understanding and measuring loudness josh derby mark edmondson

Understanding and Understanding and Measuring LoudnessMeasuring Loudness

Josh DerbyJosh Derby

Mark EdmondsonMark Edmondson

Daniel M. Hitomi © 2006 CBS Intellectual Property Management ProgramMedia Technology & Operations

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Broadcast Loudness

Overview

1. The Broadcast Loudness Problem 2. Comparing the meters3. Quantifying Art4. Applying transmission sensitivity to post

production


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Not a new problem

• Issues with television loudness are not new, but the transition to digital has added a host of new issues to the good, old fashioned problems.

• Several issues revolve around loudness:– How do you measure it?

– What is the role of dialogue?

– How do you control it?

– How do you monitor it once the program leaves your hands?

• All loudness measurements have one goal in mind: making the audio get to the consumer in a listenable condition.


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Dialogue: King or Supporting Actor

• Newer loudness systems based around dialogue measurement– Dialogue as key part of the signal, significant

sensitivity in viewers?• Dolby says “Yes”• ITU says “Not so much”

– In the documentary business, dialogue is king, and in general is the most important part of your audio.


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Dolby Loudness Research

Speech vs. Other (Footsteps) - Correlation Histogram

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2

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-8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9Error in dB

(i.e. The agreement among the 21 listeners)

Nu

mb

er o

f L

iste

ner

s Other-Footsteps

Speech

Slide courtesy of Mike Babbitt at Dolby


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How do you control it?

• Well, it’s a little better than that– Positioning content to succeed

– Knowing your distribution channels and their strengths and weaknesses.

– Customizing your mix in the post production process to complement those strengths and weaknesses

– Metadata – the “ultimate” solution, however, is only as good as the data it is describing

• May be used for good or evil


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Transmission Paths – What Happens to My Audio

Air master tape

• HD versions have Dolby E Metadata

• SD versions do not

Satellite Uplink

•Digital services, HD and SD, have Dialnorm

•Analog SD services do not

Satellite Downlink by affiliates

•Signals received by affiliates and passed into a combination of analog and digital cable systems

•In digital systems, metadata should be preserved, but sometimes is lost

•In analog systems, audio is decoded with Dialnorm applied if it was present and resultant audio is modulated and sent to consumers

Viewed by home consumer

•On what type of system and speakers?

•On what set-top box?

•With what compression settings buried in the menus?

•On which output of the STB?


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When audio goes wrong in transmission

• Original Mix

• Mix ruined by bad multi-band compression

• Mix ruined by AC-3 compression on an over-limited signal


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Loudness Standards in Post – Quantifying Art

• There’s been a generalized resistance to hard and fast loudness standards in post production– The “Yo, man, that’s my art” phenomenon

– Audio mixing as a dark science

• However, the “measure and adjust at broadcast” approach only takes you so far– Assumes that metadata is passed all the way to the

consumer

– Assumes that the whole has something to do with the parts


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Short term and long term loudness levels

• Taking long-term loudness measurements only helps you if your short term levels have something to do with your long term loudness levels– Average weight of people in this room

– You need to measure not only loudness level, but loudness consistency throughout a program

– Also need to monitor the loudness of elements within a program – what is the relationship between my dialogue and my music?


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How do you measure loudness?

• So many different types of meters out there:– LeQ(A) – long term equivalent loudness with traditional

Fletcher-Munson A– LeQ(RLB) - long term loudness with revised frequency filters– Good old fashioned VU or RMS – traditional loudness

measurement– PPM – average peaking

• Disagreement about weighting – Fletcher Munson A vs F.M. B vs ITU RL-B – Or, no weighting at all

• Unless mix is done by dogs or dolphins, mixer’s ears do their own weighting?

• All of these measurements serve different purposes and consequently all tell very different stories


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Meter Comparison

• The following graphics represent the metering of two minutes of audio– Documentary programs with “good” mixes done by

professionals

– Charted with multiple ballistics with several different meters and metering software tools


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Combined RMS


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Meter Comparison


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Why do we mix audio?

• A careful distinction between mixing and sound design• The objective of an audio mix is to combine uncontrolled

elements, control them, and appropriately emphasize and de-emphasize them so that the message is conveyed to the consumer– Audio mixes are creative works, but not art

• Artistry is used to accomplish creative tasks, but audio mixes are always meant to convey a specific meaning to the listener

• In art, the end result is subjective, and who is to say whether it is good or bad?

• All of our grandmothers can tell whether a mix is good or bad, in the sense that key elements are discernable or not

• If we can reasonably agree on the objective of the television mix, then we can agree on the correlation of the elements


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Actual feedback from viewers

• “I anticipated a wonderful program. I was disappointed! The background music was in the foreground thus the narrator was unable to be heard. Therefore I switched to the baseball game. My disappointment! Your loss.”

• “Your channel puts on some very entertaining, informative programming. CAN YOU TELL ME WHY your background music is always so annoyingly loud? It absolutely drowns out much of the spoken narrative and makes watching quite a chore.”

• “The Music accompaniment is FAR, FAR TOO LOUD. It detracts form the show immeasurably and in the end we TURNED IT OFF. Hardly the result you would wish for.”

• Clearly these viewers share similar priorities when it comes to the placement of elements in the audio mix


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The Challenge

• The challenge for Discovery, and probably many other content providers, is that current metering and monitoring can’t anticipate whether a mix will work in the consumer medium– “Sounds fine in the suite”

• Creative environment not necessarily indicative of viewer environment

• Doesn’t replicate the broadcast chain• Most post production suites are equipped with gear

that is far superior to what any consumer will have– Yes, we’ve heard of Auratones, but seriously, beyond that


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Elements of the mix

• Quantifying the elements of the television mix:– Dialogue level – measured in terms of loudness as

opposed to voltage

– Music and Effects level, in relationship to dialogue, or “mix density”

– Dynamic range

– Signal clarity / tonal quality


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A new way of measuring audio

• Can we build metering that helps us to objectively measure these elements and how they correlate to each other?– Not the Mix-o-Matic 5000

– Not replacing talented audio mixers with computers

– Tool to help those people accomplish the goal of properly making television mixes

• Grandma test

– Tool to help non-expert ears anticipate the potential problems with audio prior to broadcast


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Conclusions

• Broadcasters need to come together in agreement on some basic loudness standardization.

• Quantifying a good television mix balance is neither black magic nor voodoo.

• Professionals and non-professionals tend to generally agree on what a good mix balance is.

• Current metering and measurement technology is helpful, but falls short of painting a picture that is consistent and understandable to the broadcasters.

• Industry should be able to agree on the basic components of a mix and devise a way to measure these components objectively.


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Thanks for listening

• Josh Derby: • [email protected]

• Mark Edmondson: [email protected]

understanding and measuring loudness josh derby mark edmondson

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