ISO/IEC 23000-2:2008

Information technology — Multimedia application format (MPEG-A) — Part 2: MPEG music player application format

ISO/IEC 23000-2:2008 presents a basic architecture for constructing an annotated music library. It defines a simple file format for songs and a file format for albums and playlists. A conformant player application has to support all these specified file formats.

Technologies de l'information — Format pour application multimédia (MPEG-A) — Partie 2: Format pour application musicienne MPEG

General Information

• Status: Published
• Publication Date: 16-Jan-2008
• ICS: 35.040 - Information coding
• ICS: 35.040.40 - Coding of audio, video, multimedia and hypermedia information
• Technical Committee: ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information
• Drafting Committee: ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information
• Current Stage: 9060 - Close of review
• Completion Date: 04-Mar-2029

Relations

• Revises: ISO/IEC 23000-2:2006 - Information technology — Multimedia application format (MPEG-A) — Part 2: MPEG music player application format
• Effective Date: 15-Apr-2008

Overview

ISO/IEC 23000-2:2008 (MPEG-A Part 2) defines the MPEG music player application format - a basic architecture for constructing an annotated music library. The standard specifies simple, interoperable file formats for songs, albums, and playlists, and sets out the requirements a conformant player application must support. It shows how existing MP3 content can be carried in the MPEG-4 / MPEG-7 ecosystem and extends the player model to support protected content using MP4 and MP21 files.

Key Topics

• File formats: Defines song-level file format and album/playlist formats tailored for music libraries; built on the ISO Base Media File Format and MP4/MP21 frameworks.
• Audio support: References common audio codecs (e.g., MPEG-1 Layer III / MP3 and MPEG-4 audio) and how audio tracks are represented.
• Metadata: Uses MPEG-7 (Multimedia Description Schemes) to represent rich metadata (artist, album, title, ID3 mapping examples).
• Protection & DRM: Describes protection mechanisms including AES-128 encryption, MPEG-4 IPMP extensions, MPEG-21 IPMP, and MPEG-21 REL profiles; distinguishes fixed encryption in MP4 from flexible protection and key management in MP21.
• Conformance & reference software: Includes conformance points for devices and reference software to aid implementation and interoperability.
• Interoperability considerations: Signalling, encryption of audio and metadata, and usage of file format “brands” to ensure consistent behavior across players and services.

Applications

Who uses ISO/IEC 23000-2 and why:

• Music player developers - implementers of desktop, mobile, or embedded players that must support annotated song files, albums, and playlists.
• Device manufacturers - to ensure conformance and predictable behavior for music playback and metadata handling.
• Content distributors and streaming services - to package MP3 libraries in MPEG-4/MP21 containers with optional protection and rights information.
• DRM and security engineers - to apply AES-128 encryption and MPEG IPMP/MPEG-21 protection profiles and to design key management workflows where required.
• Archivists and metadata engineers - to migrate legacy MP3 libraries into a richer MPEG-4/MPEG-7 metadata environment for better search, organization, and long-term preservation.

Practical use-cases include building interoperable music libraries, converting MP3 collections into MP4/MP21 packages, implementing protected music players, and standardizing metadata exchange for cataloging and discovery.

Related Standards

• ISO/IEC 14496-12 / 14496-14 (ISO Base Media File Format / MP4 file format)
• ISO/IEC 14496-3 (MPEG-4 Audio)
• ISO/IEC 11172-3 / 13818-3 (MPEG-1 Layer III / MP3)
• ISO/IEC 15938-5 (MPEG-7 Multimedia Description Schemes)
• ISO/IEC 21000-2 / 4 / 5 / 9 (MPEG-21 Digital Item Declaration, IPMP, REL, File Format)

Keywords: ISO/IEC 23000-2, MPEG music player, MPEG-A, MP4, MP21, MPEG-7, MP3 migration, AES-128, IPMP, music metadata, playlist format, conformance.

