http://isdcf.com/papers/ISDCF-Doc11-MovieLoudnessMeasurement20160315.pdf

HowLoudisaMovie?–aNewMeasurementProcedure

ByIoanAllen

This advance release of the paper has been released as a courtesy to interested members of the ISDCF.

Accepted for publication and copyright SMPTE - reproduced by permission. Ioan Allen Author. ISDCF-Doc11 Movie Loudness Measurement 20160315

Leq(m10)2.0

HowLoudisaMovie?–aNewMeasurementProcedure

ByIoanAllen

Abstract:

Aprocedureisintroducedtomeasurethesubjec;veloudnessofanen;removieandtodevelopasuitablemetric.Leq(m)hasbeenusedforover15yearstomeasureandthencontroltheleveloftrailersandcommercials,bothintheUSandoverseas.Themethodtobedescribedtakesaten-minuterollingaverageofLeq(m)throughoutanen;removie,andthenintegratesthevaluesaboveagiventhreshold.Theprocedureisnotintendedtoconstrainthelevelsofmovies,simplytocomeupwithametrictodescribethesubjec;veloudness.Asuggesteddescrip;veisLeq(m10).

History:

Asthesoundqualityof35mmfilmimprovedovertheyears,fromAcademymono,throughDolbyStereo,DolbySR,andthedigitalsoundon35mmfilmformats,sodidthepeaklevelachievableoneachchannelofasoundtrack.

� Figure1.PeakLevelCapabilityofPhotographicSoundtrackFormats

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 1 17Accepted for publication and copyright SMPTE

Andeachdevelopmentalsoincreasedthechannelcount,furtherraisingthepoten;almaximumsoundpressurelevelinthecinema.

Nowthemoviebusinessisuniqueinmanyways!Andoneoftheseisthepoten'alforcontrolofimageandsoundqualitythroughoutthechainfromstudiotoexhibi;on.Incontrast,theproducerofaradioprogramortelevisionshowhasnocontrolwhatsoeverovertheconsumer’splaybackcoloradjustment,ortheseVngofthevolumecontrol.Weusedtheword“poten;al”becausethetheatreoperatorcanalwaysover-ridethereferenceseVngsofsoundandpicture.Acorrectlyalignedtheatreplayingamovieatfader7willreproducethelevelheardbythedirectorandmixeronthedubbing/mixingstage.Excessiveuseofthepowercapabili;esofcontenttechnology,though,leadstomanyatheatrefaderbeingloweredfromreference7to6,5oreven4½,areduc;onofasmuchas10dB.Needlesstosay,suchaloweringoflevelleadstoseveredialogintelligibilityproblems.

Now,afilm’sdirectormayhaveul;matecontrolofthefilmitself–buttrailersareinpartcontrolledbythestudios’marke;ngdepartment.Inevitably,thetrailerdesignersfeelthattheyareincompe;;onwithothertrailers,andwillpackeveryavailablehighlightfromthetwo-hourmovieintothe90secondtrailer.Naturally,thehighlightsmoreocenthannotwillbetheloudestelements.

Digitalsoundon35mmfilmwasintroducedin1992–andtheloudnesswarsbetweentrailersbecamesoviolentthatthereweremanycomplaintsfromtheatreownersandthegeneralpublic,highlightedbytrailersforfilmssuchasTwister(1996),StarWars(1997–re-release)andMeninBlack(1997).Astheatrechainsemployedfewerprojec;onists,andmanycinemaswerenotequippedwithautoma;oncontroloffaderseVngs,aloweredplaybacklevelofthetrailersledtothesamereducedlevelbeingappliedtothefeature.Asaresult,therewereincreasedcomplaintsofinaudibledialoglevelsonfeaturefilms–notsurprisingwhenthedialoglevelshadbeenloweredbyasmuchas10dBbelowreference!

Thestudiosrealizedthatthingswereoutofcontrol,andacommieee,laterknownasTASA,wasformedbythe(then)sevenmajorstudiostoreviewthesitua;on.

