IEC 62365:2004

INTERNATIONAL IEC
STANDARD 62365
First edition
2004-11
Digital audio –
Digital input-output interfacing –
Transmission of digital audio
over asynchronous transfer mode
(ATM) networks
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INTERNATIONAL IEC
STANDARD 62365
First edition
2004-11
Digital audio –
Digital input-output interfacing –
Transmission of digital audio
over asynchronous transfer mode
(ATM) networks
 IEC 2004  Copyright - all rights reserved
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– 2 – 62365  IEC:2004(E)
CONTENTS
FOREWORD.3

INTRODUCTION.5

1 Scope.7

2 Normative references .7

3 Terms and definitions .7

4 Format of audio data in ATM cells .8

4.1 Format of audio samples .8

4.2 Packing of sample data into cells .11

4.3 Formats.12
4.4 ATM adaptation layer .12
4.5 ATM-user-to-ATM-user indication .13
5 Switched virtual circuits .13
5.1 Addresses .13
5.2 Audio call connection: SETUP and ADD PARTY messages .13
5.3 Call disconnection .15
6 Coding of audio formats .16
6.1 Qualifying information.16
6.2 Subframe format.16
6.3 Packing of subframes into cells .17
6.4 Sampling frequency.17
7 Permanent virtual circuits .18
8 Management interface .18
8.1 Call connection: SETUP messages.18
8.2 Message encapsulation .20
8.3 Message format and action to be taken by recipient .20
8.4 Message types .20

Annex A (informative) Data protection.26
Annex B (informative) Application identifier values.28

Bibliography.29
Table 1 – Fields contained in a subframe.9

Table 2 – Combinations of subframe format and packing scheme .12
Table 3 – Default port number and packing for certain VCIs.18
Table 4 – Status enquiry message.21
Table 5 – Audio connection request message .21
Table 6 – Audio disconnection request message.22
Table 7 – Input port status message .23
Table 8 – Output port status message .24
Table 9 – Other status messages.25
Table 10 – Vendor-specific messages.25
Table A.1 – Sequence number protection field values .26
Table B.1 – Application identifier (octets 9 to 12) values in the BHLI IE.28

62365  IEC:2004(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

___________
DIGITAL AUDIO – DIGITAL INPUT-OUTPUT INTERFACING –

TRANSMISSION OF DIGITAL AUDIO OVER ASYNCHRONOUS

TRANSFER MODE (ATM) NETWORKS
FOREWORD
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International Standard IEC 62365 has been prepared by technical area 4: Digital systems
interfaces and protocols, of IEC technical committee 100: Audio, video and multimedia

systems and equipment.
The text of this standard is based on the following documents:
CDV Report on voting
100/753/CDV 100/838/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 4 – 62365  IEC:2004(E)
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in

the data related to the specific publication. At this date, the publication will be

• reconfirmed;
• withdrawn;
• replaced by a revised edition, or

• amended.
62365  IEC:2004(E) – 5 –
INTRODUCTION
This International Standard describes means for the transmission of professional audio across

digital networks, including metropolitan- and wide-area networks, to provide the best

performance with regard to latency, jitter, and other relevant factors.

Current-generation wide-area communications are based on two very similar systems,

synchronous optical network (SONET) and synchronous digital hierarchy (SDH), SONET being

used in the United States and SDH in Europe. On top of them are run integrated services digital

network (ISDN), asynchronous transfer mode (ATM), and Internet protocol (IP).

ISDN provides telephone call connections of a fixed capacity that carry one 8-bit value per
125 µs; when a call is set up, its route through the system is chosen, and the switches that
route the data are configured accordingly. Each link, between switches or between switch and
end equipment, is formatted into frames that take 125 µs to transmit, and each data byte is
identified by its position in the frame.
ATM, also called broadband ISDN, provides a service similar to ISDN, but with the capacity of
each call being specified by the caller. Links are formatted into cells, which consist of a
header and 48 data bytes; the header is typically 5 bytes long, and most of it is taken up with
the virtual channel identifier (VCI) that shows to which call the cell belongs. Call set-up,
routeing, and switching are done in the same way as in ISDN, but with calls not being
restricted to 1 byte every 125 µs.
IP provides a very different service, not designed for continuous media such as audio and
video. There is no call set-up, and each packet contains enough information within itself to
allow it to be routed to its destination. This means that the header is much larger than in the
case of ATM, typically 74 bytes, and packets will also typically be much larger, if only
because otherwise the overheads would be excessive. Each packet is liable to be routed
separately, so two packets that are part of the same flow may well take different routes. This
can mean that the one that was sent first does not arrive first.
For many professional audio applications, a round-trip time from the microphone through the
mixing desk and back t
...