IEC 60958-1:2008

IEC 60958-1 ®
Edition 3.0 2008-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Digital audio interface –
Part 1: General
Interface audionumérique –
Partie 1: Généralités
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IEC 60958-1 ®
Edition 3.0 2008-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Digital audio interface –
Part 1: General
Interface audionumérique –
Partie 1: Généralités
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX U
ICS 33.160.01 ISBN 978-2-8322-1469-5

– 2 – IEC 60958-1:2008 © IEC 2008
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Interface format . 8
4.1 Structure of format . 8
4.1.1 Sub-frame format. 8
4.1.2 Frame format . 9
4.2 Channel coding . 9
4.3 Preambles . 10
4.4 Validity bit . 11
5 Channel status . 11
5.1 General . 11
5.2 Applications. 11
5.3 General assignment of the first and second channel status bits . 12
5.4 Category code . 12
6 User data . 14
6.1 General . 14
6.2 Applications. 14
6.2.1 Professional use . 14
6.2.2 Consumer use . 14
7 Electrical requirement . 14
7.1 Consumer application . 14
7.1.1 General . 14
7.1.2 Timing accuracy . 14
7.1.3 Unbalanced line . 15
7.2 Professional application . 18
8 Optical requirements . 18
8.1 Consumer application . 18
8.1.1 Optical specification . 18
8.1.2 Optical connector . 18
8.2 Professional applications . 19
Annex A (informative) The use of the validity bit . 20
Annex B (informative) Application documents and specifications. 21
Annex C (informative) A relationship of the IEC 60958 series families. 22
Annex D (informative) Transmission of CD data other than linear PCM audio . 23
Annex E (informative) The IEC 60958 series conformant data format . 24
Annex F (informative) Stream change . 25
Annex G (informative) Characteristics of optical connection . 27
Bibliography . 29

Figure 1 – Sub-frame format (linear PCM application) . 9
Figure 2 – Frame format . 9
Figure 3 – Channel coding . 10

Figure 4 – Preamble M (shown as 11100010) . 11
Figure 5 – Simplified example of the configuration of the circuit (unbalanced) . 15
Figure 6 – Rise and fall times . 16
Figure 7 – Intrinsic jitter measurement filter . 16
Figure 8 – Eye diagram . 17
Figure 9 – Receiver jitter tolerance template . 17
Figure 10 – Basic optical connection . 18
Figure C.1 – A relationship of IEC 60958 families . 22
Figure F.1 – Audio sources and AV receiver model . 25
Figure F.2 – Switching from linear PCM to non linear PCM . 26
Figure F.3 – Switching from non linear PCM to linear PCM . 26
Figure F.4 – Switching from non-linear PCM to non-linear PCM . 26

Table 1 – Preamble coding . 10
Table 2 – Channel status data format . 13
Table B.1 – Application documents and specifications . 21
Table G.1 – Characteristics of standard optical connection (optical interface) . 27
Table G.2 – Characteristics of optical transmitter (optical interface) . 27
Table G.3 – Characteristics of optical receiver (optical interface) . 28
Table G.4 – Characteristics of fibre optic cable . 28
Table G.5 – Optical power budget for the link with plastic fibre . 28

