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{{short description|Distribution of digital audio across an Ethernet network}}
{{Short description|Live distribution of digital audio across an Ethernet network}}
{{confused|ATA over Ethernet}}
In [[audio engineering|audio]] and [[broadcast engineering|broadcast]] engineering, '''Audio over Ethernet''' (sometimes '''AoE'''—not to be confused with [[ATA over Ethernet]]) is the use of an [[Ethernet]]-based [[Computer networking|network]] to distribute real-time [[digital audio]]. AoE replaces bulky [[snake cable]]s or audio-specific installed [[low-voltage wiring]] with standard network [[structured cabling]] in a facility. AoE provides a reliable [[Backbone network|backbone]] for any audio application, such as for large-scale [[sound reinforcement]] in stadiums, airports and convention centers, multiple [[studio]]s or [[stage (theatre)|stage]]s.
In [[audio engineering|audio]] and [[broadcast engineering|broadcast]] engineering, '''audio over Ethernet''' ('''AoE''') is the use of an [[Ethernet]]-based [[Computer networking|network]] to distribute real-time [[digital audio]]. AoE replaces bulky [[snake cable]]s or audio-specific installed [[low-voltage wiring]] with standard network [[structured cabling]] in a facility. AoE provides a reliable [[Backbone network|backbone]] for any audio application, such as for large-scale [[sound reinforcement]] in stadiums, airports and convention centers, multiple [[studio]]s or [[stage (theatre)|stage]]s.


While AoE bears a resemblance to [[voice over IP]] (VoIP) and [[audio over IP]] (AoIP), AoE is intended for [[high-fidelity]], low-latency [[professional audio]]. Because of the fidelity and [[Latency (audio)|latency]] constraints, AoE systems generally do not utilize [[audio data compression]]. AoE systems use a much higher bit rate (typically 1 Mbit/s per channel) and much lower latency (typically less than 10 milliseconds) than VoIP. AoE requires a high-performance network. Performance requirements may be met through use of a dedicated [[local area network]] (LAN) or [[virtual LAN]] (VLAN), [[Overprovisioning (networking)|overprovisioning]] or [[quality of service]] features.
While AoE bears a resemblance to [[voice over IP]] (VoIP) and [[audio over IP]] (AoIP), AoE is intended for [[high-fidelity]], low-latency [[professional audio]]. Because of the fidelity and [[Latency (audio)|latency]] constraints, AoE systems generally do not utilize [[audio data compression]]. AoE systems use a much higher bit rate (typically 1 Mbit/s per channel) and much lower latency (typically less than 10 milliseconds) than VoIP. AoE requires a high-performance network. Performance requirements may be met through use of a dedicated [[local area network]] (LAN) or [[virtual LAN]] (VLAN), [[Overprovisioning (networking)|overprovisioning]] or [[quality of service]] features.
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==Protocols==
==Protocols==
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 and [[audio bit depth]]s, with a corresponding reduction in number of channels.
There are several different and incompatible protocols for audio over Ethernet. Protocols can be broadly categorized into [[layer-1]], [[layer-2]] and [[layer-3]] systems based on the layer in the [[OSI model]] where the protocol exists.

AoE is not necessarily intended for [[wireless network]]s, thus the use of various [[802.11]] devices may or may not work with various (or any) AoE protocols.<ref>{{cite web |title=Can I transport CobraNet audio over a wireless network? |publisher=[[Cirrus Logic]] |url=https://www.cobranet.info/support/faq#Q13 |access-date=2019-01-09}}</ref>

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


=== Layer-1 protocols ===
=== Layer-1 protocols ===
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====Open standards====
====Open standards====
*[[AES50]] (SuperMAC) by [[Klark Teknik]], a point-to-point interconnect for bidirectional digital audio and sync clock<ref>{{cite web |url=http://www.prosoundweb.com/article/klark_teknik_announces_several_aes50_protocol_developments/ |title=Klark Teknik Announces Several AES50 Protocol Developments |access-date=2010-06-23| archive-url= https://web.archive.org/web/20100705162715/http://www.prosoundweb.com/article/klark_teknik_announces_several_aes50_protocol_developments/| archive-date= 5 July 2010| url-status= live}}</ref>
*[[AES50]]
*[[MaGIC]] by [[Gibson Guitar Corporation|Gibson]]<ref>{{cite web |url=http://www.gibson.com/en-us/Divisions/Audio/MaGIC/THIS%20IS%20MaGIC/ |title=This Is MaGIC |accessdate=2010-06-23 |archive-url=https://web.archive.org/web/20100116040438/http://gibson.com/en%2Dus/Divisions/Audio/MaGIC/THIS%20IS%20MaGIC/ |archive-date=2010-01-16 |url-status=dead }}</ref>
*[[MaGIC]] by [[Gibson Guitar Corporation|Gibson]]<ref>{{cite web |url=http://www.gibson.com/en-us/Divisions/Audio/MaGIC/THIS%20IS%20MaGIC/ |title=This Is MaGIC |access-date=2010-06-23 |archive-url=https://web.archive.org/web/20100116040438/http://gibson.com/en%2Dus/Divisions/Audio/MaGIC/THIS%20IS%20MaGIC/ |archive-date=2010-01-16 |url-status=dead }}</ref>