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 23000-2
Second edition
2008-01-15
Corrected version
2008-04-15
Information technology — Muiltimedia
application format (MPEG-A) —
Part 2:
MPEG music player application format
Technologies de l'information — Format pour application multimédia
(MPEG-A) —
Partie 2: Format pour application musicienne MPEG

Reference number
©
ISO/IEC 2008
PDF disclaimer
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accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
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the file(s); the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the files are suitable for
use by ISO member bodies. In the unlikely event that a problem relating to them is found, please inform the Central Secretariat at the
address given below.
This CD-ROM contains:
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Adobe and Acrobat are trademarks of Adobe Systems Incorporated.
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...

INTERNATIONAL ISO/IEC
STANDARD 23000-2
Second edition
2008-01-15
Corrected version
2008-04-15
Information technology — Multimedia
application format (MPEG-A) —
Part 2:
MPEG music player application format
Technologies de l'information — Format pour application multimédia
(MPEG-A) —
Partie 2: Format pour application musicienne MPEG

Reference number
©
ISO/IEC 2008
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO/IEC 2008
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
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Published in Switzerland
ii © ISO/IEC 2008 – All rights reserved

Contents Page
Foreword. v
Introduction . vi
1 Scope. 1
2 Normative references. 1
3 Overview of MPEG Standards . 2
3.1 MPEG-1 Layer III. 2
3.2 MPEG-4 “MPEG-1/2 Audio in MPEG-4” . 2
3.3 ISO Base Media File Format . 3
3.4 MPEG-4 File Format. 3
3.5 MPEG-21 File Format. 4
3.6 MPEG-7 Multi-Media Description Scheme. 4
4 Song File Format. 4
4.1 Introduction . 4
4.2 Audio track. 5
4.3 Meta-data. 5
4.4 File Conversion . 6
4.5 Playback. 6
4.6 File Structure. 7
5 Album and Playlist Format for the Music Player . 8
5.1 Introduction . 8
5.2 Single Track Album. 9
5.3 Multiple Track Album. 10
5.4 Playlist. 11
6 Scope of the Protected Music Player Application Format. 13
7 Overview of Basic Standards for Protection . 14
7.1 Protection and MPEG-4 File Formats . 14
7.2 AES-128 encryption. 14
7.3 MPEG-4 IPMP-X. 14
7.4 MPEG-21 IPMP Base Profile . 15
7.5 MPEG-21 REL MAM Profile . 16
8 Protection of mp4 files . 16
8.1 Introduction . 16
8.2 Signalling. 16
8.3 JPEG and MPEG-7 meta-data . 20
8.4 MPEG-21 DID album . 20
9 Protection of mp21 files using MPEG-21 IPMP and MPEG-21 REL . 21
9.1 Introduction . 21
9.2 Protection of single track mp21 files. 21
9.3 Protection of mp21 album files with multiple tracks. 22
10 Content encryption using AES-128. 23
10.1 Introduction . 23
10.2 MPEG-4 IPMP-X signalling of AES-128 encryption . 24
10.3 Encrypting the audio samples. 26
10.4 Encryption of JPEG and MPEG-7 meta-data.26
11 Usage of File Format Brands. 27
12 Conformance. 27
© ISO/IEC 2008 – All rights reserved iii

12.1 Introduction . 27
12.2 File structures. 27
12.3 Music Player device conformance points . 28
13 Reference Software. 28
13.1 Player architecture. 28
13.2 Player functionalities. 29
13.3 MP3onMP4 Access Unit translator. 30
13.4 File format. 30
13.5 External dependencies. 30
Annex A (informative) Example of ID3 information mapped to MPEG-7. 31
Annex B (informative) Example of DID in MAF . 33
Annex C (informative) Examples of MPEG-21 Protection Metadata. 35
Annex D (informative) Alternative protection signalling in mp4 files . 40
D.1 Introduction . 40
D.2 Interoperability with ISMACryp. 40
D.3 Linkage to external Key Management Systems. 42
Annex E (informative) Music Player Device Behaviour . 43
E.1 Introduction . 43
E.2 Unprotected music player . 43
E.3 Protected music player using the default protection. 44
E.4 Protected music player using flexible protection.44
Bibliography . 46