– 4 – IEC 60958-1:2008 © IEC 2008
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIGITAL AUDIO INTERFACE –
Part 1: General
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard 60958-1 has been prepared by IEC technical committee 100: Audio,
video and multimedia systems and equipment.
This third edition of IEC 60958-1 cancels and replaces the second edition published in 2004
and constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition.
Electrical and optical requirements are removed from IEC 60958-3; they are specified in
IEC 60958-1.
This bilingual version (2014-04) corresponds to the English version, published in 2008-09.
The text of this standard is based on the following documents:
CDV Report on voting
100/1252/CDV 100/1337/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.
The French version of this standard has not been voted upon.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 60958 series, under the general title Digital audio interface, can
be found on the IEC website.
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.
– 6 – IEC 60958-1:2008 © IEC 2008
DIGITAL AUDIO INTERFACE –
Part 1: General
1 Scope
This part of IEC 60958 describes a serial, uni-directional, self-clocking interface for the
interconnection of digital audio equipment for consumer and professional applications.
It provides the basic structure of the interface. Separate documents define items specific to
particular applications.
The interface is primarily intended to carry monophonic or stereophonic programmes,
encoded using linear PCM and with a resolution of up to 24 bits per sample.
When used for other purposes, the interface is able to carry audio data coded other than as
linear PCM coded audio samples. Provision is also made to allow the interface to carry data
related to computer software or signals coded using non-linear PCM. The format specification
for these applications is not part of this standard.
The interface is intended for operation at audio sampling frequencies of 32kHz and above.
Auxiliary information is transmitted along with the programme.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60268-11, Sound system equipment – Part 11: Application of connectors for the
interconnection of sound system components
IEC 60874-17, Connectors for optical fibres and cables – Part 17: Sectional specification for
fibre optic connector – Type F-05 (friction lock)
IEC 60958-3, Digital audio interface – Part 3: Consumer applications
IEC 60958-4, Digital audio interface – Part 4: Professional applications
3 Terms and definitions
For the purpose of this International Standard, the following terms and definitions apply.
3.1
sampling frequency
frequency of the samples representing an audio signal
NOTE When more than one signal is transmitted through the same interface, the sampling frequencies are
identical.
3.2
audio sample word
value of a digital audio sample; representation is linear in 2's complement binary form
NOTE Positive numbers correspond to positive analogue voltages at the input of the analogue-to-digital converter
(ADC).
3.3
auxiliary sample bit
the four least significant bits (LSBs) which can be assigned as auxiliary sample bits and used
for auxiliary information when the number of audio sample bits in the main data field is less
than or equal to 20
3.4
validity bit
bit indicating whether the main data field bits in the sub-frame (time slots 4 to 27 or 8 to 27,
depending on the audio word length as described in 4.1.1) are reliable or not
3.5
channel status
the channel status carries, in a fixed format, information associated with each main data field
channel which is decodable by any interface user
NOTE Examples of information to be carried in the channel status are: length of audio sample words, pre-
emphasis, sampling frequency, time codes, alphanumeric source and destination codes.
3.6
user data
the user data channel is provided to carry any other information
3.7
parity bit
bit provided to permit the detection of an odd number of errors resulting from malfunctions in
the interface
3.8
preamble
specific patterns used for synchronization
NOTE There are three different preambles (see 4.3).
3.9
sub-frame
fixed structure used to carry information (see 4.1.14.1.1 and 4.1.2)
3.10
frame
sequence of two successive and associated sub-frames
3.11
block
group of 192 consecutive frames
NOTE The start of a block is designated by a special sub-frame preamble (see 4.3).
3.12
channel coding
coding method by which the binary digits are represented for transmission through the
interface
– 8 – IEC 60958-1:2008 © IEC 2008
3.13
unit interval (UI)
the shortest nominal time interval in the coding scheme
NOTE There are 128 UI in a sample frame.
3.14
interface jitter
deviation in the timing of interface data transitions (zero crossings) when compared with an
ideal clock
3.15
intrinsic jitter
output interface jitter of a device that is either free-running or is synchronized to a jitter-free
reference
3.16
jitter gain
ratio of the amplitude of jitter components at the output to their amplitude at the
synchronization input to the device under test
4 Interface format
4.1 Structure of format
4.1.1 Sub-frame format
Each sub-frame is divided into 32 time slots, numbered from 0 to 31 (see Figure 1).
Time slots 0 to 3 (preambles) carry one of the three permitted preambles (see 4.1.2 and 4.3;
also see Figure 2).
Time slots 4 to 27 (main data field) carry the audio sample word in linear 2's complement
representation. The most significant bit (MSB) is carried by time slot 27.
When a 24-bit coding range is used, the LSB is in time slot 4 (see Figure 1).
When a 20-bit coding range is used, time slots 8 to 27 carry the audio sample word with
the LSB in time slot 8. Time slots 4 to 7 may be used for other applications. Under
these circumstances, the bits in the time slots 4 to 7 are designated auxiliary sample bits (see
Figure 1).
If the source provides fewer bits than the interface allows (either 20 or 24), the unused LSBs
are set to a logical "0".
For a non-linear PCM audio application or a data application the main data field may carry
any other information.
Time slot 28 (validity bit) carries the validity bit associated with the main data field (see 4.4).
Time slot 29 (user data bit) carries 1 bit of the user data channel associated with the main
data field channel transmitted in the same sub-frame. For the applications, refer to the other
parts of IEC 60958.
Time slot 30 (channel status bit) carries 1 bit of the channel status information associated with
the main data field channel transmitted in the same sub-frame. For details refer to the other
parts of IEC 60958.
Time slot 31 (parity bit) carries a parity bit such that time slots 4 to 31 inclusive carry an even
number of ones and an even number of zeroes (even parity).
NOTE The preambles have even parity as an explicit property.
0 3 4 7 8 27 28 31
L
Sync M
V U C P
Aux Audio s ample word
S
Preamble S
B
B
Validity f lag
User data
Channel s tatus
Parity bit
IEC  1551/08
Figure 1 – Sub-frame format (linear PCM application)
4.1.2 Frame format
A frame is uniquely composed of two sub-frames (see Figure 2). For linear coded audio
applications, the rate of transmission of frames normally corresponds exactly to the source
sampling frequency.
In 2-channel operation mode, the samples taken from both channels are transmitted by time
multiplexing in consecutive sub-frames. The first sub-frame (left or "A" channel in
stereophonic operation and primary channel in monophonic operation) normally starts with
preamble "M". However, the preamble changes to preamble "B" once every 192 frames to
identify the start of the block structure used to organize the channel status information. The
second sub-frame (right or "B" channel in stereophonic operation and secondary channel in
monophonic operation) always starts with preamble "W".
In single channel operation mode in a professional application, the frame format is the same
as in the 2-channel mode. Data is carried in the first sub-frame and may be duplicated in the
second sub-frame. If the second sub-frame is not carrying duplicate data, then time slot 28,
(validity flag) shall be set to logical "1".
NOTE For historical reasons preambles "B", "M" and "W" are, for use in professional applications, referred to as
"Z", "X" and "Y", respectively.
X Y Z Y X Y X
M Channel 1 W Channel 2 B Channel 1 W Channel 2 M Channel 1 W Channel 2 M
Sub - frame Sub -f rame
Frame 191 Frame 0 Frame 1
Start of block
IEC  1552/08
Figure 2 – Frame format
4.2 Channel coding
To minimize the direct current (d.c.) component on the transmission line, to facilitate clock
recovery from the data stream and to make the interface insensitive to the polarity of
connections, time slots 4 to 31 are encoded in biphase-mark.
Each bit to be transmitted is represented by a symbol comprising two consecutive binary
states. The first state of a symbol is always different from the second state of the previous

– 10 – IEC 60958-1:2008 © IEC 2008
symbol. The second state of the symbol is identical to the first if the bit to be transmitted is
logical "0". However, it is different if the bit is logical "1" (see Figure 3).

Clock (twice bit rate)
Source coding
Channel coding (biphase mark)
IEC  1553/08
Figure 3 – Channel coding
4.3 Preambles
Preambles are specific patterns providing synchronization and identification of the sub-frames
and blocks.
To achieve synchronization within one sampling period and to make this process completely
reliable, these patterns violate the biphase-mark code rules, thereby avoiding the possibility of
data imitating the preambles.
A set of three preambles is used. These preambles are transmitted in the time allocated to
four time slots at the start of each sub-frame (time slots 0 to 3), and are represented by eight
successive states. The first state of the preamble is always different from the second state of
the previous symbol (representing the parity bit). Depending on this state the preambles are
as shown in Table 1.
Table 1 – Preamble coding
Preceding state 0 1
Preamble code Channel coding
“B” or “Z” 11101000 00010111 Sub-frame 1 and
(see note to 4.1.2) the start of the block
“M” or “X” 11100010 00011101 Sub-frame 1
“W” or “Y” 11100100 00011011 Sub-frame 2

Like biphase code, these preambles are d.c. free and provide clock recovery. They differ in at
least two states from any valid biphase sequence.
Figure 4 represents preamble "M".
NOTE Owing to the even-parity bit in time slot 31, all preambles start with a transition in the same direction
(see 4.1.1). Thus, only one of these sets of preambles is, in practice, transmitted through the interface. However, it
is necessary for both sets to be decodable because either polarity is possible in a connection.

