Loudness Measurement & Monitoring Yannick LE DREAU

Loudness Measurement & MonitoringYannick LE DREAU

What is Loudness ?

Loudness Standards

Measurement Method

Demonstration

Agenda

Loudness Measurement & Monitoring2

What is Loudness?

Loudness is a subjective measure– Different people perceive loudness differently

Loudness is primarily a psychological correlation of the physical intensity of the audio signal.

Different techniques have been used to provide correlation of the overall loudness of the signal.

Different filters are used to adjust the models to perceived loudness of the human ear.

Necessary to measure perceived Loudness– Radio & Television broadcasts– Music, Speech & Sound Effects


Loudness Standards

IEC 61672-1 – Electroacoustics Sound Level Meters

ITU-R.BS 1770– Algorithms to measure audio program loudness and true-peak

audio level

ITU –R.BS 1771 – Requirements of loudness and true-peak indicating meters

ATSC A/85 RP – Techniques for Establishing and Maintaining Audio Loudness for Digital

Television

P/Loud Working Group– http://wiki.ebu.ch/loud/Main_Page– Gating Measurement– Inclusion of LFE


http://wiki.ebu.ch/loud/Main_Page

Introduction to the Standard ITU-R BS 1770

ITU-R Monophonic Loudness– Measured Leq(RLB) K-weighted means square– Low computational complexity of algorithm– Leq(RLB) provides best performance of all meters tested– Simple energy-based loudness as robust as more complex models

Design of Leq(K) algorithm– High Pass Filter– Summation of energy over time

Design of Multi-Channel Loudness algorithm– Simple building blocks– Scalable from 1 to N


Measuring Loudness

Uses RLB Filter– Simpler to implement– It should be noted that BS.1770

ended up NOT incorporating Leq(RLB), BUT Leq(R2LB), now formally known as Leq(K)

Pre Filter– Accounts acoustic effects of the

head

ITU-R.BS 1770 Algorithms for audio programme loudness


True Peak Metering

Audio Meters use 4x oversampling

Allows True Peak Measurement

Other types of meter may under report audio level.

– Especially at high frequencies

ITU-R BS 1770-1 provides method for measurement of True Peak.

AEU February 2010 - Tektronix Confidential VID-11 Loudness Measurement & Monitoring7

Loudness Measurement (LKFS)

Definitions– L, C ,R, Ls, Rs & N which is total number of channels– y Input signal filtered by pre-filter and RLB weighting curve– z Weighted Mean Square level– G Channel weighting

– Pre-filter and RLB weighting curve defined as K-Weighting

AEU February 2010 - Tektronix Confidential VID-11 Loudness Measurement & Monitoring8

(LKFS)

ii

ii

EBU P/Loud Group – Rec 128

EBU P/Loud R128

The following slides draw heavily from EBU Technical documents 3341/2/3.

There are two ways to achieve loudness normalisation in the home:– the actual normalisation of the source itself, so that the

programmes are equally loud by design– the use of loudness metadata that describe how loud a

programme is.

Within the EBU R128 loudness levelling the first solution is encouraged due to the advantages:

– simplicity– potential quality gain at the source

EBU P/Loud R128 Definitions:

– ‘LUFS’ is equivalent to ‘LKFS’ (which is used in ITU-R BS.1770-1). An input document to change the nomenclature to ‘LUFS’ (which is compliant with international naming conventions) has been submitted to the ITU.

– A programme is an individual, self-contained audio-visual or audio-only item to be presented in Radio, Television or other electronic media - this includes commercials, trailers, promos, interstitials and similar items

– Programme Loudness is the integrated loudness over the duration of a programme

– Loudness Range (LRA) describes the distribution of loudness within a programme

– Maximum True Peak Level is the maximum value of the audio signal waveform of a programme in the continuous time domain

EBU P/Loud R128

The Recommendations are:

– that the descriptors Programme Loudness, Loudness Range and Maximum True Peak Level shall be used to characterise an audio signal;

– that the Programme Loudness Level shall be normalised to a Target Level of -23 LUFS with a permitted deviation of +/-1 LU for programmes where an exact normalisation to Target Level is not achievable practically (for example live programmes)

– that the audio signal shall be measured in its entirety, without emphasis on specific elements such as voice, music or sound effects

– that the measurement shall be made with a loudness meter compliant with both ITU-R BS.1770 and EBU Technical Document 3341

