ISO/IEC 14496-3:2019
(Main)Information technology — Coding of audio-visual objects — Part 3: Audio
Information technology — Coding of audio-visual objects — Part 3: Audio
This document integrates many different types of audio coding: natural sound with synthetic sound, low bitrate delivery with high-quality delivery, speech with music, complex soundtracks with simple ones, and traditional content with interactive and virtual-reality content. This document standardizes individually sophisticated coding tools to provide a novel, flexible framework for audio synchronization, mixing, and downloaded post-production. This document does not target a single application such as real-time telephony or high-quality audio compression. Rather, it applies to every application requiring the use of advanced sound compression, synthesis, manipulation, or playback. This document specifies the state-of-the-art coding tools in several domains. As the tools it defines are integrated with the rest of the ISO/IEC 14496 series, exciting new possibilities for object-based audio coding, interactive presentation, dynamic soundtracks, and other sorts of new media, are enabled.
Technologies de l'information — Codage des objets audiovisuels — Partie 3: Codage audio
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INTERNATIONAL ISO/IEC
STANDARD 14496-3
Fifth edition
2019-12
Information technology — Coding of
audio-visual objects —
Part 3:
Audio
Technologies de l'information — Codage des objets audiovisuels —
Partie 3: Codage audio
Reference number
©
ISO/IEC 2019
© ISO/IEC 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2019 – All rights reserved
Contents
Foreword iv
0 Introduction v
1 Scope 1
2 Normative references 1
3 Terms and definitions 2
4 Abbreviated terms 21
5 Structure of this document 23
Subpart 1: Main 24
Subpart 2: Speech coding — HVXC 169
Subpart 3: Speech coding — CELP 320
Subpart 4: General Audio coding (GA) — AAC, TwinVQ, BSAC 483
Subpart 5: Structured Audio (SA) 895
Subpart 6: Text To Speech Interface (TTSI) 1043
Subpart 7: Parametric Audio Coding — HILN 1053
Subpart 8: Parametric coding for high quality audio — SSC 1112
Subpart 9: MPEG-1/2 Audio in MPEG-4 1231
Subpart 10: Lossless coding of oversampled audio — DST 1244
Subpart 11: Audio lossless coding — ALS 1281
Subpart 12: Scalable lossless coding— SLS 1355
Subpart 13: Audio Synchronization 1429
© ISO/IEC 2019 – All rights reserved iii
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on the ISO
list of patent declarations received (see www.iso.org/patents) or the IEC list of patent declarations received
(see http://patents.iec.ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
This fifth edition cancels and replaces the fourth edition (ISO/IEC 14496-3:2009), which has been technically
revised. It incorporates the Amendments ISO/IEC 14496-3:2009/Amd.1:2009, ISO/IEC 14496-
3:2009/Amd.2:2010, ISO/IEC 14496-3:2009/Amd.3:2012, ISO/IEC 14496-3:2009/Amd.4:2013,
ISO/IEC 14496-3:2009/Amd.4:2013/Cor.1:2015, ISO/IEC 14496-3:2009/Amd.5:2015, ISO/IEC 14496-
3:2009/Amd.6:2017 and ISO/IEC 14496-3:2009/Amd.7:2018 as well as Technical Corrigenda ISO/IEC 14496-
3:2009/Cor.1:2009, ISO/IEC 14496-3:2009/Cor.2:2011, ISO/IEC 14496-3:2009/Cor.3:2012, ISO/IEC 14496-
3:2009/Cor.4:2012, ISO/IEC 14496-3:2009/Cor.5:2015, ISO/IEC 14496-3:2009/Cor.6:2015, ISO/IEC 14496-
3:2009/Cor.7:2015.
A list of all parts in the ISO/IEC 14496 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv © ISO/IEC 2019 – All rights reserved
0 Introduction
0.1 Overview
ISO/IEC 14496-3 (MPEG-4 Audio) is a new kind of audio standard that integrates many different types of
audio coding: natural sound with synthetic sound, low bitrate delivery with high-quality delivery, speech with
music, complex soundtracks with simple ones, and traditional content with interactive and virtual-reality
content. By standardizing individually sophisticated coding tools as well as a novel, flexible framework for
audio synchronization, mixing, and downloaded post-production, the developers of the MPEG-4 Audio
standard have created new technology for a new, interactive world of digital audio.