iv © ISO/IEC 2008 – All rights reserved

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.
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.
ISO/IEC 23000-2 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
This second edition cancels and replaces the first edition (ISO/IEC 23000-2:2006), which has been technically
revised.
ISO/IEC 23000 consists of the following parts, under the general title Information technology — Multimedia
application format (MPEG-A):
⎯ Part 1: Purpose for multimedia application formats [Technical Report]
⎯ Part 2: MPEG music player application format
⎯ Part 3: MPEG photo player application format
⎯ Part 4: Musical slide show application format
⎯ Part 5: Media streaming application format
⎯ Part 7: Open access application format
⎯ Part 8: Portable video application format
⎯ Part 9: Digital multimedia broadcasting application format
⎯ Part 10: Video surveillance application format
This corrected version of ISO/IEC 23000-2:2008 incorporates the following corrections: the provision of a
CD-ROM containing reference software for multimedia application format; an updated list of parts in the
Foreword.
© ISO/IEC 2008 – All rights reserved v

Introduction
MPEG has developed a number of standards, all of which strive to serve the needs of consumers and industry.
Among those are MPEG-4, a next-generation suite of standards for media compression, and MPEG-7, a suite
of standards for meta-data representation. MPEG-4 specifies what MPEG expects to be another very
successful specification, the MPEG-4 File Format, while MPEG-7 specifies not only signal-derived meta-data,
but also archival meta-data such as Artist, Album and Song Title.
As such, MPEG-4 and MPEG-7 represent an ideal environment to support the current “MP3 music library”
user experience, and, moreover, to extend that experience in new directions.
Firstly, this part of ISO/IEC 23000 shows how to carry MP3 information (music and meta-data) within the
MPEG-4 and MPEG-7 framework. Moving MP3 into the MPEG-4 world supports, as a baseline, everything
that users know and expect, but offers the capability to deliver a much richer music experience with
components of MPEG-4, MPEG-7 and MPEG-21 at our disposal.
Secondly, this part of ISO/IEC 23000 builds on the music player and extends it to the Protected Music Player
for both mp4 and mp21 file types including (1) mp4 file as protected content format with fixed encryption,
without key management components and (2) protected mp21 file with flexible tool selection and key
management components.
This part of ISO/IEC 23000 contains conformance and reference software.

vi © ISO/IEC 2008 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 23000-2:2008(E)

Information technology — Multimedia application format
(MPEG-A) —
Part 2:
MPEG music player application format
1 Scope
This part of ISO/IEC 23000 presents a basic architecture for constructing an annotated music library. It
defines a simple file format for songs and a file format for albums and playlists. A conformant player
application has to support all these specified file 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.
ISO/IEC 11172-3:1993, Information technology — Coding of moving pictures and associated audio for digital
storage media at up to about 1,5 Mbit/s — Part 3: Audio
ISO/IEC 13818-3:1998, Information technology — Generic coding of moving pictures and associated audio
information — Part 3: Audio
ISO/IEC 14496-2:2004, Information technology — Coding of audio-visual objects — Part 2: Visual
ISO/IEC 14496-3:2005, Information technology — Coding of audio-visual objects — Part 3: Audio
ISO/IEC 14496-12:2005, Information technology — Coding of audio-visual objects — Part 12: ISO base media
file format
ISO/IEC 14496-13:2004, Information technology — Coding of audio-visual objects — Part 13: Intellectual
Property Management and Protection (IPMP) extensions
ISO/IEC 14496-14:2003, Information technology — Coding of audio-visual objects — Part 14: MP4 file format
ISO/IEC 15938-5:2003, Information technology — Multimedia content description interface — Part 5:
Multimedia description schemes
ISO/IEC TR 15938-8:2002, Information technology — Multimedia content description interface — Part 8:
Extraction and use of MPEG-7 descriptions
ISO/IEC 21000-2:2005, Information technology — Multimedia framework (MPEG-21) — Part 2: Digital Item
Declaration
ISO/IEC 21000-4:2006, Information technology — Multimedia framework (MPEG-21) — Part 4: Intellectual
Property Management and Protection Components
ISO/IEC 21000-5:2004, Information technology — Multimedia framework (MPEG-21) — Part 5: Rights
Expression Language
ISO/IEC 21000-9:2005, Information technology — Multimedia framework (MPEG-21) — Part 9: File Format
© ISO/IEC 2008 – All rights reserved 1

