AES47
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AES47 is a standard which describes a method for transporting
AES3 AES3 is a standard for the exchange of digital audio signals between professional audio devices. An AES3 signal can carry two channels of pulse-code-modulated digital audio over several transmission media including balanced lines, unbalanced ...
professional digital audio streams over
Asynchronous Transfer Mode Asynchronous Transfer Mode (ATM) is a telecommunications standard defined by American National Standards Institute (ANSI) and ITU-T (formerly CCITT) for digital transmission of multiple types of traffic. ATM was developed to meet the needs of ...
(ATM) networks. The
Audio Engineering Society The Audio Engineering Society (AES) is a professional body for engineers, scientists, other individuals with an interest or involvement in the professional audio industry. The membership largely comprises engineers developing devices or product ...
(AES) published AES47 in 2002. The method described by AES47 is also published by the
International Electrotechnical Commission The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and ...
as IEC 62365.


Introduction

Many professional audio systems are now combined with telecommunication and IT technologies to provide new functionality, flexibility and connectivity over both
local Local may refer to: Geography and transportation * Local (train), a train serving local traffic demand * Local, Missouri, a community in the United States * Local government, a form of public administration, usually the lowest tier of administrat ...
and
wide area network A wide area network (WAN) is a telecommunications network that extends over a large geographic area. Wide area networks are often established with leased telecommunication circuits. Businesses, as well as schools and government entities, u ...
s. AES47 was developed to provide a standardised method of transporting the standard digital audio per
AES3 AES3 is a standard for the exchange of digital audio signals between professional audio devices. An AES3 signal can carry two channels of pulse-code-modulated digital audio over several transmission media including balanced lines, unbalanced ...
over telecommunications networks that provide a
quality of service Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitat ...
required by many professional
low-latency Latency, from a general point of view, is a time delay between the cause and the effect of some physical change in the system being observed. Lag, as it is known in gaming circles, refers to the latency between the input to a simulation and ...
live audio uses. AES47 may be used directly between specialist audio devices or in combination with telecommunication and computer equipment with suitable network interfaces. In both cases, AES47 the same physical structured cable used as standard by the telecommunications networks. Common network protocols like
Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1 ...
use large packet sizes, which produce a larger minimum latency. Asynchronous transfer mode divides data into 48-byte ''cells'' which provide lower latency.


History

The original work was carried out at the
British Broadcasting Corporation #REDIRECT BBC #REDIRECT BBC Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board exam. ...
...
’s R&D department and published as "White Paper 074", which established that this approach provides the necessary performance for professional media production. AES47 was originally published in 2002 and was republished with minor revisions in February 2006. Amendment 1 to AES47 was published in February 2009, adding code points in the ATM Adaptation Layer Parameters Information Element to signal that the time to which each audio sample relates can be identified as specified in
AES53 AES47 is a standard which describes a method for transporting AES3 professional digital audio streams over Asynchronous Transfer Mode (ATM) networks. The Audio Engineering Society (AES) published AES47 in 2002. The method described by AES47 is al ...
. The change in thinking from traditional ATM network design is not to necessarily use ATM to pass IP traffic (apart from management traffic) but to use AES47 in parallel with standard Ethernet structures to deal with extremely high performance secure media streams. AES47 has been developed to allow the simultaneous transport and switched distribution of a large number of
AES3 AES3 is a standard for the exchange of digital audio signals between professional audio devices. An AES3 signal can carry two channels of pulse-code-modulated digital audio over several transmission media including balanced lines, unbalanced ...
linear audio streams at different sample frequencies. AES47 can support any of the standard AES3 sample rates and word size.
AES11 The AES11 standard published by the Audio Engineering Society provides a systematic approach to the synchronization of digital audio signals. AES11 recommends using an AES3 signal to distribute audio clocks within a facility. In this application, th ...
Annex D (the November 2005 printing or version of AES11-2003) shows an example method to provide
isochronous A sequence of events is isochronous if the events occur regularly, or at equal time intervals. The term ''isochronous'' is used in several technical contexts, but usually refers to the primary subject maintaining a constant period or interval ( ...
timing relationships for distributed AES3 structures over asynchronous networks such as AES47 where reference signals may be locked to common timing sources such as
GPS The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
.
AES53 AES47 is a standard which describes a method for transporting AES3 professional digital audio streams over Asynchronous Transfer Mode (ATM) networks. The Audio Engineering Society (AES) published AES47 in 2002. The method described by AES47 is al ...
specifies how timing markers within AES47 can be used to associate an absolute time stamp with individual audio samples as described in AES47 Amendment 1. An additional standard has been published by the
Audio Engineering Society The Audio Engineering Society (AES) is a professional body for engineers, scientists, other individuals with an interest or involvement in the professional audio industry. The membership largely comprises engineers developing devices or product ...
to extend
AES3 AES3 is a standard for the exchange of digital audio signals between professional audio devices. An AES3 signal can carry two channels of pulse-code-modulated digital audio over several transmission media including balanced lines, unbalanced ...
digital audio carried as AES47 streams to enable this to be transported over standard physical
Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1 ...
hardware. This additional standard is known as
AES51 AES51 is a standard first published by the Audio Engineering Society in June 2006 that specifies a method of carrying Asynchronous Transfer Mode (ATM) cells over Ethernet physical structure intended in particular for use with AES47 to carry AES3 d ...
-2006.


