IP Audio Distribution Moves Into the Studio by Clark Novak

IP Audio Distribution Moves Into the Studio by Clark Novak
Radio Guide
Radio Technology for Engineers and Managers
January 2005
IP-Audio Distribution Moves Into the Studio
Inside
Radio Guide
IP-Audio Routing
Page 4
When we say “network” today, most folks immediately think of Ethernet.
Devised in the 1970s at Xerox’s PARC, this use of distributed packet switching
to connect local computer networks has evolved into a high-speed universal
connection method for sharing all sorts of digital information.
You may or may not have thought about it, but Ethernet is actually the most
common digital audio transmission method in today’s broadcast facilities,
connecting audio delivery servers with studio computers. A natural extension of
the technology would be to use Ethernet as a low-cost, universal way to connect
audio and data for everything – including real-time audio – in broadcast studios.
IP-Audio Routing
by Clark Novak, Axia Audio
The Technology
Underlying Axia
As more and more stations transition to or plan for
digital audio plants, it is important to understand the
technologies that make it work. This month Clark Novak,
from Axia Audio, explains how the IP-Audio Routing
brings benefits to users.
[CLEVELAND, Ohio - January 2005] As long as
there has been information, people have searched for
efficient ways of sharing and distributing it. History
credits the first “information system” to the French,
who in 1791 developed an “Optical Telegraph Network” that used a system of cross-arms and pulleys to
transmit messages at the blinding speed of 20 characters per minute.
A WHOLE DIFFERENT NETWORK
When we say “network” today, most folks immediately think of Ethernet. Devised in the 1970s at Xerox’s
PARC, this use of distributed packet switching to connect local computer networks has evolved into a highspeed universal connection method for sharing all sorts
of digital information.
You may or may not have thought about it, but
Ethernet is actually the most common digital audio
transmission method in today’s broadcast facilities,
connecting audio delivery servers with studio computers. A natural extension of the technology would be to
use Ethernet as a low-cost, universal way to connect
audio and data for everything – including real-time
audio – in broadcast studios.
Of course, it is not just the connection that is needed, but
a connection with a pipe big enough and reliable enough to
handle low-delay, high-reliability uncompressed audio
over switched Ethernet. Axia Audio’s solution for professional audio delivery is called “Livewire™.”
Livewire is the core technology in all Axia products. It allows transport of real-time, “live” audio, plus
Program Associated Data (PAD) and machine remote
control over a network of switched Ethernet, a technique called “IP-Audio.” This network can also carry
file transfers, messaging and other routine traffic,
resulting in a true “converged” network for the broadcast plant.
NO MORE PATCH BAYS
“Ethernet connects everything,” says Axia President
Michael “Catfish” Dosch. “Two devices connect with a
length of CAT-6 cable; multiple devices connect through
an Ethernet switch. The same wire conveys audio, logic
and control messaging, program-associated data – even
general IP traffic. Very clean, simple and elegant.”
Ethernet has more than enough bandwidth
for uncompressed digital audio.
The Axia Livewire network replaces the need for a
cross-point audio switcher, since every source is avail-
Page 4
able to every destination on the network. The network is
designed to be naturally scalable, and can effectively
cross-connect either a few studios, or a few dozen. This
way a single Ethernet switch will support hundreds of
cross-points.
Ethernet’s enormous data capacity makes it possible
for a 100Base-T segment to carry 25 stereo channels of
48 kHz, 24-bit linear PCM audio in both directions. A
1000Base-T or Gigabit fiber link can handle ten times
that amount – up to 32,000 stereo channels per system.
HOW IT ALL WORKS
Livewire networks have three parts: the Ethernet
backbone, the software layer, and the user layer.
Why Ethernet? According to Telos founder Steve
Church, “Low-cost mass-market Ethernet switches offer us something very interesting. Since their function is
to direct packets from port-to-port, we can use them to
move our audio signals from whatever source to whatever destinations we want. This means we get a simple,
flexible, facility-wide audio routing system for almost
free.”
Livewire has an audio advertising system based on
the familiar concept of IP addressing, Church continues.
“Every source has a text name and numeric ID. These
are transmitted from source devices to the network.
Receivers can build lists of all available sources from
which users can select. With hardware nodes, you enter
the names, numbers, and other configuration information via an attached PC with a web browser. With PC
nodes, you open a configuration window.”
In this manner, Livewire networks are constructed
using a “building block” approach: determine the location and number of your audio inputs, then place Axia
Audio Nodes next to them. There is an Analog Node for
line-level sources, an AES/EBU Node to handle digital
streams, a Microphone Node (with internal preamps)
for microphone inputs, a General Purpose I/O (GPIO)
Node for logic-follows-source machine control, and a
Router Selector Node, a unique hybrid X-Y controller
with its own AES and analog I/O ports.
Users like the fact that routing systems built using
Livewire typically cost about half that of a hardwired
TDM router. “With a traditional router, you spend
something in the neighborhood of $100,000 just to
put one console on the air, plus you need the special
links to get audio into the frame, and adding another
room means you have to invest in even more proprietary gear,” explains Jim Hibbard of Pacific Mobile
Recorders.
Hibbard, who installed Axia for Univision’s Austin,
Texas cluster notes, “Adding another studio with Axia
is real simple, not a break-the-bank proposition. All we
have to do is plug it in.”
AVOIDING TRAFFIC DELAYS
In the “software layer,” audio is sent in two ways:
livestreams, which use small, fast packets to send
uncompressed 48 kHz/24-bit PCM audio to network
destinations in real time, and standard streams, whose
larger, slower packets use the Internet’s RTP/IP protocol to transfer pre-recorded audio. All Axia hardware
transmits and receives both stream types; path selection
happens transparently, without user intervention.