MPEG-4, unlike previous audio standards created by ISO/IEC and other groups, does not target a single
application such as real-time telephony or high-quality audio compression. Rather, MPEG-4 Audio is a
standard that applies to every application requiring the use of advanced sound compression, synthesis,
manipulation, or playback. The subparts that follow specify the state-of-the-art coding tools in several
domains; however, MPEG-4 Audio is more than just the sum of its parts. As the tools described here are
integrated with the rest of the MPEG-4 standard, exciting new possibilities for object-based audio coding,
interactive presentation, dynamic soundtracks, and other sorts of new media, are enabled.
Since a single set of tools is used to cover the needs of a broad range of applications, interoperability is a
natural feature of systems that depend on the MPEG-4 Audio standard. A system that uses a particular coder
— for example a real-time voice communication system making use of the MPEG-4 speech coding toolset —
can easily share data and development tools with other systems, even in different domains, that use the same
tool — for example a voicemail indexing and retrieval system making use of MPEG-4 speech coding.
The remainder of this clause gives a more detailed overview of the capabilities and functioning of MPEG-4
Audio. First a discussion of concepts, that have changed since the MPEG-2 audio standards, is presented.
Then the MPEG-4 Audio toolset is outlined.
0.2 Concepts of MPEG-4 Audio
0.2.1 General
As with previous MPEG standards, MPEG-4 does not standardize methods for encoding sound. Thus, content
authors are left to their own decisions as to the best method of creating bitstream payloads. At the present
time, methods to automatically convert natural sound into synthetic or multi-object descriptions are not mature;
therefore, most immediate solutions will involve interactively-authoring the content stream in some way. This
process is similar to current schemes for MIDI-based and multi-channel mixdown authoring of soundtracks.
Many concepts in MPEG-4 Audio are different than those in previous MPEG Audio standards. For the benefit
of readers who are familiar with MPEG-1 and MPEG-2 we provide a brief overview here.
0.2.2 Audio storage and transport facilities
In all of the MPEG-4 tools for audio coding, the coding standard ends at the point of constructing access units
that contain the compressed data. The MPEG-4 Systems (ISO/IEC 14496-1) specification describes how to
convert these individually coded access units into elementary streams.
There is no standard transport mechanism of these elementary streams over a channel. This is because the
broad range of applications that can make use of MPEG-4 technology have delivery requirements that are too
wide to easily characterize with a single solution. Rather, what is standardized is an interface (the Delivery
Multimedia Interface Format, or DMIF, specified in ISO/IEC 14496-6) that describes the capabilities of a
transport layer and the communication between transport, multiplex, and demultiplex functions in encoders
and decoders. The use of DMIF and the MPEG-4 Systems specification allows transmission functions that are
much more sophisticated than are possible with previous MPEG standards.
However, LATM and LOAS were defined to provide a low overhead audio multiplex and transport mechanism
for natural audio applications, which do not require sophisticated object-based coding or other functions
provided by MPEG-4 Systems.
© ISO/IEC 2019 – All rights reserved v
Table 0.1 gives an overview about the multiplex, storage and transmission formats currently available for
MPEG-4 Audio within the MPEG-4 framework:
Table 0.1 – MPEG-4 Audio multiplex, storage and transmission formats
Format Functionality defined in Functionality originally Description
MPEG-4: defined in:
M4Mux ISO/IEC 14496-1 - MPEG-4 Multiplex scheme
(normative)
LATM ISO/IEC 14496-3 - Low Overhead Audio Transport
(normative) Multiplex
ADIF ISO/IEC 14496-3 ISO/IEC 13818-7 Audio Data Interchange Format,
(informative) (normative) (AAC only)
MP4FF ISO/IEC 14496-12 - MPEG-4 File Format
(normative)
ADTS ISO/IEC 14496-3 ISO/IEC 13818-7 Audio Data Transport Stream,
(informative) (normative, exemplarily) (AAC only)
LOAS ISO/IEC 14496-3 - Low Overhead Audio Stream, based
(normative, exemplarily) on LATM, three versions are
available:
AudioSyncStream()
EPAudioSyncStream()
AudioPointerStream()
To allow for a user on the remote side of a channel to dynamically control a server streaming MPEG-4
content, MPEG-4 defines backchannel streams that can carry user interaction information.
0.2.3 MPEG-4 Audio supports low-bitrate coding
Previous MPEG Audio standards have focused primarily on transparent (undetectable) or nearly transparent
coding of high-quality audio at whatever bitrate was required to provide it. MPEG-4 provides new and
improved tools for this purpose, but also standardizes (and has tested) tools that can be used for transmitting
audio at the low bitrates suitable for Internet, digital radio, or other bandwidth-limited delivery. The new tools
specified in MPEG-4 are the state-of-the-art tools that support low-bitrate coding of speech and other audio.
