measurement and has a line strobe facility. Someimprovement can
also be obtained by using a 200 kHz low-pass filter in the display
circuit of avectorscope.
3.2.5 NoiseNoise measurements should be made using a 50%
pedestal test signal.
When measurements are made on equipment incorporating digital
timebase correctors the pedestallevel may be adjusted slightly to
minimise the effects of quantisation noise.
(a) Weighted LuminanceMeasurement is made in the band 10 kHz
(7.5 kHz) - 5.0 MHz using RMS detection. Thecharacteristic of the
luminance weighting filter is shown in Reference Section, Ref.
7.
(b) Weighted ChrominanceMeasurement is made in the band 3.5 MHz
- 5.5 MHz as defined only by the characteristic of theweighting
filter as shown in Reference Section, Ref. 7 and using RMS
detection.
(c) Total LF Random and PeriodicThe total LF noise should be
measured peak-to-peak in the frequency band 40 Hz -10 kHz (7.5
kHz).
(d) Moire and Chrominance Modulation NoiseNoise measurements are
made using 100% colour bars as the test signal (Reference Section,
Ref. 8).The VTR replay output is fed to a PAL decoder and the RED
output measured on an RMS noisemeasuring set over a frequency band
of 0 - 3 MHz. The figure obtained is increased by 8 dB to convertto
peak-to-peak and to allow for the weighting of the decoder. Each
colour bar is sampled in turn in themiddle of the bar and the worst
figure is taken as the result.
100% saturated full field Y, C, G, M, R, B colours may be used
instead of colour bars.
Moire may also be measured on a spectrum analyzer. An assessment
of the combined effect can beobtained by a square law addition of
the individual components.
AUDIO MEASUREMENTS
3.2.6 Output Signal Level(a) Signal level at output after
line-up using the EBU alignment tape or a recording made to the
same standard.
(b) Gain StabilityThe greatest change occurring in the output
level over a period of 1 hour, using the same recording.
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3.2.7 Amplitude/Frequency ResponseThe input level to the
recorder should be -10 dBu. As this test is a measurement of the
variation of gainof the equipment with frequency, corrections
should be made for any variation of the input level
withfrequency.
Tests should be made at the following frequencies and the
measurements should be referenced to thelevel at 1 kHz:-
40 Hz, 60 Hz, 125 Hz, 250 Hz, 500 Hz,
1 kHz, 2 kHz, 4 kHz, 6 kHz, 8 kHz,
10 kHz, 12 kHz, 15 kHz,Additional tests should be made to ensure
that the overall response falls off smoothly outside thefrequency
band.
3.2.8 Total Harmonic DistortionThe input level to the VTR should
be +8 dBu at each frequency.
3.2.9 Signal/Noise RatioThe noise levels are measured using a
test set incorporating a standard PPM (to BS 6840), and a lownoise
amplifier with calibrated variable gain. The 'unweighted' bandwidth
is constrained in accordancewith ITU-R BT.468-4, shown in Reference
Section, Ref. 9(a), and the 'weighted' frequency response
isdetermined by the ITU network as defined in ITU-R BT.468-4 shown
in Reference Section, Ref. 9(b).
With the VTR under test lined up to its normal gain setting, it
is first supplied with 1 kHz tone at0 dBu and a recording is made.
The input signal is then replaced by a 600 ohm termination and
afurther recording is made. The output of the VTR is connected to
the test set and the recordings playedback. The gain of the test
set is adjusted so that, on the first recording, the PPM gives a
scale readingof '4' (i.e. 0 dBu); with the second recording, the
gain of the test set is re-adjusted so that the PPMagain peaks to a
scale reading of '4'. The signal/noise ratio is the difference
between the two settings ofthe test set gain.
3.2.10 Interchannel CrosstalkThis test is intended to measure
the crosstalk performance from unrelated tracks such as those used
fortimecode and unrelated audio signals.
The test signals at a level of -10 dBu should be fed to tracks
likely to cause interference to the trackbeing measured. The input
to the track being measured should be terminated in 600 ohms. Upon
replayof the recorded signals the crosstalk is determined from the
difference in measured level of the twotracks under
consideration.
