Practical Applications of Digital Audio Networking

Practical Applications for
Digital Audio Networking

Umberto Zanghieri - ZP Engineering srl
(The Smart Guy who is not here today and would be happy to talk about this
topic for two days)

Bob Vanden Burgt - Link USA/Link Italy
(The Not So Smart Guy doing the Presentation who promises to be done in
one hour)
People and Products connecting the world of entertainment

History of Digital Audio Networking
AES & Evolution of OSI Layers
The Current State of the Industry
(fragmented at best)
Transport Protocol Wars
Remote Control & Monitoring
Today’s Digital Challenge & Examples
Where are We Going from Here?


Moving Audio Around in a Live
Production Environment
Things to Care About
Quality (Fidelity)
Speed & Priority (Latency - milliseconds/
microseconds, QoS)
Synchronization (Clocking)
Distance (Coax, CAT6, MMF, SMF)
Flexibility / Compatibility (Topologies /
Sharing Hardware)
Cost
Reliability / Redundancy
Compatibility / Standards AES, IEEE


History of Digital Networking
Pulse Code Modulation (PCM) & Sampling
In 1924 while working for AT&T Harry
Nyquist studied this sampling
technique and developed the Nyquist
Sampling Theorem. This theorem
states that an analog signal can be
uniquely reconstructed, without error,
from samples taken at equal time
intervals if the sampling rate is equal
Sampling Rate = 2(BW) = 2(3300 Hz) = to, or greater than, twice the highest
6600 Samples per Second frequency component in the analog
signal.


Public Switched Telephone Network (PSTN)
Coder-Decoder (CODEC) or ADC / DAC


Pulse Code Modulation
Public Switched Telephone Network (PSTN)

CODECs use a method called
Pulse Code Modulation (PCM)
to convert the analog signals
to digital bit streams. PCM
uses a technique called
sampling to obtain
instantaneous voltage values
at speciﬁc times in the analog
signal cycle. This sample
generates a Pulse Amplitude
Modulated (PAM) signal.


Pro Audio & PCM
Linear PCM (uncompressed), typ. Wordlength (bit depth) from 16 to 24 bits with
sampling frequencies between 44-192kHz

Pulse-code modulation (PCM) is a method used to digitally represent sampled analog
signals. It is the standard form for digital audio in computers and various Blu-ray, DVD and
Compact Disc formats, as well as other uses such as digital telephone systems. A PCM
stream is a digital representation of an analog signal, in which the magnitude of the analog
signal is sampled regularly at uniform intervals, with each sample being quantized to the
nearest value within a range of digital steps.

PCM streams have two basic properties that determine their fidelity to the original analog
signal: the sampling rate, which is the number of times per second that samples are
taken; and the bit depth, which determines the number of possible digital values that
each sample can take.


Audio-over-Ethernet
Linear PCM (Reference – CD is 16 bit resolution, 44.1kHz)



Recording in the 1990’s
• Digital Audio Workstations

• Token Ring Networks for moving
audio data (not real time)

• Evolution of the DSP > Why
shouldn’t the transport be digital?


AES Standards
• 1985 AES3 – AES/EBU
(RS422 Derived)
2 Channels @ 192kHz

• 1991 AES10 – MADI

(FDDI – Fibre Disrtib Data Interface)

56 > 64 Channels @ 96kHz

• 2005 AES50>SuperMAC/
HyperMAC (Midas-KT)
24 Ch @ 96kHz/192 Ch @ 96kHz


Ethernet – Evolution of OSI

Drawing Courtesy of Pro AV

Layer 1 Protocols i.e. A-Net, REAC, Rocknet, AES50

Layer 2 Protocols i.e.EtherSound, CobraNet

Layer 3/4 Protocols i.e. Dante, Livewire, Q-Lan / Q-Sys, RAVENNA,

Emerging Standards - Avnu & AVB

Audio-over-Ethernet
What is it?
Deployment of an Ethernet network to transfer digital audio streams in real-time

Linear PCM (uncompressed), typ. Wordlength (bit depth) from 16 to 24
bits with sampling frequencies between 44-192kHz

• multichannel, high channel count (~60 channels in each direction)

• audo channels are generally bundled in clusters

• low latency (< 6 ms) but with DSP transport expectations = <1ms

• no packet loss in normal operating conditions


Audio-over-Ethernet
(AoE) – why?
Larger maximum distance
(60-70 m with analog cables, ~ 100 m AoE on copper , ~2km AoE on fibre)

rerouting and splitting are now possible
(without manual changes to connections, without manual patch bays)

redundancy at reasonable costs

control data and audio transport can be combined on a single connection

cables are less expensvie and less bulky
64-channel balanced analog multicore (data from Eurocable)
Weight ! around 1,3 kg/m
Cost ! around20 times the cost of a ruggedized CAT5e cable


Audio-over-Ethernet
Ethernet transport (IEEE 802.3)
1980  Ethernet
1985  IEEE 802.3

1990  10 Mbps (10baseT) Used for first AoE implementations CobraNet

Enough bandwidth for reasonable multichannel
1995  100 Mbps (100baseTX) operation

1999  1000 Mbps (1000baseT) Hundreds of channels can be allocated

2002-2008  10 Gbps (10GbaseT)

