IEC 61937-12:2010

IEC 61937-12 ®
Edition 1.0 2010-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
IEC 60958 –
Part 12: Non-linear PCM bitstreams according to the DRA formats

Audionumérique – Interface pour les flux de bits audio à codage MIC non
linéaire conformément à la CEI 60958 –
Partie 12: Flux de bits MIC non linéaire selon les formats DRA

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IEC 61937-12 ®
Edition 1.0 2010-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
IEC 60958 –
Part 12: Non-linear PCM bitstreams according to the DRA formats

Audionumérique – Interface pour les flux de bits audio à codage MIC non
linéaire conformément à la CEI 60958 –
Partie 12: Flux de bits MIC non linéaire selon les formats DRA

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
N
CODE PRIX
ICS 33.160.30; 33.170 ISBN 978-2-88912-146-5
– 2 – 61937-12 © IEC:2010
CONTENTS
FOREWORD.3
1 Scope.5
2 Normative references .5
3 Terms and definitions .5
3.1 Terms and definitions .5
3.2 Abbreviations .6
3.3 Presentation convention .6
4 DRA burst-info.6
5 Format of DRA data-bursts .6
5.1 General .6
5.2 Pause data-burst.7
5.3 Audio data-bursts .7
5.3.1 DRA condition .7
5.3.2 DRA half-rate low sampling frequency condition .9
5.3.3 DRA quarter-rate low sampling frequency condition.11
Bibliography.14

Figure 1 – DRA data-burst .8
Figure 2 – Latency of DRA decoding.9
Figure 3 – DRA data-burst half-rate low sampling frequency.10
Figure 4 – Latency of DRA decoding half-rate low sampling frequency .11
Figure 5 – DRA data-burst quarter-rate low sampling frequency.12
Figure 6 – Latency of DRA decoding quarter-rate low sampling frequency .13

Table 1 – Fields of burst-info .6
Table 2 – Data-type-dependent information for data-type DRA.7
Table 3 – Repetition period of pause data-bursts .7

61937-12 © IEC:2010 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –

Part 12: Non-linear PCM bitstreams according to the DRA formats

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
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6) All users should ensure that they have the latest edition of this publication.
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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 IEC 61937-12 has been prepared by technical area 4: Digital system
interfaces and protocols, of IEC technical committee 100: Audio, video and multimedia
systems and equipment.
This bilingual version, published in 2010-10, corresponds to the English version.
The text of this standard is based on the following documents:
CDV Report on voting
100/1578/CDV 100/1651/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.

– 4 – 61937-12 © IEC:2010
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.
The committee has decided that the contents of this publication 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.
61937-12 © IEC:2010 – 5 –
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –

Part 12: Non-linear PCM bitstreams according to the DRA formats

1 Scope
This part of IEC 61937 specifies the method for IEC 60958 to convey non-linear PCM
bitstreams encoded in accordance with the DRA formats.
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 60958 (all parts), Digital audio interface
IEC 61937 (all parts), Digital audio – Interface for non-linear PCM encoded audio bitstreams
applying IEC 60958
IEC 61937-1:2007, Digital audio – Interface for non-linear PCM encoded audio bitstreams
applying IEC 60958 – Part 1: General
IEC 61937-2, Digital audio – Interface for non-linear PCM encoded audio bitstreams
applying IEC 60958 – Part 2: Burst-info
3 Terms and definitions
For the purposes of this document, the following terms, definitions, abbreviations and
presentation conventions apply.
3.1 Terms and definitions
3.1.1
sub data-type
type of payload of the data-burst for use with the specified data-type
3.1.2
latency
delay time of an external audio decoder to decode a DRA data-burst
NOTE It is defined as the sum of two values of the receiving delay time and the decoding delay time.
3.1.3
length code
indicates the length of the data-burst payload in bits or bytes
NOTE See Table 3 of IEC 61937-1.

– 6 – 61937-12 © IEC:2010
3.2 Abbreviations
DRA Digital Rise Audio
3.3 Presentation convention
01 Value “01” in binary format
4 DRA burst-info
The general coding method of the bitstream and data-burst is according to IEC 61937-1 and
IEC 61937-2. The 16-bit burst-info (Pc) is defined in Table 1.
Table 1 – Fields of burst-info
Repetition period
Reference
Bits of Pc Value Contents of data-burst in
point R
IEC 60958 frames
Data-type
0-22 In accordance with IEC 61937-2
DRA or other MPEG applications according to
0 – 4
IEC 61937-2, depending on sub data-type
24-31 In accordance with IEC 61937-2
Subdata-type
00 -10 In accordance with IEC 61937-2
2 2
5 – 6
Depending on bits
11 DRA Bit 0 of Pa
8-9 of Pc
7 In accordance with IEC 61937-1
data-type-dependent information for
8 – 12
data-type DRA
13 – 15 In accordance with IEC 61937-1