Leq(m):

Foryearsaprocesshadbeenu;lizedtomeasuretheaveragesoundleveloftypicallyindustrialnoiseover;me,referredtoasLeq.Thisaveragingmethodcommonlyu;lizesa“weigh;ng”characteris;c,whichhighlightscertainfrequenciesdependingontheapplica;on.Seebelow,andFigure2.DolbyLaboratoriescarriedoutsomeresearchworkin1996todeterminetheidealweigh;ngcharacteris;cforthemeasurementoftrailersandcommercials,bothofwhichtypicallyhaveaforcefuluppermid-frequencydominance.

ThisledtotheirproposalforameasurementprocedurecalledLeq(m),with“m”standingfor“movies”.(1)

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 2 17Accepted for publication and copyright SMPTE

Hierarchy:

Theinten;onofaloudnessmeasurementsystem,notsurprisingly,istogetaseriesofnumberswhichmatchthesubjec;veloudness.Inotherwords,ifsampleAissubjec;velylouderthansampleB,andsampleBlouderthanC,thenthemeasurementsystemshouldalsoshowthatA>B>C.Inthiscontext,thescaleA>B>Ccanbereferredtoasa“hierarchy.”

Therearenumerousweigh;ngcurvesinusefordifferentapplica;ons.MostcommonisprobablyA-weigh;ng,typicallyusedtomeasuretheannoyancefromindustrialnoise.Itwasfoundwhenevalua;nganumberoftrailersandcinemaspecificcommercialsthattheM-weigh;ngcurve,favoringthe2kHzto3kHzregions,createdabeeer“hierarchy”thanC-weigh;ng,A-weigh;ngandnoweigh;ngatall.SeeFigure2.

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Figure2:M-Weigh;ngcurve

TASA:

TASA(theTrailerAudioStandardsAssocia;on)haditsfirstmee;nginAugust1997.Theinten;onwastomeasureandcontroltheleveloftrailers.Theassocia;onadoptedLeq(m)asthemeasurementprocedure,andtoformalizecontrolprocedure;edtheTASAprogramwiththera;ngsprocedureoftheMPAA.InJune1999theMPAAadministra;onformallybegan,andsincethatdatenoapprovalra;nghasbeengiventoanytrailerwithoutTASAcer;fica;on.Anini;almaximumlevelwas87dBLeq(m),andthiswasloweredintwostepsto85dBLeq(m)in

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 3 17Accepted for publication and copyright SMPTE

2001,andremainstheretodayforbothfilmanddigitalcinema.Comparethiswith1996and1997whentheloudesttrailersmeasured92and93dBLeq(m).Thismeansthattheloudesttrailerstodayare8dBquieterthanbeforeTASAwasintroduced.Italsomeantthatthetrailersbeeermatchedthelevelofthefeatures.

Over6000trailersforUSfeatureshavenow(2015)passedthroughtheTASAapprovalrou;ne.Theprocesshasbeenadoptedbyseveralna;onalstandardsbodies,andbytheInterna;onalStandardsOrganiza;on.(2)

PotenIallegislaIon:

“It’sthesqueakywheelthatgetstheoil.”Surveysandcinemaexitpollssuggestthatmostmovie-goersarecontentwiththevolumelevelsofcommercials,currenttrailersandthefeatures.Butthecomplaintsthatdoarrivefrequentlygetwidelyreportedinthepress–wherethear;cleswillrarely,ifever,pointoutthatthemovie-goingexperienceisfarquieterthanthesustainedloudnessofafootballgame,orevenahigh-schoolbasketballgame.

From;me-to-;mepoli;cianshavereactedtothesepressar;clesbythreateninglegisla;on.Butunfortunatelysomeofthepoten;allegisla;onhassuggestedconstrainingthepeaklevelheardinthecinema.Thiswouldbewrongfromtwostandpoints.First,itputstheonusonthetheatreownertocheckandcontrolthelevels–asmen;onedpreviously,withacorrectlyalignedtheatre,thelevelsaresetbythefilm-maker.Secondly,controlofpeaklevelscouldwellconstrainthear;s;cintentofthefilm-maker–asinglegun-shotatpeaklevelsurprises,but10minutesofsustainedmachine-gunfirewouldproveextremelyannoying!