====Proprietary====
====Proprietary====
*[[:es:SuperMAC|SuperMAC]], an implementation of AES50<ref>{{cite web |url=http://www.prosoundweb.com/article/klark_teknik_announces_several_aes50_protocol_developments/ |title=Klark Teknik Announces Several AES50 Protocol Developments |accessdate=2010-06-23| archiveurl= https://web.archive.org/web/20100705162715/http://www.prosoundweb.com/article/klark_teknik_announces_several_aes50_protocol_developments/| archivedate= 5 July 2010| url-status= live}}</ref>
*HyperMAC, a [[gigabit Ethernet]] variant of SuperMAC<ref>{{cite web|url=http://www.supermac-hypermac.com/ |title=Digital Audio Interconnections |publisher=[[Klark Teknik]] |access-date=2014-09-15 |url-status=dead |archive-url=https://web.archive.org/web/20141114221604/http://www.supermac-hypermac.com/ |archive-date=2014-11-14 }}</ref>
*HyperMAC, a [[gigabit Ethernet]] variant of SuperMAC<ref>{{cite web|url=http://www.supermac-hypermac.com/ |title=Digital Audio Interconnections |publisher=[[Klark Teknik]] |accessdate=2014-09-15 |url-status=dead |archiveurl=https://web.archive.org/web/20141114221604/http://www.supermac-hypermac.com/ |archivedate=2014-11-14 }}</ref>
*[[A-Net]] by [[Aviom]]<ref>{{cite web|url=http://www.aviom.com/Products/Aviom-About-A-Net.cfm |title=About A-Net |access-date=2010-06-23 |url-status=dead |archive-url=https://web.archive.org/web/20081011192134/http://www.aviom.com/Products/Aviom-About-A-Net.cfm |archive-date=2008-10-11 }}</ref>
*[[A-Net]] by [[Aviom]]<ref>{{cite web|url=http://www.aviom.com/Products/Aviom-About-A-Net.cfm |title=About A-Net |accessdate=2010-06-23 |url-status=dead |archiveurl=https://web.archive.org/web/20081011192134/http://www.aviom.com/Products/Aviom-About-A-Net.cfm |archivedate=2008-10-11 }}</ref>
*AudioRail<ref>{{cite web|url=http://www.audiorail.com |title=AudioRail Technologies |publisher=Audiorail.com |access-date=2010-10-15}}</ref>
*AudioRail<ref>{{cite web|url=http://www.audiorail.com |title=AudioRail Technologies |publisher=Audiorail.com |accessdate=2010-10-15}}</ref>
*ULTRANET By [[Behringer]]<ref>{{Cite web|url=https://reverseengineering.stackexchange.com/questions/10860/how-do-i-work-out-the-ultranet-protocol|title=packet - How do I work out the Ultranet protocol?|website=Reverse Engineering Stack Exchange|access-date=2019-02-06}}</ref>
*ULTRANET By [[Behringer]]<ref>{{Cite web|url=https://reverseengineering.stackexchange.com/questions/10860/how-do-i-work-out-the-ultranet-protocol|title=packet - How do I work out the Ultranet protocol?|website=Reverse Engineering Stack Exchange|access-date=2019-02-06}}</ref>


