Audio over Ethernet

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In audio engineering and broadcast engineering, Audio over Ethernet (sometimes AoE—not to be confused with ATA over Ethernet) is the use of an Ethernet-based network to distribute real-time digital audio.

It is designed to replace bulky snake cables and fixed wiring, and instead use a standard network structured cabling in a facility, providing a reliable backbone for any audio application, such as for large-scale sound reinforcement in stadiums, airports and convention centers, multiple studios or stages.

While on the surface AoE bears a resemblance to Voice over IP (VoIP), AoE is intended for high-fidelity, low-latency professional audio. Because of the fidelity and latency constraints, audio over Ethernet systems generally do not utilize audio data compression. AoE systems use a much higher bit rate (typically 1 Mbit per channel) and much lower latency (typically less than 10 milliseconds) than VoIP.

Audio over Ethernet requires a high-performance network. Performance requirements may be met through use of a dedicated local-area network (LAN) or virtual LAN (VLAN), Overprovisioning and/or Quality of service features.

Most AoE systems use proprietary protocol(s) (at the higher OSI layers) which create data packets and data frames that are transmitted directly onto the Ethernet (layer 2) for efficiency and reduced overhead. The word clock may be provided by broadcast packets.

Protocols[edit]

There are several different and incompatible protocols for audio over Ethernet. For example, using category 5 cable and 100BASE-TX signaling at 100 Mbits/second, each link can generally transmit between 32 and 64 channels at a 48 kHz sampling rate. Some can handle other rates, such as 44.1 kHz (CD-quality), 88.2 and 96 kHz (2× oversampling), even 192 kHz (4×), as well as up to 32-bit samples, with a corresponding reduction in channel capacity. On some, this is accomplished through channel bonding, while others use individually scalable channels.

AoE is not necessarily intended for wireless networks, thus the use of various 802.11 devices may or may not work with various (or any) AoE protocols.

Protocols can be broadly categorized into Layer 1, Layer 2 and Layer 3 systems based on the lowest layer in the OSI model where the protocol exists.

Layer 1 protocols[edit]

Layer 1 protocols use Ethernet wiring and signaling components but do not use the Ethernet frame structure. Layer 1 protocols often use their own media access control (MAC) rather than the one native to Ethernet, which generally creates Computer compatibility issues.

Open standards[edit]

Proprietary[edit]

Layer 2 protocols[edit]

Layer 2 protocols encapsulate audio data in standard Ethernet packets. Most can make use of standard Ethernet hubs and switches though some require that the network (or at least a VLAN) be dedicated to the audio distribution application.

Open standards[edit]

Proprietary[edit]

Layer 3 protocols[edit]

Layer 3 audio over Ethernet protocols encapsulate audio data in Open Systems Interconnection model (OSI model) Layer 3 (Network Layer) packets. By definition it does not limit the choice of protocol to be the most popular Layer 3 protocol - the Internet Protocol (IP). In some implementations, the Layer 3 audio data packets are further packaged inside OSI model Layer 4 (Transport Layer) packets, which is usually the User Datagram Protocol (UDP). Use of the UDP/IP protocol to carry audio data enables them to be distributed through standard computer routers, thus a large distribution audio network can be built economically using commercial off-the-shelf equipment.

Although by definition, IP packets can traverse the Internet, the Layer 3 audio over Ethernet protocols are not designed to traverse the Internet and provide reliable audio transmission due to the limited bandwidth and significant transmission delay usually encountered by data flow over the Internet. Due to similar reason, transmission of Layer 3 audio over wireless LAN are also not supported by most implementations.

Open standards[edit]

Proprietary[edit]

Similar concepts[edit]

  • Audio Video Bridging, listed above for both "Layer 2" and "Layer 3" technologies, provides several distinct services. In particular, any encapsulation of time-sensitive data on top of Ethernet can theoretically benefit from the 802.1AS (high-precision timing), 802.1Qat (bandwidth reservation) and 802.1Qav (low-latency forwarding) standards that AVB builds on. This generally falls through on missing support for these protocols throughout the network.
  • AES47 from the Audio Engineering Society provides linear audio networking by passing AES3 audio transport over an ATM network using structured network cabling (both copper and fibre). This is used extensively by contractors supplying the BBC's wide area real-time audio connectivity around the UK.

In broadcasting and to some extent in studio and even live production, many manufacturers equip their own audio engines to be tied together with Ethernet. This may also be done with gigabit Ethernet and optical fibre rather than wire. This allows each studio to have its own engine, or for auxiliary studios to share an engine. By connecting them together, different sources can be shared among them. Logitek Audio is one such company using this approach.

References[edit]

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  3. ^ "About A-Net". Retrieved 2010-06-23. 
  4. ^ "AudioRail Technologies". Audiorail.com. Retrieved 2010-10-15. 
  5. ^ "About RockNet". Riedel Communications. Retrieved 2011-06-08. 
  6. ^ "Network Wednesdays: Hydra2". 2013-04-13. Retrieved 2013-05-04. 
  7. ^ "RAVE Systems". Archived from the original on 23 May 2010. Retrieved 2010-06-23. 
  8. ^ "Technology: Overview". Retrieved 2010-06-23. 
  9. ^ AES67-2013: AES standard for audio applications of networks - High-performance streaming audio-over-IP interoperability, Audio Engineering Society, 2013-09-11 
  10. ^ "A user guide to using JACK over a network". Retrieved 2012-08-19. 
  11. ^ "WheatNet-IP Intelligent Network Media Page". Retrieved 2011-03-06. 

See also[edit]