3 Overview of MPEG Standards
3.1 MPEG-1 Layer III
ISO/IEC 11172-3:1993 specifies MPEG-1 Audio. From that specification, MPEG-1 Layer III (or MP3) is one of
the most widely deployed MPEG audio standards ever. Its wide appeal is due to both its good compression
performance and its simplicity of implementation. The vast majority of compressed music archives use MP3
encoding.
One aspect of the simplicity of Layer III is that it specifies a self-synchronizing transport, making it amenable
to both storage in a computer file and transmission over a channel without byte framing. In the context of
transmission channels, Layer III can operate over a constant-rate isocronous link, and has constant-rate
headers (as does Layer I and II). However Layer III is an instantaneously-variable-rate coder, which adapts to
the constant-rate channel by using a “bit buffer” and “back pointers.” Each of the headers signals the start of
another block of audio signal, however due to the Layer III syntax, the data associated with that next block of
audio signal may be in a prior segment of the bitstream, pointed to by the back pointer (see Figure 1,
specifically the curved arrow pointing to main_data_begin). We note that this is in contrast to the MPEG-4
view of data stream segmentation, in which one Access Unit contains all information necessary to decode one
segment of audio.
Figure 1 — Layer III bitstream organization

3.2 MPEG-4 “MPEG-1/2 Audio in MPEG-4”
ISO/IEC 14496-3:2005 subpart 9 “MPEG-1/2 Audio in MPEG-4” specifies a method for segmenting and
formatting Layer III bitstreams into MPEG-4 Access Units, and therefore is often referred to as “MP3onMP4”.
This consists primarily of re-arranging the compressed data associated with a given header such that it follows
the header. This typically results in new segments that are no longer of constant length, but that is perfectly in
accordance with the definition of MPEG-4 Access Units. See example in Figure 2.
2 © ISO/IEC 2008 – All rights reserved

Figure 2 — Converting an MPEG-1/2 Layer 3 bitstream into mp3_channel_elements

3.3 ISO Base Media File Format
ISO/IEC 14496-12:2005 specifies the ISO Base Media File Format that is designed to contain timed media
information for a presentation in a flexible, extensible format that facilitates interchange, management, editing,
and presentation of the media. The ISO Base Media File Format is a base format for media file formats. In
particular, the MPEG-4 file format derives from this base file format.

ISO file
Movie data   Media data
trak (video)
…other boxes
Interleaved, time-ordered, video
trak (audio)   and audio frames

Figure 3 — Example of a simple ISO file used for interchange, containing two streams

The file structure is object-oriented as shown in Figure 3 which means that a file can be decomposed into
constituent objects very simply, and the structure of the objects inferred directly from their type. The file format
is designed to be independent of any particular network protocol while enabling efficient support for them in
general.
3.4 MPEG-4 File Format
ISO/IEC 14496-12:2005 and ISO/IEC 14496-14:2003 together specify the MPEG-4 File Format. This supports
storage of compressed audio data (e.g. MP3onMP4) in tracks. It also provides support for metadata in the
form of ‘meta’ boxes at the File, Movie and Track level. This allows support for static (un-timed) meta-data.
Figure 4 schematically illustrates the location of these un-timed MPEG-7 Metadata boxes. 4.6 provides details
as to when the Metadata boxes at each level are used.
© ISO/IEC 2008 – All rights reserved 3

Trak
Movie
meta
meta Mdat
meta
Trak
meta
Figure 4 — Support of Static un-timed Metadata in ISO/MP4 Files