As crosstalk performance can approach, or be better than, the
noise performance in tape recorders, itmay be necessary to employ
selective filtering in this measurement.
A profile is shown in Reference Section, Ref. 19 (c)
3.2.11 Wow And FlutterMeasurements are made by first recording a
test frequency of 3.15 kHz at standard reference level. Onreplay
wow and flutter amplitudes should be measured using an instrument
complying with IECPublication 386, the relevant details of which
are given in Reference Section, Ref. 10.
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DUAL CHANNEL SOUND RECORDING
3.2.12 Level Difference Between A and B ChannelsTest signals
(initially at 1 kHz) from a common source at a level of -10 dBu
should be fed into theequipment under test. The output levels from
the A and B channels on the replay should be measuredat frequencies
between 40 Hz and 15 kHz and the differences calculated.
3.2.13 Crosstalk Between A and B ChannelsTest signals (initially
at 1 kHz) at a level of -10 dBu should be fed into one input of the
recorder, and a600ohm termination connected to the other. The
Crosstalk is calculated from the measured outputs ofthe A and B
channels. Measurements should be made at frequencies between 40 Hz
and 15 kHz.
The measurements should be repeated with the input signals
reversed.
As crosstalk performance can approach, or be better than, the
noise performance in tape recorders, itmay be necessary to employ
selective filtering in this measurement.
A profile is shown in Reference Section, Ref. 19 (d)
3.2.14 Phase Difference Between A and B ChannelsTest Signals
(initially at 1 kHz) from a common source at a level of -10 dBu
should be fed into theequipment under test. The phase difference
between the outputs form the A and B channels on replayshould be
measured at frequencies between 40 Hz and 15 kHz. When the
difference is not constant,the mean difference is taken as the
result, though a note should be made of the maximum difference
aswell.
A profile is shown in Reference Section, Ref. 19 (h)
3.3 PERFORMANCE FIGURES (COMPONENT RECORDERS)This section gives
the performance figures for component VTRs:
The figures refer to a single recording and replay not
necessarily on the same machine.
When more than one head is used each head should perform within
the given limits.
3.3.2 Signal Levels(a) Signal Level (Adjustment Error) 0.7V
(2%)(b) Signal Level Gain Stability (over 1 hour) 2%(c) Interfield
Flicker : Luminance 1%
Chrominance 2%
3.3.3 Linear Waveform Distortions (2T Pulse and Bar in Luminance
and 5T Pulse and Barin Colour Difference Channels)
Y Pr & Pb(a) Pulse-to-Bar Ratio 1.5% K 2.0% K(b) Pulse
Response 1.5% K 2.0% K(c) Bar Response 1.5% K 1.5% K(d) 50 Hz
Square Wave Response 1.5% K 1.5% K3.3.4 Delay Inequality between
all Component Channels(a) Mean Timing difference 20 ns(b) Timing
perturbations (p-p) 10 ns
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3.3.5 Non-Linear Waveform Distortions(a) Amplitude Non-Linearity
4%(b) Component Crosstalk -43 dB3.3.6 Noise(a) Weighted Luminance
(RMS) -52 dB(b) Colour Difference (RMS) 1.6 MHz low pass filter -48
dB(c) Total Low Frequency in Luminance channel (p-p) -45 dB(d)
Total Low Frequency in Colour Difference Channels (p-p) -43 dB
3.4 RECOMMENDED TEST METHODS (COMPONENT RECORDERS)
3.4.1 Test ConditionsThe analogue component signals (Y, Pr and
Pb) will be related to the colour separation signals (R, Gand B) by
the following matrix equations.
Y 0.299 0.587 0.114 RPb = -0.169 -0.331 0.500 . GPr 0.500 -0.419
-0.081 B
The colour separation signals have normal peak amplitudes of 700
mV. Synchronising signals may beadded to or kept separate from the
luminance component.