EBU P/Loud R128 Further recommendations:

– that this measurement shall include a gating method with a relative threshold of 8 LU below the ungated LUFS loudness level as specified in EBU Technical Document 3341

– that Loudness Range shall be measured with a meter compliant with EBU Technical Document 3342

– that the Maximum Permitted True Peak Level of a programme during production shall be -1 dBTP (dB True Peak), measured with a meter compliant with both ITU-R BS.1770 and EBU Technical Document 3341

– that loudness metadata shall be set to indicate -23 LUFS for each programme which has been loudness normalised to the Target Level of -23 LUFS

– that loudness metadata shall always correctly indicate the actual programme loudness, even if for any reason a programme may not be loudness normalised to -23 LUFS

Measuring Loudness

LKFS Meter & Target Loudness

Audio Meter Scale in LKFS

Settings– Number of Channels– Duration of Average– Gating– Threshold settings

EBU R128 standard -23 LKFS with deviation of +/-1 LKFS

User Defined Limits


EBUTarget Loudness-23LKFS-23LKFS(+/- 1)(+/- 1)User DefinedUser Defined

Too LoudUser DefinedUser Defined

iLoudness = - 0.691 +10 log Loudness = - 0.691 +10 log ∑∑ G . z (LKFS) G . z (LKFS)10

NN

i i

Too QuietUser DefinedUser Defined

WFM7120 Loudness Configuration

Press Config button

Navigate to Loudness Settings

Enter sub menu and select Loudness Preset EBU R128

Yellow text indicates changing of settings


WFM7120 Elements of Loudness Monitoring


WFM7120 Elements of Loudness Monitoring


EBU R128-23LKFS-23LKFS(+/- 1)(+/- 1)User DefinedUser Defined

Too LoudUser DefinedUser Defined

WFM7120 Audio Session


Summary of Audio

Clips, Over, Mute, Silence, Peak/ High Level

Loudness MeasurementPer ChannelPer PairInfinite LoudnessShort Loudness

Loudness InformationDuration of Short PeriodChannel Used in summation

Loud Alarm

Run Time of Session

WFM7120 Loudness Session


Loudness Chart

Logs Loudness value every second

Trend Chart

90 Seconds

180 Seconds

Bar Chart

9 minutes to 6 hours

Save Loudness value to USB or via network.

WFM7120 Loudness Session


Loudness Chart

Bar Chart

From 9 minutes to 6 hours

LKFS Short

LKFS Infinite

Dialnorm

True Peak

Max / Min Value LKFS

Summary Information

Channel Summation

Short PeriodTarget Loudness

Save Loudness Session to USB or via network.

WFM7120 Loudness Session Export


WFM7120 Loudness Session Export


Multichannel Audio & Distribution Systems

Dolby Metadata

AC-3 Metadata includes 28 parameters Informational

– Seven optional parameter– No effect on audio decoding

Basic– Nineteen parameter– Dynamic Range, Downmix– Optimize the listening experience

Critical– Required for proper encoding and decoding– Channel Mode (acmod)

– Describes channel format– Dialog Level (dialnorm)

– Sets dialog level


Dolby Metadata Management

Requirements for accurate Metadata Methods

Fixed Method AC-3 encoder Dialog Level Is

“fixed” to a single value

Preset Metadata AC-3 encoder “presets” are

programmed, each with different dialnorm

Agile Metadata AC-3 encoder is configured to

receive external metadata


Fixed Metadata

Simply “Fix” AC-3 Encoder dialnorm setting Measure long term loudness and set dialnorm to this value Content Delivery specification should set Target Loudness of ingest

material Non-conforming content needs to be measured and offset applied

Poses mininal risk to content. Simplifies system requirementsLoudness Measurement & Monitoring27

ConsumerAC-3

Decoder

Process,Storage

Distributionand

Switching

AC-3Encoder

Source 1Audio

Source nAudio

Audio

ATSCDistribution

Audio

InternalMetadata

Values

Preset Metadata

Change between preset metadata values via external control Preset are loaded into AC-3 encoder based on known differences in

content loudness Automation system used to recall presets based on content and channel

modes AC-3 Framesync some encoders disrupt audio bit stream when preset is

changed.Loudness Measurement & Monitoring28

ConsumerAC-3

Decoder

Process,Storage

Distributionand

Switching

AC-3Encoder

Source 1Audio

Source nAudio

Audio

ATSCDistribution

Audio

InternalMetadata

Values

Auto-mation

ExternalControl

Agile Metadata

Setting different dialnorm values for different content Embed the metadata parameters within the SDI ANC data De-Embed metadata just prior to AC-3 Encoder Dialnorm settings change appropriately on boundaries of content Needs to be employed throughout the whole system