0.2.4 MPEG-4 Audio is an object-based coding standard with multiple tools
Previous MPEG Audio standards provided a single toolset, with different configurations of that toolset
specified for use in various applications. MPEG-4 provides several toolsets that have no particular relationship
to each other, each with a different target function. The profiles of MPEG-4 Audio specify which of these tools
are used together for various applications.
Further, in previous MPEG standards, a single (perhaps multi-channel or multi-language) piece of content was
transmitted. In contrast, MPEG-4 supports a much more flexible concept of a soundtrack. Multiple tools may
be used to transmit several audio objects, and when using multiple tools together an audio composition
system is provided to create a single soundtrack from the several audio substreams. User interaction, terminal
capability, and speaker configuration may be used when determining how to produce a single soundtrack from
the component objects. This capability gives MPEG-4 significant advantages in quality and flexibility when
compared to previous audio standards.
0.2.5 MPEG-4 Audio provides capabilities for synthetic sound
In natural sound coding, an existing sound is compressed by a server, transmitted and decompressed at the
receiver. This type of coding is the subject of many existing standards for sound compression. In contrast,
MPEG-4 standardizes a novel paradigm in which synthetic sound descriptions, including synthetic speech and
synthetic music, are transmitted and then synthesized into sound at the receiver. Such capabilities open up
new areas of very-low-bitrate but still very-high-quality coding.
vi © ISO/IEC 2019 – All rights reserved
Transmission Storage Multiplex
0.2.6 MPEG-4 Audio provides capabilities for error robustness
Improved error robustness capabilities for all coding tools are provided through the error resilient bitstream
payload syntax. This tool supports advanced channel coding techniques, which can be adapted to the special
needs of given coding tools and a given communications channel. This error resilient bitstream payload syntax
is mandatory for all error resillient object types.
The error protection tool (EP tool) provides unequal error protection (UEP) for MPEG-4 Audio in conjunction
with the error resilient bitstream payload. UEP is an efficient method to improve the error robustness of source
coding schemes. It is used by various speech and audio coding systems operating over error-prone channels
such as mobile telephone networks or Digital Audio Broadcasting (DAB). The bits of the coded signal
representation are first grouped into different classes according to their error sensitivity. Then error protection
is individually applied to the different classes, giving better protection to more sensitive bits.
Improved error robustness for AAC is provided by a set of error resilience tools. These tools reduce the
perceived degradation of the decoded audio signal that is caused by corrupted bits in the bitstream payload.
0.2.7 MPEG-4 Audio provides capabilities for scalability
Previous MPEG Audio standards provided a single bitrate, single bandwidth toolset, with different
configurations of that toolset specified for use in various appl
...
INTERNATIONAL ISO/IEC
STANDARD 14496-3
Fifth edition
2019-12
Information technology — Coding of
audio-visual objects —
Part 3:
Audio
Technologies de l'information — Codage des objets audiovisuels —
Partie 3: Codage audio
Reference number
©
ISO/IEC 2019
© ISO/IEC 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2019 – All rights reserved
Contents
Foreword iv
0 Introduction v
1 Scope 1
2 Normative references 1
3 Terms and definitions 2
4 Abbreviated terms 21
5 Structure of this document 23
Subpart 1: Main 24
Subpart 2: Speech coding — HVXC 169
Subpart 3: Speech coding — CELP 320
Subpart 4: General Audio coding (GA) — AAC, TwinVQ, BSAC 483
Subpart 5: Structured Audio (SA) 895
Subpart 6: Text To Speech Interface (TTSI) 1043
Subpart 7: Parametric Audio Coding — HILN 1053
Subpart 8: Parametric coding for high quality audio — SSC 1112
Subpart 9: MPEG-1/2 Audio in MPEG-4 1231
Subpart 10: Lossless coding of oversampled audio — DST 1244
Subpart 11: Audio lossless coding — ALS 1281
Subpart 12: Scalable lossless coding— SLS 1355
Subpart 13: Audio Synchronization 1429
© ISO/IEC 2019 – All rights reserved iii
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on the ISO
list of patent declarations received (see www.iso.org/patents) or the IEC list of patent declarations received
(see http://patents.iec.ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
This fifth edition cancels and replaces the fourth edition (ISO/IEC 14496-3:2009), which has been technically
revised. It incorporates the Amendments ISO/IEC 14496-3:2009/Amd.1:2009, ISO/IEC 14496-
3:2009/Amd.2:2010, ISO/IEC 14496-3:2009/Amd.3:2012, ISO/IEC 14496-3:2009/Amd.4:2013,
ISO/IEC 14496-3:2009/Amd.4:2013/Cor.1:2015, ISO/IEC 14496-3:2009/Amd.5:2015, ISO/IEC 14496-
3:2009/Amd.6:2017 and ISO/IEC 14496-3:2009/Amd.7:2018 as well as Technical Corrigenda ISO/IEC 14496-
3:2009/Cor.1:2009, ISO/IEC 14496-3:2009/Cor.2:2011, ISO/IEC 14496-3:2009/Cor.3:2012, ISO/IEC 14496-
3:2009/Cor.4:2012, ISO/IEC 14496-3:2009/Cor.5:2015, ISO/IEC 14496-3:2009/Cor.6:2015, ISO/IEC 14496-
3:2009/Cor.7:2015.
