IEC 61937-14:2017

IEC 61937-14 ®
Edition 1.0 2017-08
INTERNATIONAL
STANDARD
Digital audio – Interface for non-linear pcm encoded audio bitstreams applying
IEC 60958 –
Part 14: Non-linear PCM bit streams according to the AC-4 format
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IEC 61937-14 ®
Edition 1.0 2017-08
INTERNATIONAL
STANDARD
Digital audio – Interface for non-linear pcm encoded audio bitstreams applying

IEC 60958 –
Part 14: Non-linear PCM bit streams according to the AC-4 format

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.160.30; 33.170 ISBN 978-2-8322-4705-1

– 2 – IEC 61937-14:2017 © IEC 2017
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviated terms . 6
3.6 Abbreviated terms . 7
4 Mapping of the audio bit stream on to IEC 61937-1 . 7
4.1 General . 7
4.2 AC-4 burst-info . 7
5 Format of AC-4 data-bursts . 8
5.1 General . 8
5.2 Pause data-burst . 8
5.3 Audio data-burst . 8
5.3.1 The AC-4 data . 8
5.3.2 Latency of the AC-4 decoder . 12
5.3.3 The AC-4 HBR4 data . 13
5.3.4 Latency of the AC-4 HBR4 decoder . 16
5.3.5 The AC-4 HBR16 data . 17
5.3.6 Latency of the AC-4 HBR16 decoder . 20
5.3.7 The AC-4 LD data . 21
5.3.8 Latency of the AC-4 LD decoder . 23
Annex A (normative) AC-4 sync frame . 25

Figure 1 – AC-4 data-burst . 9
Figure 2 – Latency of AC-4 decoding . 12
Figure 3 – AC-4 HBR4 data-burst . 13
Figure 4 – Latency of AC-4 HBR4 decoding . 16
Figure 5 – AC-4 HBR16 data-burst. 17
Figure 6 – Latency of AC-4 HBR16 decoding . 21
Figure 7 – AC-4 LD data-burst . 22
Figure 8 – Latency of AC-4 LD decoding . 24
Figure A.1 – An AC-4 sync frame . 25

Table 1 – Shorthand notation for fractional frame rates . 7
Table 2 – Fields of burst-info . 8
Table 3 – Repetition period of the Pause data-bursts . 8
Table 4 – Data-type-dependent information for AC-4. 9
Table 5 – AC-4 base sampling frequency, AC-4 audio framerate and corresponding
AC-4 data-burst repetition period . 10
Table 6 – AC-4 data-burst sequence and repetition period variance at 29,97, 59,94
and 119,88 fps . 10
Table 7 – AC-4 data-burst: meaning of Pc bits 8 to 11 at an IEC 60958 frame rate of
48 kHz . 11
Table 8 – AC-4 data-burst: meaning of Pc bits 8 to 11 at an IEC 60958 frame rate of
44,1 kHz . 11
Table 9 – Maximum burst-length values per AC-4 data-burst repetition period . 12

Table 10 – Data-type-dependent information for AC-4 HBR4. 13
Table 11 – AC-4 base sampling frequency, AC-4 audio frame rate and corresponding
AC-4 HBR4 data-burst repetition period . 14
Table 12 – AC-4 HBR4 data-burst sequence and repetition period variance at 29,97,
59,94 and 119,88 fps . 14
Table 13 – AC-4 HBR4 data-burst: meaning of Pc bits 8 to 11 at an IEC 60958 frame
rate of 192 kHz . 15
Table 14 – AC-4 HBR4 data-burst: meaning of Pc bits 8 to 11 at an IEC 60958 frame
rate of 176,4 kHz . 15
Table 15 – Maximum burst-length values per AC-4 HBR4 data-burst repetition period . 16
Table 16 – Data-type-dependent information for AC-4 HBR16 . 18
Table 17 – AC-4 base sampling frequency, AC-4 audio frame rate and corresponding
AC-4 HBR16 data-burst repetition period . 18
Table 18 – AC-4 HBR16 data-burst sequence and repetition period variance at 29,97,
59,94 and 119,88 fps . 19
Table 19 – AC-4 HBR16 data-burst: meaning of Pc bits 8 – 11 at an IEC 60958 frame
rate of 768 kHz . 19
Table 20 – AC-4 HBR16 data-burst: meaning of Pc bits 8 to 11 at an IEC 60958 frame
rate of 705,6 kHz . 19
Table 21 – Maximum burst-length values per AC-4 HBR16 data-burst repetition period . 20
Table 22 – Data-type-dependent information for AC-4 LD . 22
Table 23 – AC-4 base sampling frequency, AC-4 audio frame rate and corresponding
AC-4 LD data-burst repetition period . 22
Table 24 – AC-4 LD data-burst sequence and repetition period variance at 119,88 fps . 23
Table 25 – AC-4 LD data-burst: meaning of Pc bits 8 to 11 . 23
Table 26 – Maximum burst-length values per AC-4 data-burst repetition period . 23
Table A.1 – AC-4 sync frame syntax . 25
Table A.2 – framesize() . 25
Table A.3 – AC-4 syncword values . 26

– 4 – IEC 61937-14:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED AUDIO BITSTREAMS
APPLYING IEC 60958 –
Part 14: Non-linear PCM bit streams according to the AC-4 format

FOREWORD
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