ISO/IEC 23003-3:2012

INTERNATIONAL ISO/IEC
STANDARD 23003-3
First edition
2012-04-01
Information technology — MPEG audio
technologies —
Part 3:
Unified speech and audio coding
Technologies de l'information — Technologies audio MPEG —
Partie 3: Discours unifié et codage audio

Reference number
©
ISO/IEC 2012
©  ISO/IEC 2012
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ii © ISO/IEC 2012 – All rights reserved

Contents Page
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Symbols and abbreviated terms . 2
4 Technical Overview . 2
4.1 Decoder block diagram . 2
4.2 Overview of the decoder tools . 5
4.3 Combination of USAC with MPEG Surround and SAOC . 8
4.4 Interface between USAC and Systems . 9
4.5 USAC Profiles and Levels. 9
5 Syntax . 12
5.1 General . 12
5.2 Decoder configuration (UsacConfig) . 12
5.3 USAC bitstream payloads . 17
6 Data Structure . 50
6.1 USAC configuration . 50
6.2 USAC payload . 63
7 Tool Descriptions . 81
7.1 Quantization . 81
7.2 Noise Filling . 82
7.3 Scalefactors . 84
7.4 Spectral Noiseless coding . 84
7.5 enhanced SBR Tool (eSBR). 90
7.6 Inter-subband-sample Temporal Envelope Shaping (inter-TES) . 139
7.7 Joint Stereo Coding . 142
7.8 TNS . 149
7.9 Filterbank and block switching . 151
7.10 Time-Warped Filterbank and Blockswitching . 159
7.11 MPEG Surround for Mono to Stereo upmixing . 167
7.12 AVQ decoding . 180
7.13 LPC-filter . 186
7.14 ACELP. 193
7.15 MDCT based TCX . 202
7.16 Forward Aliasing Cancellation (FAC) tool . 206
7.17 Post-processing of the synthesis signal . 208
Annex A (normative) Tables . 211
Annex B (informative) Encoder Tools . 216
Annex C (normative) Tables for Arithmetic Decoder . 254
Annex D (normative) Tables for Predictive Vector Coding . 260
Annex E (informative) Adaptive Time / Frequency Post-Processing . 269
Annex F (informative) Audio/Systems Interaction . 275
Annex G (informative) Patent Statements . 277
Bibliography . 278
© ISO/IEC 2012 – 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. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
ISO/IEC 23003-3 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
ISO/IEC 23003 consists of the following parts, under the general title Information technology — MPEG audio
technologies:
 Part 1: MPEG Surround
 Part 2: Spatial Audio Object Coding (SAOC)
 Part 3: Unified speech and audio coding
iv © ISO/IEC 2012 – All rights reserved

Introduction
As mobile appliances become multi-functional, multiple devices converge into a single device. Typically, a
wide variety of multimedia content is required to be played on or streamed to these mobile devices, including
audio data that consists of a mix of speech and music.
This part of ISO/IEC 23003 Unified Speech and Audio Coding (USAC) is a new audio coding standard that
allows for coding of speech, audio or any mixture of speech and audio with a consistent audio quality for all
sound material over a wide range of bitrates. It supports single and multi-channel coding at high bitrates and
provides perceptually transparent quality. At the same time, it enables very efficient coding at very low bitrates
while retaining the full audio bandwidth.
Where previous audio codecs had specific strengths in coding either speech or audio content, USAC is able to
encode all content equally well, regardless of the content type.
In order to achieve equally good quality for coding audio and speech, the developers of USAC employed the
proven MDCT-based transform coding techniques known from MPEG-4 audio and combined them with
specialized speech coder elements like ACELP. Parametric coding tools such as MPEG-4 spectral band
replication (SBR) and MPEG-D MPEG surround were enhanced and tightly integrated into the codec. The
result delivers highly efficient coding and operates down to the lowest bit rates.
The main focus of this codec are applications in the field of typical broadcast scenarios, multi-media download
to mobile devices, user-generated content such as podcasts, digital radio, mobile TV, audio books, etc.
The International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC)
draw attention to the fact that it is claimed that compliance with this document may involve the use of patents.
ISO and the IEC take no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured ISO and the IEC that he is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this respect,
the statement of the holder of this patent right is registered with ISO and the IEC. Information may be obtained
from the companies listed in Annex G.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights other than those identified in Annex G. ISO and the IEC shall not be held responsible for identifying any
or all such patent rights.
© ISO/IEC 2012 – All rights reserved v

INTERNATIONAL STANDARD ISO/IEC 23003-3:2012(E)

Information technology — MPEG audio technologies —
Part 3:
Unified speech and audio coding
1 Scope
This part of ISO/IEC 23003 specifies a unfied speech and audio codec which is capable of coding signals
having an arbitrary mix of speech and audio content. The codec has a performance comparable to or better
than the best known coding technology that might be tailored specifically to coding of either speech or general
audio content. The codec supports single and multi-channel coding at high bitrates and provides perceptually
transparent quality. At the same time, it enables very efficient coding at very low bitrates while retaining the full
audio bandwidth.
This part of ISO/IEC 23003 incorporates several perceptually-based compression techniques developed in
previous MPEG standards: perceptually shaped quantization noise, parametric coding of the upper spectrum
region and parametric coding of the stereo sound stage. However, it combines these well-known perceptual
techniques with a source coding technique: a model of sound production, specifically that of human speech.
2 Normative references
The following referenced documents are indispensible for the application of this document. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 14496-3, Information technology — Coding of audio-visual objects — Part 3: Audio
ISO/IEC 23003-1, Information technology — MPEG audio technologies — Part 1: MPEG Surround
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 14496-3, ISO/IEC 23003-1 and
the following apply.
3.1.1
algebraic codebook
fixed codebook where an algebraic code is used to populate the excitation vectors (innovation vectors)
NOTE The excitation contains a small number of nonzero pulses with predefined interlaced sets of potential positions.
The amplitudes and positions of the pulses of the kth excitation codevector can be derived from its index k through a rule
requiring no or minimal physical storage, in contrast with stochastic codebooks whereby the path from the index to the
associated codevector involves look-up tables.
© ISO/IEC 2012 – All rights reserved 1

3.1.2
AVQ
Algebraic Vector Quantizer
process associating, to an input bl
...