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Loudness Measurement & Monitoring Yannick LE DREAU.

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1 Loudness Measurement & Monitoring Yannick LE DREAU

2 What is Loudness ? Loudness Standards Measurement Method Demonstration Agenda Loudness Measurement & Monitoring 2

3 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 Measurement & Monitoring 3

4 Loudness Standards  IEC –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_Pagehttp://wiki.ebu.ch/loud/Main_Page –Gating Measurement –Inclusion of LFE Loudness Measurement & Monitoring 4

5 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 Loudness Measurement & Monitoring 5

6 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 Loudness Measurement & Monitoring 6

7 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 provides method for measurement of True Peak. AEU February Tektronix ConfidentialVID-11 Loudness Measurement & Monitoring7

8 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 Tektronix ConfidentialVID-11 Loudness Measurement & Monitoring8 (LKFS) i i i i

9 EBU P/Loud Group – Rec 128

10 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

11 EBU P/Loud R128  Definitions: –‘LUFS’ is equivalent to ‘LKFS’ (which is used in ITU-R BS ). 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

12 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

13 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

14 Measuring Loudness

15 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 Loudness Measurement & Monitoring 15 EBU Target Loudness-23LKFS (+/- 1) User Defined Too Loud User Defined i Loudness = log ∑ G. z (LKFS) 10N i i Too Quiet User Defined

16 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 Loudness Measurement & Monitoring 16

17 WFM7120 Elements of Loudness Monitoring Loudness Measurement & Monitoring 17 Loudness Meter Loudness Measurements Short Infinite True Peak Dialnorm Run Time Green Audio Labels Channels Summed into Loudness Measurement Program Loudness

18 WFM7120 Elements of Loudness Monitoring Loudness Measurement & Monitoring 18 EBU R128-23LKFS (+/- 1) User Defined Too Loud User Defined In-Bar Message LOUD, QUIET, GATED

19 WFM7120 Audio Session Loudness Measurement & Monitoring 19  Summary of Audio Clips, Over, Mute, Silence, Peak/ High Level Loudness Measurement Per Channel Per Pair Infinite Loudness Short Loudness Loudness Information Duration of Short Period Channel Used in summation Loud Alarm Run Time of Session

20 WFM7120 Loudness Session Loudness Measurement & Monitoring 20  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.

21 WFM7120 Loudness Session Loudness Measurement & Monitoring 21  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 Period Target Loudness Save Loudness Session to USB or via network.

22 WFM7120 Loudness Session Export Loudness Measurement & Monitoring 22

23 WFM7120 Loudness Session Export Loudness Measurement & Monitoring 23

24 Multichannel Audio & Distribution Systems

25 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 Loudness Measurement & Monitoring 25

26 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 Loudness Measurement & Monitoring 26

27 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 requirements Loudness Measurement & Monitoring 27 Consumer AC-3 Decoder Consumer AC-3 Decoder Process, Storage Distribution and Switching Process, Storage Distribution and Switching AC-3 Encoder AC-3 Encoder Source 1 Audio Source n Audio ATSC Distribution Audio Internal Metadata Values

28 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 & Monitoring 28 Consumer AC-3 Decoder Consumer AC-3 Decoder Process, Storage Distribution and Switching Process, Storage Distribution and Switching AC-3 Encoder AC-3 Encoder Source 1 Audio Source n Audio ATSC Distribution Audio Internal Metadata Values Auto- mation Auto- mation External Control

29 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 Loudness Measurement & Monitoring 29 Consumer AC-3 Decoder Consumer AC-3 Decoder Process, Storage Distribution and Switching Process, Storage Distribution and Switching Source 1 Audio Source n Audio ATSC Distribution Audio AC-3 Encoder AC-3 Encoder Internal Metadata Values De- Embed De- Embed Audio Embed Process, Storage Distribution and Switching Process, Storage Distribution and Switching Embed Meta- Data Values Meta- Data Values

30 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 Loudness Measurement & Monitoring 30

31 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 Loudness Measurement & Monitoring 31 L-Band ASI VANC Inserter HD-SDI Dolby E MUX IRD Ch 1/2 L/R Ch 3/4 C/Lfe Ch 5/6 Ls/Rs Ch 7/8 Lt/Rt Dolby E Decoder Dolby E Decoder To Facility HD Router HD-SDI With SMPTE 2020 BB Reference

32 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 Loudness Measurement & Monitoring 32 ASI HD-SDI Dolby E DEMUXDEMUX Ch 1/2 L/R Ch 3/4 C/Lfe Ch 5/6 Ls/Rs Ch 7/8 Lt/Rt Dolby E Encoder Dolby E Encoder HD-SDI With SMPTE 2020 HD Router HD Router HD Master Control HD Master Control VANC Decoder Metadata MPEG Encoder MPEG Encoder BB Ref. Stereo Downmix Stereo Downmix AES L/tRt Stereo

33 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 Loudness Measurement & Monitoring 33

34 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” Loudness Measurement & Monitoring 34

35 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 Loudness Measurement & Monitoring 35

36 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 & Monitoring 36

37 TEKTRONIX PRODUCTS AND DOLBY

38 Dolby LM100 and Tektronix Products TitleDuration Mathematical LKFS UnGatedLM100WFM7120Cerify Comedy03:56-14 The Potters Field03: Somebody To Love04: Another One Bites the Dust03:

39 Questions?


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