IPTV@IBC2010 special report
With governments from many European countries, the US and other parts of the world close to establishing laws surrounding audio loudness guidelines, loudness control is an issue on all broadcasters’ minds these days. In order to prepare for the coming mandates, broadcasters are looking for technologies that will help ensure they stay within legal limits, not just for regular over-the-air broadcasts, but for their IPTV services as well. Kirk Marple, president and chief software architect at RadiantGrid Technologies, reports.
pay per view (PPV) and online video services, along with varying delivery chains, including computers, set-top boxes and mobile devices, among others. This requires broadcasters to handle loudness control for the multiple platforms and the file formats associated with each. For example, the volume levels for a computer or a home theatre are going to be drastically different than those for mobile devices, which often only transmit in stereo and are regularly viewed in environments with a lot of background noise.
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Two important factors to consider when it comes to implementing a loudness control into a file-based workflow are flexibility and performance. When dealing with
Loudness control for an IPTVworkflow
andling loudness control for IPTV can be
challenging, as it entails various programming options, including IPTV, video on demand (VOD),
Radiant Grid’s Operations Manager:
RadiantGrid has been working with Linear Acoustic, a leader in television audio control from production to transmission, to develop a means to provide
broadcasters with more control over audio loudness within a file-based workflow.
multiple file formats, the loudness control technology needs to be supported across all media containers and codecs. It cannot be limited to specific formats. On the plus side, file- based systems can also deliver advanced automatic upmixing, which enables programming to maintain a consistent surround field without relying on metadata or operator intervention. This means that once the appropriate parameters have been decided upon and applied, there will not be as much for users to maintain on an everyday basis.
An effective loudness control solution should be able to support multiple presets and parameters, giving the user maximum control over loudness processing. It should also be relatively easy to integrate into an existing workflow, as for the most part these new technologies will replace baseband workflows, making performance key. Adding loudness processing to a file-based workflow should not inflict a serious performance penalty on the users’ workflows. As there may still be portions of the workflow that users would prefer to handle with a hardware-based solution, this combination of file-based and software-based workflows must also be considered.
Until now, broadcasters looking to control volume levels in this sort of situation had only one option: level scaling. While this will re-align either
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the overall loudness of each programme segment or the loudness of the anchor element of each segment (dialogue, for example), it may not go far enough for programmes whose loudness range exceeds the target for a given channel. In other words, a range that might be appropriate for a movie channel might not be appropriate for an over-the-air channel or a mobile service. RadiantGrid has been working with Linear Acoustic, a leader in television audio control from production to transmission, to develop a means to provide broadcasters with more control over audio loudness within a file-based workflow. During the ingestion process, the RadiantGrid platform manages the audio in complex formats, such as LXF, MXF and GXF, by demuxing the compressed audio streams, and creating uncompressed multichannel broadcast WAV mezzanine files. This removes the complications of working with multichannel audio in various container formats, stream layouts and source codecs.
Once the file has been ingested, the audio files can be processed. RadiantGrid has incorporated the Linear Acoustic AERO.qc loudness correction module (LCM) within the RadiantGrid platform. AERO.qc (LCM) is a triple-pass approach providing a first measurement of the entire programme segment, a second pass
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