SIST EN IEC 60985-1:2021

Digital audio interface - Part 1: General (IEC 60958-1:2021)

Digitalton-Schnittstelle - Teil 1: Allgemeines (IEC 60958-1:2021)

Interface audionumérique - Partie 1: Généralités (IEC 60958-1:2021)

Digitalni zvokovni vmesnik - 1. del: Splošno (IEC 60958-1:2021)

General Information

• Status: Not Published
• Public Enquiry End Date: 30-Mar-2021
• ICS: 33.160.01 - Audio, video and audiovisual systems in general
• ICS: 33.160.30 - Audio systems
• ICS: 35.200 - Interface and interconnection equipment
• Technical Committee: AVM - Audio, video and multimedia systems and equipment
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 21-Oct-2021
• Due Date: 26-Dec-2021
• Ref Project: EN IEC 60958-1:2021 - Digital audio interface - Part 1: General

RELATIONS

• Revised: SIST EN 60958-1:2008 - Digital audio interface - Part 1: General (IEC 60958-1:2008)
• Effective Date: 11-Aug-2020
• Revised: SIST EN 60958-1:2008/A1:2014 - Digital audio interface -- Part 1: General (IEC 60958-1:2008/A1:2014)
• Effective Date: 11-Aug-2020
• Replaces: SIST EN 60958-1:2008 - Digital audio interface - Part 1: General (IEC 60958-1:2008)
• Effective Date: 12-Oct-2021
• Replaces: SIST EN 60958-1:2008/A1:2014 - Digital audio interface -- Part 1: General (IEC 60958-1:2008/A1:2014)
• Effective Date: 12-Oct-2021

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN IEC 60985-1:2021
01-marec-2021
Digitalni zvokovni vmesnik - 1. del: Splošno (TA 20)
Digital audio interface - Part 1: General (TA 20)
Digitalton-Schnittstelle - Teil 1: Allgemeines
Interface audionumérique - Partie 1: Généralités
Ta slovenski standard je istoveten z: prEN IEC 60985-1:2021
ICS:
33.160.30 Avdio sistemi Audio systems
35.200 Vmesniška in povezovalna Interface and interconnection
oprema equipment
oSIST prEN IEC 60985-1:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN IEC 60985-1:2021
100/3544/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 60958-1 ED4
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2021-01-22 2021-04-16
SUPERSEDES DOCUMENTS:
100/3467/CD, 100/3498/CC
IEC TA 20 : ANALOGUE AND DIGITAL AUDIO
SECRETARIAT: SECRETARY:
Japan Mr Gen Ichimura
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:
Other TC/SCs are requested to indicate their interest, if
any, in this CDV to the secretary.
FUNCTIONS CONCERNED:
EMC ENVIRONMENT QUALITY ASSURANCE SAFETY

SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING

Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft
for Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.

This document is still under study and subject to change. It should not be used for reference purposes.

Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of

which they are aware and to provide supporting documentation.
TITLE:
Digital audio interface - Part 1: General (TA 20)
PROPOSED STABILITY DATE: 2023
NOTE FROM TC/SC OFFICERS:

Copyright © 2020 International Electrotechnical Commission, IEC. All rights reserved. It is permitted to download

this electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee

positions. You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other

purpose without permission in writing from IEC.
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100/3544/CDV – 2 – IEC 60958-1 ED4 CDV © IEC 2020
1 CONTENTS

3 CONTENTS ............................................................................................................................ 2

4 FOREWORD ........................................................................................................................... 4

5 1 Scope .............................................................................................................................. 6

6 2 Normative references ...................................................................................................... 6

7 3 Terms and definitions ...................................................................................................... 6

8 4 Interface format ............................................................................................................... 8

9 4.1 Structure of format .................................................................................................. 8

10 4.1.1 Sub-frame format ............................................................................................. 8

11 4.1.2 Frame format ................................................................................................... 9

12 4.2 Channel coding ..................................................................................................... 10

13 4.3 Preambles ............................................................................................................ 10

14 4.4 Validity bit ............................................................................................................. 11

15 5 Channel status .............................................................................................................. 11

