AES Standards News Blog

AES62-2011 AES standard for audio connectors - Modified XLR-3 Connector for Digital Audio has been published.

http://www.aes.org/publications/standards/search.cfm?docID=86

This new standard covers new connector types in order to identify AES3 equipment, signals and transmission circuits (tie lines). By extension, the same connectors will also identify AES42 microphone connections. The new “digital” connectors are based on the conventional analogue three pole XLR-type connectors with the difference of additional keying. The keying is realized in a manner as to prevent mating with conventional XLR-type connectors. Furthermore new “compatible” connectors that mate with both “digital” and conventional types are specified. 

This standard specifies variants of the XLR connector family to be used for professional audio applications that include AES3 digital audio interfaces.

Test methods to confirm the correct function of the keying are indicated. Additional means supporting identification of different connector types are under consideration. 

The document does not include any electrical requirements.

AES-6id-2006 (r2011) AES information document for digital audio - Personal computer audio quality measurements has been reaffirmed in a new printing.

This document focuses on the measurement of audio quality specifications in a PC environment. Each specification listed has a definition and an example measurement technique.  Also included is a detailed description of example test setups to measure each specification.

 AES-12id (r2011) AES Information Document for digital audio measurements - Jitter performance specifications has been reaffirmed in a new printing.

The question of sample-clock quality is a perennial one for digital audio equipment designers, yet most chip makers provide very little information about the jitter performance of their products. Consequently, equipment designers are sometimes caught out by jitter issues. The increasing use of packet-based communications and class-D amplification is throwing these matters into sharper relief. This information document reviews various ways of characterizing and quantifying jitter, and refines several of them for audio purposes. It also attempts to present a common, unambiguous terminology. Its focus includes wideband jitter, baseband jitter, jitter spectra, period jitter, long-term jitter and jitter signatures. Comments are made on jitter transfer through phase-locked loops and on the jitter susceptibility of audio converters. 

AES26-2001 (r2011) AES recommended practice for professional audio interconnections — Conservation of the polarity of audio signals has been reaffirmed in a new printing.

This document standardizes the polarity of the signals at the various interface points between different items of equipment, in particular from the acoustical, electrical, mechanical, digital, and magnetic aspects. Each item of equipment complies separately with the polarity requirements for the input and output signals.

 AES45-2001 (r2011) AES standard for single programme connectors — Connectors for loudspeaker-level patch panels has been reaffirmed in a new printing.

This standard complements IEC 60268-12 including amendments 1 and 2, extending the standardization of the application of AES45-series connectors to their use for loudspeaker-level patch panels.

AES60-2011 addresses the creation, management and preservation of material that can be re-used as originally produced, or may provide input material for new production projects. Material is expected to be exchanged between various organisations or between production facilities in a distributed environment.

The core set of metadata presented in this specification is a co-publication of EBU Tech3293-2008 EBU Core, itself an extension to and a refinement of the Dublin Core. EBUCore is a minimum list of attributes characterizing video and / or audio media resources. An XML representation is also provided in case this metadata would be implemented, for example in archive exchange projects using the Open Archive Initiative's Protocol for Metadata Harvesting (OAI-PMH).

http://www.aes.org/publications/standards/search.cfm?docID=85

AES57-2011 sets out the vocabulary to be used in describing digital and analog audio formats, including both those formats that exist in some tangible form such as a reel of tape and those that exist only as a set of bits, untied to a single audio carrier, such as a broadcast wave file. This vocabulary takes the form of an Extensible Markup Language (XML) schema. By doing so it provides a structured human readable instance document that can be easily parsed and manipulated using any of a number of freely available programming libraries and tools. The schema is designed for flexibility, providing a number of data elements that are optional. This is necessary since often there will be certain information that cannot be known, particularly in archive settings where technicians are asked to preserve materials that have little or no accompanying documentation. As a result the base set of required elements does not necessarily represent the minimal description necessary for preservation, but rather is the set of elements that is expected to be known or determinable at a minimum.

