In Broadcast - March 2014 - 80


I N T E R N A T I O N A L

WWW.INBROADCAST.COM | ISSUE 29 - MARCH 2014

N E W S

InTECH

'AES67 Now!' Highlights
Interoperability With RAVENNA
ALCNetworX addresses the key issue of interoperability with "AES67 Now!"...
Proﬁles For
Interoperability
By Andreas Hildebrand
A potential issue with RAVENNA is
Senior Product Manager, ALCNetworX that the full breadth and ﬂexibility

LC N e t wo rX 's A n d r e a s
Hildebrand
recently
participated in the AudioForum
seminar at ISE hoste d by
Connessioni and sponsored by
the AES.
The theme was "Protocols and
systems of integrated digital audio
transport," a topic that resonates
with audio professionals everywhere.
We are all ensconced in the digital
age, and today it is inconceivable
that a complex audio system be
designed without some form of
audio networking. Given the wide
choice of equipment, protocols and
technologies available to designers
and integrators, the question of
interoperability is clearly a key
issue. Andreas addressed this
important subject in his talk entitled
"AES67 Now!" and explained how it
relates to RAVENNA.

A

80

AES67 Standard
AES67 is the published standard
which resulted from the AES-X192
project to develop audio network
interoperability, because until now
no such standard existed. Headed
up by respected industry veteran
of media networking and the father
of CobraNet, Kevin Gross of AVA
Networks, the stated goals of
the project were to develop an
interoperability standard for high
performance professional digital
IP networking and to define
synchronisation, encoding format
and QoS provision for delivering
audio data and connection
management functions associated
with audio delivery. AES67 uses
existing and standard protocols
and technology from the IEEE, IETF
and other standards developing
organisations. It does not invent
new protocols or technologies;
rather, AES67 deﬁnes how to use
existing protocols as a system in
an interoperable manner.
Published in September 2013, the
standard provides comprehensive
interoperability recommendations

in the key areas of synchronisation,
media clock identiﬁcation, network
transport, encoding and streaming,
session description, connection
management, and advertisement
and discovery.
AES67 is not intended to be
a solution on its own, but rather
providing means for exchanging
audio streams between areas with
different networking solutions or
technologies already in place. It can
be expected that the various IPbased solutions currently available
will enhance their capabilities in
order to adopt an AES67-compliant
stream mode to facilitate intersystem interoperability.

AES67 & RAVENNA
RAVENNA is an open technology
for real-time distribution of audio
and other media content in IPbased network environments.
Utilising standardised network
protocols and technologies,
RAVENNA can integrate and operate
on existing network infrastructures.
Performance and capacity scale
with the capabilities of the
underlying network architecture.
It is aimed at applications in
professional environments where
networks are planned and managed,
and where performance has
to surpass the requirements of
consumer applications.
Its functional principles are
publically available and RAVENNA
t e c h n o l o g y c a n b e f re e l y
implemented and used without
any proprietary licensing policy.
Numerous industry partners
are supporting the RAVENNA
technology and a variety of
RAVENNA-enabled devices are
already commercially available.
W h a t m a k e s R AV E N N A
more interesting still is that
since RAVENNA's fundamental
operational principles, protocols
and formats are all in line with
what has been deﬁned in AES67,
RAVENNA is already fully
compatible with AES67. Indeed,
not only is RAVENNA AES67
compatible, but largely exceeds
A E S 6 7 's re c o m m e n d a t i o n s
at every level.

it offers might be intimidating,
especially for newcomers.
This is true for both users and
manufacturers and may lead to
operational incompatibilities.
Proﬁles are a way around this.
RAVENNA deﬁnes a set of proﬁles
for key application areas. Each
proﬁle contains a minimum set of
features collected from devices and
the networks that are likely to be
required by the application.
Manufacturer s have the
freedom to implement these
profiles in their devices
as appropriate for their
requirements. Of course devices
can support multiple proﬁles
concurrently, thus allowing a
wider ﬁeld of application and
increased interoperability.
A generic proﬁ le has been
defined to describe a base
line of features considered to be
indispensable for most devices; it
contains a small set of requirements
that almost every device should be
able to meet, and can therefore be
expected by the user to be available
in most RAVENNA devices.
As previously stated, since all
relevant standard ingredients of
AES67 are either identical or very
similar to RAVENNA's operating
principles, RAVENNA can naturally
fully support interoperability as
deﬁned within AES67.
However, since the RAVENNA
technology framework offers
performance and functionality
superior to the AES67
interoperability guidelines, AES67
can be seen as one of many possible
operational proﬁles for RAVENNA.
In fact, the AES67 speciﬁcation is
very close to the RAVENNA Generic
Profile, hence all RAVENNAenabled devices that support the
RAVENNA Generic Proﬁle will also
support AES67.

Assessment And Outlook
Other IP-based technologies were
in existence prior to RAVENNA
but, although featuring some
commonalities, they were not able
to interoperate with each other.
The motivation, therefore, for
AES67 was to deﬁne interoperability
guidelines to which existing
solutions can be adapted with
reasonable effort in order to

The RAVENNA based mastercard the interface card for all members
of the mc² series and Nova73 HD
router systems

facilitate synchronised inter-system
stream exchange.
AES67 and RAVENNA share
the same fundamental principles
for synchronisation and transport,
while AES67 packet setup and
payload formats are functional
subsets of RAVENNA.

Connection Management
Minor differences exist with stream
connection management, which
can easily be adopted by the
RAVENNA technology framework.
Consequently, AES67 will be
supported by RAVENNA devices
as an operational profile.
RAVENNA is currently the only
IP audio distribution technology
to offer such complete AES67
compatibility "out of the box".
Other audio-over-IP solutions will
certainly continue to exist, as most
of them already have a signiﬁcantly
large installed base.
Most of them also offer
application-speciﬁc functionality
beyond the scope of AES67,
even though most will have to
be modified or enhanced to
support AES67.
This will open up the landscape
of product diversity and widen
the ﬁeld of application for AES67capable devices.
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