Audio loudness for video post


TV-Bay Magazine
Read ezine online
For decades audiences have been complaining about the differences in perceived loudness between different parts of a television service, most commonly that the commercials seem louder than the programmes. Finally broadcasters, prompted in many cases by regulators, have addressed the issue. Over the last decade research has determined what it is that makes something sound loud – which is not the same as the measured audio level – and determined the parameters by which it can be measured.
These principles are enshrined in EBU recommended practice R 128, which is based on ITU recommendations BS1770. In America, the Calm legislation (the Commercial Advertisement Loudness Mitigation Act) follows the same principles. Many countries in Europe (although not as yet the UK) have legislated for audio loudness.
The problem is that, while the parameters are clearly defined in these various international standards, the absolute numbers are not. The inevitable has happened: specifications of what constitutes maximum loudness vary from country to country.
As with all other critical signal parameters, when you deliver a piece of work the first thing that the receiving broadcaster will do is run a QC check on it and, if it fails, bounce it back to you. So you need to be sure you do not exceed loudness norms, just as you need to ensure the picture is within colour gamut.
If you are an edit house, you may not have not worked on the audio, but received it from an external facility. So it is sensible to check it when it arrives and, if there is a problem, get your audio house to rework it while there is still time.
Even starting with a good track, it may get modified accidentally as it passes through the finishing process, so when you run out the final uncompressed master Quicktime it is appropriate to run another check. Finally, when you create the deliverables, in MPEG or MXF, from the master, you probably should check loudness in case something unexpected happened in the compression. If you are delivering to multiple territories this is the moment to check against local specifications.
Should one of these later checks reveal a loudness problem and there is no time for reworking, at least you can attenuate the whole soundtrack to pull it down to an acceptable level.
All of this suggests that it would be good if the loudness monitoring is automatic, rather than continually taking an engineer out to run it through audio meters. More important, though, is that the EBU defines three parameters for loudness: momentary (up to 400ms), short term (up to 3s) and long term (the length of the content). Watching three loudness meters and a level meter simultaneously is neither an easy nor rewarding task for a commercial, and impossible if you are mastering a drama series.
Emotion Systems talked to a number of people from audio and video post houses and broadcasters about this issue. One common view was that checking loudness should be a matter of pushing a button, and should result in a report with some detail as well as a simple pass or fail. Customers also pointed out that as they needed different profiles for different delivery regimes, it had to be easy to configure parameters.
With all these requirements in mind, we have produced a software product called 'eFF'. This application pulls in the content file in any of the common working or delivery formats. At the front end it might be a .wav file from an audio house; later it will be a video file. The software reads through the audio component, much faster than real time, and checks it against the loudness specifications.
Because of the need to accommodate different regimes, the software incorporates a profile structure. Should the broadcast authorities in, say, Austria change their loudness requirements within the R128 specification, that can be handled by simply downloading a replacement profile.
Operationally, the user simply selects the profiles to be checked against, and requests either a report or a report and fix. If the latter, for each profile the software attenuates the audio file if necessary, without affecting the video or metadata content of the file.
In either case a report is generated in XML and as a graph. These can be included with the content on delivery, to demonstrate to the broadcaster that the file was checked against the appropriate profile and, as the saying goes, it was all right leaving me.

Tags: iss061 | loudness | bs1770 | eby | r128 | itu | calm | N/A
Contributing Author N/A

Read this article in the tv-bay digital magazine
Article Copyright tv-bay limited. All trademarks recognised.
Reproduction of the content strictly prohibited without written consent.