16 5.1 General ................................................................................................................. 11

17 5.2 Applications .......................................................................................................... 11

18 5.3 General assignment of the first and second channel status bits ............................ 12

19 5.4 Category code ...................................................................................................... 12

20 6 User data ...................................................................................................................... 14

21 6.1 General ................................................................................................................. 14

22 6.2 Applications .......................................................................................................... 14

23 6.2.1 Professional use ............................................................................................ 14

24 6.2.2 Consumer use ............................................................................................... 14

25 7 Electrical requirement .................................................................................................... 14

26 7.1 Consumer application ........................................................................................... 14

27 7.1.1 General ......................................................................................................... 14

28 7.1.2 Timing accuracy ............................................................................................ 14

29 7.1.3 Unbalanced line ............................................................................................. 15

30 7.2 Professional application ........................................................................................ 18

31 8 Optical requirements ..................................................................................................... 18

32 8.1 Consumer application ........................................................................................... 18

33 8.1.1 Optical specification ...................................................................................... 18

34 8.1.2 Optical connector .......................................................................................... 18

35 8.2 Professional applications ...................................................................................... 19

36 Annex A (informative) The use of the validity bit .................................................................. 20

37 Annex B (informative) Application documents and specifications.......................................... 21

38 Annex C (informative) A relationship of the IEC 60958 series families.................................. 22

39 Annex D (informative) Transmission of CD data other than linear PCM audio ...................... 24

40 Annex E (informative) The IEC 60958 series conformant data format ................................... 25

41 Annex F (informative) Stream change .................................................................................. 26

42 Annex G (informative) Characteristics of optical connection ................................................. 28

43 Bibliography .......................................................................................................................... 30

45 Figure 1 – Sub-frame format (linear PCM application) ............................................................. 9

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46 Figure 2 – Frame format ......................................................................................................... 9

47 Figure 3 – Channel coding .................................................................................................... 10

48 Figure 4 – Preamble M (shown as 11100010) ....................................................................... 11

49 Figure 5 – Simplified example of the configuration of the circuit (unbalanced) ....................... 15

50 Figure 6 – Rise and fall times ............................................................................................... 16

51 Figure 7 – Intrinsic jitter measurement filter .......................................................................... 16

52 Figure 8 – Eye diagram ......................................................................................................... 17

53 Figure 9 – Receiver jitter tolerance template ......................................................................... 17

54 Figure 10 – Basic optical connection ..................................................................................... 18

55 Figure C.1 – Relationships of the IEC 60958 families ............................................................ 22

56 Figure F.1 – Audio sources and AV receiver model ............................................................... 26

57 Figure F.2 – Switching from linear PCM to non linear PCM ................................................... 27

58 Figure F.3 – Switching from non linear PCM to linear PCM ................................................... 27

59 Figure F.4 – Switching from non-linear PCM to non-linear PCM ............................................ 27

61 Table 1 – Preamble coding ................................................................................................... 10

62 Table 2 – Channel status data format ................................................................................... 13

63 Table B.1 – Application documents and specifications .......................................................... 21

64 Table C.1 – data_type values and application ....................................................................... 23

65 Table G.1 – Characteristics of standard optical connection (optical interface) ....................... 28

66 Table G.2 – Characteristics of optical transmitter (optical interface) ...................................... 28

67 Table G.3 – Characteristics of optical receiver (optical interface) .......................................... 29

68 Table G.4 – Characteristics of fibre optic cable ..................................................................... 29

69 Table G.5 – Optical power budget for the link with plastic fibre ............................................. 29

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72 INTERNATIONAL ELECTROTECHNICAL COMMISSION
73 ____________
75 DIGITAL AUDIO INTERFACE –
77 Part 1: General
81 FOREWORD

82 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

83 all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

84 international co-operation on all questions concerning standardization in the electrical and electronic fields. To

85 this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

86 Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

87 Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

88 in the subject dealt with may participate in this preparatory work. International, governmental and non-

89 governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

90 with the International Organization for Standardization (ISO) in accordance with conditions determined by

91 agreement between the two organizations.