Clock
Parity
LSB
Lack of transition at bit boundary
IEC  1554/08
Figure 4 – Preamble M (shown as 11100010)
4.4 Validity bit
The validity bit is logical "0" if the information in the main data field is reliable, and it is logical
"1" if it is not. There is no default state for the validity bit.
NOTE For transmissions not using a linear PCM coding, this bit may be set. This is intended to prevent accidental
decoding of non-audio data to analogue before a complete channel status block is received. See annex A.
5 Channel status
5.1 General
For every sub-frame the channel status provides information related to the data carried in the
main data field of that same sub-frame.
Channel status information is organised in a 192-bit block, subdivided into 24 bytes. The first
bit of each block is carried in the frame with preamble "B”. The channel status data format is
defined in Table 2.
The specific organisation depends on the application. In the descriptions, the suffix "0"
designates the first byte or bit. Where channel status bits are combined to form non-binary
values, the least significant bit should be transmitted first, unless otherwise indicated.
5.2 Applications
The primary application is indicated by the first channel status bit (bit 0) of a block as defined
in clause 5.3.
For professional applications refer to IEC 60958-4.
For consumer applications refer to IEC 60958-3.
Secondary applications may be defined within the framework of these primary applications.
Application documents or specifications are listed in Annex B.

– 12 – IEC 60958-1:2008 © IEC 2008
5.3 General assignment of the first and second channel status bits
The first and second channel status bits (bit 0 and bit 1) are specified as follows.
Byte 0
Bit 0 “0” Consumer use of channel status block.
“1” Professional use of channel status block.

Bit 1 “0” Main data field represents linear PCM samples.
“1” Main data field used for other purposes.

5.4 Category code
Channel status including category code is defined in IEC 60958-3 for consumer applications,
these category codes are used for other variations of IEC 60958 for consumer use such as
IEC 61937.
Also channel status is defined in IEC 60958-4 for professional applications, these channel
status are used for other variations for professional use such as SMPTE 337M and others.

Table 2 – Channel status data format

Byte
0 a b
bit 0 1 2 3 4 5 6 7
bit 8 9 10 11 12 13 14 15
bit 16 17 18 19 20 21 22 23
bit 24 25 26 27 28 29 30 31
bit 32 33 34 35 36 37 38 39
bit 40 41 42 43 44 45 46 47
bit 48 49 50 51 52 53 54 55
bit 56 57 58 59 60 61 62 63
bit 64 65 66 67 68 69 70 71
bit 72 73 74 75 76 77 78 79
bit 80 81 82 83 84 85 86 87
bit 88 89 90 91 92 93 94 95
bit 96 97 98 99 100 101 102 103
bit 104 105 106 107 108 109 110 111
bit 112 113 114 115 116 117 118 119
bit 120 121 122 123 124 125 126 127
bit 128 129 130 131 132 133 134 135
bit 136 137 138 139 140 141 142 143
bit 144 145 146 147 148 149 150 151
bit 152 153 154 155 156 157 158 159
bit 160 161 162 163 164 165 166 167
bit 168 169 170 171 172 173 174 175
bit 176 177 178 179 180 181 182 183
bit 184 185 186 187 188 189 190 191
a: use of channel status block.
b: linear PCM identification.
– 14 – IEC 60958-1:2008 © IEC 2008
6 User data
6.1 General
The default value of the user bits is logical "0".
6.2 Applications
6.2.1 Professional use
User data may be used in any way required by the user. Application details are described in
IEC 60958-4.
6.2.2 Consumer use
The application of the user data in digital audio equipment for consumer use is according to
rules described in IEC 60958-3.
7 Electrical requirement
7.1 Consumer application
7.1.1 General
Two types of transmission lines are defined: unbalanced line and optical fibre.
7.1.2 Timing accuracy
7.1.2.1 Accuracy of sampling frequency (clock accuracy)
Three levels of sampling frequency accuracy are defined to meet various requirements of the
frequency accuracy. These levels shall be indicated in the channel status data.
7.1.2.1.1 Level I: high-accuracy mode
–6
The transmitted sampling frequency shall be within a tolerance of ±50 × 10 .
7.1.2.1.2 Level II: normal-accuracy mode
–6
The transmitted sampling frequency shall be within a tolerance of ±1 000 × 10 .
7.1.2.1.3 Level III: variable pitch shifted clock mode
The signal in this mode can be received by specially designed receivers.
NOTE The frequency range is under consideration. A range of ±12,5 % is envisaged.
7.1.2.1.4 Interface frame rate not matched to sampling frequency
This state is used to indicate high speed and other transfers where the interface does not
carry an embedded sampling frequency clock.
7.1.2.2 Receiver locking range
By default, receivers should be able to lock to signals of level II accuracy with respect to the
supported standard sampling frequencies.

If a receiver is only capable of normal operation with a narrower locking range, then this
range should exceed the sample frequency tolerance of level I and it shall be specified as a
level I receiver.
If a receiver is capable of normal operation at sample rate variations corresponding to level III,
then this shall be specified as a level III receiver.
NOTE Until the range for level III has been defined the frequency range supported by a level III receiver should
be at least ±12,5 %. For clarity the actual value should be specified.
7.1.2.3 Receiver sampling frequency support
The product specification or application standard may define the sampling frequencies that
shall be supported by a receiver. In the absence of such a definition the receiver shall support
32 kHz, 44,1 kHz and 48 kHz operation.
7.1.3 Unbalanced line
7.1.3.1 General characteristics
The interconnecting cable shall be unbalanced and screened (shielded) with a nominal
characteristic impedance of (75 ± 26,25) Ω at frequencies from 0,1 MHz to 128 times the
maximum frame rate.
The transmission circuit configuration shown in Figure 5 may be used.

Transmitter Interconnecting cable Receiver

IEC  1555/08
Figure 5 – Simplified example of the configuration of the circuit (unbalanced)
NOTE For implementation additional components may be needed. A transformer in the transmitter with a floating
(non-earthed) secondary can be used to avoid any potential earth loops and provide a useful bandwidth limitation
to reduce high-frequency radiation.
7.1.3.2 Line driver characteristics
7.1.3.2.1 Output impedance
The line driver shall have an unbalanced output with an internal impedance of (75 ± 15) Ω,
when measured at the terminals to which the line is connected, at frequencies from 0,1 MHz
to 128 times the maximum frame rate.
7.1.3.2.2 Signal amplitude
The signal amplitude shall be (0,5 ± 0,1) V peak-to-peak, when measured across a (75 ± 0,75) Ω
resistor connected to the output terminals, without any interconnecting cable present.

