EtherSound Overview .pdf



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Overview An Introduction
to the ES-100 Technology
Rev. 3.0b
August 29, 2006

Copyright © 2006 Digigram. All rights reserved.
No portion of this document may be reproduced without prior written consent from Digigram. The copyright protection claimed here includes photocopying,
translation and/or reformatting of the information contained in this manual.
While every effort has been made to ensure accuracy, Digigram is not responsible for errors and omissions, and reserves the right to make improvements or
changes in the products and programs described without notice.
Digigram, EtherSound, ES8in, ES8mic, ES8micCL, ES8out, ES220, ES220-L, ES881, ES1241, ES16161, EtherSound ESnet, EtherSound ESnet Evaluation Kit, ES
Reference Design, MS88 Eeprom 300k, MSx88 Eeprom 200k, and S2 Prom 100k are registered trademarks or trademarks of Digigram. Other trademarks are
property of their respective holders.
EtherSound technology is protected by international patents and patent applications, including, but not limited to, the following:
FR 2 829 655, WO 03/023759, US 2003/0050989

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Table of Contents
1 Introduction ..................................................................................................................................................................................................3
2 About this document ..............................................................................................................................................................................4
3 Why EtherSound .......................................................................................................................................................................................5
4 What is EtherSound ................................................................................................................................................................................6
4.1 Ethernet / IEEE 802.3 compatibility ...................................................................................................................................................6
4.2 Audio clock..................................................................................................................................................................................................6
4.3 Timing and Latency of the Digigram Reference Designs ..............................................................................................................6
4.4 Audio format and channels....................................................................................................................................................................7
4.5 Network architecture...............................................................................................................................................................................7
4.5.1 Daisy-chain topology.......................................................................................................................................................................7
4.5.2 A bi-directional high speed, high capacity link using EtherSound ......................................................................................8
4.5.3 Star topology .....................................................................................................................................................................................8
4.5.4 Ring topology and redundancy.....................................................................................................................................................9
4.6 Controlling EtherSound devices ......................................................................................................................................... 10
4.6.1 Introduction .................................................................................................................................................................................... 10
4.6.2 Control by embedded application ............................................................................................................................................ 10
4.6.3 Control by PC based application .............................................................................................................................................. 10
4.6.4 EScontrol application ................................................................................................................................................................... 11
5 Technology available through a licensing program ....................................................................................................... 12
6 Evaluating the EtherSound technology .................................................................................................................................. 13
7 Appendix A: Glossary .......................................................................................................................................................................... 14

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EtherSound
Overview – An introduction to the

technology

1 Introduction
EtherSound is a technology patented by Digigram providing easy-to-implement, deterministic, very low-latency,
synchronized, multi-channel, bi-directional PCM audio transport over standard, switched Ethernet networks.
ES-100 is a 100 MBit/s network implementation, ES-Giga is a 1 GBit/s network implementation.
EtherSound maintains a fully digital path between networked audio devices.


Using an ES-100 100 Mbit/s EtherSound network, up to 64 channels of 48 kHz 24-bit bi-directional
PCM digital audio and bi-directional control data may be transported among the connected devices.



Using an ES-Giga 1 Gbit/s EtherSound network, up to 256 channels of 48 kHz 24-bit bi-directional PCM
digital audio and bi-directional control data may be transported among the connected devices. A data
path is available to carry proprietary control traffic including Ethernet based protocols such as IP.

Launched in 2002, the 100 Mbit/s EtherSound implementation was the first EtherSound implementation
available.
Off-the-shelf Ethernet components (i.e. switches, media converters, etc.) can be used to extend the distance
between the devices on the network (i.e. using optical fiber). A list of tested Ethernet components is available on
the www.ethersound.com.

EtherSound provides a means of communication between EtherSound capable devices:


Providing very low-latency synchronous transport of multiple audio channels



Providing remote control of the connected devices



Allowing the use of standard Ethernet switches

EtherSound is available in off-the-shelf products and is made available to any audio manufacturer through a
flexible licensing program.

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2 About this document
This document reflects the outlines of the ES-100 technology.
More detailed information on how to set up an EtherSound network is available in the document ‘Building
EtherSound networks’.

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EtherSound
Overview – An introduction to the

technology

3 Why EtherSound
With its technical features, EtherSound is suited for any time-critical audio application requiring a large number
of audio channels to be distributed in fields such as Live Sound, theater facilities, or radio broadcast studios.
EtherSound drastically reduces system installation costs compared to analog systems thanks to an easy and
straightforward set-up and extremely flexible re-configuration.

