Audio Services Over ATSC 3.0

The improvements ATSC 3.0 brings to television often get most of the attention, and while those improvements matter, they are not the whole story. Under the hood, ATSC 3.0 is an IP-based broadcast system with a level of flexibility broadcast television has never had before. Once you stop thinking only in terms of linear video, a much broader set of services becomes possible.

One of the most compelling examples is audio. Through our lab work and real world testing we found that ATSC 3.0 can deliver multiple radio-style audio services with equal or better quality, tuning speed, and reception than analog FM, while using less spectrum than a single FM channel.

Rethinking How Audio Fits Into ATSC 3.0

ATSC 3.0 already defines audio-only services, but the standard approach brings a lot of overhead. When you are working with video bitrates, overhead fades into the noise, but when your payload is 24 to 48 kbps, overhead becomes a problem. Early tests showed traditional service packaging could add two to four times the bitrate of the audio itself, so any efficiency gains from modern codecs disappeared immediately.

This work leveraged ATSC 3.0’s unidirectional IP pipe. We avoided unnecessary signaling overhead while keeping compatibility with existing MPEG-based tools and receivers by injecting multicast streams directly at the scheduler and carrying audio as Pro-MPEG RTP. Forward Error Correction could be added where useful, and removed where testing showed it was not needed.

This approach treats ATSC 3.0 more like a managed IP network delivered over RF, rather than a legacy broadcast system.

Codec Choices Matter More Than Ever

At low bitrates, codec selection becomes critical. AC-4 brings real advantages for television, but client support outside TVs remains limited, especially in offline environments like cars. xHE-AAC showed outstanding performance and flexibility for both music and speech, but broad platform support was still emerging during the project timeline.

HE-AACv2 struck the right balance. It delivered stereo music at acceptable quality around 32 kbps with wide device support across phones, tablets, and computers. For spoken word content, tests showed usable quality at even lower rates. The key takeaway is not a single winning codec, but the reminder that ATSC 3.0 does not lock broadcasters into one audio format. Audio services can be tailored to content type, receiver capability, and bitrate goals.

Making Mobile Reception the Priority

If audio services are meant to compete with radio, mobile reception is non-negotiable. The physical layer configuration focused on surviving real-world driving conditions rather than chasing maximum throughput. Smaller FFT sizes, realistic guard intervals based on measured echoes, and pilot configurations tuned for mobility made a measurable difference.

The result was a physical layer pipe carrying roughly 1.2 Mbps that remained solid at highway speeds well beyond typical FM coverage in multiple directions from the transmitter. This was not a theoretical model. It was validated with on-road testing across highways, urban streets, wooded areas, and terrain transitions.

One important lesson came from field data rather than assumptions. Guard intervals did not need to be pushed as far as initially expected. Reducing unnecessary margin freed up bitrate without harming reception. Planning for efficiency across encoding, delivery, and physical layers proved far more effective than brute-force modulation choices.

Real-World Results Against FM

Drive testing in the Baltimore market showed consistent, uninterrupted audio reception over distances comparable to or better than local FM stations used for comparison. In several directions, ATSC 3.0 audio maintained clean playback past points where analog FM began to degrade or drop out. In non-highway environments, audio services showed no decode failures during testing.

This is not about declaring a winner over FM. FM coverage depends heavily on terrain, interference, and crowded spectrum. What matters is that ATSC 3.0 audio proved it can meet or exceed the listener experience people expect from radio while consuming a fraction of the spectrum.

When fifteen audio services fit comfortably inside roughly ten percent of a 6 MHz channel, the efficiency argument becomes hard to ignore.

Receivers Are the Real Bottleneck

The most challenging part of this project was not transmission. It was reception. Audio services like this need gateway-style receivers that work well in motion, expose multicast and non-real-time data, and serve multiple client devices with low latency.

Custom firmware on an HDHomeRun device made this possible. It handled UserDefined table signaling, buffered streams to reduce tuning time, and supported multiple listeners without extra tuners. Combined with a local web interface and native apps, the system worked without any internet connection, which is essential in vehicles.

The tuning experience ended up close to FM. After an initial tune, switching services took roughly half a second. For audio, that matters more than end-to-end latency.

This highlights the gap in the current receiver market. ATSC 3.0 can already support advanced datacasting and service models, but most consumer hardware is still built around traditional TV assumptions.

Conclusion

Audio services over ATSC 3.0 show what happens when broadcasters use the full flexibility of the standard. Efficient audio delivery opens doors to new programming models, market-spanning services, and hybrid broadcast experiences that work offline and at scale.

This approach also reinforces a broader point. ATSC 3.0 does not need to be reinvented to support new ideas. The tools already exist. Multicast injection, custom signaling, and flexible physical layer design make it possible to deploy services the original authors of the standard could not fully anticipate.

As receiver ecosystems mature and audio-specific signaling becomes more standardized, this kind of service gets easier to deploy and easier to consume. The result is more value extracted from spectrum broadcasters already own, and more choice for listeners without relying on cellular networks.

ATSC 3.0 is not just the future of television. It is a general-purpose broadcast data platform. Audio services make that clear in a way few other applications can.