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====Open standards====
====Open standards====
* [[AES51]], A method of passing ATM services over Ethernet that allows [[AES3]] audio to be carried in a similar way to [[AES47]]
* [[AES51]], a method of passing ATM services over Ethernet that allows [[AES3]] audio to be carried in a similar way to [[AES47]]
* [[Audio Video Bridging]] (AVB), when used with the IEEE 1722 AV Transport Protocol profile (which transports [[IEEE 1394]]/[[IEC 61883]] over Ethernet frames, using [[Precision Time Protocol|IEEE 802.1AS]] for timing)
* [[Audio Video Bridging]] (AVB), when used with the IEEE 1722 AV Transport Protocol profile (which transports [[IEEE 1394]]/[[IEC 61883]] (FireWire) over Ethernet frames, using [[Precision Time Protocol|IEEE 802.1AS]] for timing)


====Proprietary====
====Proprietary====
*[[CobraNet]]
*[[CobraNet]]
**RAVE by [[QSC Audio Products|QSC Audio]], an implementation of CobraNet<ref>{{cite web| url= http://www.qscaudio.com/products/network/rave/rave.htm| title= RAVE Systems| accessdate= 2010-06-23| archiveurl= https://web.archive.org/web/20100523191023/http://www.qscaudio.com/products/network/rave/rave.htm| archivedate= 23 May 2010| url-status= dead| df= dmy-all}}</ref>
**RAVE by [[QSC Audio Products|QSC Audio]], an implementation of CobraNet<ref>{{cite web| url= http://www.qscaudio.com/products/network/rave/rave.htm| title= RAVE Systems| access-date= 2010-06-23| archive-url= https://web.archive.org/web/20100523191023/http://www.qscaudio.com/products/network/rave/rave.htm| archive-date= 23 May 2010| url-status= dead| df= dmy-all}}</ref>
*[[EtherSound]] by [[Digigram]]<ref>{{cite web |url=http://www.ethersound.com/technology/overview.php |title=Technology: Overview |accessdate=2010-06-23 |archive-url=https://web.archive.org/web/20100612115721/http://www.ethersound.com/technology/overview.php |archive-date=2010-06-12 |url-status=dead }}</ref>
*[[EtherSound]] by [[Digigram]]<ref>{{cite web |url=http://www.ethersound.com/technology/overview.php |title=Technology: Overview |access-date=2010-06-23 |archive-url=https://web.archive.org/web/20100612115721/http://www.ethersound.com/technology/overview.php |archive-date=2010-06-12 |url-status=dead }}</ref>
**NetCIRA, a rebranded EtherSound by [[Fostex]]
**NetCIRA, a rebranded EtherSound by [[Fostex]]
*REAC and RSS digital snake technology by [[Roland Corporation|Roland]]<ref>{{cite web |url=http://www.roland.com/products/en/exp/REAC.html |archive-url=https://web.archive.org/web/20150118052923/http://www.roland.com/products/en/exp/REAC.html |archive-date=2015-01-18 |publisher=[[Roland Corporation]] |title=What is REAC? |accessdate=2014-09-15}}</ref><ref>{{cite web |title=Digital Snales |url=https://proav.roland.com/global/categories/digital_snakes/ |access-date=2018-07-26}}</ref>
*REAC and RSS digital snake technology by [[Roland Corporation|Roland]]<ref>{{cite web |url=http://www.roland.com/products/en/exp/REAC.html |archive-url=https://web.archive.org/web/20150118052923/http://www.roland.com/products/en/exp/REAC.html |archive-date=2015-01-18 |publisher=[[Roland Corporation]] |title=What is REAC? |access-date=2014-09-15}}</ref><ref>{{cite web |title=Digital Snakes |url=https://proav.roland.com/global/categories/digital_snakes/ |access-date=2018-07-26}}</ref>
*[[SoundGrid]] by [[Waves Audio]]
*[[SoundGrid]] by [[Waves Audio]]
*dSNAKE by [[Allen & Heath]]
*dSNAKE by [[Allen & Heath]]
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=== Layer-3 protocols ===
=== Layer-3 protocols ===
{{see also|Audio over IP}}
{{see also|Audio over IP}}
Layer-3 protocols encapsulate audio data in [[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, most commonly [[User Datagram Protocol]] (UDP) or [[Real-time Transport Protocol]] (RTP). Use of UDP or RTP to carry audio data enables them to be distributed through standard computer [[Router (computing)|routers]], thus a large distribution audio network can be built economically using commercial off-the-shelf equipment.
Layer-3 protocols encapsulate audio data in 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, most commonly [[User Datagram Protocol]] (UDP) or [[Real-time Transport Protocol]] (RTP). Use of UDP or RTP to carry audio data enables them to be distributed through standard computer [[Router (computing)|routers]], thus a large distribution audio network can be built economically using commercial off-the-shelf equipment.