5 Format of DRA data-bursts
5.1 General
This clause specifies the audio data-bursts of DRA. Specific properties such as reference
points, repetition period, the method of filling stream gaps, and decoding latency are specified
for the DRA data-type.
61937-12 © IEC:2010 – 7 –
The decoding latency (or delay), indicated for the DRA data-type, should be used by the
transmitter to schedule data-bursts as necessary to establish synchronization between the
video and the decoded audio.
The data-type-dependent information assignment for DRA is given in Table 2. As shown in
Table 2, bits 8-9 of Pc are used to identify the relation between the sampling frequencies of
DRA and the IEC 60958 frame rate.
Table 2 – Data-type-dependent information for data-type DRA
Bits of Pc
Repetition period of
Value Contents
data-burst in IEC 60958 frames
LSB.MSB
00 DRA 1 024
DRA half-rate low sampling
01 2 048
frequency
8 – 9
DRA quarter-rate low
10 4 096
sampling frequency
11 Reserved -
Reserved, shall be used until further
definition
10 – 12
Reserved, shall not be used until further
001 – 111
2 2
definition
5.2 Pause data-burst
The pause data-burst for DRA is given in Table 3.
Table 3 – Repetition period of pause data-bursts
Repetition period of pause data-burst
Type of audio data-burst indicated by bits 8-9
of Pc
Mandatory Recommended
DRA - 32 IEC 60958 frames
DRA half-rate low sampling frequency - 64 IEC 60958 frames
DRA quarter-rate low sampling frequency - 128 IEC 60958 frames

5.3 Audio data-bursts
5.3.1 DRA condition
5.3.1.1 Data for DRA
The streams of the data-bursts of DRA consist of sequences of DRA frames. The data-type
and sub-data-type of a DRA data-burst are 23 and 3 respectively with the bits 8-9 of Pc equal
to 00 . The data-burst is headed with a burst-preamble, followed by the burst-payload, and
stuffed with stuffing bits. The burst-payload of each data-burst of DRA data shall contain one

– 8 – 61937-12 © IEC:2010
complete DRA frame and represents 1 024 samples for each encoded channel. The length of
the DRA data-burst depends on the encoded bit rate, which determines the DRA frame length.
The specification of the DRA frame can be found in GB/T 22726-2008. The units of length-
code (Pd) shall be in bytes.
DRA DRA
Pa Pb Pc Pd Pa Pb Pc Pd
burst_payload burst_payload
Bit 0 of Pa
Bit 0 of Pa
DRA frame
DRA frame Stuffing
Regular rate of the DRA
Repetition period of the burst
IEC  1059/10
Figure 1 – DRA data-burst
The reference point of a DRA data-burst is bit 0 of Pa and occurs exactly once every 1 024
sampling periods. The data-burst containing DRA frames shall occur at a regular rate, with the
reference point of each DRA data-burst beginning 1 024 IEC 60958 frames after the reference
point of the preceding DRA data-burst of the same bitstream number.
It is recommended that pause data-bursts are used to fill stream gaps in the DRA bitstream as
described in IEC 61937-1, and that pause data-bursts be transmitted with a repetition period
of 32 IEC 60958 frames, except when other repetition periods are necessary to fill the precise
stream-gap length, which may not be a multiple of 32 IEC 60958 frames, or to meet the
requirement on burst spacing of IEC 61937.
When a stream gap in a DRA stream is filled by a sequence of pause data-bursts, the Pa of
the first pause data-burst shall be located at 1 024 sampling periods following the Pa of the
previous DRA frame. It is recommended that the sequence(s) of pause data-bursts which fill
the stream gap should continue from this point up to (as close as possible to, considering the
32 IEC 60958 frame length of the pause data-burst) the Pa of the DRA data-burst which
follows the stream gap. The gap-length parameter contained in the pause data-burst is
intended to be interpreted by the DRA decoder as an indication of the number of decoded
PCM samples which are missing, due to the resulting audio gap.
5.3.1.2 Latency of DRA decoding
The latency of an external audio decoder to decode DRA is defined as the sum of the
receiving delay time and the decoding delay time.

