Tale of Two Standards: ATSC Puts MPEG-H, AC-4 Audio Technologies rough their Paces

The winning proposal will be included in the ATSC 3.0 next-generation digital TV standard, which is expected to be released in early 2017.

ATSC is evaluating proposals from Dolby and an alliance of Fraunhofer, Qualcomm and Technicolor. DTS, which had planned a third approach to the immersive audio standard, withdrew its proposal earlier this year.

Aiming to deliver a more immersive audio experience to TV and mobile devices, the Advanced Television Systems Committee (ATSC) has been focused on a technical review of the two proposals - including demonstrations of the two approaches - in its quest for a comprehensive audio system for ATSC 3.0, the next-generation digital TV standard now under development.

Dolbys AC-4 was published by the European Telecommunications Standards Institute (ETSI) as an international standard last April. AC-4 supports audio channels as well as objects over the end-to-end broadcast chain.

MPEG-H Audio is the Fraunhaufer, Technicolor and Qualcomm proposal, which builds a suite of advanced functionalities around a core audio codec. For the immersive reproduction of content it is possible to use channels based and/or sound scene based technology in combination with audio objects. Audio objects also add interactivity and personalization capabilities to the mix.

Although both of the competing standards proposals are able to support 2.0 channels, 5.1 channels, and object-based 3D surround sounds, there are substantive differences in the ways they are approaching the task.

In Atlanta between July 13-16 2015, ATSCs S34-2 working group offered real-time comparisons of the MPEG-H and AC-4 immersive audio candidates. The event enabled third-party broadcast-technology-equipment manufacturers to line up behind either Dolby's AC-4 or the MPEG-H Audio Alliance of Fraunhofer, Technicolor, and Qualcomm.

J nger Audio and Fraunhofer IIS presented a prototype multi-channel monitoring, authoring and loudness processor for the new MPEG-H TV audio system. The J nger Audio technology allows broadcasters using the MPEG-H system to maintain compliance with loudness regulations, while avoiding the processing artifacts of traditional loudness control approaches.

This iteration of the company's Level Magic processor allows broadcasters using the MPEG-H system to maintain compliance with loudness regulations while avoiding the processing artifacts of traditional loudness-control approaches.

Specifically, content in the MPEG-H audio system may be tagged to indicate it already has been processed or leveled for proper loudness control. This allows for managed loudness processing where loudness control is only engaged on unprocessed content, avoiding the degradation of multiple leveling passes. This happens in real time as the content is broadcast.

Another critical point of differentiation stressed by the MPEG-H Audio team is that it can be implemented today using existing equipment to attain the benefits of offering immersive and interactive audio experiences. By contrast, any system based on Dolbys AC-4, according to executives on that team, is not designed to backward compatible with current ATSC equipment.

Other key points of consideration that ATSC 3.0 may be looking for is how well the competing teams to not only deliver immersive sound, but also offer new and intuitive interactive services (allowing consumers to select what they want to hear and how they want to hear it) and multi-platform support (since consumers have clearly embraced dynamic viewing habits and increasingly expect to seamlessly move from traditional television environments to tablets and even smart-phone form factors.)

As the industry leverages cutting-edge technology to deliver an immersive visual experience with 4K UHD, HDR, WCG - not to mention preparing for the emerging demand that is forming for Virtual Reality/Augmented Reality content - there is a clear need to offer audio experiences that are more robust than today's 5.1 surround sound. Multichannel immersive audio must deliver enhanced surround sound and the ability for consumers to personalize the audio program to meet specific consumption preferences over variety of devices. No decisions will be announced until the fall, but the stakes are extremely high for Dolby and the MPEG-H Audio Alliance.

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