Although IP packets can traverse the [[Internet]], most layer-3 protocols cannot provide reliable transmission over the Internet due to the limited [[Bandwidth (computing)|bandwidth]], significant [[End-to-end delay]] and [[packet loss]] that can be encountered by data flow over the Internet. For similar reasons, transmission of layer-3 audio over [[wireless LAN]] are also not supported by most implementations.
Although IP packets can traverse the [[Internet]], most layer-3 protocols cannot provide reliable transmission over the Internet due to the limited [[Bandwidth (computing)|bandwidth]], significant [[End-to-end delay]] and [[packet loss]] that can be encountered by data flow over the Internet. For similar reasons, transmission of layer-3 audio over [[wireless LAN]] are also not supported by most implementations.
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*[[Audio Contribution over IP]] standardized by the [[European Broadcasting Union]]
*[[Audio Contribution over IP]] standardized by the [[European Broadcasting Union]]
*[[Audio Video Bridging]] (AVB), when used with IEEE 1733 or AES67 (which uses standard [[Real-time Transport Protocol|RTP]] over UDP/IP, with extensions for linking [[IEEE 802.1AS]] [[Precision Time Protocol]] timing information to payload data)
*[[Audio Video Bridging]] (AVB), when used with IEEE 1733 or AES67 (which uses standard [[Real-time Transport Protocol|RTP]] over UDP/IP, with extensions for linking [[IEEE 802.1AS]] [[Precision Time Protocol]] timing information to payload data)
*NetJack, a network backend for the [[JACK Audio Connection Kit]]<ref>{{cite web|url=http://trac.jackaudio.org/wiki/WalkThrough/User/NetJack |title=A user guide to using JACK over a network |accessdate=2012-08-19 |url-status=dead |archiveurl=https://web.archive.org/web/20120902124453/http://trac.jackaudio.org/wiki/WalkThrough/User/NetJack |archivedate=2012-09-02 }}</ref>
*NetJack, a network backend for the [[JACK Audio Connection Kit]]<ref>{{cite web|url=http://trac.jackaudio.org/wiki/WalkThrough/User/NetJack |title=A user guide to using JACK over a network |access-date=2012-08-19 |url-status=dead |archive-url=https://web.archive.org/web/20120902124453/http://trac.jackaudio.org/wiki/WalkThrough/User/NetJack |archive-date=2012-09-02 }}</ref>
*[http://kokkinizita.linuxaudio.org/linuxaudio/index.html Zita-njbridge], a set of clients for the [[JACK Audio Connection Kit]]
*[http://kokkinizita.linuxaudio.org/linuxaudio/index.html Zita-njbridge], a set of clients for the [[JACK Audio Connection Kit]]
*[[RAVENNA (networking)|RAVENNA]] by ALC NetworX (uses [[Precision Time Protocol|PTPv2]] timing)
*[[RAVENNA (networking)|RAVENNA]] by ALC NetworX (uses [[Precision Time Protocol|PTPv2]] timing)
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====Proprietary====
====Proprietary====
*[[Livewire (networking)|Livewire]] by Axia Audio, a division of [[Telos Systems]]
*[[Livewire (networking)|Livewire]] by Axia Audio, a division of [[Telos Systems]]
*[[Dante (networking)|Dante]] by Audinate (PTPv1 timing)
*[[Dante (networking)|Dante]] by Audinate ([[Precision Time Protocol|PTP]] version 1 timing)
*[[Q-LAN]] by [[QSC Audio Products]] (PTPv2 timing)<ref>{{cite web |title=PTPv2 Timing protocol in AV networks |url=https://www.luminex.be/improve-your-timekeeping-with-ptpv2/ |date=June 6, 2017 |quote=Q-LAN updated to PTPv2 approximately two years ago. |publisher=Luminex}}</ref>
*[[Q-LAN]] by [[QSC Audio Products]] (PTP version 2 timing)<ref>{{cite web |title=PTPv2 Timing protocol in AV networks |url=https://www.luminex.be/improve-your-timekeeping-with-ptpv2/ |date=June 6, 2017 |quote=Q-LAN updated to PTPv2 approximately two years ago. |publisher=Luminex}}</ref>
*WheatNet-IP by [[Wheatstone Corporation]]<ref>{{cite web |url=http://www.wheatip.com/ |title=WheatNet-IP Intelligent Network Media Page |accessdate=2011-03-06}}</ref>
*WheatNet-IP by [[Wheatstone Corporation]]<ref>{{cite web |url=http://www.wheatip.com/ |title=WheatNet-IP Intelligent Network Media Page |access-date=2011-03-06}}</ref>


