Presently, the audio playback of various streams from different sources causes quite often an annoying experience for the listeners. The reason behind that is that the loudness levels of these different streams can be completely different and do not match a comfortable listening experience on the end users’ devices.
Measurements in the past have shown that even similar audio streams which are broadcast via the broadcast network and simultaneously on the Web, e.g. Internet radio services, might have very different loudness levels. Even more different levels can be expected if various streams from completely different sources are collected to form a Rich Media Service.
Why is this of interest to NoTube?
In the NoTube platform, media coming from different sources are presented to the end user. This brings along a high risk of annoying loudness jumps, among others between news items that are provided by different broadcasters. The use of a loudness module in the NoTube platform could eliminate this effect by normalising the loudness levels.
What NoTube has done so far in this area
A loudness analysis component has been developed as a first element of the NoTube loudness module which analyses the loudness of the media which is entering the NoTube platform. It creates loudness descriptors for each media item which are used subsequently for the normalisation. This metadata type is generated by loudness measurements according to ITU‑R BS.1770 and EBU Technical Recommendation R128.
The loudness analyser has been implemented as a web service. The service returns loudness descriptors. One of those descriptors characterises the loudness level of each audio item. The extracted loudness descriptors are added to the metadata set which is associated to the media item. They can then be applied in order to normalise the loudness level before reproduction, i.e. playback of the media clips.
Furthermore, the harmonisation of the loudness by applying the metadata from this analysis (loudness descriptors) has been evaluated in a comprehensive user test. The evaluation shows a significant improvement compared to the original clip without any normalisation,the Peak normalisation 0 dBFS (used in CD mastering) and to the European broadcast PPM normalisation -9dBFS.
The following video demonstrates the discrepancy of the different ways to normalise the audio level.
Future plans in NoTube
The results of further evaluations will be incorporated in the development of the loudness analysis service to improve and enhance the functionality of this component.
In collaboration with RAI the loudness analysis component will be integrated into the NoTube platform to adapt audio with respect to the use case Personalised Semantic News. The loudness module will be enhanced adding the loudness normalisation component which will perform an individual loudness adjustment.
Furthermore the loudness module will utilize the additional loudness descriptors not only for loudness normalisation but for adapting the reproduced audio to individual playback environments.
Find out more: See the Things to use section of this site and check out the Update on Loudness Harmonisation.
Who’s involved? Institut fuer Rundfunktechnik with RAI in collaboration with other project partners.
Interested in collaborating with NoTube? Drop us a line and sign-up to our public mailing list (public-notube@few.vu.nl).
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Click here for further information on loudness normalisation
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