92 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

93 consensus of opinion on the relevant subjects since each technical committee has representation from all

94 interested IEC National Committees.

95 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

96 Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

97 Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

98 misinterpretation by any end user.

99 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

100 transparently to the maximum extent possible in their national and regional publications. Any divergence

101 between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

102 the latter.

103 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

104 assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

105 services carried out by independent certification bodies.

106 6) All users should ensure that they have the latest edition of this publication.

107 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

108 members of its technical committees and IEC National Committees for any personal injury, property damage or

109 other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

110 expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

111 Publications.

112 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

113 indispensable for the correct application of this publication.

114 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

115 patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

116 International Standard 60958-1 has been prepared by technical area 20: Analogue and digital

117 audio of IEC technical committee 100: Audio, video and multimedia systems and equipment. It is

118 an International Standard.
119 This 4th edition cancels and replaces the 3.1rd edition published in 2014.

120 This edition includes the following significant technical changes with respect to the previous

121 edition:
122 a) The relevant part of IEC 60958-5 is supported.

123 A list of all parts of the IEC 60958 series, under the general title Digital audio interface, can

124 be found on the IEC website.
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125 The text of this International Standard is based on the following documents:
Draft Report on voting
XX/XX/FDIS XX/XX/RVD
126

127 Full information on the voting for its approval can be found in the report on voting indicated in

128 the above table.

129 The language used for the development of this International Standard is English.

130 This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in

131 accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,

132 available at www.iec.ch/members_experts/refdocs. The main document types developed by

133 IEC are described in greater detail at www.iec.ch/standardsdev/publications.

134 The committee has decided that the contents of this document will remain unchanged until the

135 stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

136 the specific document. At this date, the document will be
137 • reconfirmed,
138 • withdrawn,
139 • replaced by a revised edition, or
140 • amended.
141
142
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143 DIGITAL AUDIO INTERFACE –
144
145 Part 1: General
146
147
148
149 1 Scope

150 This part of IEC 60958 describes a serial, uni-directional, self-clocking interface for the

151 interconnection of digital audio equipment for consumer and professional applications.

152 It provides the basic structure of the interface. Separate documents define items specific to

153 particular applications.

154 The interface is primarily intended to carry monophonic or stereophonic programmes,

155 encoded using linear PCM and with a resolution of up to 24 bits per sample.

156 When used for other purposes, the interface is able to carry audio data coded other than as

157 linear PCM coded audio samples. Provision is also made to allow the interface to carry data

158 related to computer software, multimedia technologies or signals coded using non-linear PCM.

159 The format specification for these applications is not part of this standard.

160 The interface is intended for operation at audio sampling frequencies of 32kHz and above.

161 Auxiliary information is transmitted along with the programme.
162 2 Normative references

163 The following documents are referred to in the text in such a way that some or all of their

164 content constitutes requirements of this document. For dated references, only the edition

165 cited applies. For undated references, the latest edition of the referenced document (including

166 any amendments) applies.

167 IEC 60268-11:1987, Sound system equipment – Part 11: Application of connectors for the

168 interconnection of sound system components
169 IEC 60958-3:2021, Digital audio interface – Part 3: Consumer applications

170 IEC 60958-4(all subparts):2016, Digital audio interface – Part 4: Professional applications

171 IEC 60958-5:2020 (in preparation), Digital audio interface – Part 5 : Consumer application

172 enhancement
173 3 Terms and definitions

174 For the purposes of this document, the following terms and definitions apply.

175 ISO and IEC maintain terminological databases for use in standardization at the following

176 addresses:
177 • IEC Electropedia: available at http://www.electropedia.org/
178 • ISO Online browsing platform: available at http://www.iso.org/obp
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179 3.1
180 sampling frequency
181 frequency of the samples representing an audio signal

182 Note 1 to entry: When more than one signal is transmitted through the same interface, the sampling frequencies

183 are identical.
184 3.2
185 audio sample word

186 value of a digital audio sample; representation is linear in 2's complement binary form

187 Note 1 to entry: Positive numbers correspond to positive analogue voltages at the input of the analogue-to-digital

188 converter (ADC).
189 3.3
190 auxiliary sample bit

191 four least significant bits (LSBs) which can be assigned as auxiliary sample bits and used for