Whichever path is used, Livewire audio overcomes typical network issues such as the delay that
Radio Guide January 2005
plagues Internet audio. Such delay is often multiple
seconds because of the long buffers needed to ride out
network problems and the delays inherent in multiplehop router paths.
On the other hand, without the limitations of the
public Internet, and with 100% control over all parts of
the system, live audio can be transported without delay
or dropouts at full quality. Livewire’s specifications
show live audio delay to be less than 1 millisecond per
network hop – comparable to any professional A/D or
D/A converter.
The Livewire network capacity is tremendous (up to
32,000 stereo channels) – well above the needs of a
typical broadcast facility. The capacity is enhanced by
the fact that all audio streams stop at the local Ethernet
switch, consuming no network bandwidth unless and
until a receiver subscribes to them. Each receiver takes
only the stream it needs, eliminating the problem of
unrequested data flooding the network.
A small (16x16 stereo)
routing switcher configuration.
EXTERNAL CONNECTIONS
Since Livewire networks are Ethernet-based, the
time and effort needed to install and configure components is significantly less than that needed for a comparable hard-wired router.
Axia’s “user layer” consists of the devices used to
translate analog and digital audio into network data
packets. These “Audio Nodes” come in several different
versions, each providing eight inputs to feed audio into
the network, and eight programmable outputs to send
audio back to studio devices or monitors.
Each studio’s equipment list includes an Ethernet
switch such as HP’s ProCurve 2626, which has the
guaranteed bandwidth and IGMP support necessary for
Livewire. Setup begins by connecting each studio’s
audio nodes to that room’s local switch using CAT-6
cable; inter-studio connections are made using a single
1000-BaseT link between switches.
Mark Manolio, Chief Engineer of Cleveland’s
WCSB-FM (where he installed one of the first Livewire
systems) and an Axia support technician, gives us an
overview of how Livewire studios are configured: “First,
you connect your studio devices to Axia Audio Nodes.
Audio Node inputs use standard RJ-45 jacks – except
for mic inputs, which take XLRs. Users can crimp their
own cables or use prewired adaptors.
Browsing the Audio I/O Node
“Next, you assign each Audio Node its own IP. This
is done using the Node’s front-panel controls. Then you
can use any networked computer to access the Node’s
setup screens using your Web browser.
“Using these setup screens, sources and destinations
can be defined by giving them descriptive names, choosing
stream priority and input gain settings, and defining GPIO
options if needed,” Manolio says.
(Continued on Page 6)
IP-Audio Routing
by Clark Novak
Continued from Page 4
Mixing and studio control is handled by the Axia
SmartSurface™, a programmable 16-fader controller
with all the functions
of a traditional console – plus a bunch
that were never possible on your BMX.
The SmartSurface
has four program busses, extensive monitoring and talkback caWCSB-FM, Cleveland
pabilities, and a GPIO
interface to control connected devices. Users
can save unique profiles with different layouts and defaults, any of which can be recalled on any networked SmartSurface.
LINUX ENGINE
UNDER THE HOOD
The actual audio mixing is handled by
the Axia StudioEngine, a network-based
DSP mixing engine running real-time Linux
to ensure bullet-proof, 24/7 operation. Axia
plans to make additional control surfaces
available in 2005.
To eliminate any need for D-to-A conversions in the sound card, the IP-Audio
Driver enables computers to exchange audio directly using their Ethernet ports on
the Livewire network. A multi-channel
version of the IP-Audio Driver for use
with audio delivery systems is available
from Axia development partners Enco Systems, Prophet Systems and Scott Studios.
To assign and control the audio sources
iPlay, an audio monitoring application for
Windows workstations, allows individuals to select and monitor any networked
audio stream.
“We have been using this system for about 10
months. I could not be happier with the products, service, and dependability that Telos
has assembled in
their Axia equipment,” says station
Chief Engineer
Marc Johnson.
“The Axia equipRadio Skonto, Riga, Latvia
ment came straight
out of the box and was on the air in a matter of hours. All
we did was place the new gear, plug in the power, and
connect it to the network.”
Ivo Bankavs, CE at Radio Skonto in Riga, Latvia –
the first international installation of Livewire technology – is pleased with the reliability.
“We’ve had no failure or downtime of any kind
since we installed Axia,” says Bankavs. “The company
warned us that we would be among the first to use this
tech, so we were ready for start-up bugs,” he says, “but
we’ve been happy – there have been none.”
While early adopters have been smaller stations, the
Livewire concept will get its first major-market workout
when WOR installs it in a new ten-studio facility in New
York City, as part of a move in early 2005.
Chief Engineer Tom Ray says it was an easy
choice: “WOR was looking for a high tech digital
solution that was also cost effective. The Axia system provides all the flexibility the WOR operation
requires, allows a mixture of analog and digital I/O,
and was extremely cost effective. The ability to
access virtually any audio source anywhere in the
facility is mind-boggling,” says Ray.
Clark Novak is a marketing team leader for Axia
products. He is happy to answer questions at:
[email protected]
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iPlay assignment screen.
Another powerful network configuration tool – PathfinderPC – lets authorized
users control the Audio Nodes, allowing
engineers to build and manage facilitywide routing applications.
PathfinderPC can change between presets manually, on a day-part schedule, or
in response to an external trigger from an
automation system or other source. Developed by longtime Telos’ partner Software
Authority (whose work will be known to
many Zephyr users), it can even be programmed to sense problems such as silence at a particular audio port, and patch
around it without user intervention.
EARLY REPORTS
In early 2004, Auburn University’s
WEGL-FM, in Auburn, AL became the
first station to build a studio using Livewire.
Page 6
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Radio Guide January 2005
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