At the ITU-R meetings in Geneva (Switzerland) this week, ITU experts in 'Working Party 6C' (WP6C) have now reached agreement on a Loudness Recommendation. Although this Recommendation concerns programmes produced for international exchange and not broadcasting, it still is a milestone in the shift from peak measurement and normalisation to loudness metering and normalisation. The key elements in the new Recommendation are:


- For loudness measurement ITU BS.1770 compatible meters should be used.

- The programme provider can choose to measure the whole programme or the dialogue only.

- The programme provider has the option to use metadata and if so, he should set it to the measured loudness.

- The target level is -24 LKFS (ungated, as per the current BS.1770).





The EBU P/LOUD Group, amongst others, had provided input to the meeting, aiming to harmonise as much as possible the work going on in different parts of the world. The result is roughly in line with the P/LOUD Group's thinking, although there are differences. First of all, P/LOUD will advise on broadcasting and provide detailed practical guidelines, where the ITU Recommendation only covers programmes for international exchange. Further in P/LOUD the overall preference is to measure the complete mix and not only the dialogue component. Also the loudness range (LR) descriptor has not been adopted by the ITU. P/LOUD recommends it as a very useful parameter to describe any audio signal in addition to the average loudness (gated) and the maximum true peak level.   
Conceptual loudness meter (BBC)


There still is work to do. The main open issue is how to use gating to leave out parts of the programme that are not relevant for the measurement. The P/LOUD Group is currently performing subjective evaluations to advise on this topic. The EBU aims to publish five pieces of advice in early 2010, to help broadcasters switch to loudness measurement and normalisation:


1. A main Loudness Recommendation for broadcasting

2. A document explaining how to measure the Loudness Range

3. Detailed Practical Guidelines, helping engineers implement the new techniques

4. Distribution Guidelines, advising distributors (such as cable operators) on how to work with loudness

5. Meter Requirements, specifying what functionality loudness meters should offer



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