Luckily,atleastintheUS,nothreatenedlegisla;onhassofarbeenenacted.

Whatistheloudnessofafeaturefilm?

Theauthorisfirmlyagainstanyconstraintoflevelsoffeaturesfilms,believingthattobethedomainofthefilm’sdirectorandsoundcrew.Ifthefilm-makersarefoolhardyenoughtoover-abusethetechnologybypilinguptheloudness,that’suptothem.

Butthatsaid,thereisonemissinglink–thereisnoestablishedmethodofdeterminingthesubjec;veloudnessofanen;refeaturefilm.IthasbeensuggestedthatanLeq(longtermaverage),suchasLeq(m),couldbeused.Thisdoesn’twork–thinkofafilmhaving6twenty-minutereels.Imaginereels1-5beingveryquiet,butthewholeofreel6beingat100%peaklevel.AnLeqreadingwouldcomeoutquitelow,buttheaudiencewouldcomeoutscreamingattheendofreel6.Twentyminutesat100%isobviouslytoomuchsustainedloudness.

So,atanyonepointin;me,let’sconsidertheideaofmeasuringtheLeqoftheprior(let’ssay)10minutes.(SeeFigure3)

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 4 17Accepted for publication and copyright SMPTE

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Figure3:Notthecurrentvalue,butanaverageoftheprevioustenminutes

Thiswouldbeausefulstar;ngtool–theLeqmeasurementwouldnotbeundulyinfluencedbyafewsuddenpeaks,butwouldclearlyshowupprolongeduseof100%capability.

Andbecausewe’retryingtoassesstypicalfilmprogrammaterialhere,applyingthesameM-weigh;ngasisbeingusedforthesubjec;vemeasurementoftrailers,thisten-minuteaverage

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 5 17Accepted for publication and copyright SMPTE

wouldbeweightedinthesameway–let’scallitLeq(m10).Hereareafewexamples

� Figure4:StarWarsEpisodeII

� Figure5:MasterandCommander

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 6 17Accepted for publication and copyright SMPTE

� Figure6:MissionImpossible3

� Figure7:VeerZara

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 7 17Accepted for publication and copyright SMPTE

Ametric:

Butthisinitselfisnotveryuseful.It’snotveryhelpful,forexample,justtosaythatat23minutesintothefilm,theLeq(m10)fortheprevioustenminuteswas85dB,ortostateitmorecorrectly,85dBLeq(m10).

So,let’stryaddingtogetheralltheLeq(m10)readingsatsomegivenconstantclockfrequency(samplerate),andthendividingbythedura;onofthefilm.

Forthefirsttenminutesofthemovie,thedatawillshowaconven;onalLeqreading.Attheten-minutepoint,thepre-tenminutesampleswillbedroppedoff.ThelastreadingwillbetakenatLFOA.

Tomakeafurtherimprovement,wedon’twanttohavetheresultinfluencedinanywaybysustainedlow-levelmaterial.Asanexample,thedifferencebetweenquietdialogandquietatmospheresshouldhaveminimaleffect.Ourinterestisonlyinsustainedmaterialaboveacertainlevel.So,let’ssetathresholdpoint.

Ourstar;ngparameterswere:

1. Windowdura;on–currently10minutes

2. Threshold–ini;ally85dBLeq(m10),butchangedlater(seebelow)

3. Samplerate–currently750mS-nota;meconstant,butthepointatwhichasampleistaken.

4. Filmdura;onunits–minutes(whynot?)

Abunchoffilmsweremeasuredusingtheseparameters,crea;ngasinglemetric,andahierarchyclosetosubjec;veanalysiswasrevealed.