– 16 – IEC 60958-1:2008 © IEC 2008
7.1.3.2.3 DC output voltage
The d.c. voltage shall be less than 0,05 V, when measured across a (75 ± 0,75) Ω resistor
connected to the output terminals, without any interconnecting cable present.
7.1.3.2.4 Rise and fall times
The time difference between the 10 % and 90 % points of any transition shall be less than
0,4 UI (see Figure 6).
1,0 UI 1,0 UI
90 %
50 %
10 %
< 0,4 UI < 0,4 UI
IEC  1556/08
Figure 6 – Rise and fall times

7.1.3.2.5 Intrinsic jitter
The peak intrinsic output jitter measured at all the data transition zero crossings shall be less
than 0,05 UI when measured with the intrinsic jitter measurement filter.
NOTE This applies both when the equipment is locked to an effectively jitter-free timing reference (which may be
a modulated digital audio signal) and when the equipment is free-running.
The jitter weighting filter is shown in Figure 7. It is a minimum-phase high pass filter with a
3 dB frequency of 700 Hz, a first order roll-off to 70 Hz and with a passband gain of unity.

700 Hz, −3 dB
−10
−20
70 Hz, −20 dB
−30
1 2 3 4 5 6 7
10 10 10 10 10 10 10
Jitter frequency  (Hz)
IEC  1557/08
Figure 7 – Intrinsic jitter measurement filter
7.1.3.2.6 Jitter gain or peaking
The sinusoidal jitter gain from any timing reference input to the signal output shall be less
than 3 dB at all frequencies.
Gain  (dB)
7.1.3.3 Line receiver characteristics
7.1.3.3.1 Terminating impedance
The receiver shall present a substantially resistive impedance of (75 ± 3,75) Ω to the inter-
connecting cable over the frequency band 0,1 MHz to 128 times the maximum frame rate.
7.1.3.3.2 Maximum input signals
The receiver shall correctly interpret the data when presented with a signal whose peak-to-
peak voltage, measured in accordance with 7.1.3.2.2, is 0,6 V.
7.1.3.3.3 Minimum input signals
The receiver shall correctly sense the data when a random input signal produces the eye
diagram characterized by a V of 200 mV and T of 0,5 UI (see Figure 8).
min min
Figure 8 – Eye diagram
NOTE This diagram does not define the tolerance to deviation in the zero crossings. These are defined by the
jitter tolerance template in 7.1.3.3.4, which requires that the minimum pulse width is not smaller than 0,8 UI.
7.1.3.3.4 Receiver jitter tolerance
An interface data receiver should correctly decode an incoming data stream with any
sinusoidal jitter defined by the jitter tolerance template of Figure 9.
5 Hz, 10 UI
200 Hz, 0,25 UI
>400 kHz, 0,2 UI
0,1
4 5 6
0 1 2 3
10 10 10
10 10 10 10
Jitter frequency  (Hz)
IEC  1559/08
Figure 9 – Receiver jitter tolerance template
NOTE The template requires a jitter tolerance of 0,2 UI peak-to-peak at frequencies above 400 kHz, 0,25 UI
between 400 kHz and 200 Hz, increasing with the inverse of frequency below 200 Hz to level off at 10 UI peak-to-
peak below 5 Hz.
Jitter tolerance  (UI)
– 18 – IEC 60958-1:2008 © IEC 2008
7.1.3.4 Connectors
The standard connector for both outputs and inputs shall be the free pin connector and fixed
socket connector described in 8.6 of Table IV of IEC 60268-11.
A male plug shall be used at both ends of the cable.
Equipment manufacturers shall clearly label digital audio inputs and outputs.
7.2 Professional application
Electrical requirements for professional applications are described in IEC 60958-4.
8 Optical requirements
8.1 Consumer application
8.1.1 Optical specification
8.1.1.1 Configuration of optical connection
The basic optical connection configuration is shown in Figure 10. The optical matching values
are described in Annex G, these values apply at the reference points 2 and 3.
The overall characteristics of a fibre optic cable plant are described in IEC 60793-2 and
IEC 60794-2 for fibre and cable and in IEC 60874-1 for the connectors.
The reference points 1 and 4 apply to the electrical input and output of the electro-optical and
opto-electrical converter respectively. Detailed specifications are provided only in relation to
optical reference points 2 and 3.

Receiver :
Transmitter :
Fibre optic
Optial to
Electrical to
cable plant
electorical
opitcal
1 2 3 4
IEC  1560/08
Figure 10 – Basic optical connection
In Figure 10, reference point 1 is the electrical input of the optical transmitter, reference
point 2 is the optical interface between optical transmitter and FOCP, reference point 3 is the
optical interface between FOCP and optical receiver and reference point 4 is the electrical
output of the optical receiver. FOCP means fibre optic cable plant that is the serial
combination of fibre optic cable sections, connectors and splices providing the optical path
between two terminal devices, between two optical devices or between terminal devices and
an optical device.
8.1.2 Optical connector
8.1.2.1 Circular type
Refer to EIAJ RC-5720B (see Bibliography).

8.1.2.2 Rectangular type
Refer to IEC 60874-17.
8.2 Professional applications
Optical requirements for professional applications are described in IEC 60958-4.

– 20 – IEC 60958-1:2008 © IEC 2008
Annex A
(informative)
The use of the validity bit
The IEC 60958 series is based on two different industry standards: the AES/EBU digital audio
interface standard (AES3 and EBU Tech. 3250-E) and the digital interface specification by
Sony and Philips (Sony-Philips Digital Interface Format (SPDIF)) introduced with the Compact
Disc Digital Audio system.
Unfortunately, significant differences between the two standards exist, which can contribute in
part to the different application areas: professional and consumer. The differences have
contributed to many misunderstandings about the use and compatibility of the standards.
Originally, the definition of validity was, in both industry standards, that it indicated whether or
not the associated audio sample was "secure and error free". Although, at first glance this
may seem a clear definition, in practice it has led to important practical problems. It is unclear
how the receiver should interpret this. When the sample is signalled not to be in error, it is not
clear whether the transmitter has performed a successful concealment. If a sample is
signalled in error, it is not clear whether the sample should be passed on unchanged,
concealed or muted.
As a result, the AES has adopted in the 1992 revision of the AES3 standard a different
wording: Validity indicates "whether the audio sample bits are suitable for conversion to an
analogue audio signal".
Over the years, the application of the IEC 60958 series has gained popularity, resulting in a
growing number of products conforming to its provisions. With these in use, applications other
than strictly linear PCM audio transmission started to appear as well. The same basic frame
structure is used, but the information transferred in the "audio sample word" is not encoded as
linear PCM audio. As it is not always clearly indicated what kind of signal is carried,
connection of such a transmitter to a linear PCM receiver may result in a very loud and noisy
audio signal.
Therefore, it has been proposed in the revision of IEC 60958 to also adopt the wor
...