Related Interviews
  • NUGEN Audio: Loudness Toolkit at NAB 2013

    NUGEN Audio: Loudness Toolkit at NAB 2013

  • Nugen Audio Loudness Meter, Halo Upmix and Halo Downmix at NAB 2018

    Nugen Audio Loudness Meter, Halo Upmix and Halo Downmix at NAB 2018

  • Nugen Audio Loudness Toolkit at BVE 2016

    Nugen Audio Loudness Toolkit at BVE 2016

  • NUGEN Loudness Toolkit at NAB 2015

    NUGEN Loudness Toolkit at NAB 2015

  • Junger Audio at IBC2011

    Junger Audio at IBC2011

  • Nugen Audio at NAB 2014

    Nugen Audio at NAB 2014

  • TSL Products SAM1 MADI at BVE 2014

    TSL Products SAM1 MADI at BVE 2014

  • Emotion Systems at NAB 2012

    Emotion Systems at NAB 2012

  • DK-Technologies at NAB 2012

    DK-Technologies at NAB 2012

  • The Telos Alliance at IBC 2016

    The Telos Alliance at IBC 2016

  • Wohler at IBC 2016

    Wohler at IBC 2016

  • NUGEN Audio at IBC 2015

    NUGEN Audio at IBC 2015

  • NUGEN Audio at BVE 2015

    NUGEN Audio at BVE 2015

  • RTW at IBC 2014

    RTW at IBC 2014

  • RTW at NAB 2014

    RTW at NAB 2014

  • Cobalt Digital at NAB 2014

    Cobalt Digital at NAB 2014

  • RTW at IBC 2013

    RTW at IBC 2013

  • NuGen Audio at IBC 2013

    NuGen Audio at IBC 2013

  • TSL Products at NAB 2013

    TSL Products at NAB 2013

  • TSL Systems at BVE 2013

    TSL Systems at BVE 2013

  • TSL Products at BVE 2013

    TSL Products at BVE 2013

  • RTW at NAB 2012

    RTW at NAB 2012

  • Triveni Digital at NAB 2012

    Triveni Digital at NAB 2012

  • Qualis at NAB 2012

    Qualis at NAB 2012

  • TSL at BVE 2012

    TSL at BVE 2012

  • Sonifex at BVE 2012

    Sonifex at BVE 2012

  • Emotion Systems at BVE 2012

    Emotion Systems at BVE 2012

  • HHB and TC Electronic at BVE North2011

    HHB and TC Electronic at BVE North2011

  • Volicon at IBC2011

    Volicon at IBC2011

  • TC Electronic at IBC2011

    TC Electronic at IBC2011

  • Cobalt Digital at IBC2011

    Cobalt Digital at IBC2011

  • RTW at IBC2011

    RTW at IBC2011

  • DK Technology at IBC2011

    DK Technology at IBC2011

  • Linear Acoustic at IBC2011

    Linear Acoustic at IBC2011

  • ProVideo2011

    ProVideo2011

  • IOV at ProVideo2011

    IOV at ProVideo2011

  • IAC at ProVideo2011

    IAC at ProVideo2011


Related Shows
  • Training for the future with ITTP: BVE Day 2

    Training for the future with ITTP: BVE Day 2


Articles
Switching to Internet Based Distribution
Chris Clark

"An IP status check for the broadcast industry", "Resistance is futile", "IP points the way forward for the broadcast industry"...

Yes, we've read the headlines too. But rather than force you into submission, scare you, or leave you feeling like you have no other choice, we want to give you the information that helps you to make a sensible decision about Internet-based distribution.

So what’s stopping you from making the switch right now?

Tags: iss135 | ip | internet | distribution | cerberus | Chris Clark
Contributing Author Chris Clark Click to read or download PDF
21st Century Technology for 20th Century Content
James Hall A big challenge facing owners of legacy content is rationalising and archiving their tape and film-based media in cost effective and efficient ways, whilst also adding value. Normally the result of this is to find a low cost means of digitising the content – usually leaving them with a bunch of assets on HDD. But then what? How can content owners have their cake and eat it?
Tags: iss135 | legacy | digitising | digitizing | archive | James Hall
Contributing Author James Hall Click to read or download PDF
Future proofing post production storage
Josh Goldenhar Advancements in NVMe (Non-Volatile Memory Express), the storage protocol designed for flash, are revolutionising data storage. According to G2M Research, the NVMe market will grow to $60 billion by 2021, with 70 percent of all-flash arrays being based on the protocol by 2020. NVMe, acting like steroids for flash-based storage infrastructures, dynamically and dramatically accelerates data delivery.
Tags: iss135 | nvme | sas | sata | it | storage | post production | Josh Goldenhar
Contributing Author Josh Goldenhar Click to read or download PDF
Your two week editing future
Alex Macleod

So here we are - January again! Usually a good time to reflect on the year just gone by, and a good time to look forward to the coming months as the new year begins.

When I was reflecting on my 2018, and when thinking about what to write for my first article for Kit Plus - I kept coming back to one theme - organisation.

Tags: iss135 | editing | mediacity training | premiere pro | dit | Alex Macleod
Contributing Author Alex Macleod Click to read or download PDF
Test, Measurement and Standards
Alan Wheable The Alliance for IP Media Solutions (AIMS), is a non-profit trade alliance that fosters the adoption of one set of common, ubiquitous, standards-based protocols for interoperability over IP in the media and entertainment, and professional audio/video industries.
Tags: iss135 | omnitek | aims | SNMP | hdr | ai | Alan Wheable
Contributing Author Alan Wheable Click to read or download PDF