61937-12 © IEC:2010 – 9 –
IEC  1060/10
Figure 2 – Latency of DRA decoding
EXAMPLE The receiving delay time to receive a whole data-burst with maximum length is
calculated as follows. The length of preamble is 64 bits. The maximum length of whole data
payload is 4 096 bit for a maximum bit rate of 192 kbit/s. In this case, the maximum length of
data-bursts is 4 160 bits. The receiving delay is 2,708 ms (4 160 × 2/48/64) at 48 kHz
sampling frequency. The decoding delay is 21,333 ms, corresponding to one DRA frame.
Hence, the latency of DRA decoding is approximately 24,041 ms.
The absolute maximum length of the data-burst is calculated as follows. Each data-burst
contains a minimum of 4 stuffing 16-bit words. The repetition period of data-burst is 1 024
IEC 60958 frames. Therefore, the maximum length of data-burst leads as follows:
1 024 samples × 2 channels × 16 bits – 4 words × 16 bits = 32 704 bits
The receiving delay time is 21,292 ms (32 704 × 2/48/64) at 48 kHz sampling frequency,
which leads to the absolute maximum DRA decoding latency of 42,625 ms with the decoding
delay 21,333 ms as above.
5.3.2 DRA half-rate low sampling frequency condition
5.3.2.1 Data for DRA half-rate low sampling frequency
The streams of the data-bursts for DRA half-rate low sampling frequency consist of
sequences of DRA half-rate low sampling frequency frames. The data-type and sub-data-type
of a DRA data-burst are 23 and 3 respectively with the bits 8-9 of Pc equal to 01 . The data-
burst is headed with a burst-preamble, followed by the burst-payload, and stuffed with stuffing
bits. The burst-payload of each data-burst of DRA half-rate low sampling frequency data shall
contain one complete DRA half-rate low sampling frequency frame and represents 2 048
samples for each encoded channel. In the context of this standard, terms relating to “half-rate
low sampling frequency” mean the sampling frequency of the IEC 60958 frame (i.e.,
IEC 60958 frame rate) increases to 2 × original sampling frequency for DRA encoding process.
The units of length-code (Pd) shall be in bytes.

– 10 – 61937-12 © IEC:2010
IEC  1061/10
Figure 3 – DRA data-burst half-rate low sampling frequency
The reference point of a DRA half-rate low sampling frequency data-burst is bit 0 of Pa and
occurs exactly once every 2 048 sampling periods. The data-burst containing DRA half-rate
low sampling frequency frames shall occur at a regular rate, with the reference point of each
DRA half-rate low sampling frequency data-burst beginning 2 048 IEC frames after the
reference point of the preceding DRA half-rate low sampling frequency burst of the same
bitstream number.
It is recommended that pause data-bursts are used to fill stream gaps in the DRA half-rate low
sampling frequency bitstream as described in IEC 61937-1, and that pause data-bursts be
transmitted with a repetition period of 64 IEC 60958 frames, except when other repetition
periods are necessary to fill the precise stream-gap length, which may not be a multiple of
64 IEC 60958 frames, or to meet the requirement on burst spacing of IEC 61937.
When a stream gap in a DRA half-rate low sampling frequency stream is filled by a sequence
of pause data-bursts, the Pa of the first pause data-burst shall be located at 2 048 sampling
periods following the Pa of the previous DRA half-rate low sampling frequency frame. It is
recommended that the sequence(s) of pause data-bursts which fill the stream gap should
continue from this point up to (as close as possible to, considering the 64 IEC 60958 frame
length of the pause data-burst) the Pa of the DRA half-rate low sampling frequency data-burst
which follows the stream gap. The gap-length parameter contained in the pause data-burst is
intended to be interpreted by the DRA decoder as an indication of the number of decoded
PCM samples which are missing, due to the resulting audio gap.
5.3.2.2 Latency of DRA decoding half-rate low sampling frequency
The latency of an external audio decoder to decode DRA at half-rate low sampling frequency
is defined as the sum of the receiving delay time and the decoding delay time.

