AES Standards News Blog

As predicted in the foreword to AES41 in 2000, digital compression techniques now dominate the broadcast television environment. In addition to the problems foreseen relating to cascaded compression, new problems have arisen because of the use of loudness control and surround sound with those digital compression techniques.

Metadata within the compressed audio bit-stream is used to control loudness and the mixing down of multichannel surround sound to two-channel stereo. These metadata are usually known by terms such as "dialnorm", "prog_ref_level", and "down-mix coefficients".

Whilst this might seem unrelated to the original scope of AES41, dealing with bit allocations and scale factors, it is simply another form of data that can affect a later encoding of the audio: this time is it is more macroscopic than microscopic.

The metadata is lost when the bit-stream is uncompressed unless provision is made to transport it or store it somewhere. Existing methods rely on non-audio mechanisms to convey the metadata alongside the audio, for example a serial data link like RS-422 and serial digital video SMPTE 259M, or a "chunk" in an audio file (for metadata that does not change).

This revision extends AES41 to include data formats for carrying this loudness and down-mix metadata with the uncompressed PCM using the same transport mechanism as before. The metadata can therefore be carried in the audio to which it relates.

A Call for Comment on DRAFT AES59-xxxx, AES standard for professional audio - Audio application of 25-way D-type connectors in balanced circuits has been published: 2009-12-08.  http://www.aes.org/standards/comments/cfc-draft-aes59-xxxx.cfm.

This document describes a standard contact assignment and gender convention for users of the 25-contact D-type connector as a multi-channel balanced audio interconnection, in analogue or AES3 digital form, to facilitate interconnection of equipment from different suppliers using standardized cables.

A Call for Comment on reaffirmation of AES14-1992 (r2004), AES standard for professional audio equipment - Application of connectors, part 1, XLR-type polarity and gender was published in accordance with our 5-year review policy on 2009-12-07.  http://www.aes.org/standards/comments/cfc-reaffirm-aes14-xxxx.cfm

A Call for Comment on REAFFIRMATION of AES17-1998 (r2004), AES standard method for digital audio equipment - Measurement of digital audio equipment has been published in accordance with our 5-year review policy on 2009-12-07.  http://www.aes.org/standards/comments/cfc-reaffirm-aes17-xxxx.cfm

The synchronization of audio and video (A-V sync, or lip sync) in television continues to pose a problem for
producers and broadcasters, because errors in synchronization continue to be a source of audience
dissatisfaction.

Although digital television includes timing information that should keep audio and video properly
synchronized, this in itself can simply be another source of problems. New display technologies, and separate
audio and video signal paths within the living room, present new challenges for lip sync.

This project was started in an effort to help with creating the solution to the problem. It had the aim of
standardizing a simple method of measuring lip sync. The task proved more difficult than anticipated and the
project was subsequently closed. However this report gathers together two relevant documents that were
produced by the British Broadcasting Corporation during the life-time of the project. One is a study of factors
that affect perception of lip sync, the other is a study of operational practices in a real broadcast chain.