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4 What is EtherSound
4.1 Ethernet / IEEE 802.3 compatibility




The EtherSound technology is compatible with IEEE 802.3x standards and operates on full duplex
switched, Fast Ethernet networks.
o

EtherSound technology includes a proprietary network (Layer 3) protocol developed by
Digigram based on the standard Ethernet (IEEE 802.3) Data Link (Layer 2). It therefore
benefits from many Ethernet compliant hardware solutions available such as switches, CAT5,
CAT6, CAT7 cables, media converters, fiber optics, etc...

o

EtherSound frames are transported via a dedicated Local Area Network (LAN) and require an
available bandwidth of 100 Mbit/s full duplex.

The default connectivity is 100 BaseT using the Ethernet-standard Category 5 cabling and RJ45
connectors.
o



Long distances may be covered using media converters and fiber optic based links.

An EtherSound device combining a traditional power supply with an IEEE 802.3af POE based power
supply can benefit from a power supply redundancy, provided that the previous device, a switch or
another EtherSound device, presents the same feature.

4.2 Audio clock
An EtherSound network is fully synchronous and carries its own clock. All devices are synchronous with the
Primary Master.
An EtherSound network can be synchronized on an external clock such as word clock or AES11.
The Primary Master generates the network audio clock (44.1 or 48 kHz) using either its own local clock or an
external clock. Each downstream EtherSound device (called slave device) derives its clock from the EtherSound
network:



An embedded PLL lowers the audio clock jitter.
Phase varies according to network propagation delay.

External synchronization can be used locally on any slave device, when phase accurate synchronization across
inputs and outputs of several devices is required. Depending on the network architecture, up to eight consequent
devices can be kept in phase. The external synchronization clock has to be in sync with the Primary Master.

4.3 Timing and Latency of the Digigram Reference Designs





6

Typical end-to-end EtherSound transmission time is 5 samples (44.1 kHz or 48 kHz).
a. If including A/D and D/A conversions, this latency is about 1.5 milliseconds, the major part of
this latency being caused by the converters.
Less than 1.4 µs of deterministic latency is added per EtherSound device in a daisy chain.
Inserting a store-and-forward switch typically adds a one-sample latency (about 20 µs @ 48 kHz).

EtherSound
Overview – An introduction to the

technology

4.4 Audio format and channels
ES-100 technology supports up to 64 channels of 44.1 or 48 kHz 24-bit PCM audio.
An ES-100 network is also capable of carrying synchronous audio streams at 96 kHz or 192 kHz.
Any combination is possible, such as:









64 audio streams at 48 kHz
62 audio streams at 48 kHz and one audio stream at 96 kHz
60 audio streams at 48 kHz and one audio stream at 192 kHz
48 audio streams at 48 kHz and 8 audio streams at 96 kHz
32 audio streams at 48 kHz and 16 audio streams at 96 kHz
32 audio streams at 96 kHz
32 audio streams at 48 kHz and 8 audio streams at 192 kHz
16 audio streams at 192 kHz
and so on…

4.5 Network architecture
4.5.1 Daisy-chain topology
The easiest way to connect several EtherSound devices is to use a daisy chain. Each device features two network
ports for easy setup.
A daisy-chain topology allows easily creating EtherSound networks without additional hardware.
The bi-directional audio capabilities of EtherSound allow creating an audio bus. In other words, audio can be
inserted anywhere and is available everywhere.
The first device is the Primary Master. The other devices are called slaves.

PM

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4.5.2 A bi-directional high speed, high capacity link using EtherSound
One specific application of daisy-chain topology consists in building a high speed, high capacity bridge between
two audio devices: the Primary Master writes audio data into the stream which is read by the other device which
in turn writes audio data into the stream read by the Primary Master. In this configuration, 64 channels of 24-bit
48 kHz audio are available in both directions for a combined link capacity of 128 channels.

Single cable
64 ch
64 ch

PM

4.5.3 Star topology
A star topology is a common network topology and requires switches. Use of hubs is strictly forbidden.
Fully IEEE 802.3 compliant, EtherSound supports both unmanaged and managed Level 2 switches.

Embedded
control

A star topology supports uni-directional audio transport only.

Embedded
control

PM

Audio data inserted in each daisy chain is only available to devices located downstream.

8

EtherSound
Overview – An introduction to the

technology

4.5.4 Ring topology and redundancy
A ring topology may be opted for to further increase reliability reasons. This topology is to be considered an
extension of the daisy-chain topology, where the last device is physically connected back to the first.
The Primary Master is designated by the network administrator.

Preferred
Primary Master



In case of a cable failure, the first device after this failure automatically switches to Primary Master
operation. The network remains completely functional, there is no audio channel loss.



In case of a device failure, the same recovery mechanism applies, but - obviously - audio connected to the
failing device is missing.

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4.6 Controlling EtherSound devices
4.6.1 Introduction
Control of EtherSound devices is done by means of write and read functions of EtherSound devices’ internal
registers.