The following methods are relevant when component recorders are
being measured and it may beconvenient to use a waveform monitor
capable of displaying the three components simultaneously:
3.4.2 Signal Levels
(a) Signal Level Adjustment ErrorA recording is made of the
Pulse and Bar signals shown in the Reference Section, Ref. 1
afteradjustment of the bar amplitudes to 700 mV at the generator
output. The 2T signal is fed to the Ychannel and the 5T signal is
fed to Pr and Pb. The tape is replayed and the amplitude of the bar
centreat the output of each of the component channels, expressed as
a percentage of 700 mV, is taken as thesignal level adjustment
error.
In some cases the "Lightning" method of measurement described in
Part B Guidelines may be useful.
(b) Gain StabilityThe greatest change occuring in the output
level of each channel over a period of 1 hour, using thesame
recording.
(c) Interfield FlickerThe odd and even fields of each component
channel are examined separately and the maximumamplitude difference
between the two fields, expressed as a percentage of 700 mV, is
taken as theflicker.
3.4.3 Linear Waveform DistortionsLinear waveform distortions (a)
to (c) are measured using the 2T Pulse and Bar test signal in the
Y(luminance) channel and the 5T Pulse and Bar test signal in the Pr
and Pb (colour difference) channels.The waveforms are shown in the
Reference Section, Ref. 1.
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(a) Pulse-to-Bar RatioThe pulse-to-bar K rating is defined
as:
%1004
xP
PBK =
where B and P are the amplitudes of the bar and pulse
respectively.
In practice, the pulse will be taken as the reference during
measurement.
Set the pulse amplitude to be 100% on the centre scale of an
appropriate graticule (Reference Section,Ref. 4) and divide by four
the percentage difference in amplitude between the pulse and the
barmeasured at its mid-point, to obtain the K rating.
When the waveform is subject to line tilt or an extended
distortion along the leading edge at the top ofthe bar, the
amplitude of the bar must be measured at its mid-point after first
setting the reference level(blanking for Y) mid-way between two
successive bars to 0%.
(b) Pulse ResponseMeasurement may be made using a graticule such
as that shown in the Reference Section, Ref. 4.
The vertical gain is adjusted to make the pulse amplitude 100%
and then the vertical shift moved tobring the reference level
(blanking for Y) onto the baseline at 30%. The horizontal gain is
advancedand the horizontal shift adjusted to make the waveform
touch the H.A.D. markers on the 80% line.With normal gain the
graticule markers are 2% K and 4% K. For 1% K and 2% K the
calibratedvertical gain is increased by x2. For 0.5% K and 1% K the
pulse amplitude is first set to 80% and thecalibrated vertical gain
is increased to x5.
If it is desired to measure the K rating exactly, the variable
vertical gains should be adjusted until theworst pulse overshoot
just touches the inner limits. The calibration gain is then
returned to normal andthe amplitude of the pulse measured (P%)
then
%200GainCalibratedxP
K =
This is illustrated in the following table:
Pulse Amplitude 5 Gain100 0.4% K80 0.5% K67 0.6% K
57.5 0.7% K50 0.8% K
(c) Bar ResponseThe horizontal timebase of the waveform monitor
or oscilloscope is adjusted so that the half amplitudepoints of the
bar reach the outer limits marked on a graticule such as that shown
in the ReferenceSection, Ref. 4.
Ignoring the first and last 2.5% (0.625ms) of the bar, the
deviation from its mid-point, expressed as apercentage of its
amplitide at that point, is the K rating of the bar. It must be
emphasised thatmeasurements are made using only half the bar, the
worst half being quoted as the result. It is wrong tomeasure the
whole bar and divide by two to obtain the K rating.
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(d) 50 Hz Square Wave ResponseThe test signals are the 50 Hz
square waves shown in the Reference Section, Ref. 5. The 0V to700
mV signal is used in the Y channel and the -350 mV to +350 mV
signal is used in the Pr and Pbchannels.
With the horizontal scan at field rate the 50 Hz signal is
adjusted to coincide with the appropriate barmarkings on the
graticule. For a stationary display the signal must contain field
synchronising pulses(Y) or the waveform monitor must be externally
triggered from the same synchronising pulses (Pr andPb). Ignoring
the first and last 2.5% (250 ms) of the bar, the percentage
deviation of the worst halfdivided by two is the K rating of the
bar. (It may be noted that for the same deviation on the display
a4% K figure for the bar response looks the same as a 2% K figure
for 50 Hz).