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IEC 60958-1 ®
Edition 3.1 2014-04
CONSOLIDATED
VERSION
VERSION
CONSOLIDÉE
colour
inside
Digital audio interface –
Part 1: General
Interface audionumérique –
Partie 1: Généralités
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.160.01 ISBN 978-2-8322-1561-6

IEC 60958-1 ®
Edition 3.1 2014-04
REDLINE VERSION
VERSION REDLINE
colour
inside
Digital audio interface –
Part 1: General
Interface audionumérique –
Partie 1: Généralités
– 2 – IEC 60958-1:2008
+AMD1:2014 CSV © IEC 2014
CONTENTS
FOREWORD . 4

INTRODUCTION to Amendment 1 . 6

1 Scope . 7

2 Normative references . 7

3 Terms and definitions . 7

4 Interface format . 9

4.1 Structure of format . 9
4.1.1 Sub-frame format. 9
4.1.2 Frame format . 10
4.2 Channel coding . 10
4.3 Preambles . 11
4.4 Validity bit . 12
5 Channel status . 12
5.1 General . 12
5.2 Applications. 12
5.3 General assignment of the first and second channel status bits . 13
5.4 Category code . 13
6 User data . 15
6.1 General . 15
6.2 Applications. 15
6.2.1 Professional use . 15
6.2.2 Consumer use . 15
7 Electrical requirement . 15
7.1 Consumer application . 15
7.1.1 General . 15
7.1.2 Timing accuracy . 15
7.1.3 Unbalanced line . 16
7.2 Professional application . 19
8 Optical requirements . 19
8.1 Consumer application . 19

8.1.1 Optical specification . 19
8.1.2 Optical connector . 19
8.2 Professional applications . 20
Annex A (informative) The use of the validity bit . 21
Annex B (informative) Application documents and specifications. 22
Annex C (informative) A relationship of the IEC 60958 series families. 23
Annex D (informative) Transmission of CD data other than linear PCM audio . 26
Annex E (informative) The IEC 60958 series conformant data format . 27
Annex F (informative) Stream change . 28
Annex G (informative) Characteristics of optical connection . 30
Bibliography . 32

Figure 1 – Sub-frame format (linear PCM application) . 10

+AMD1:2014 CSV © IEC 2014
Figure 2 – Frame format . 10

Figure 3 – Channel coding . 11

Figure 4 – Preamble M (shown as 11100010) . 12

Figure 5 – Simplified example of the configuration of the circuit (unbalanced) . 16

Figure 6 – Rise and fall times . 17

Figure 7 – Intrinsic jitter measurement filter . 17

Figure 8 – Eye diagram . 18

Figure 9 – Receiver jitter tolerance template . 18

Figure 10 – Basic optical connection . 19
Figure C.1 – A Relationships of the IEC 60958 families . 24
Figure F.1 – Audio sources and AV receiver model . 28
Figure F.2 – Switching from linear PCM to non linear PCM . 29
Figure F.3 – Switching from non linear PCM to linear PCM . 29
Figure F.4 – Switching from non-linear PCM to non-linear PCM . 29

Table 1 – Preamble coding . 11
Table 2 – Channel status data format . 14
Table B.1 – Application documents and specifications . 22
Table C.1 – data_type values and application . 25
Table G.1 – Characteristics of standard optical connection (optical interface) . 30
Table G.2 – Characteristics of optical transmitter (optical interface) . 30
Table G.3 – Characteristics of optical receiver (optical interface) . 31
Table G.4 – Characteristics of fibre optic cable . 31
Table G.5 – Optical power budget for the link with plastic fibre . 31

– 4 – IEC 60958-1:2008
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INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
DIGITAL AUDIO INTERFACE –
Part 1: General
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

This Consolidated version of IEC 60958-1 bears the edition number 3.1. It consists of
the third edition (2008-09) [documents 100/1252/CDV and 100/1337/RVC] and its
amendment 1 (2014-04) [documents 100/2164/CDV and 100/2253/RVC]. The technical
content is identical to the base edition and its amendment.
In this Redline version, a vertical line in the margin shows where the technical content
is modified by amendment 1. Additions and deletions are displayed in red, with
deletions being struck through. A separate Final version with all changes accepted is
available in this publication.
This publication has been prepared for user convenience.

+AMD1:2014 CSV © IEC 2014
International Standard 60958-1 has been prepared by IEC technical committee 100: Audio,
video and multimedia systems and equipment.

This edition includes the following significant technical changes with respect to the previous
edition.
Electrical and optical requirements are removed from IEC 60958-3; they are specified in
IEC 60958-1.
The French version of this standard has not been voted upon.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 60958 series, under the general title Digital audio interface, can
be found on the IEC website.
The committee has decided that the contents of the base publication and its amendment will
remain unchanged until the stability 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.
IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.

– 6 – IEC 60958-1:2008
+AMD1:2014 CSV © IEC 2014
INTRODUCTION to Amendment 1
The revision of IEC 60958-1:2008 has become necessary in order to revise Annexes B and C,

and the Bibliography. Additional information for the use of the IEC 60958 conformant data

format has also been included.

