The Evolution of Audio-over-IP: From AES67 to Next-Generation Standards

The world of audio technology has experienced rapid advancements over the past two decades. One of the most significant developments has been the evolution of Audio-over-IP (AoIP) protocols, transforming how audio signals are transmitted in broadcast, live sound, and recording environments. What began as a niche technical solution has become the backbone of modern professional audio infrastructure, offering unprecedented flexibility, scalability, and cost-effectiveness compared to traditional analog or digital audio connections.

Audio-over-IP refers to the transmission of audio signals over standard IP networks, such as Ethernet. Unlike dedicated point-to-point cabling (e.g., XLR or MADI), AoIP allows multiple channels of audio to share a single network cable, simplifying installs and enabling remote production workflows. This paradigm shift has been driven by the need for higher channel counts, lower latency, and interoperability between equipment from different manufacturers.

The Foundation: AES67

Launched in 2013, AES67 is an interoperability standard developed by the Audio Engineering Society (AES). It was designed to enable different AoIP systems to communicate seamlessly, regardless of manufacturer. Prior to AES67, proprietary protocols such as Dante, Ravenna, Livewire, and Q-LAN operated in silos, forcing users to commit to a single ecosystem. AES67 broke down these barriers by defining a common set of transport, timing, and media format parameters.

AES67 is not a full networking protocol itself but rather a profile that specifies how existing standards (e.g., RTP, PTPv2) should be used for high-quality audio streaming with low latency. It mandates support for 48 kHz sample rate, 24-bit depth, and prescribes synchronization using Precision Time Protocol (IEEE 1588-2008). The standard also defines a unique stream identification method via Session Description Protocol (SDP).

Key Features of AES67

  • Interoperability – Works with Ravenna, Dante, Livewire, and others, allowing mixed-vendor networks.
  • Synchronization – Uses Precision Time Protocol (PTP) to achieve sample-accurate timing across all devices.
  • High Audio Quality – Standardized at 48 kHz/24-bit, supporting up to 8 channels per stream.
  • Low Latency – Configurable packet times (1 ms, 125 µs) suitable for live sound reinforcement.
  • Media Transport – Employs RTP over UDP with optional FEC for error resilience.

Thanks to these features, AES67 became the backbone for many professional audio networks, fostering interoperability and expanding the adoption of AoIP technology worldwide. It is widely used in broadcast studios, concert touring, and installed sound systems where multi-vendor environments are common.

How AES67 Works in Practice

In a typical AES67 network, all devices synchronize their clocks to a grandmaster clock using PTPv2. Audio samples are packetized into RTP streams, with each stream identified by a unique multicast IP address and UDP port. Devices advertise their streams via SAP (Session Announcement Protocol) or manual SDP files. Receivers listen for the multicast group and reconstruct the audio with sub-microsecond jitter. The network must be configured for Quality of Service (QoS) to prioritize audio traffic and avoid packet loss. This architecture allows for hundreds of channels over a single Gigabit Ethernet link.

Despite its success, AES67 has limitations. It is inherently connectionless and does not include native discovery, device control, or redundancy mechanisms. These gaps led to the development of more comprehensive next-generation standards.

The Next Generation: SMPTE ST 2110

Building on AES67, the industry is now moving toward next-generation standards that address emerging needs such as higher resolutions, increased security, and enhanced synchronization. The most influential is SMPTE ST 2110, a suite of standards developed by the Society of Motion Picture and Television Engineers for professional media over IP networks. Originally targeted at broadcast television, ST 2110 has been adopted by audio engineers for its ability to transport uncompressed high-resolution audio and video streams with precise synchronization.

Key Differences from AES67

  • Separate Essence Transport – ST 2110 defines individual streams for video (ST 2110-20), audio (ST 2110-30), and ancillary data (ST 2110-40). Audio uses AES67 as its baseline for audio transport but adds support for higher sampling rates and channel counts.
  • Narrow Streaming – Each channel or group is sent as a separate RTP stream, enabling granular routing and resource allocation.
  • Precise Synchronization – ST 2110 mandates PTPv2 with tighter timing requirements (≤1 µs in many profiles), essential for lip-sync and multi-channel immersive audio.
  • Hitless Redundancy – The standard defines mechanisms for seamless switchover between redundant streams, critical for live broadcast.
  • DSCP Qo – Defines specific Differentiated Services Code Point values for audio, video, and control traffic.

SMPTE ST 2110 is the foundation of the AES67-2018 revision and is widely deployed in IP-based broadcast plants (e.g., NBC Olympics, BBC). It supports sample rates up to 96 kHz and beyond, and bit depths up to 32 bits, enabling immersive audio formats like Dolby Atmos and 3D audio.

AES70: Device Control for AoIP Networks

Another important next-generation standard is AES70 (also known as OCA – Open Control Architecture). While AES67 and ST 2110 handle transport, AES70 provides a standardized framework for discovering, configuring, and controlling AoIP devices over the network. It defines a common command set for volume, routing, presets, and metering, allowing control systems (e.g., Q-SYS, Crestron) to interoperate with any AES70-compliant device. This eliminates the need for proprietary APIs and simplifies system integration.

AES70 uses TCP/IP for reliable control and can coexist with AES67 streams on the same network. It is increasingly adopted in installed sound, conference systems, and broadcast monitoring applications.

The evolution of AoIP standards continues to shape the future of audio production, offering more flexible, scalable, and efficient solutions for professionals worldwide. Several key trends are driving innovation:

Higher Bit Depths and Sample Rates

With the rise of immersive audio formats (Dolby Atmos, MPEG-H), demand for 96 kHz and even 192 kHz with 32-bit float is growing. Next-generation profiles of AES67 and ST 2110 are extending support for these parameters, enabling pristine quality for critical listening and post-production.

Enhanced Security Protocols

As AoIP networks become more critical, security is paramount. Emerging standards incorporate encryption (e.g., AES-128/256 for payloads) and authentication (802.1X, TLS) to prevent unauthorized access and tampering. The AES has formed a working group to define security guidelines for AoIP.

Cloud-Based Audio Solutions

The pandemic accelerated adoption of remote production and cloud mixing. Standards like AES67 and ST 2110 are being adapted for transmission over wide-area networks (WAN) with support for FEC and adaptive bitrate streaming. Companies like LiveU and Lawo offer cloud-native AoIP solutions that integrate with on-premises networks.

Integration with IP-Based Control Systems

AES70 and other control protocols are merging with network management (NMOS) for automated discovery and device control. The AMWA NMOS specifications provide RESTful APIs for stream registration and connection management, complementing AES67 and ST 2110 in complex IP facilities.

Conclusion

The journey from proprietary point-to-point audio connections to open, standards-based AoIP has been transformative. AES67 broke the interoperability barrier, while SMPTE ST 2110, AES70, and emerging profiles are addressing the demands of high-resolution, secure, and cloud-integrated workflows. For audio professionals, understanding these standards is essential to designing future-proof systems that deliver reliability, scalability, and superior sound quality. As the industry continues to evolve, one thing remains clear: the network is the audio bus.

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