==Similar concepts==
==Similar concepts==
High quality digital audio distribution was patented in 1988 by Tareq Hoque at the [[MIT Media Lab]].<ref>{{cite web |last1=Hoque |first1=Tareq |title=US Patent 4922536 - Digital audio transmission for use in studio, stage or field applications |url=https://patents.google.com/patent/US4922536 |access-date=28 December 2021}}</ref> The technology was licensed to several leading OEM audio and chip manufacturers that were further developed into commercial products.{{cn|reason=Which manufacturers, products?|date=December 2021}}


RockNet by Riedel Communications,<ref>{{cite web|url=https://www.riedel.net/en/products/audio-networks/rocknet/ |title=RockNet |publisher=Riedel Communications |accessdate=2016-12-27}}</ref> uses Cat-5 cabling. Hydra2 by Calrec<ref>{{cite web|url=http://community.calrec.com/network-wednesdays-hydra/ |archive-url=https://archive.is/20130628203747/http://community.calrec.com/network-wednesdays-hydra/ |url-status=dead |archive-date=2013-06-28 |title=Network Wednesdays: Hydra2 |date=2013-04-13 |accessdate=2013-05-04 }}</ref> uses Cat-5e cabling or fiber through [[Small form-factor pluggable transceiver|SFP transceivers]].<ref>{{Cite web|url=http://calrec.com/hydra2/ |title=Hydra2 |publisher=Calrec |accessdate=2016-12-27}}</ref>
RockNet by Riedel Communications,<ref>{{cite web|url=https://www.riedel.net/en/products/audio-networks/rocknet/ |title=RockNet |publisher=Riedel Communications |access-date=2016-12-27}}</ref> uses Cat-5 cabling. Hydra2 by Calrec<ref>{{cite web|url=http://community.calrec.com/network-wednesdays-hydra/ |archive-url=https://archive.today/20130628203747/http://community.calrec.com/network-wednesdays-hydra/ |url-status=dead |archive-date=2013-06-28 |title=Network Wednesdays: Hydra2 |date=2013-04-13 |access-date=2013-05-04 }}</ref> uses Cat-5e cabling or fiber through [[Small form-factor pluggable transceiver|SFP transceivers]].<ref>{{Cite web|url=http://calrec.com/hydra2/ |title=Hydra2 |publisher=Calrec |access-date=2016-12-27}}</ref>


[[MADI]] uses 75-[[ohm]] [[coaxial cable]] with [[BNC connector]]s or optical fibre to carry up to 64 channels of digital audio in a point-to-point connection. It is most similar in design to [[AES3]], which can carry only two channels.
[[MADI]] uses 75-[[ohm]] [[coaxial cable]] with [[BNC connector]]s or optical fibre to carry up to 64 channels of digital audio in a point-to-point connection. It is most similar in design to [[AES3]], which can carry only two channels.
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[[AES47]] provides audio networking by passing AES3 audio transport over an ATM network using structured network cabling (both copper and fibre). This was used extensively by contractors supplying the [[BBC]]'s wide area real-time audio connectivity around the UK.
[[AES47]] provides audio networking by passing AES3 audio transport over an ATM network using structured network cabling (both copper and fibre). This was used extensively by contractors supplying the [[BBC]]'s wide area real-time audio connectivity around the UK.


[[Audio over IP]] differs in that it works at a higher layer, [[encapsulation (networking)|encapsulated]] within Internet Protocol. Some of these systems are usable on the [[Internet]], but may not be as instantaneous, and are only as reliable as the [[network route]] &mdash; such as the path from a [[remote broadcast]] back to the main studio, or the [[studio/transmitter link]] (STL), the most critical part of the [[airchain]]. This is similar to VoIP, however AoIP is comparable to AoE for a small number of channels, which are usually also data-compressed. Reliability for permanent STL uses comes from the use of a [[virtual circuit]], usually on a [[leased line]] such as [[Digital Signal 1|T1]]/[[E-carrier level 1|E1]], or at minimum [[ISDN]] or [[DSL]].
[[Audio over IP]] differs in that it works at a higher layer, [[encapsulation (networking)|encapsulated]] within Internet Protocol. Some of these systems are usable on the Internet, but may not be as instantaneous, and are only as reliable as the [[network route]] &mdash; such as the path from a [[remote broadcast]] back to the main studio, or the [[studio/transmitter link]] (STL), the most critical part of the [[airchain]]. This is similar to VoIP, however AoIP is comparable to AoE for a small number of channels, which are usually also data-compressed. Reliability for permanent STL uses comes from the use of a [[virtual circuit]], usually on a [[leased line]] such as [[Digital Signal 1|T1]]/[[E-carrier level 1|E1]], or at minimum [[ISDN]] or [[DSL]].


