ISO/IEC 13818-7:2004
(Main)Information technology — Generic coding of moving pictures and associated audio information — Part 7: Advanced Audio Coding (AAC)
Information technology — Generic coding of moving pictures and associated audio information — Part 7: Advanced Audio Coding (AAC)
ISO/IEC 13818-7:2004 specifies MPEG-2 Advanced Audio Coding (AAC), a multi-channel audio coding standard that delivers higher quality than is achievable when requiring MPEG-1 backwards compatibility. It provides ITU-R "indistinguishable" quality at a data rate of 320 kbit/s for five full-bandwidth channel audio signals. In comparison to ISO/IEC 13818-7:2003, ISO/IEC 13818-7:2004 supplements information on how to transmit and obtain MPEG-4 SBR data as part of the MPEG-2 AAC access unit.
Technologies de l'information — Codage générique des images animées et du son associé — Partie 7: Codage du son avancé (AAC)
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Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 13818-7
Third edition
2004-10-15
Information technology — Generic
coding of moving pictures and
associated audio information —
Part 7:
Advanced Audio Coding (AAC)
Technologies de l’information — Codage générique des images
animées et du son associé —
Partie 7: Codage du son avancé (AAC)
Reference number
ISO/IEC 13818-7:2004(E)
©
ISO/IEC 2004
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ISO/IEC 13818-7:2004(E)
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ISO/IEC 13818-7:2004(E)
Contents Page
1 Scope. 1
1.1 MPEG-2 AAC Tools Overview . 1
2 Normative References . 8
3 Terms and Definitions . 8
4 Symbols and Abbreviations. 15
4.1 Arithmetic Operators . 15
4.2 Logical Operators. 16
4.3 Relational Operators . 16
4.4 Bitwise Operators. 17
4.5 Assignment . 17
4.6 Mnemonics. 17
4.7 Constants . 17
5 Method of Describing Bitstream Syntax.17
6 Syntax. 19
6.1 Audio Data Interchange Format, ADIF. 19
6.2 Audio Data Transport Stream, ADTS. 20
6.3 Raw Data . 22
7 Profiles and Profile Interoperability . 34
7.1 Profiles . 34
7.2 Profile Interoperability . 36
8 General Information. 37
8.1 Audio Data Interchange Format (ADIF) and Audio Data Transport Stream (ADTS). 37
8.2 Decoding of Raw Data . 42
8.3 Decoding of a single_channel_element() (SCE), a channel_pair_element() (CPE) or an
individual_channel_stream() (ICS). 47
8.4 Low Frequency Enhancement Channel (LFE). 54
8.5 program_config_element() (PCE) . 55
8.6 Data Stream Element (DSE). 59
8.7 Fill Element (FIL). 60
8.8 Dedoding of extension_payload() . 60
8.9 Tables. 66
8.10 Figures . 74
9 Noiseless Coding . 74
9.1 Tool Description . 74
9.2 Definitions . 75
9.3 Decoding Process. 77
9.4 Tables. 80
10 Quantization . 81
10.1 Tool Description . 81
10.2 Definitions . 81
10.3 Decoding Process. 81
11 Scalefactors. 82
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ISO/IEC 13818-7:2004(E)
11.1 Tool Description .82
11.2 Definitions.82
11.3 Decoding Process .83
12 Joint Coding.84
12.1 M/S Stereo.84
12.2 Intensity Stereo .86
12.3 Coupling Channel.88
13 Prediction.92
13.1 Tool Description .92
13.2 Definitions.92
13.3 Decoding Process .93
13.4 Diagrams .100
14 Temporal Noise Shaping (TNS).100
14.1 Tool Description .100
14.2 Definitions.101
14.3 Decoding Process .101
15 Filterbank and Block Switching.103
15.1 Tool Description .103
15.2 Definitions.103
15.3 Decoding Process .104
16 Gain Control.108
16.1 Tool Description .108
16.2 Definitions.109
16.3 Decoding Process .109
16.4 Diagrams .115
16.5 Tables.115
Annex A (normative) Huffman Codebook Tables.117
Annex B (informative) Information on Unused Codebooks .138
Annex C (informative) Encoder .139
C.1 Psychoacoustic Model.139
C.2 Gain Control .171
C.3 Filterbank and Block Switching .172
C.4 Prediction.175
C.5 Temporal Noise Shaping (TNS) .178
C.6 Joint Coding.179
C.7 Quantization .181
C.8 Noiseless Coding .188
C.9 Features of AAC dynamic range control .191
Annex D (informative) Patent Holders .193
D.1 List of Patent Holders .193
Annex E (informative) Registration Procedure.194
E.1 Procedure for the Request of a Registered Identifier (RID).194
E.2 Responsibilities of the Registration Authority.194
E.3 Contact Information of the Registration Authority .194
E.4 Responsibilities of Parties Requesting a RID.195
E.5 Appeal procedure for Denied Applications.195
Annex F (informative) Registration Application Form.196
Annex G (informative) Registration Authority.197
Bibliography.198
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ISO/IEC 13818-7:2004(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
ISO/IEC 13818-7 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
This third edition cancels and replaces the second edition (ISO/IEC 13818-7:2003), which has been
technically revised. It also incorporates the Amendment ISO/IEC 13818-7:2003/Amd.1:2004.