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DIGITAL AUDIO INTERFACE –
Part 1: General
1 Scope
This part of IEC 60958 describes a serial, uni-directional, self-clocking interface for the

interconnection of digital audio equipment for consumer and professional applications.
It provides the basic structure of the interface. Separate documents define items specific to
particular applications.
The interface is primarily intended to carry monophonic or stereophonic programmes,
encoded using linear PCM and with a resolution of up to 24 bits per sample.
When used for other purposes, the interface is able to carry audio data coded other than as
linear PCM coded audio samples. Provision is also made to allow the interface to carry data
related to computer software or signals coded using non-linear PCM. The format specification
for these applications is not part of this standard.
The interface is intended for operation at audio sampling frequencies of 32kHz and above.
Auxiliary information is transmitted along with the programme.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60268-11, Sound system equipment – Part 11: Application of connectors for the
interconnection of sound system components
IEC 60874-17, Connectors for optical fibres and cables – Part 17: Sectional specification for
fibre optic connector – Type F-05 (friction lock)
IEC 60958-3, Digital audio interface – Part 3: Consumer applications

IEC 60958-4, Digital audio interface – Part 4: Professional applications
3 Terms and definitions
For the purpose of this International Standard, the following terms and definitions apply.
3.1
sampling frequency
frequency of the samples representing an audio signal
NOTE When more than one signal is transmitted through the same interface, the sampling frequencies are
identical.
– 8 – IEC 60958-1:2008
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3.2
audio sample word
value of a digital audio sample; representation is linear in 2's complement binary form

NOTE Positive numbers correspond to positive analogue voltages at the input of the analogue-to-digital converter

(ADC).
3.3
auxiliary sample bit
the four least significant bits (LSBs) which can be assigned as auxiliary sample bits and used

for auxiliary information when the number of audio sample bits in the main data field is less

than or equal to 20
3.4
validity bit
bit indicating whether the main data field bits in the sub-frame (time slots 4 to 27 or 8 to 27,
depending on the audio word length as described in 4.1.1) are reliable or not
3.5
channel status
the channel status carries, in a fixed format, information associated with each main data field
channel which is decodable by any interface user
NOTE Examples of information to be carried in the channel status are: length of audio sample words, pre-
emphasis, sampling frequency, time codes, alphanumeric source and destination codes.
3.6
user data
the user data channel is provided to carry any other information
3.7
parity bit
bit provided to permit the detection of an odd number of errors resulting from malfunctions in
the interface
3.8
preamble
specific patterns used for synchronization
NOTE There are three different preambles (see 4.3).
3.9
sub-frame
fixed structure used to carry information (see 4.1.14.1.1 and 4.1.2)
3.10
frame
sequence of two successive and associated sub-frames
3.11
block
group of 192 consecutive frames
NOTE The start of a block is designated by a special sub-frame preamble (see 4.3).
3.12
channel coding
coding method by which the binary digits are represented for transmission through the
interface
+AMD1:2014 CSV © IEC 2014
3.13
unit interval (UI)
the shortest nominal time interval in the coding scheme

NOTE There are 128 UI in a sample frame.

3.14
interface jitter
deviation in the timing of interface data transitions (zero crossings) when compared with an

ideal clock
3.15
intrinsic jitter
output interface jitter of a device that is either free-running or is synchronized to a jitter-free
reference
3.16
jitter gain
ratio of the amplitude of jitter components at the output to their amplitude at the
synchronization input to the device under test
4 Interface format
4.1 Structure of format
4.1.1 Sub-frame format
Each sub-frame is divided into 32 time slots, numbered from 0 to 31 (see Figure 1).
Time slots 0 to 3 (preambles) carry one of the three permitted preambles (see 4.1.2 and 4.3;
also see Figure 2).
Time slots 4 to 27 (main data field) carry the audio sample word in linear 2's complement
representation. The most significant bit (MSB) is carried by time slot 27.
When a 24-bit coding range is used, the LSB is in time slot 4 (see Figure 1).
When a 20-bit coding range is used, time slots 8 to 27 carry the audio sample word with
the LSB in time slot 8. Time slots 4 to 7 may be used for other applications. Under
these circumstances, the bits in the time slots 4 to 7 are designated auxiliary sample bits (see
Figure 1).
If the source provides fewer bits than the interface allows (either 20 or 24), the unused LSBs
are set to a logical "0".
For a non-linear PCM audio application or a data application the main data field may carry
any other information.
Time slot 28 (validity bit) carries the validity bit associated with the main data field (see 4.4).
Time slot 29 (user data bit) carries 1 bit of the user data channel associated with the main
data field channel transmitted in the same sub-frame. For the applications, refer to the other
parts of IEC 60958.
Time slot 30 (channel status bit) carries 1 bit of the channel status information associated with
the main data field channel transmitted in the same sub-frame. For details refer to the other
parts of IEC 60958.
– 10 – IEC 60958-1:2008
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Time slot 31 (parity bit) carries a parity bit such that time slots 4 to 31 inclusive carry an even

number of ones and an even number of zeroes (even parity).

NOTE The preambles have even parity as an explicit property.

0 3 4 7 8 27 28 31
L
Sync M
V U C P
Aux Audio s ample word
S
Preamble S
B
B
Validity f lag
User data
Channel s tatus
Parity bit
IEC  1551/08
Figure 1 – Sub-frame format (linear PCM application)
4.1.2 Frame format
A frame is uniquely composed of two sub-frames (see Figure 2). For linear coded audio
applications, the rate of transmission of frames normally corresponds exactly to the source
sampling frequency.
In 2-channel operation mode, the samples taken from both channels are transmitted by time
multiplexing in consecutive sub-frames. The first sub-frame (left or "A" channel in
stereophonic operation and primary channel in monophonic operation) normally starts with
preamble "M". However, the preamble changes to preamble "B" once every 192 frames to
identify the start of the block structure used to organize the channel status information. The
second sub-frame (right or "B" channel in stereophonic operation and secondary channel in
monophonic operation) always starts with preamble "W".
In single channel operation mode in a professional application, the frame format is the same
as in the 2-channel mode. Data is carried in the first sub-frame and may be duplicated in the
second sub-frame. If the second sub-frame is not carrying duplicate data, then time slot 28,
(validity flag) shall be set to logical "1".
NOTE For historical reasons preambles "B", "M" and "W" are, for use in professional applications, referred to as
"Z", "X" and "Y", respectively.
X Y Z Y X Y X
M Channel 1 W Channel 2 B Channel 1 W Channel 2 M Channel 1 W Channel 2 M
Sub - frame Sub -f rame
Frame 191 Frame 0 Frame 1
Start of block
IEC  1552/08
Figure 2 – Frame format
4.2 Channel coding
To minimize the direct current (d.c.) component on the transmission line, to facilitate clock
recovery from the data stream and to make the interface insensitive to the polarity of
connections, time slots 4 to 31 are encoded in biphase-mark.
Each bit to be transmitted is represented by a symbol comprising two consecutive binary
states. The first state of a symbol is always different from the second state of the previous

+AMD1:2014 CSV © IEC 2014
symbol. The second state of the symbol is identical to the first if the bit to be transmitted is

logical "0". However, it is different if the bit is logical "1" (see Figure 3).