In broadcasting and to some extent in studio and even live production, many [[manufacturer]]s equip their own [[audio engine]]s 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.
In broadcasting, and to some extent in studio and even live production, many [[manufacturer]]s equip their own [[audio engine]]s to be tied together. 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.

AoE is not necessarily intended for [[wireless network]]s, thus the use of various [[802.11]] devices may or may not work with various (or any) AoE protocols.<ref>{{cite web |title=Can I transport CobraNet audio over a wireless network? |publisher=[[Cirrus Logic]] |url=https://www.cobranet.info/support/faq#Q13 |access-date=2019-01-09}}</ref>


==See also==
==See also==

Latest revision as of 18:07, 19 March 2024

In audio and broadcast engineering, audio over Ethernet (AoE) is the use of an Ethernet-based network to distribute real-time digital audio. AoE replaces bulky snake cables or audio-specific installed low-voltage wiring with standard network structured cabling in a facility. AoE provides 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 AoE bears a resemblance to voice over IP (VoIP) and audio over IP (AoIP), AoE is intended for high-fidelity, low-latency professional audio. Because of the fidelity and latency constraints, AoE systems generally do not utilize audio data compression. AoE systems use a much higher bit rate (typically 1 Mbit/s per channel) and much lower latency (typically less than 10 milliseconds) than VoIP. AoE requires a high-performance network. Performance requirements may be met through use of a dedicated local area network (LAN) or virtual LAN (VLAN), overprovisioning or quality of service features.

Some AoE systems use proprietary protocols (at the lower OSI layers) which create Ethernet 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. Protocols can be broadly categorized into layer-1, layer-2 and layer-3 systems based on the 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 compatibility issues and thus requires a dedicated network for the protocol.

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 protocols encapsulate audio data in 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, most commonly User Datagram Protocol (UDP) or Real-time Transport Protocol (RTP). Use of UDP or RTP 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 IP packets can traverse the Internet, most layer-3 protocols cannot provide reliable transmission over the Internet due to the limited bandwidth, significant End-to-end delay and packet loss that can be encountered by data flow over the Internet. For similar reasons, transmission of layer-3 audio over wireless LAN are also not supported by most implementations.

Open standards

[edit]

Proprietary

[edit]

Similar concepts

[edit]

High quality digital audio distribution was patented in 1988 by Tareq Hoque at the MIT Media Lab.[15] The technology was licensed to several leading OEM audio and chip manufacturers that were further developed into commercial products.[citation needed]

RockNet by Riedel Communications,[16] uses Cat-5 cabling. Hydra2 by Calrec[17] uses Cat-5e cabling or fiber through SFP transceivers.[18]

MADI uses 75-ohm coaxial cable with BNC connectors or optical fibre to carry up to 64 channels of digital audio in a point-to-point connection. It is most similar in design to AES3, which can carry only two channels.

AES47 provides audio networking by passing AES3 audio transport over an ATM network using structured network cabling (both copper and fibre). This was used extensively by contractors supplying the BBC's wide area real-time audio connectivity around the UK.

Audio over IP differs in that it works at a higher layer, encapsulated within Internet Protocol. Some of these systems are usable on the Internet, but may not be as instantaneous, and are only as reliable as the network route — such as the path from a remote broadcast back to the main studio, or the studio/transmitter link (STL), the most critical part of the airchain. This is similar to VoIP, however AoIP is comparable to AoE for a small number of channels, which are usually also data-compressed. Reliability for permanent STL uses comes from the use of a virtual circuit, usually on a leased line such as T1/E1, or at minimum ISDN or DSL.

In broadcasting, and to some extent in studio and even live production, many manufacturers equip their own audio engines to be tied together. 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.

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.[19]

See also

[edit]

References

[edit]
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