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 8 17Accepted for publication and copyright SMPTE

� Figure8:StarwarsEpisodeII–with85dBthresholdandshowingsinglemetric

� Figure9:MasterandCommander

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 9 17Accepted for publication and copyright SMPTE

� Figure10:MissionImpossible3

� Figure11:VeerZara

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 10 17Accepted for publication and copyright SMPTE

Butacoupleoffilmsseemtocomeoutwithtoolowanumberwhencomparedwiththesubjec;velevel.No;ceablewasSlumdogMillionaire,wherealotofenergywasconcentratedintheregionbetween80dBLeq(m)and85dBLeq(m).

ThresholdSelecIon:

Wetooksomeselected;tles,andcomparedan85dBthresholdwitha70dBthreshold,andtheresultsareshowninFigure12.

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Figure12:Comparisonof85dBand70dBthresholds

Next,wemadeananalysisof“loud”moviesversus“quiet”moviesatdifferentthresholds,asshowninFigure13.

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 11 17Accepted for publication and copyright SMPTE

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Figure13:Comparisonof“loud”and“quiet”moviesatdifferentthresholds

Thefinalconclusionwasthatan80dBthresholdgavethebesthierarchy,andacomparisonof85dBand80dBcanbeseeninFigure14.Notonlyagoodhierarchy,butmoreevenlyspread.

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 12 17Accepted for publication and copyright SMPTE

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Figure14:Effectofchangingthresholdfrom85dBto80dB–normalizedtoVeerZara,theloudestmoviemeasuredtodate

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 13 17Accepted for publication and copyright SMPTE

WindowduraIon:

Asstatedearlier,tooshortawindowandpeaklevelswouldberestricted.Toolongawindowcouldallowabuse.10minutesseemsaboutright.Thiswasasubjec;vecall,butminorrevisionswouldprobablynotcausemajorchangesinthehierarchy.

SourceContent:

AllthematerialcitedinthispapercamefromDCPpackages,withtheexcep;onofFigure19whichforhistoricalreferenceshowstheLeq(m10)ofthe35mmDolbyDigitalversionofApocalypseNow.

WehavecarriedonmeasuringselectedfeaturesandafewoftheseareshowninFigures15,16,17,18.

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Figure15:U23D--80dBthreshold

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 14 17Accepted for publication and copyright SMPTE

� Figure16:Birdman

� Figure17:Hobbit3

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 15 17Accepted for publication and copyright SMPTE

� Figure18:AmericanSniper

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Figure19:ApocalypseNow–35mmDolbyDigital

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 16 17Accepted for publication and copyright SMPTE

SomeselectedfilmsareshowninorderofLeq(m10)inthetable:

• U23D 528• MadMax:FuryRoad 422• TransformersIII 360• MissionImpossibleIII 356• StarWars:TheForceAwakens 317• ApocalypseNow 255• Tron:Legacy 240• SlumdogMillionaire 231• Hobbit3 225• Skyfall 170• AmericanSniper 139• MoonriseKingdom 86• Birdman 77• GrandTorino 0

Conclusion:

Onceagain,weareinnowaysugges;ngthatfeaturefilmsshouldberegulated.Theproceduredescribedisprimarilybeingofferedasamuchbeeermethodofderivinganumberwhichreportsthesubjec;veloudnessofamovie–farbeeerthanmeasuringthepeaklevelsreached.Anditshouldbepointedoutthatthemetricdescribedhasnoabsolutevalue–itsvalueispurelyrela;ve,revealingwhichfilmsaresubjec;velylouderthanothers.

Reference:

1. “Aremoviestooloud?”SMPTEJournal,vol.107,pg30,1998

2. ISO21727,“MethodofMeasurementofPerceivedLoudnessofShortDura;onMo;on-pictureAudioMaterial.”

Notes:

1. Someofthematerialcontainedinthispaperisupdatedcontentfrompresenta;onsmadetotheSMPTEOctober2007andTheHollywoodPostAlliance,February2009.

2. ThispaperiscopyrightbytheSMPTE,andhasbeenapprovedforpublica;onintheSMPTEMo;onImagingJournal.

HowLoudisaMovie?–aNewMeasurementProcedure Ioan Allen Page ! /! 17 17Accepted for publication and copyright SMPTE