ConsumerAC-3

Decoder

Process,Storage

Distributionand

Switching

Source 1Audio

Source nAudio

ATSCDistribution

Audio

AC-3Encoder

InternalMetadata

Values

De-Embed

Audio

EmbedProcess,Storage

Distributionand

Switching

Embed

Meta-Data

Values

Agile Metadata

Complex System

Requires full Loudness measurement of each piece of content

Loss of metadata could result in an audio discrepancy– AC-3 encoder will revert to units metadata settings

Requires an agile infrastructure throughout Broadcast plant

Equipment deployed at all input, output and monitoring locations

Agile systems provide the greatest flexibility for the content provider– Does not impose creative limitations


Fixed Agile Hybrid

Broadcast Example

Live productions– Metadata delivered via Dolby E

Broadcast Center infrastructure– Metadata extracted from Dolby E signal– Inserted into HDSDI VANC line 9

Routed through plant– To Distribution system


L-Band

ASI

VANCInserter

HD-SDI

Dolby E

MUXIRD

Ch 1/2 L/R

Ch 3/4 C/Lfe

Ch 5/6 Ls/Rs

Ch 7/8 Lt/Rt

Dolby EDecoder

To FacilityHD Router

HD-SDIWith

SMPTE 2020

BB Reference

Fixed Agile Hybrid – Network Distribution

Broadcast Center Signal Flow

Multiple Sources

Signals Routed to Transmission– Dolby E encoding– Audio Metadata In VANC

Metadata Extracted from VANC and delivered to Dolby E encoder

Also extracted by transmission encoder

Delivered to Network as private MPEG data service


HD-SDI

Dolby E

DEMUX

Ch 1/2 L/R

Ch 3/4 C/Lfe

Ch 5/6 Ls/Rs

Ch 7/8 Lt/Rt

Dolby EEncoder

HD-SDIWith

SMPTE 2020

HDRouter

HDMasterControl

VANCDecoder

Metadata

MPEGEncoder

BB Ref.

StereoDownmix

AES L/tRtStereo

Effectively control of program-to-interstitial loudness

Fixed dialnorm– Ensure all content meets Target Loudness– Long term loudness matches dialnorm– File based use a scaling device to match long term loudness– Real-time loudness processing device to match loudness

Agile dialnorm– Measure all program content– Dialnorm must match actual calculated loudness– Filebased set dialnorm to measured loudness of specific content– Real-time process to match content specific loudness and set dialnorm

based on this loudness value


Dynamic Range Control DRC calculations based on the indicated loudness

Dialnorm need to accurately reflect loudness

Profession Encoding profiles for DRC– Music Light– Music Standard– Film Light– Film Standard– Speech

Dolby Digital (AC-3) modes– Line Mode– RF Mode

DRC – “None”– Inhibits Generation of DRC profiles– Prevents viewer selection– Protection Limiting will not be available– Recommend profile other than “None”


Dynamic Range Control Monitoring

Dynamic range values shown in Dolby Status display.

Monitoring function allows dynamic range parameters to be applied

– Selection for:-– Line Mode– RF Mode


Conclusion

Audio Loudness is becoming a critical measurement

ITU-R BS 1770/1 and ATSC A/85 have been adopted by broadcasters

We expect EBU R128 will be adopted by EBU member broadcasters

New Audio measurement tools are needed

New work practices need to be adhere by program producers and broadcasters

VID-11 Loudness Measurement & Monitoring36

TEKTRONIX PRODUCTS AND DOLBY

Dolby LM100 and Tektronix Products

Title DurationMathematical LKFS

UnGated LM100 WFM7120 Cerify

Comedy 03:56 -14 -14 -14 -14

The Potters Field 03:08 -18.1 -18 -18 -18.1

Somebody To Love 04:57 -13.9 -14 -14 -13.9

Another One Bites the Dust 03:37 -15.9 -16 -16 -15.9

Questions?

Documents

Loudness Measurement & Monitoring Yannick LE DREAU