ISO/IEC 13818 consists of the following parts, under the general title Information technology — Generic
coding of moving pictures and associated audio information:
— Part 1: Systems
— Part 2: Video
— Part 3: Audio
— Part 4: Conformance testing
— Part 5: Software simulation
— Part 6: Extensions for DSM-CC
— Part 7: Advanced Audio Coding (AAC)
— Part 9: Extension for real time interface for systems decoders
— Part 10: Conformance extensions for Digital Storage Media Command and Control (DSM-CC)
— Part 11: IPMP on MPEG-2 systems
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ISO/IEC 13818-7:2004(E)
Introduction
The standardization body ISO/IEC JTC 1/SC 29/WG 11, also known as the Moving Pictures Experts Group
(MPEG), was established in 1988 to specify digital video and audio coding schemes at low data rates. MPEG
completed its first phase of audio specifications (MPEG-1) in November 1992, ISO/IEC 11172-3. In its second
phase of development, the MPEG Audio subgroup defined a multichannel extension to MPEG-1 audio that is
backwards compatible with existing MPEG-1 systems (MPEG-2 BC) and defined an audio coding standard at
lower sampling frequencies than MPEG-1, ISO/IEC 13818-3.
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.
The ISO and IEC take no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured the ISO and 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 the ISO and IEC. Information may be obtained
from the companies listed in Annex D.
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 D. ISO and IEC shall not be held responsible for identifying any or
all such patent rights.
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INTERNATIONAL STANDARD ISO/IEC 13818-7:2004(E)
Information technology — Generic coding of moving pictures
and associated audio information —
Part 7:
Advanced Audio Coding (AAC)
1 Scope
This International Standard describes the MPEG-2 audio non-backwards compatible
standard called MPEG-2 Advanced Audio Coding, AAC [1], a higher quality multichannel
standard than achievable while requiring MPEG-1 backwards compatibility. This MPEG-2
AAC audio standard allows for ITU-R ‘indistinguishable’ quality according to [2] at data rates
of 320 kbit/s for five full-bandwidth channel audio signals.
The AAC decoding process makes use of a number of required tools and a number of
optional tools. Table 1 lists the tools and their status as required or optional. Required tools
are mandatory in any possible profile. Optional tools may not be required in some profiles.
Table 1 – AAC decoder tools
Tool Name Required / Optional
Bitstream Formatter Required
Noiseless Decoding Required
Inverse quantization Required
Rescaling Required
M/S Optional
Prediction Optional
Intensity Optional
Dependently switched coupling Optional
TNS Optional
Filterbank / block switching Required
Gain control Optional
Independently switched coupling Optional
1.1 MPEG-2 AAC Tools Overview
The basic structure of the MPEG-2 AAC system is shown in Figure 1 and Figure 2. As is
shown in Table 1, there are both required and optional tools in the decoder. The data flow
in this diagram is from left to right, top to bottom. The functions of the decoder are to find
the description of the quantized audio spectra in the bitstream, decode the quantized values
and other reconstruction information, reconstruct the quantized spectra, process the
reconstructed spectra through whatever tools are active in the bitstream in order to arrive at
the actual signal spectra as described by the input bitstream, and finally convert the
frequency domain spectra to the time domain, with or without an optional gain control tool.
Following the initial reconstruction and scaling of the spectrum reconstruction, there are
many optional tools that modify one or more of the spectra in order to provide more efficient
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ISO/IEC 13818-7:2004(E)
coding. For each of the optional tools that operate in the spectral domain, the option to
“pass through” is retained, and in all cases where a spectral operation is omitted, the
spectra at its input are passed directly through the tool without modification.
The input to the bitstream demultiplexer tool is the MPEG-2 AAC bitstream. The
demultiplexer separates the parts of the MPEG-AAC data stream into the parts for each
tool, and provides each of the tools with the bitstream information related to that tool.
The outputs from the bitstream demultiplexer tool are:
• The sectioning information for the noiselessly coded spectra
• The noiselessly coded spectra
• The M/S decision information (optional)
• The predictor state information (optional)
• The intensity stereo control information and coupling channel control information
(both optional)
• The temporal noise shaping (TNS) information (optional)
• The filterbank control information
• The gain control information (optional)
The noiseless decoding tool takes information from the bitstream demultiplexer, parses that
information, decodes the Huffman coded data, and reconstructs the quantized spectra and
the Huffman and DPCM coded scalefactors.
