AES50 is an Audio over Ethernet protocol for multichannel

digital audio Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, sa ...

. It is defined by the AES50-2011 standard for ''High-resolution multi-channel audio interconnection (HRMAI)''.

Origins

AES50 is based on the SuperMAC protocol created by Sony Pro Audio Lab (now Oxford Digital). The preliminary standard was assigned the AES-X140 project designation in 2003, and was finally approved in 2005 as a

royalty-free Royalty-free (RF) material subject to copyright or other intellectual property rights may be used without the need to pay royalties or license fees for each use, per each copy or volume sold or some time period of use or sales. Computer standard ...

open standard An open standard is a standard that is openly accessible and usable by anyone. It is also a prerequisite to use open license, non-discrimination and extensibility. Typically, anybody can participate in the development. There is no single definition ...

. HyperMAC is an improved protocol based on Gigabit Ethernet physical layer, allowing more channels and lower

audio latency Latency refers to a short period of delay (usually measured in milliseconds) between when an audio signal enters a system and when it emerges. Potential contributors to latency in an audio system include analog-to-digital conversion, buffering, d ...

. It was considered for an alternate physical layer in a future revision of AES50, but standardisation did not move forward. Sony licensed its proprietary software implementations of SuperMAC and HyperMAC to

Midas Consoles Midas is a company that designs professional audio consoles. Founded in London in 1970 by Jeff Byers and Charles Brooke, today the company is part of the Music Tribe group of brands. Midas consoles are used by audio engineers for live sound mix ...

for their

Midas XL8 The Midas XL8 was the first digital mixing console produced by Midas, previously a leading manufacturer of analogue mixing consoles for live sound. The introduction of the console came after years of digital console competition by Yamaha, Digidesign ...

digital mixer. Midas parent

Klark Teknik Klark Teknik is a company that designs and develops professional signal processing and audio equipment. Located in Kidderminster, Worcestershire, UK, the company was founded in 1974 by brothers Terence and Phillip Clarke. It developed a number o ...

took over the SuperMAC and HyperMAC patents in 2007, then in 2009 Midas and Klark Teknik were acquired by

Uli Behringer Behringer is an audio equipment company founded by the Swiss engineer Uli Behringer on 25 January 1989, in Willich, Germany. Behringer was the 14th largest manufacturer of music products in 2007. Behringer is a worldwide, multinational grou ...

's Music Group. The AES50 protocol is implemented in digital mixing consoles by Midas and Behringer to transfer digital audio between the remote stage boxes.

Specifications

AES50 is a point-to-point interconnect which carries multiple channels of AES3,

PCM Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amp ...

or DSD bitstream formats, along with system clock and synchronisation signals, over

Cat 5 cable Category 5 cable (Cat 5) is a twisted pair cable for computer networks. Since 2001, the variant commonly in use is the Category 5e specification (Cat 5e). The cable standard provides performance of up to 100 MHz and is ...

using 100 Mbit/s Fast Ethernet physical layer. AES50 uses the four pairs of the Cat 5 cable in the

8P8C A modular connector is a type of electrical connector for cords and cables of electronic devices and appliances, such as in computer networking, telecommunication equipment, and audio headsets. Modular connectors were originally developed for ...

connector: # Audio data transmit + # Audio data transmit – # Audio data receive + # Sync signal transmit + # Sync signal transmit – # Audio data receive – # Sync signal receive + # Sync signal receive – Audio data is transmitted in bidirectional full-duplex mode over two differential pairs used by the

100BASE-TX In computer networking, Fast Ethernet physical layers carry traffic at the nominal rate of 100 Mbit/s. The prior Ethernet speed was 10 Mbit/s. Of the Fast Ethernet physical layers, 100BASE-TX is by far the most common. Fast Ethern ...

standard, and word clock sync signal is transmitted over the remaining differential pairs not used by the Fast Ethernet layer. Using separate copper pairs for clock signal simplifies connection setup and allows phase-accurate low-

jitter In electronics and telecommunications, jitter is the deviation from true periodicity of a presumably periodic signal, often in relation to a reference clock signal. In clock recovery applications it is called timing jitter. Jitter is a significa ...

clock sync. AES50 only employs the Ethernet protocol's physical layer (layer 1), relying on Ethernet frames to continuously stream audio data. A proprietary link layer (layer 2) implements a point-to-point audio transmission protocol. It uses a

cyclic redundancy check A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to digital data. Blocks of data entering these systems get a short ''check value'' attached, based on t ...

(CRC) for each Ethernet frame and a

Hamming code In computer science and telecommunication, Hamming codes are a family of linear error-correcting codes. Hamming codes can detect one-bit and two-bit errors, or correct one-bit errors without detection of uncorrected errors. By contrast, the sim ...

scheme can recover from individual bit errors. The audio data is interleaved so that neighbouring bits belong to different samples, allowing the receiving end to correct burst errors. Specialised cross-point routers can converrt multiple point-to-point AES50 links to a centralised

star topology A star network is an implementation of a spoke–hub distribution paradigm in computer networks. In a star network, every host is connected to a central hub. In its simplest form, one central hub acts as a conduit to transmit messages. Th ...

. The AES50 protocol supports

24-bit Notable 24-bit machines include the CDC 924 – a 24-bit version of the CDC 1604, CDC lower 3000 series, SDS 930 and SDS 940, the ICT 1900 series, the Elliott 4100 series, and the Datacraft minicomputers/Harris H series. The term SWORD is ...

PCM audio and delta-sigma bistream formats ( Direct Stream Digital), with sample rates that are a multiple of 44.1 or 48 kHz. The bandwidth of 100 Mbit/s allows 48 channels at 48 kHz sample rate, or 24 channels at 96 kHz sample rate. The latency is 6 samples at 96 kHz and 3 samples at 48 kHz, or 62.50 μs. In practical implementations of the SuperMAC and HyperMAC protocols, only 96 kHz PCM formats are supported. AES50 also supports packet-based auxiliary channel for control data over the same data link. The control channel is allocated a fixed bandwidth of 5 Mbit/s; control data are embedded in the same Ethernet frame as the audio data.

HyperMAC

The HyperMAC protocol is based on the Gigabit Ethernet physical layer for Cat 5e cable (up to 100 m) or OM2 multi-mode fibre (up to 500 m) with embedded clocking. It allows up to 192 bidirectional channels at 96 kHz and 384 channels at 48 kHz; the latency is 4 samples at 96 kHz or 2 samples at 48 kHz, or 41.66 μs. The bandwidth of the auxilliary data link is increased to 200 Mbit/s and control data is transmitted with separate control frames.

Implementations

digital mixer * Midas PRO6 digital mixer * Behringer X32 digital mixer * Midas M32 digital mixer * Behringer S32/S16/S8 digital stage boxes * Behringer SD8/SD16 digital stage boxes * Midas DL461 Audio System Signal Router * Klark Teknik DN9650 network bridge

References

External links

* {{Digital audio and video protocols Audio network protocols Networking standards Audio engineering Audio Engineering Society standards