2007-2011  40/100 Gbps

2010/11  Ethernet AVB


Audio-over-Ethernet


Linear PCM
requirements
ANALOG
SIGNAL One audio channel
48 kHz 96 kHz 192 kHz
24-bit PCM
ADC 1.15 Mbps 2.30 Mbps 4.60 Mbps

Protocol Bit rate (48 Bit rate (96
format Channels
overhead kHz) kHz)

AES/EBU 2 (48, 96, 192 kHz) 25% 3 Mbps 6 Mbps

ADAT 8 (48 kHz) 25% 12.3 Mbps 24.5 Mbps


Audio-over-Ethernet
Ethernet transport
is packet-based
At layer/2 level, in order to ensure compatbility with
Ethernet devices (such as switches, fomat converters) and with electronic
devices it is required to generate frames
starting from audio data

 Compromise between latency, max channel count and cluster size


Audio-over-Ethernet
The User Datagram Protocol (UDP) provides a
very efﬁcient, message oriented encapsulation
for data. It is well suited to real time applications
and forms the basis for the Realtime Transport
Protocol (RTP)


Audio-over-Ethernet

Fewer channels and low latency  optimal
bandwidth
More Channelsand higher latency  usage


Audio-over-Ethernet
Cobranet
• designed on 10 Mbps networks in the 90s, compatible with modern networks
• sync propogation (audio clock) with beat packets
• over 1 million nodes installed worldwide
• designed in USA by Peak Audio
• available as an OEM module
• the technology has been acquired by a silicon foundry
• now available on a single chip
• switch-compatible protocol
• non-audio data traffic can interfere
• latency = 1.33-5 ms, allows routing of low-channel count clusters (bundles)


Audio-over-Ethernet
Ethersound
• designed for 100 Mbps networks
• uses all the available bandwidth, to transfer the maximum number of channels
• designed for maximum reliability and minimum latency (125 us)
• designed in France by Digigram
• available and an OEM module and under license
• compatiile with some switches (verified by the technology provider)
• does not allow simultaneous non/audio data traffic


Audio-over-Ethernet
AES50, HyperMAC

• designed by Sony Oxford labs
• adopted by Midas / Klark Teknik
• now promoted by Midas/KlarkTeknik
• AES50: audio and clock transmission over cat5 and 100BaseT
• 48x48 ch @ 48 kHz
• 24x24 ch @ 96 kHz
• HyperMAC: 256x256 ch on 1000BaseT


Audio-over-Ethernet
Dante
• designed for 1 Gbps networks, external branches can go at 10 Mbps
• clock recovery is based on packet timestamping (IEEE-1588)
• compatible with non-audio traffic (switches need management configuration)
• designed in Australia by Audinate
• available as an OEM module
• native driver on host
• high-performance PCI-Express card available (128x128 ch at 96 kHz)


AudVidBridge & Dante


How Many More RJ45 Jacks…?


Digital Networking Today
The Current State of the Industry
Transport Protocol Wars, It’s a Mess!
Many are Proprietary
Lack of easy digital interoperability
Require multiple cabling topologies and disparate
signal types
Non Standard or Specialized Equipment
Remote Control & Monitoring for Devices is a
Completely Separate Issue (Open Control Alliance)


The Digital Challenge

AES-EBU MADI CobraNet EtherSound Dante

75 Ohm With SD
Digico x
Coax Rack

Avid
75 Ohm
Venue x
Proﬁle Coax

Soundcraft
x CAT5/7 CAT5 CAT 5
Vi

Yamaha
x x CAT5 CAT5/6 CAT6
M7 CL


The Digital Challenge


Solution Examples
AES/EBU Drive + Canbus D&B
PM1D, Link Yamaha system
Midas Pro6 AES50 & HyperMAC
Avid Venue with 6x75 Cable
PM5D, Dante, Dglink,
M7CL ES, EtherSound / Dante DGLink,
LabGruppen
Digico SD7, SD Rack, 6 x75 Cable


AES Drive & Remote

 6 / 12 / 24 AES-EBU

 2 CAT6

 LKA 54 or 85 Pin
Connector


CS1D/DSP1D

 50 Ohm Coax Control

 75 Ohm Coax Word
Clock

 8 – AES-EBU

 34 Pair 26 AWG SCSI


MADI with Multicore


AES50 & HyperMAC


AES50 & HyperMAC
Nobel Peace Prize 2008, Oslo


Redundant Dante with LabGruppen
PLM Series Ampliﬁers

Sender

Switch Switch

Primary Secondary
Receiver
Link Link


Solution Examples


Dual PM5D Ethersound


LS9-32 Dante


M7CL Hybrid ES/Dante


What to Expect

• AVB / AVnu Alliance will Move
Forward
• Open Control Alliance (OCA)
• Dante is a Solution Available Today
and Future Compatible with AVB
• Link will Continue to Track &
Support Multiple Options


One Perspective from the Real World



THANK YOU
Umberto Zanghieri – ZP Engineering S.r.l.
Bob Vanden Burgt - Link USA

Slides & References
www.linkusa-inc.com
Additional Questions
Link at Booth 322


Practical Applications of Digital Audio Networking

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