The inputs to the noiseless decoding tool are:
• The sectioning information for the noiselessly coded spectra
• The noiselessly coded spectra
The outputs of the Noiseless Decoding tool are:
• The decoded integer representation of the scalefactors:
• The quantized values for the spectra
The inverse quantizer tool takes the quantized values for the spectra, and converts the
integer values to the non-scaled, reconstructed spectra. This quantizer is a non-uniform
quantizer.
The input to the Inverse Quantizer tool is:
• The quantized values for the spectra
The output of the inverse quantizer tool is:
• The un-scaled, inversely quantized spectra
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ISO/IEC 13818-7:2004(E)
The rescaling tool converts the integer representation of the scalefactors to the actual
values, and multiplies the un-scaled inversely quantized spectra by the relevant
scalefactors.
The inputs to the rescaling tool are:
• The decoded integer representation of the scalefactors
• The un-scaled, inversely quantized spectra
The output from the scalefactors tool is:
• The scaled, inversely quantized spectra
The M/S tool converts spectra pairs from Mid/Side to Left/Right under control of the M/S
decision information in order to improve coding efficiency.
The inputs to the M/S tool are:
• The M/S decision information
• The scaled, inversely quantized spectra related to pairs of channels
The output from the M/S tool is:
• The scaled, inversely quantized spectra related to pairs of channels, after M/S
decoding
Note: The scaled, inversely quantized spectra of individually coded channels are not processed by the M/S block, rather they are passed
directly through the block without modification. If the M/S block is not active, all spectra are passed through this block unmodified.
The prediction tool reverses the prediction process carried out at the encoder. This
prediction process re-inserts the redundancy that was extracted by the prediction tool at the
encoder, under the control of the predictor state information. This tool is implemented as a
second order backward adaptive predictor. The inputs to the prediction tool are:
• The predictor state information
• The scaled, inversely quantized spectra
The output from the prediction tool is:
• The scaled, inversely quantized spectra, after prediction is applied.
Note: If the prediction is disabled, the scaled, inversely quantized spectra are passed directly through the block without modification.
The intensity stereo tool implements intensity stereo decoding on pairs of spectra.
The inputs to the intensity stereo tool are:
• The inversely quantized spectra
• The intensity stereo control information
The output from the intensity stereo tool is:
• The inversely quantized spectra after intensity channel decoding.
Note: The scaled, inversely quantized spectra of individually coded channels are passed directly through this tool without modification, if
intensity stereo is not indicated. The intensity stereo tool and M/S tool are arranged so that the operation of M/S and intensity stereo are
mutually exclusive on any given scalefactor band and group of one pair of spectra.
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ISO/IEC 13818-7:2004(E)
The coupling tool for dependently switched coupling channels adds the relevant data from
dependently switched coupling channels to the spectra, as directed by the coupling control
information.
The inputs to the coupling tool are:
• The inversely quantized spectra
• The coupling control information
The output from the coupling tool is:
• The inversely quantized spectra coupled with the dependently switched coupling
channels.
Note: The scaled, inversely quantized spectra are passed directly through this tool without modification, if coupling is not indicated.
Depending on the coupling control information, dependently switched coupling channels might either be coupled before or after the TNS
processing.
The coupling tool for independently switched coupling channels adds the relevant data from
independently switched coupling channels to the time signal, as directed by the coupling
control information.
The inputs to the coupling tool are:
• The time signal as output by the filterbank
• The coupling control information
The output from the coupling tool is:
• The time signal coupled with the independently switched coupling channels.
Note: The time signal is passed directly through this tool without modification, if coupling is not indicated.
The temporal noise shaping (TNS) tool implements a control of the fine time structure of the
coding noise. In the encoder, the TNS process has flattened the temporal envelope of the
signal to which it has been applied. In the decoder, the inverse process is used to restore
the actual temporal envelope(s), under control of the TNS information. This is done by
applying a filtering process to parts of the spectral data.
The inputs to the TNS tool are:
• The inversely quantized spectra
• The TNS information
The output from the TNS block is:
• The inversely quantized spectra
Note: If this block is disabled, the inversely quantized spectra are passed through without modification.
The filterbank / block switching tool applies the inverse of the frequency mapping that was
carried out in the encoder. An inverse modified discrete cosine transform (IMDCT) is used
for the filterbank tool. The IMDCT can be configured to support either one set of 128 or
1024, or four sets of 32 or 256 spectral coefficients.
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The inputs to the filterbank tool are:
• The inversely quantized spectra
• The filterbank control information
The output(s) from the filterbank tool is (are):
• The time domain reconstructed audio signal(s).
When present, the gain control tool applies a separate time domain gain control to each of
4 frequency bands that have been created by the gain control PQF filterbank in the
encoder. Then, it assembles the 4 frequency bands and reconstructs the time waveform
through the gain control tool’s filterbank.
The inputs to the gain control tool are:
• The time domain reconstructed audio signal(s)
• The gain control information
The output(s) from the gain control tool is (are):
• The time domain reconstructed audio signal(s)
If the gain control tool is not active, the time domain reconstructed audi
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