TC Electronic SYSTEM 6000 MKII Algorithm Manual

113
lM6
Long-term measurements
Universaldescriptorsmaybeusedtomake
program-durationmeasurements,oryoumay“spot-check”
regular dialog or individual scenes as required. It is
recommended not to measure programs of a shorter
duration than appoximately 10 seconds, while the
maximum duration may be 24 hours or longer.
Reset Key
Beforeanewmeasurement,presstheResetkey.This
resetsthedescriptors,theradarandthetrue-peakmeters.
Run the audio, and watch the radar and descriptor fields
update accordingly. It is normal that the descriptors wait
five seconds into the program before showing the first
readings, while the radar updates instantly. The first
five seconds of a program are included in the descriptor
calculations, even though they are not shown instantly.
LM6 incorporates an intelligent gate, which discriminates
betweenforegroundandbackgroundmaterialofa
program.Consequently,ameasuredoesn’tstartbefore
audio has been identfied. It also pauses the measurement
duringperiodsofonlybackgroundnoise,andinthe
fade-outofamusictrack.
Universal Descriptors and Dolby LM100
Unlikemethodsthatmeasuredialogonly,LM6maybe
used with any type of audio – which includes dialog, of
course.Ifyouwishtomeasuredialog,it’srecommendedto
doamanualspotcheckofaprogramorafilm.Find10-30
secs of regular dialog and measure it with LM6 . Where
dialog may be soft, regular or loud, and shift by more
than15dBinsideafilm,regulardialogtendstobeless
ambiguous and more consistent across a program.
Forcompatibilitywithaproprietarymeasuresuch
as Dolby LM100, only some of these meters are
updatedtouseITU-RBS.1770andLeq(K)while
othersarelockedatLeq(A).Thesoftwareversionof
LM100shouldbe1.3.1.5orhigherinorderforittocomply
with BS.1770, and to have its average loudness reading be
compatiblewithCenterofGravityinLM5orProgram
LoudnessinLM6.Evenusedjustonspeech,Leq(A)isnot
a precise approximation to perceived loudness, so please
update the unit to BS.1770 to obtain similar readings and
predictable results.
To measure dialog with LM6 the same way Dolby LM100
is sometimes used, solo the Center channel during a
spotchecktomomentarilydisablethechannelweighting
specifiedinBS.1770,ifyou’reworkingona5.1stem.
Universal Descriptors and AC3 Metadata
The“Dialnorm”parameterinAC3metadatashouldindicate
the average loudness of a program. Basic dynamic range
andlevelcontrolthatrelyonthisparametermaytakeplace
intheconsumer’sreceiver.Therefore,itsvalueshouldnot
be far off target, or the consumer results become highly
unpredictable.
Program Loudness in LM6 is directly compatible with
DialnorminAC3.Mostbroadcaststationsworkwithafixed
dialnormsetting,forinstance–23LUFS.Thiswouldbethe
Program Loudness target level for any program.
If your station is more music than speech, better
inter- channel leveling may be obtained with dialnorm
permanentlyset1or2LUlowerthantheProgram
Loudness target level.
True-peak meters
ThepeakmetersofLM6displaytrue-peakasspecifiedin
ITU-RBS.1770.True-peakmetersgiveabetterindication
ofheadroomandriskofdistortionindowstreamequipment
such as sample rate converters, data reduction systems
and consumer electronics than digital sample meters used
e.g. in CD mastering. Note that the standard level meters in
mostdigitalworkstationsandmixersareonlysamplepeak
(FinalCut,Avid,ProTools,Yamahaetc.),andshouldonly
be used as a rough guideline of the headroom.
Notethatthemeterscaleisextendedabove0dBFS.
Most consumer equipment distorts if you see readings
above0.It’snotaproblemtohavetrue-peaklevelgoing
to-1dBFSinproduction,butlegacyplatforms(analog,
NICAM etc.) and some data-reduction codecs may distort
unlesstrue-peakleveliskeptlower.WithDolbyAC3and
withlowbitratecodecs,-3dBFSshouldbeconsidered
the limit, while legacy platforms requiring emphasis may
needevenfurtherrestriction.LikedescribedinEBUR128,
it’srecommendedtomakefulluseoftheheadroomwith
true-peaksgoingto-1dBFSinproduction,andtoonly
restrictpeaklevelfurtherduringdistribution/transmission.

TC Electronic SYSTEM 6000 MKII Specifications

General

Brand	TC Electronic
Model	SYSTEM 6000 MKII
Category	Computer Hardware
Language	English