A list of all parts in the ISO/IEC 14496 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv © ISO/IEC 2019 – All rights reserved
0 Introduction
0.1 Overview
ISO/IEC 14496-3 (MPEG-4 Audio) is a new kind of audio standard that integrates many different types of
audio coding: natural sound with synthetic sound, low bitrate delivery with high-quality delivery, speech with
music, complex soundtracks with simple ones, and traditional content with interactive and virtual-reality
content. By standardizing individually sophisticated coding tools as well as a novel, flexible framework for
audio synchronization, mixing, and downloaded post-production, the developers of the MPEG-4 Audio
standard have created new technology for a new, interactive world of digital audio.
MPEG-4, unlike previous audio standards created by ISO/IEC and other groups, does not target a single
application such as real-time telephony or high-quality audio compression. Rather, MPEG-4 Audio is a
standard that applies to every application requiring the use of advanced sound compression, synthesis,
manipulation, or playback. The subparts that follow specify the state-of-the-art coding tools in several
domains; however, MPEG-4 Audio is more than just the sum of its parts. As the tools described here are
integrated with the rest of the MPEG-4 standard, exciting new possibilities for object-based audio coding,
interactive presentation, dynamic soundtracks, and other sorts of new media, are enabled.
Since a single set of tools is used to cover the needs of a broad range of applications, interoperability is a
natural feature of systems that depend on the MPEG-4 Audio standard. A system that uses a particular coder
— for example a real-time voice communication system making use of the MPEG-4 speech coding toolset —
can easily share data and development tools with other systems, even in different domains, that use the same
tool — for example a voicemail indexing and retrieval system making use of MPEG-4 speech coding.
The remainder of this clause gives a more detailed overview of the capabilities and functioning of MPEG-4
Audio. First a discussion of concepts, that have changed since the MPEG-2 audio standards, is presented.
Then the MPEG-4 Audio toolset is outlined.
0.2 Concepts of MPEG-4 Audio
0.2.1 General
As with previous MPEG standards, MPEG-4 does not standardize methods for encoding sound. Thus, content
authors are left to their own decisions as to the best method of creating bitstream payloads. At the present
time, methods to automatically convert natural sound into synthetic or multi-object descriptions are not mature;
therefore, most immediate solutions will involve interactively-authoring the content stream in some way. This
process is similar to current schemes for MIDI-based and multi-channel mixdown authoring of soundtracks.
Many concepts in MPEG-4 Audio are different than those in previous MPEG Audio standards. For the benefit
of readers who are familiar with MPEG-1 and MPEG-2 we provide a brief overview here.
0.2.2 Audio storage and transport facilities
In all of the MPEG-4 tools for audio coding, the coding standard ends at the point of constructing access units
that contain the compressed data. The MPEG-4 Systems (ISO/IEC 14496-1) specification describes how to
convert these individually coded access units into elementary streams.
There is no standard transport mechanism of these elementary streams over a channel. This is because the
broad range of applications that can make use of MPEG-4 technology have delivery requirements that are too
wide to easily characterize with a single solution. Rather, what is standardized is an interface (the Delivery
Multimedia Interface Format, or DMIF, specified in ISO/IEC 14496-6) that describes the capabilities of a
transport layer and the communication between transport, multiplex, and demultiplex functions in encoders
and decoders. The use of DMIF and the MPEG-4 Systems specification allows transmission functions that are
much more sophisticated than are possible with previous MPEG standards.
However, LATM and LOAS were defined to provide a low overhead audio multiplex and transport mechanism
for natural audio applications, which do not require sophisticated object-based coding or other functions
provided by MPEG-4 Systems.