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

193 or equal to 20
194 3.4
195 validity bit

196 bit indicating whether the main data field bits in the sub-frame (time slots 4 to 27 or 8 to 27,

197 depending on the audio word length as described in 4.1.1) are reliable or not

198 3.5
199 channel status

200 data carrying, in a fixed format, information associated with each main data field channel

201 which is decodable by any interface user

202 Note 1 to entry: Examples of information to be carried in the channel status are: length of audio sample words,

203 pre-emphasis, sampling frequency, time codes, alphanumeric source and destination codes.

204 3.6
205 user data
206 data providing to carry any other information
207 3.7
208 parity bit

209 bit provided to permit the detection of an odd number of errors resulting from malfunctions in

210 the interface
211 3.8
212 preamble
213 specific patterns used for synchronization
214 Note 1 to entry: There are three different preambles (see 10).
215 3.9
216 sub-frame
217 fixed structure used to carry information (see 4.1.1 and 4.1.2)
218 3.10
219 frame
220 sequence of two successive and associated sub-frames
221 3.11
222 block
223 group of 192 consecutive frames
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224 Note 1 to entry: The start of a block is designated by a special sub-frame preamble (see 10).

225 3.12
226 channel coding

227 coding method by which the binary digits are represented for transmission through the

228 interface
229 3.13
230 unit interval (UI)
231 shortest nominal time interval in the coding scheme
232 Note 1 to entry: There are 128 UI in a sample frame.
233 3.14
234 interface jitter

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

236 ideal clock
237 3.15
238 intrinsic jitter

239 output interface jitter of a device that is either free-running or is synchronized to a jitter-free

240 reference
241 3.16
242 jitter gain

243 ratio of the amplitude of jitter components at the output to their amplitude at the

244 synchronization input to the device under test
245 4 Interface format
246 4.1 Structure of format
247 4.1.1 Sub-frame format

248 Each sub-frame is divided into 32 time slots, numbered from 0 to 31 (see Figure 1).

249 Time slots 0 to 3 (preambles) carry one of the three permitted preambles (see 4.1.2 and 4.3;

250 also see Figure 2).

251 Time slots 4 to 27 (main data field) carry the audio sample word in linear 2's complement

252 representation. The most significant bit (MSB) is carried by time slot 27.

253 When a 24-bit coding range is used, the LSB is in time slot 4 (see Figure 1).

254 When a 20-bit coding range is used, time slots 8 to 27 carry the audio sample word with

255 the LSB in time slot 8. Time slots 4 to 7 may be used for other applications. Under

256 these circumstances, the bits in the time slots 4 to 7 are designated auxiliary sample bits (see

257 Figure 1).

258 If the source provides fewer bits than the interface allows (either 20 or 24), the unused LSBs

259 are set to a logical "0".

260 For a non-linear PCM audio application or a data application the main data field may carry

261 any other information.

262 Time slot 28 (validity bit) carries the validity bit associated with the main data field (see 4.4).

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263 Time slot 29 (user data bit) carries 1 bit of the user data channel associated with the main

264 data field channel transmitted in the same sub-frame. For the applications, refer to the other

265 parts of IEC 60958.

266 Time slot 30 (channel status bit) carries 1 bit of the channel status information associated with

267 the main data field channel transmitted in the same sub-frame. For details refer to the other

268 parts of IEC 60958.

269 Time slot 31 (parity bit) carries a parity bit such that time slots 4 to 31 inclusive carry an even

270 number of ones and an even number of zeroes (even parity).
271 NOTE The preambles have even parity as an explicit property.
0 3 4 7 8 27 28 31
Sync M
V U C P
Aux Audio s ample word
Preamble S
Validity f lag
User data
Channel s tatus
Parity bit
IEC 1551/08
272
273 Figure 1 – Sub-frame format (linear PCM application)
274 4.1.2 Frame format

275 A frame is uniquely composed of two sub-frames (see Figure 2). For linear coded audio

276 applications, the rate of transmission of frames normally corresponds exactly to the source

277 sampling frequency.