AES47 details

For minimum latency, AES47 uses "raw" ATM cells,
ATM adaptation layer The use of Asynchronous Transfer Mode (ATM) technology and services creates the need for an adaptation layer in order to support information transfer protocols, which are not based on ATM. This adaptation layer defines how to segment higher-la ...
0. Each ATM virtual circuit negotiates the parameters of a stream at connection time. In addition to the same rate and number of channels (which may be more than the 2 supported by AES3), the negotiation covers the number of bits per sample and the presence of an optional data byte. The total must be 1, 2, 3, 4 or 6 bytes per sample, so it evenly divides the ATM cell size. AES3 uses 4 bytes per sample (24 bits of sample plus the optional data byte), but AES47 supports additional formats. The optional data byte contains four "ancillary" bits corresponding to the AES3 VUCP bits. However, the P (parity) bit is replaced by a B bit which is set on the first sample of each audio block, and clear at all other times. This serves the same function as the B (or Z) synchronization preamble. The other half of the data byte contains three "data protection" bits for
error control In information theory and coding theory with applications in computer science and telecommunication, error detection and correction (EDAC) or error control are techniques that enable reliable delivery of digital data over unreliable communic ...
and a sequencing bit. The concatenation of the sequencing bits from all samples in a cell (combined little-endian) form a sequencing word of 8, 12, 16, or 24 bits. Only the first 12 bits are defined. The first four bits of the sequencing word are a sequencing number, used to detect dropped cells. This increments by 1 for each cell transmitted. The second four bits are for error detection, with bit 7 being an
even parity A parity bit, or check bit, is a bit added to a string of binary code. Parity bits are a simple form of error detecting code. Parity bits are generally applied to the smallest units of a communication protocol, typically 8-bit octets (bytes), ...
bit for the first byte. The third four bits, if present, are a second sequencing number which can be used to align multiple virtual circuits.


AES53

AES53 is a standard first published in October 2006 by the
Audio Engineering Society The Audio Engineering Society (AES) is a professional body for engineers, scientists, other individuals with an interest or involvement in the professional audio industry. The membership largely comprises engineers developing devices or product ...
that specifies how the timing markers specified in AES47 may be used to associate an absolute time-stamp with individual audio samples. A recommendation is made to refer these timestamps to the
SMPTE The Society of Motion Picture and Television Engineers (SMPTE) (, rarely ), founded in 1916 as the Society of Motion Picture Engineers or SMPE, is a global professional association of engineers, technologists, and executives working in the m ...
epoch which in turn provides a reference to UTC and
GPS The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
time. It thus provides a way of aligning streams from disparate sources, including synchronizing audio to video, and also allows the total delay across a network to be controlled when the transit time of individual cells is unknown. This is most effective in systems where the audio is aligned with an absolute time reference such as
GPS The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
, but can also be used with a local reference. This standard may be studied by downloading a copy of the latest version from the AES standards web site the AES standards web site
/ref> as AES53-2018.


See also

*
AES51 AES51 is a standard first published by the Audio Engineering Society in June 2006 that specifies a method of carrying Asynchronous Transfer Mode (ATM) cells over Ethernet physical structure intended in particular for use with AES47 to carry AES3 d ...
* Voice over ATM *
Audio over Ethernet In audio 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. AoE replaces bulky snake cables or audio-specific ...


References

{{List of International Electrotechnical Commission standards Audio engineering Networking standards Broadcast engineering Audio network protocols IEC standards Audio Engineering Society standards