© ISO/IEC 2019 – All rights reserved v
Table 0.1 gives an overview about the multiplex, storage and transmission formats currently available for
MPEG-4 Audio within the MPEG-4 framework:
Table 0.1 – MPEG-4 Audio multiplex, storage and transmission formats
Format Functionality defined in Functionality originally Description
MPEG-4: defined in:
M4Mux ISO/IEC 14496-1 - MPEG-4 Multiplex scheme
(normative)
LATM ISO/IEC 14496-3 - Low Overhead Audio Transport
(normative) Multiplex
ADIF ISO/IEC 14496-3 ISO/IEC 13818-7 Audio Data Interchange Format,
(informative) (normative) (AAC only)
MP4FF ISO/IEC 14496-12 - MPEG-4 File Format
(normative)
ADTS ISO/IEC 14496-3 ISO/IEC 13818-7 Audio Data Transport Stream,
(informative) (normative, exemplarily) (AAC only)
LOAS ISO/IEC 14496-3 - Low Overhead Audio Stream, based
(normative, exemplarily) on LATM, three versions are
available:
AudioSyncStream()
EPAudioSyncStream()
AudioPointerStream()
To allow for a user on the remote side of a channel to dynamically control a server streaming MPEG-4
content, MPEG-4 defines backchannel streams that can carry user interaction information.
0.2.3 MPEG-4 Audio supports low-bitrate coding
Previous MPEG Audio standards have focused primarily on transparent (undetectable) or nearly transparent
coding of high-quality audio at whatever bitrate was required to provide it. MPEG-4 provides new and
improved tools for this purpose, but also standardizes (and has tested) tools that can be used for transmitting
audio at the low bitrates suitable for Internet, digital radio, or other bandwidth-limited delivery. The new tools
specified in MPEG-4 are the state-of-the-art tools that support low-bitrate coding of speech and other audio.
0.2.4 MPEG-4 Audio is an object-based coding standard with multiple tools
Previous MPEG Audio standards provided a single toolset, with different configurations of that toolset
specified for use in various applications. MPEG-4 provides several toolsets that have no particular relationship
to each other, each with a different target function. The profiles of MPEG-4 Audio specify which of these tools
are used together for various applications.
Further, in previous MPEG standards, a single (perhaps multi-channel or multi-language) piece of content was
transmitted. In contrast, MPEG-4 supports a much more flexible concept of a soundtrack. Multiple tools may
be used to transmit several audio objects, and when using multiple tools together an audio composition
system is provided to create a single soundtrack from the several audio substreams. User interaction, terminal
capability, and speaker configuration may be used when determining how to produce a single soundtrack from
the component objects. This capability gives MPEG-4 significant advantages in quality and flexibility when
compared to previous audio standards.
0.2.5 MPEG-4 Audio provides capabilities for synthetic sound
In natural sound coding, an existing sound is compressed by a server, transmitted and decompressed at the
receiver. This type of coding is the subject of many existing standards for sound compression. In contrast,
MPEG-4 standardizes a novel paradigm in which synthetic sound descriptions, including synthetic speech and
synthetic music, are transmitted and then synthesized into sound at the receiver. Such capabilities open up
new areas of very-low-bitrate but still very-high-quality coding.
vi © ISO/IEC 2019 – All rights reserved
Transmission Storage Multiplex
0.2.6 MPEG-4 Audio provides capabilities for error robustness
Improved error robustness capabilities for all coding tools are provided through the error resilient bitstream
payload syntax. This tool supports advanced channel coding techniques, which can be adapted to the special
needs of given coding tools and a given communications channel. This error resilient bitstream payload syntax
is mandatory for all error resillient object types.
The error protection tool (EP tool) provides unequal error protection (UEP) for MPEG-4 Audio in conjunction
with the error resilient bitstream payload. UEP is an efficient method to improve the error robustness of source
coding schemes. It is used by various speech and audio coding systems operating over error-prone channels
such as mobile telephone networks or Digital Audio Broadcasting (DAB). The bits of the coded signal
representation are first grouped into different classes according to their error sensitivity. Then error protection
is individually applied to the different classes, giving better protection to more sensitive bits.
Improved error robustness for AAC is provided by a set of error resilience tools. These tools reduce the
perceived degradation of the decoded audio signal that is caused by corrupted bits in the bitstream payload.
0.2.7 MPEG-4 Audio provides capabilities for scalability
Previous MPEG Audio standards provided a single bitrate, single bandwidth toolset, with different
configurations of that toolset specified for use in various appl
...
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