61937-12 © IEC:2010 – 11 –
DRA half-rate DRA half-rate
Pa Pb Pc Pd Pa Pb Pc Pd
burst_payload burst_payload
Bit 0 of Pa
DRA frame
DRA frame Stuffing
Regular rate of the DRA
Receiving delay Decoding delay
Latency of DRA decoder
IEC  1062/10
Figure 4 – Latency of DRA decoding half-rate low sampling frequency
EXAMPLE The receiving delay time to receive a whole data-burst with maximum length is
calculated as follows. The length of preamble is 64 bits. The maximum length of whole data
payload is 4 096 bits for a maximum bit rate of 96 kbit/s. In this case, the maximum length of
data-bursts is 4 160 bits. The receiving delay is 2,708 ms (4 160 × 2/48/64) at 48 kHz
sampling frequency. The decoding delay is 42,667 ms, corresponding to one DRA half-rate
low sampling frequency frame. Hence, the latency of DRA decoding half-rate low sampling
frequency is approximately 45,375 ms.
The absolute maximum length of the data-burst is calculated as follows. Each data-burst
contains a minimum of 4 stuffing 16-bit words. The repetition period of data-burst is 2 048
IEC 60958 frames. Therefore, the maximum length of half-rate low sampling frequency data-
burst leads as follows:
2 048 samples × 2 channels × 16 bits – 4 words × 16 bits = 65 472 bits
The receiving delay time is 42,625 ms (65 472 × 2/48/64) at 48 kHz sampling frequency,
which leads to the absolute maximum DRA decoding half-rate low sampling frequency latency
of 85,292 ms with the decoding delay 42,667 ms as above.
5.3.3 DRA quarter-rate low sampling frequency condition
5.3.3.1 Data for DRA quarter-rate low sampling frequency
The streams of the data-bursts for DRA quarter-rate low sampling frequency consist of
sequences of DRA quarter-rate low sampling frequency frames. The data-type and sub-data-
type of a DRA data-burst are 23 and 3 respectively with the bits 8-9 of Pc equal to 10 . The
data-burst is headed with a burst-preamble, followed by the burst-payload, and stuffed with
stuffing bits. The burst-payload of each data-burst of DRA quarter-rate low sampling
frequency data shall contain one complete DRA quarter-rate low sampling frequency frame
and represents 4 096 samples for each encoded channel. In the context of this standard,
terms relating to “quarter-rate low sampling frequency” mean the sampling frequency of IEC
60958 frame increases to 4 × original sampling frequency for DRA encoding process. The
units of length-code (Pd) shall be in bytes.

– 12 – 61937-12 © IEC:2010
IEC  1063/10
Figure 5 – DRA data-burst quarter-rate low sampling frequency
The reference point of a DRA quarter-rate low sampling frequency data-burst is bit 0 of Pa
and occurs exactly once every 4 096 sampling periods. The data-burst containing DRA
quarter-rate low sampling frequency frames shall occur at a regular rate, with the reference
point of each DRA quarter-rate low sampling frequency data-burst beginning 4 096 IEC
frames after the reference point of the preceding DRA quarter-rate low sampling frequency
burst of the same bitstream number.
It is recommended that pause data-bursts are used to fill stream gaps in the DRA quarter-rate
low sampling frequency bitstream as described in IEC 61937-1, and that pause data-bursts be
transmitted with a repetition period of 128 IEC 60958 frames, except when other repetition
periods are necessary to fill the precise stream-gap length, which may not be a multiple of
128 IEC 60958 frames, or to meet the requirement on burst spacing of IEC 61937.
When a stream gap in a DRA quarter-rate low sampling frequency stream is filled by a
sequence of pause data-bursts, the Pa of the first pause data-burst shall be located 4 096
sampling periods following the Pa of the previous DRA quarter-rate low sampling frequency
frame. It is recommended that the sequence(s) of pause data-bursts which fill the stream gap
should continue from this point up to (as close as possible to, considering the 128 IEC 60958
frame length of the pause data-burst) the Pa of the DRA quarter-rate low sampling frequency
data-burst which follows the stream gap. The gap-length parameter contained in the pause
data-burst is intended to be interpreted by the DRA decoder as an indication of the number of
decoded PCM samples which are missing, due to the resulting audio gap.
5.3.3.2 Latency of DRA decoding quarter-rate low sampling frequency
The latency of an external audio decoder to decode DRA at quarter-rate low sampling
frequency is defined as the sum of the receiving delay time and the decoding delay time.

61937-12 © IEC:2010 – 13 –
IEC  1064/10
Figure 6 – Latency of DRA decoding quarter-rate low sampling frequency
The absolute maximum length of the data-burst is calculated as follows. Each data-burst
contains a minimum of 4 stuffing 16-bit words. The repetition period of data-burst is 4 096
IEC 60958 frames. Therefore, the maximum length of quarter-rate low sampling frequency
data-burst leads as follows:
4 096 samples × 2 channels × 16 bits – 4 words × 16 bits = 131 008 bits
The receiving delay time is 85,292 ms (131 008 × 2/48/64) at 48 kHz sampling frequency,
which leads to the absolute maximum DRA decoding quarter-rate low sampling frequency
latency of 170,625 ms with the decoding delay 85,333 ms.
For synchronization (for example, with video), the recommended value of quarter-rate low
sampling frequency latency is 170,625 ms. A shorter latency is acceptable when
synchronization is not required.

– 14 – 61937-12 © IEC:2010
Bibliography
IEC 60958-1, Digital audio interface – Part 1: General
IEC 60958-3, Digital audio interface – Pa
...