3.4.4 Delay Inequality
(a) Timing DifferencesThe test signal consists of sinusoids as
shown in the Reference Section, Ref. 20 where the frequency ofthe
sinusoid applied to the luminance channel is 500 kHz and that to
the colour difference channels is502 kHz. When these signals are
subtracted a null appears half way along active line time giving
theappearance of a "bowtie". A timing difference in the components
gives rise to a positionaldisplacement of the null by 1ms for about
4ns of timing error. Markers on some of the picture linesenable a
direct reading of any timing errors to be made. The method is not
well suited for showingtiming differences that are not constant
throughout the line time.
In this situation, or when there is noise or the sine waves are
distorted, a dual channel oscilloscopewith delayed timebase and
writing speed in the order of 20 ns per division should be used to
comparethe coincidence of rising or falling slopes of the sine
waves shown in the Reference Section, Ref. 20.
The delaying timebase should be triggered from the rising edge
of the luminance pedestal so that Prand Pb can be compared with Y.
High gain should be used in the vertical amplifiers to give a
steepslope to the edges being measured and the oscilloscope delay
time multiplier control used to inspectthe full line period. The
worst error should be quoted.
The tracking of the oscilloscope input amplifier controls can be
checked using the staircase at the startof the waveform, the step
amplitudes being designed to match the 5, 10 and 20 mV per
divisionsequence of many general purpose instruments. When this
method is used, it is also beneficial if somelines of the test
signals are left unmodulated to give a line through the sine wave
crossings, aiding thevertical positioning of the traces at high
magnifications.
If a high speed oscilloscope is not available, an estimate can
be made using matched and calibratedswitchable delays in both
oscilloscope inputs (to account for insertion delay) and adjusted
for a visualtiming null. Again this should be checked across the
line period.
In some cases the "Lightning" method of measurement described in
Part B Guidelines may be useful.
(b) Timing PerturbationsIn component analogue television tape
recorders, time division multiplex techniques are used to sharethe
luminance and colour difference signals between the recording
channels and, as a consequence ofthis, the three component signals
are not recorded simultaneously. In replay this gives rise to to
timingdifferences between the signals in addition to the absolute
timing jitter. Even after timebase correctionit is likely that some
errors will remain.
Timing perturbations can be measured using any of the methods
described for Delay Inequality in3.4.4 (a). In all cases the
oscilloscope should be externally triggered from the studio
reference pulses.
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3.4.5 Non-Linear Waveform Distortion
(a) Amplitude Non-LinearityThe waveforms used are ramp signals
shown as typical examples in the Reference Section, Ref. 21.
Inorder that the system may be tested under a wide range of APL,
the signal should consist of 6 lines oframp in every 24, with the
intervening lines at black or white. Measurements are made with 18
lines ofwhite (bar on) and then 18 lines of black (bar off) and the
worst result quoted.
To make the measurement, the output of the appropriate component
channel is differentiated by asuitable network as in the Reference
Section, Ref.3 and the mid-point of the resultant signal level
madeto occupy 100% on an oscilloscope. The error is then the
peak-to-peak percentage deviation over theduration of the
differentiated ramp.
If significant noise is present, making the assessment of
non-linearity difficult and the ramp waveformshave been inspected
to ensure that there are no quantisation errors, then staircase
waveforms similar tothose shown in the Reference Section, Ref. 22
may be used. The signal should consist of 6 lines ofstaircase in
every 24 with the intervening lines at black and white.
Measurements are made with 18 linesof white (bar on) and then with
18 lines of black (bar off) and the worst result quoted.
On replay the signal is passed through the differentiating
network and displayed on an oscilloscope toshow a train of five
pulses. Non-linearity is given by the difference in amplitude
between the largestand smallest pulse expressed as a percentage of
the largest.
i.e. %100max
minmax xE
EE
NOTE: Some waveform monitors may have insufficient gain to
achieve 100% amplitude when a linerate ramp such as that shown in
Ref. 21 is differentiated. In cases such as these, the rampsignals
provided as `valid' waveforms from Component Test Signal Generators
may be used,as the shorter duration of these ramps give a larger
amplitude pedestal when differentiated.Alternatively, the line rate
signal may be used as for the case when noise is present.