AES50-2011, AES standard for digital audio engineering - High-resolution multi-channel audio interconnection (HRMAI) has been published.  This new edition revises AES50-2005 and contains amendments resulting from a real-world implementation of the standard.

AES50 specifies a means to carry multiple channels of digital audio in AES3 or bit-stream formats, plus system synchronisation information, over a structured data cable using the IEEE Std 802.3 physical layer. It includes a means to convey arbitrary packet-based data over the link, in addition to the specified audio interconnection.

HRMAI provides a professional multi-channel audio interconnection with a number of distinctive characteristics:

• Support for a wide range of commonly-used digital audio coding formats, including “high-resolution” formats such as high sample-rate linear PCM, and one-bit delta-sigma modulated formats.

• Low and deterministic latency (< 100 μs)

• Use of ubiquitous “Category-5” data cable

• Interconnect span up to 100 m

• High-quality full-duplex clocks transmitted in parallel with audio data

• Full-duplex audio interconnection

• 5 Mbit/sec full-duplex auxiliary data connection, compatible with Ethernet networks.

HRMAI is a high-performance point-to-point audio interconnection, rather than a network (although the auxiliary data may operate as a true network, independently of the audio). It is thus an alternative to AES10 (MADI). AES10 lacks many of the features listed above, which are enabled by developments in underlying technology in the thirteen years since AES10 was introduced. However, for applications which do not need these additional facilities, AES10 will continue to be appropriate.

 AES-R6-2011, AES project report - Guidelines for AES standard for digital audio engineering - High resolution multi-channel audio interconnection (HRMAI), AES50 has been published

This edition revises AES-R6-2005 to complement the latest revision of AES50.

This report is intended to accompany AES50, “High-resolution multi-channel audio interconnection”. It provides additional background, rationale and implementation advice and should be read in conjunction with AES50-2011 which revises the earlier AES50-2005. In particular, the first clause of this document provides an overview of the technology, which may aid understanding of the context of the standard.

The High Resolution Multi-channel Audio Interconnection provides a bi-directional, point-to-point connection for up to 48 channels of digital audio in a variety of formats. The link uses a single Category 5 (or better) structured-wiring data cable, and is designed for operation in a studio environment.

The system uses the 100Base-TX physical layer of Fast Ethernet (ISO/IEC 8802.3:2000(E) Sections 22/23, together with ANSI X3.263-1995) to transfer framed digital audio data. Audio synchronization is maintained by transmitting a 64fs (for example, 2,8224 MHz, if fs = 44,1 kHz) audio clock signal in parallel with the audio data, utilising the extra signal pairs on a structured wiring data cable.

Throughout this document, the term “fs” is used to denote a base audio sampling frequency. This may be 44,1 kHz or 48 kHz, irrespective of sampling frequency multipliers typically used for high-resolution digital audio (e.g. 2, 4, 8). If variable sample rate operation (“varispeed”) is required, fs may range from 44,1 kHz -12,5 % to 48 kHz +12,5 % (38,5875 kHz to 54 kHz). Varispeed capability is optional.

AES Standards project AES-X196, Revision of AES3 to use high sampling rates to carry multi-channel audio, has been initiated and will be developed in the SC-02-02 Working Group on Digital Input/Output Interfacing.

An AES3 interface running at 192kHz could be adapted to carry 8 channels of linear audio sampled at 48kHz.  The scope of this project is to formalise the use of the interface in this way, and to specify a means of signalling the use of an AES3 interface in this way to cover various use cases such as asynchronous switching, behaviour of existing devices, equipment not designed for this mode, and so on. Operational guidance may also be developed, if necessary.

Multichannel audio, whether planar surround (5.1), or periphony, or simply multi-language commentary & effects, is necessary in everyday broadcasting.  Much infrastructure now using multiple AES3 interfaces could carry this as a single AES3 stream, thus simplifying interconnections, and reducing cost.

This project wil benefit broadcast equipment developers, installers and users; and other users of multichannel audio.

http://www.aes.org/standards/meetings/new-projects.cfm