Clock (twice bit rate)
Source coding
Channel coding (biphase mark)
IEC  1553/08
Figure 3 – Channel coding
4.3 Preambles
Preambles are specific patterns providing synchronization and identification of the sub-frames
and blocks.
To achieve synchronization within one sampling period and to make this process completely
reliable, these patterns violate the biphase-mark code rules, thereby avoiding the possibility of
data imitating the preambles.
A set of three preambles is used. These preambles are transmitted in the time allocated to
four time slots at the start of each sub-frame (time slots 0 to 3), and are represented by eight
successive states. The first state of the preamble is always different from the second state of
the previous symbol (representing the parity bit). Depending on this state the preambles are
as shown in Table 1.
Table 1 – Preamble coding
Preceding state 0 1
Preamble code Channel coding
“B” or “Z” 11101000 00010111 Sub-frame 1 and
(see note to 4.1.2) the start of the block
“M” or “X” 11100010 00011101 Sub-frame 1
“W” or “Y” 11100100 00011011 Sub-frame 2

Like biphase code, these preambles are d.c. free and provide clock recovery. They differ in at
least two states from any valid biphase sequence.
Figure 4 represents preamble "M".
NOTE Owing to the even-parity bit in time slot 31, all preambles start with a transition in the same direction
(see 4.1.1). Thus, only one of these sets of preambles is, in practice, transmitted through the interface. However, it
is necessary for both sets to be decodable because either polarity is possible in a connection.

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Clock
Parity
LSB
Lack of transition at bit boundary
IEC  1554/08
Figure 4 – Preamble M (shown as 11100010)
4.4 Validity bit
The validity bit is logical "0" if the information in the main data field is reliable, and it is logical
"1" if it is not. There is no default state for the validity bit.
NOTE For transmissions not using a linear PCM coding, this bit may be set. This is intended to prevent accidental
decoding of non-audio data to analogue before a complete channel status block is received. See annex A.
5 Channel status
5.1 General
For every sub-frame the channel status provides information related to the data carried in the
main data field of that same sub-frame.
Channel status information is organised in a 192-bit block, subdivided into 24 bytes. The first
bit of each block is carried in the frame with preamble "B”. The channel status data format is
defined in Table 2.
The specific organisation depends on the application. In the descriptions, the suffix "0"
designates the first byte or bit. Where channel status bits are combined to form non-binary
values, the least significant bit should be transmitted first, unless otherwise indicated.
5.2 Applications
The primary application is indicated by the first channel status bit (bit 0) of a block as defined
in clause 5.3.
For professional applications refer to IEC 60958-4.
For consumer applications refer to IEC 60958-3.
Secondary applications may be defined within the framework of these primary applications.
Application documents or specifications are listed in Annex B.

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5.3 General assignment of the first and second channel status bits

The first and second channel status bits (bit 0 and bit 1) are specified as follows.

Byte 0
Bit 0 “0” Consumer use of channel status block.

“1” Professional use of channel status block.

Bit 1 “0” Main data field represents linear PCM samples.

“1” Main data field used for other purposes.

5.4 Category code
Channel status including category code is defined in IEC 60958-3 for consumer applications,
these category codes are used for other variations of IEC 60958 for consumer use such as
IEC 61937.
Also channel status is defined in IEC 60958-4 for professional applications, these channel
status are used for other variations for professional use such as SMPTE 337M and others.

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Table 2 – Channel status data format

Byte
0 a b
bit 0 1 2 3 4 5 6 7
bit 8 9 10 11 12 13 14 15
bit 16 17 18 19 20 21 22 23
bit 24 25 26 27 28 29 30 31
bit 32 33 34 35 36 37 38 39
bit 40 41 42 43 44 45 46 47
bit 48 49 50 51 52 53 54 55
bit 56 57 58 59 60 61 62 63
bit 64 65 66 67 68 69 70 71
bit 72 73 74 75 76 77 78 79
bit 80 81 82 83 84 85 86 87
bit 88 89 90 91 92 93 94 95
bit 96 97 98 99 100 101 102 103
bit 104 105 106 107 108 109 110 111
bit 112 113 114 115 116 117 118 119
bit 120 121 122 123 124 125 126 127
bit 128 129 130 131 132 133 134 135
bit 136 137 138 139 140 141 142 143
bit 144 145 146 147 148 149 150 151
bit 152 153 154 155 156 157 158 159
bit 160 161 162 163 164 165 166 167
bit 168 169 170 171 172 173 174 175
bit 176 177 178 179 180 181 182 183
bit 184 185 186 187 188 189 190 191
a: use of channel status block.
b: linear PCM identification.
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6 User data
6.1 General
The default value of the user bits is logical "0".

6.2 Applications
6.2.1 Professional use
User data may be used in any way required by the user. Application details are described in

IEC 60958-4.
6.2.2 Consumer use
The application of the user data in digital audio equipment for consumer use is according to
rules described in IEC 60958-3.
7 Electrical requirement
7.1 Consumer application
7.1.1 General
Two types of transmission lines are defined: unbalanced line and optical fibre.
7.1.2 Timing accuracy
7.1.2.1 Accuracy of sampling frequency (clock accuracy)
Three levels of sampling frequency accuracy are defined to meet various requirements of the
frequency accuracy. These levels shall be indicated in the channel status data.
7.1.2.1.1 Level I: high-accuracy mode
–6
The transmitted sampling frequency shall be within a tolerance of ±50 × 10 .
7.1.2.1.2 Level II: normal-accuracy mode
–6
The transmitted sampling frequency shall be within a tolerance of ±1 000 × 10 .

7.1.2.1.3 Level III: variable pitch shifted clock mode
The signal in this mode can be received by specially designed receivers.
NOTE The frequency range is under consideration. A range of ±12,5 % is envisaged.
7.1.2.1.4 Interface frame rate not matched to sampling frequency
This state is used to indicate high speed and other transfers where the interface does not
carry an embedded sampling frequency clock.
7.1.2.2 Receiver locking range
By default, receivers should be able to lock to signals of level II accuracy with respect to the
supported standard sampling frequencies.

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If a receiver is only capable of normal operation with a narrower locking range, then this

range should exceed the sample frequency tolerance of level I and it shall be specified as a

level I receiver.
If a receiver is capable of normal operation at sample rate variations corresponding to level III,

then this shall be specified as a level III receiver.

NOTE Until the range for level III has been defined the frequency range supported by a level III receiver should

be at least ±12,5 %. For clarity the actual value should be specified.