278 In 2-channel operation mode, the samples taken from both channels are transmitted by time

279 multiplexing in consecutive sub-frames. The first sub-frame (left or "A" channel in

280 stereophonic operation and primary channel in monophonic operation) normally starts with

281 preamble "M". However, the preamble changes to preamble "B" once every 192 frames to

282 identify the start of the block structure used to organize the channel status information. The

283 second sub-frame (right or "B" channel in stereophonic operation and secondary channel in

284 monophonic operation) always starts with preamble "W".

285 In single channel operation mode in a professional application, the frame format is the same

286 as in the 2-channel mode. Data is carried in the first sub-frame and may be duplicated in the

287 second sub-frame. If the second sub-frame is not carrying duplicate data, then time slot 28,

288 (validity flag) shall be set to logical "1".

289 NOTE For historical reasons preambles "B", "M" and "W" are, for use in professional applications, referred to as

290 "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
291
292 Figure 2 – Frame format
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293 4.2 Channel coding

294 To minimize the direct current (d.c.) component on the transmission line, to facilitate clock

295 recovery from the data stream and to make the interface insensitive to the polarity of

296 connections, time slots 4 to 31 are encoded in biphase-mark.

297 Each bit to be transmitted is represented by a symbol comprising two consecutive binary

298 states. The first state of a symbol is always different from the second state of the previous

299 symbol. The second state of the symbol is identical to the first if the bit to be transmitted is

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

301
Clock (twice bit rate)
Source coding
Channel coding (biphase mark)
IEC 1553/08
302
303
304 Figure 3 – Channel coding
305 4.3 Preambles

306 Preambles are specific patterns providing synchronization and identification of the sub-frames

307 and blocks.

308 To achieve synchronization within one sampling period and to make this process completely

309 reliable, these patterns violate the biphase-mark code rules, thereby avoiding the possibility of

310 data imitating the preambles.

311 A set of three preambles is used. These preambles are transmitted in the time allocated to

312 four time slots at the start of each sub-frame (time slots 0 to 3), and are represented by eight

313 successive states. The first state of the preamble is always different from the second state of

314 the previous symbol (representing the parity bit). Depending on this state the preambles are

315 as shown in Table 1.
316 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
317

318 Like biphase code, these preambles are d.c. free and provide clock recovery. They differ in at

319 least two states from any valid biphase sequence.
320 Figure 4 represents preamble "M".

321 NOTE Owing to the even-parity bit in time slot 31, all preambles start with a transition in the same direction

322 (see 4.1.1). Thus, only one of these sets of preambles is, in practice, transmitted through the interface. However, it

323 is necessary for both sets to be decodable because either polarity is possible in a connection.

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324
Clock
Parity
LSB
Lack of transition at bit boundary
IEC 1554/08
325
326
327 Figure 4 – Preamble M (shown as 11100010)
328 4.4 Validity bit

329 The validity bit is logical "0" if the information in the main data field is reliable, and it is logical

330 "1" if it is not. There is no default state for the validity bit.

331 NOTE For transmissions not using a linear PCM coding, this bit may be set. This is intended to prevent accidental

332 decoding of non-audio data to analogue before a complete channel status block is received. See 20.

333 5 Channel status
334 5.1 General

335 For every sub-frame the channel status provides information related to the data carried in the

336 main data field of that same sub-frame.

337 Channel status information is organised in a 192-bit block, subdivided into 24 bytes. The first

338 bit of each block is carried in the frame with preamble "B”. The channel status data format is

339 defined in Table 2.

340 The specific organisation depends on the application. In the descriptions, the suffix "0"

341 designates the first byte or bit. Where channel status bits are combined to form non-binary

342 values, the least significant bit should be transmitted first, unless otherwise indicated.

343 5.2 Applications

344 The primary application is indicated by the first channel status bit (bit 0) of a block as defined

345 in subclause 12.
346 For professional applications refer to IEC 60958-4.
347 For consumer applications refer to IEC 60958-3 and IEC 60958-5.
348 Secondary applications may be defined within the framewor
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