(b) Component CrosstalkRecordings are made with two of the
component channels energised with the multiburst test signalsshown
in the Reference Section, Ref. 23 and the crosstalk into the
"dormant" third component ismeasured peak-to-peak. The result is
expressed in dB relative to 700 mV.
3.4.6 NoiseMeasurement is made using a 10% lift signal. Care
should be taken that the noise of the generatedsignal is not
significant. When measurements are made on VTRs containing digital
processingequipment the 10% lift signal may be adjusted slightly to
minimise the effects of quantisation noise.
(a) Weighted LuminanceMeasurement is made on the Y channel in
the band 10 kHz (7.5 kHz) - 5.0 MHz using RMSdetection. The
characteristic of the luminance weighting filter is shown in the
Reference Section,Ref. 7.
(b) Colour Difference NoiseMeasurement is made on the Pr and Pb
channels in the band 10 kHz -1.6 MHz using rms detection. TheColour
Difference filter having the characteristic shown in the Reference
Section, Ref. 24 should beused. Note that this network has a 6 dB
insertion loss and therefore the measured figure should becorrected
accordingly.
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(c) Total Low Frequency Noise in Luminance ChannelMeasurement is
made unweighted in the band 40 Hz - 10 kHz (7.5 kHz) using
peak-to-peak detection.
(d) Total Low Frequency Noise in Colour Difference
ChannelsMeasured the same as in the Luminance Channel.
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SECTION 4AUDIO RECORDERS
4.1. PERFORMANCE FIGURES
4.1.1 Definitions and Operational PracticesThis section is
applicable to all recording media including hard disc recorders,
sprocketed soundfollowers, high quality tape recorders and less
high quality tape equipments.
"High quality" tolerances apply to equipments, including
multi-track recorders, used for the recordingand replaying of
significant speech and music.
"Less high quality" applies to audio cartridge equipment for NAB
type B audio cartridges or similarequipment used for effects.
Tolerances listed refer to a single recording and replay not
necessarily on the same machine.
Tape recorders and reproducers should preferably employ ITU/IEC
equalisation characteristics inaccordance with IEC Publication 94,
3rd Edition 1968.
Related tracks are defined as those which normally carry
specific contributions to a composite sound,such as the orchestral
components of a musical balance.
Unrelated tracks are defined as those carrying information which
is acoustically dissimilar, such astime-code or other synchronising
signals, effects and foreign language tracks.
SoundFollowers
HighQuality
Less HighQuality
4.1.2 Output Signal Level(a) Insertion Gain Adjustment Error 1.0
dB 1.0 dB 1.5 dB(b) Gain Stability 0.5 dB 0.5 dB 1.0 dB4.1.3
Amplitude/Frequency Response(a) 40 Hz to 15 kHz w.r.t. 1 kHz 1.5 dB
1.5 dB 2.0 dB(b) 125 Hz to 10 kHz w.r.t. 1 kHz 1.0 dB 1.0 dB 1.5
dB4.1.4 Signal/Noise Ratio(a) Weighted, Random, Peak 42 dB 42 dB 38
dB(b) Unweighted, Random, Peak 46 dB 46 dB 42 dB4.1.5 Interchannel
Crosstalk(a) 40 Hz -45 dB -45 dB -45 dB(b) 40 Hz - 125 Hz oblique
segment(c) 125 Hz - 10 kHz -55 dB -55 dB -55 dB(d) 10 kHz - 15 kHz
oblique segment(e) 15 kHz -45 dB -45 dB -45 dB(f) 15 kHz - 80 kHz
-35 dB -35 dB -35 dBA profile is shown in Reference Section, Ref.
19 (c)4.1.6 Timecode Crosstalk
500 Hz - 20 kHz - -65 dB -
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Section 4: Audio Recorders On-line version source EBU
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ITC Handbook of Technical Standards for Television Programme
Production Issue