7.1.2.3 Receiver sampling frequency support

The product specification or application standard may define the sampling frequencies that
shall be supported by a receiver. In the absence of such a definition the receiver shall support
32 kHz, 44,1 kHz and 48 kHz operation.
7.1.3 Unbalanced line
7.1.3.1 General characteristics
The interconnecting cable shall be unbalanced and screened (shielded) with a nominal
characteristic impedance of (75 ± 26,25) Ω at frequencies from 0,1 MHz to 128 times the
maximum frame rate.
The transmission circuit configuration shown in Figure 5 may be used.

Transmitter Interconnecting cable Receiver

IEC  1555/08
Figure 5 – Simplified example of the configuration of the circuit (unbalanced)
NOTE For implementation additional components may be needed. A transformer in the transmitter with a floating
(non-earthed) secondary can be used to avoid any potential earth loops and provide a useful bandwidth limitation
to reduce high-frequency radiation.
7.1.3.2 Line driver characteristics
7.1.3.2.1 Output impedance
The line driver shall have an unbalanced output with an internal impedance of (75 ± 15) Ω,
when measured at the terminals to which the line is connected, at frequencies from 0,1 MHz
to 128 times the maximum frame rate.
7.1.3.2.2 Signal amplitude
The signal amplitude shall be (0,5 ± 0,1) V peak-to-peak, when measured across a (75 ± 0,75) Ω
resistor connected to the output terminals, without any interconnecting cable present.

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7.1.3.2.3 DC output voltage
The d.c. voltage shall be less than 0,05 V, when measured across a (75 ± 0,75) Ω resistor

connected to the output terminals, without any interconnecting cable present.

7.1.3.2.4 Rise and fall times
The time difference between the 10 % and 90 % points of any transition shall be less than
0,4 UI (see Figure 6).
1,0 UI 1,0 UI
90 %
50 %
10 %
< 0,4 UI < 0,4 UI
IEC  1556/08
Figure 6 – Rise and fall times

7.1.3.2.5 Intrinsic jitter
The peak intrinsic output jitter measured at all the data transition zero crossings shall be less
than 0,05 UI when measured with the intrinsic jitter measurement filter.
NOTE This applies both when the equipment is locked to an effectively jitter-free timing reference (which may be
a modulated digital audio signal) and when the equipment is free-running.
The jitter weighting filter is shown in Figure 7. It is a minimum-phase high pass filter with a
3 dB frequency of 700 Hz, a first order roll-off to 70 Hz and with a passband gain of unity.

700 Hz, −3 dB
−10
−20
70 Hz, −20 dB
−30
1 2 3 4 5 6 7
10 10 10 10 10 10 10
Jitter frequency  (Hz)
IEC  1557/08
Figure 7 – Intrinsic jitter measurement filter
7.1.3.2.6 Jitter gain or peaking
The sinusoidal jitter gain from any timing reference input to the signal output shall be less
than 3 dB at all frequencies.
Gain  (dB)
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7.1.3.3 Line receiver characteristics

7.1.3.3.1 Terminating impedance

The receiver shall present a substantially resistive impedance of (75 ± 3,75) Ω to the inter-
connecting cable over the frequency band 0,1 MHz to 128 times the maximum frame rate.

7.1.3.3.2 Maximum input signals

The receiver shall correctly interpret the data when presented with a signal whose peak-to-

peak voltage, measured in accordance with 7.1.3.2.2, is 0,6 V.

7.1.3.3.3 Minimum input signals
The receiver shall correctly sense the data when a random input signal produces the eye
diagram characterized by a V of 200 mV and T of 0,5 UI (see Figure 8).
min min
Figure 8 – Eye diagram
NOTE This diagram does not define the tolerance to deviation in the zero crossings. These are defined by the
jitter tolerance template in 7.1.3.3.4, which requires that the minimum pulse width is not smaller than 0,8 UI.
7.1.3.3.4 Receiver jitter tolerance
An interface data receiver should correctly decode an incoming data stream with any
sinusoidal jitter defined by the jitter tolerance template of Figure 9.
5 Hz, 10 UI
200 Hz, 0,25 UI
>400 kHz, 0,2 UI
0,1
4 5 6
0 1 2 3
10 10 10
10 10 10 10
Jitter frequency  (Hz)
IEC  1559/08
Figure 9 – Receiver jitter tolerance template
NOTE The template requires a jitter tolerance of 0,2 UI peak-to-peak at frequencies above 400 kHz, 0,25 UI
between 400 kHz and 200 Hz, increasing with the inverse of frequency below 200 Hz to level off at 10 UI peak-to-
peak below 5 Hz.
Jitter tolerance  (UI)
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7.1.3.4 Connectors
The standard connector for both outputs and inputs shall be the free pin connector and fixed

socket connector described in 8.6 of Table IV of IEC 60268-11.

A male plug shall be used at both ends of the cable.

Equipment manufacturers shall clearly label digital audio inputs and outputs.

7.2 Professional application
Electrical requirements for professional applications are described in IEC 60958-4.
8 Optical requirements
8.1 Consumer application
8.1.1 Optical specification
8.1.1.1 Configuration of optical connection
The basic optical connection configuration is shown in Figure 10. The optical matching values
are described in Annex G, these values apply at the reference points 2 and 3.
The overall characteristics of a fibre optic cable plant are described in IEC 60793-2 and
IEC 60794-2 for fibre and cable and in IEC 60874-1 for the connectors.
The reference points 1 and 4 apply to the electrical input and output of the electro-optical and
opto-electrical converter respectively. Detailed specifications are provided only in relation to
optical reference points 2 and 3.

Receiver :
Transmitter :
Fibre optic
Optial to
Electrical to
cable plant
electorical
opitcal
1 2 3 4
IEC  1560/08
Figure 10 – Basic optical connection

In Figure 10, reference point 1 is the electrical input of the optical transmitter, reference
point 2 is the optical interface between optical transmitter and FOCP, reference point 3 is the
optical interface between FOCP and optical receiver and reference point 4 is the electrical
output of the optical receiver. FOCP means fibre optic cable plant that is the serial
combination of fibre optic cable sections, connectors and splices providing the optical path
between two terminal devices, between two optical devices or between terminal devices and
an optical device.
8.1.2 Optical connector
8.1.2.1 Circular type
Refer to EIAJ RC-5720B (see Bibliography).

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