Telos Alliance – Next Generation Audio and its benefits to viewers
Larry Schindel, Senior Product Manager, Telos Alliance
Next Generation Audio (NGA) brings some long-overdue enhancements to broadcast and streaming audio. Immersive audio, personalization, and dialog enhancement are features that provide the most noticeable and substantive changes from the viewer’s standpoint. Under the hood, object-based audio and new emerging industry standards for metadata in the form of Serial ADM (S-ADM) are examples of the technologies that enable some of these new features for the viewer.
Immersive Audio
Immersive audio – which viewers commonly know as Dolby® Atmos® or MPEG-H 3D Audio – brings a far more cinematic experience to the viewer and can make them feel like they have seats right on the 50-yard line. In contrast to mixes designed for a cinematic setting, immersive audio for broadcast is accomplished in a much simpler manner. In television, we mix to a specific channel configuration, such as 5.1+4 employing overhead speakers.
One of the challenges in producing immersive audio programming is that not all of the content you want to use is in the same format. Using live sports as an example, a highlights clip from the last time the teams played each other, an interstitial element, or a commercial might be in 5.1 or even stereo. Airing this content directly as it was recorded causes sudden jumps in the sound field and is disconcerting for the viewer. Using a tool like the Linear Acoustic® UPMAX ISC to upmix audio to the desired immersive format allows a consistent soundfield regardless of the input source. Upmixing can be used as a quick and easy way to launch a surround or immersive service while the rest of the infrastructure is built up to produce and distribute content in this format natively. It can also be used to creatively enhance a mix; for example, inserting an upmixer on a subgroup of audience mics can make the audience feel larger and less correlated.
Personalized audio
Object-based audio (OBA), where each audio element and sound is its own standalone audio “object,” enables features like personalization and receiver mixing. Today, broadcasters deliver a complete mix containing the music, effects, and dialog. When multiple versions are needed to provide different languages or AD descriptive services, they are still delivered as a complete mix, which is not the most efficient use of the limited bandwidth available for transmission to the viewer and the reason why such content is usually delivered in stereo or even mono.
OBA and the personalization enabled by NGA really shine here, even compared to the immersive audio experience. By using one of the latest audio emission codecs, like Dolby AC-4 or MPEG-H from Fraunhofer IIS, it is possible to push the final mix of dialog with the M&E bed to the viewer’s environment, based on combinations, constraints, and limits of which the broadcaster has complete control. The M&E bed and individual dialogs – such as different languages, team announcers, and descriptive services – are sent individually at a much lower bitrate than required to deliver multiple complete mixes.
This not only allows for greater efficiency for the broadcaster but also ensures that every viewer can enjoy the full immersive or surround experience. Visually impaired consumers benefit in particular, as today, they are denied the immersive experience and are forced to listen in mono.
With the improved efficiency of NGA emission codecs, it is possible to fit immersive and personalized services into the same data footprint needed for 5.1-channel audio today.
Meanwhile, advances in supporting technology, such as Serial ADM (S-ADM), provide a standardized, vendor-agnostic approach to the metadata required to support NGA in the production, distribution, and playout stages of the broadcast chain. S-ADM can identify aspects of the various audio elements used to make up the complete audio program. At its most basic level, S-ADM can signal which channels comprise the bed mix, which is dialog, and the type of dialog (language, AD, team announcer, etc.). Since S-ADM is synchronous with the audio itself, similar to the older proprietary Dolby metadata carried in a SMPTE RP 2020 stream, it can be carried as an audio stream or in a SMPTE ST 2110-41 stream, making it compatible with both baseband and ST 2110-based workflows.
Telos Alliance is at the forefront of these next-generation audio workflows with products like the Linear Acoustic UPMAX ISC immersive audio upmixer, the Linear Acoustic LA-5291 and LA-5300 broadcast audio processors with integrated Dolby Atmos encoders, the Linear Acoustic AMS MPEG-H Authoring and Monitoring system, and the Jünger Audio™ flexAI platform which supports both MPEG-H and S-ADM workflows.