Some of these registers are reserved for control of the technology:
o

Device identification

o

Operational modes

o

Audio routing

o

Network error detection

The other registers are kept free for the product manufacturer to implement specific features.
o

Gain, vu-meter, effect parameters, …

These internal registers may be accessed:


By an embedded application running on the EtherSound device (DSP, microcontroller or FPGA)



Through software running on a computer connected to an EtherSound device.

If required, multiple control applications may manage the network.
The maximum bit rate is 768 kbit/s for write commands.

4.6.2 Control by embedded application
The host interface between the embedded application and the EtherSound technology (internal registers) is
customized by the product manufacturer.

4.6.3 Control by PC based application
A controlling PC is connected through a third physical Ethernet port to access the product’s internal EtherSound
registers or the EtherSound registers of another connected EtherSound device.
Digigram provides a PC/Windows SDK allowing the easy development of a PC-based control application.
No knowledge of the Ethernet protocol is needed as this API provides a strong level of abstraction of the
underlying network.

10

EtherSound
Overview – An introduction to the

technology

4.6.4 EScontrol application
Digigram provides an application using this SDK. The Microsoft Windows-based graphical interface of EScontrol
ensures easy control of an EtherSound network.

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5 Technology available through a licensing program
EtherSound technology is available through a flexible licensing program.
It includes full documentation and a FPGA firmware for easy customization to specific manufacturer needs.

12

EtherSound
Overview – An introduction to the

technology

6 Evaluating the EtherSound technology
The EtherSound Evaluation Board is a ready-to-use platform for testing and evaluating the EtherSound
technology.

(Picture non-contractual)
Each Digigram EtherSound Evaluation Kit comes complete with two EtherSound Evaluation Boards, software and
documentation to help you set-up and test a minimum EtherSound environment.
The Evaluation Boards include a large variety of connections in order to provide a comprehensive range of test
and evaluation capabilities.

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7 Appendix A: Glossary
BROADCAST
A configuration where an equipment transmits
simultaneously towards all the other equipments.
DAISY CHAIN
The Daisy Chain is a network topology where all
devices are “serially” linked one to the other.
ETHERNET
Most used Local Area Network (LAN), originally
developed by Digital Equipment Corporation, Intel
Corporation and Xerox Corporation (DIX),
standardized by the IEEE Committee, ISO
normalized. Standard off-the-shelf components
widely available at reasonable cost.
FPGA
A Field Programmable Gate Array is a
programmable electronic device and allows for
flexible designs along with on the field software
updates.
FRAME
A Frame is a set of characters that are transmitted as
an entity according to a defined format. The frame
follows a coding procedure at the physical level
before emission. The EtherSound Frame is fully
compliant to Ethernet 802.3 standard.
FULL DUPLEX
A transmission is said to be Full Duplex when data
can be transmitted and received simultaneously.

Layers (MAC) from the ISO OSI reference model.
Those different physical layers can interface with the
IEEE 802.2 norm that describes the upper part of
the Link Layer (LLC).
LATENCY
The latency of a device measures the insertion delay
it will add in a system.
MULTICAST
A configuration where an equipment transmits
simultaneously towards a group or list of other
equipment.
PRIMARY MASTER
The first EtherSound device in the network is called
the Primary Master. Besides being a source of audio
for the network, the Primary Master provides the
commands and audio clock.
Slave
The EtherSound devices that are not Primary master
of an EtherSound network are called slaves.
SSI
The Synchronous Serial Interface is the most
common way to send/receive data to/from a
Standard Audio DAC or ADC.
STAR
Star is a network topology where all devices are
connected to a same unit (a switch in the following
picture) that is handling all the communications.
PRIMAR Y
MA STER

GPIO

ES

GPIO stands for General Purpose Inputs Outputs.

Switch 1

HOST PORT

SLAV E 3

SLAV E 1

The Host Port is an interface provided for
communication with a µController or a DSP on an
Application Board.

SLAV E 2
ES

Switch 2

ES

ES

SLAV E 6

SLAV E 4
SLAV E 5
ES

The communication will be performed via the
EtherSound Device Registers.
IEEE 802
Committee created in 1980 that has established
standards for informatics equipment connection.
IEEE 802.3-4-5 describes the Physical and Link
14

ES

ES

UNICAST
A configuration where one equipment transmits
towards a single equipment.

Digigram S.A.

Digigram Inc.

Digigram Asia Pte Ltd.

Parc de Pré Milliet
38330 Montbonnot
FRANCE
Tel: +33 (0)4 76 52 55 01
Fax: +33 (0) 4 76 52 53 07
E-mail: info@digigram.com

2101 Wilson Boulevard, Suite 1004,
Arlington, VA 22201
USA
Tel: +1 703 875 9100
Fax: +1 703 875 9161
E-mail: input@digigram.com

350 Orchard Road - #19-07 Shaw House
Singapore 238868
SINGAPORE
Tel: +65 6291 2234
Fax: +65 6291 3433
E-mail: info_asia@digigram.com

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