3.5 MPEG-21 File Format
ISO/IEC 21000-9:2005 specifies the MPEG-21 File Format. It uses the file-level ‘meta’ box of the ISO Base
Media File Format to store an MPEG-21 Digital Item Declaration. The resources are either included in the
file‘s mdat box or are externally referenced. The ‘iloc’ and the ‘iinf’ boxes in the meta box are used to address
the resources. Figure 5 shows a simple example of an MPEG-21 file.
ftyp meta mdat
brand=’mp21’  hldr=’mp21’
iloc/iinf
item_count=n
item_ID, item_name, content_type
…
xml
MPEG-21 DID
Figure 5 — Basic structure of an MPEG-21 File

3.6 MPEG-7 Multi-Media Description Scheme
ISO/IEC 15938-5:2003, the Multimedia Description Scheme (MDS) specifies all non-Visual and non-Audio
specific metadata (e.g. Artist, Title, Date) in the MPEG-7 standard. As such it is able to represent all of the
information found in the ID3v1 [3] metadata tagging format, as well as the corresponding information in the
ID3v2 format, with its most popular version ID3v2.3 [4].

4 Song File Format
4.1 Introduction
This clause defines a format that contains a single music track with associated meta-data and a single still
image containing cover art.
4 © ISO/IEC 2008 – All rights reserved

4.2 Audio track
The audio track contains encoded audio data according to ISO/IEC 11172-3 Layer III (“MP3”) in the form of
MPEG-4 audio samples.
ISO/IEC 11172-3 Layer III (“MP3”) specifies a music compression scheme that results in a sequence of bits,
forming a bitstream file. In contrast, ISO/IEC 14496-3:2005 specifies a music compression scheme that
results in a sequence of packets (Access Units) that contain all data corresponding to one fraction of playout
time. Access Units and their corresponding timing information is stored directly into the MPEG-4 File Format,
specified in ISO/IEC 14496-14:2003. An MP3 bitstream can be translated into a series of MP3 Access Units
using the “MP3onMP4” conversion as specified in ISO/IEC 14496-3:2005 subpart 9. This conversion allows to
use mp3 encoded audio data like audio data encoded with any MPEG-4 audio codec type (e.g. AAC) within
an MPEG-4 system, e.g. store the MP3 access units to an MPEG-4 file.
4.3 Meta-data
The MPEG-4 file format supports the storage of meta-data associated to a data track. Associated meta-data
describing the audio track, like artist or song name, is expressed in MPEG-7 nomenclature, as specified in
ISO/IEC 15938-5:2003. MP3 bitstream files can contain associated meta-data, typically ID3 tags [3,4]. The
specific mapping from ID3 v1.1 tags and the corresponding ID3 v2.3 frames to MPEG-7 meta-data is show in
Table 1. Parenthetical comments under Artist clarify that MPEG-7 is able to make a distinction between Artist
as a person and Artist as a group name.
Table 1 — Mapping from ID3 v1.1 and ID3 v2.3 Tags to MPEG-7
ID3 v1 ID3 v2.3 Frame Description MPEG-7 Path
Artist TOPE Artist performing CreationInformation/Creation/Creator[Role/@href=”urn:mpeg:mp
the song eg7:RoleCS:2001:PERFORMER”]/Agent[@xsi:type=”PersonTyp
(Original artist /
e”]/Name/{FamilyName, GivenName} (Artist Name)
performer)
CreationInformation/Creation/Creator[Role/@href=”urn:mpeg:mp
eg7:RoleCS:2001:PERFORMER”]/Agent[@xsi:type=”PersonGro
upType”]/Name (Group Name)
Album TALB Title of the album CreationInformation/Creation/Title[@type=”albumTitle”]
(Album / Movie /
Show title)
Song Title TIT2 Title of the song CreationInformation/Creation/Title[@type=”songTitle”]
(Title / Songname /
Content description)
Year TORY Year of the CreationInformation/CreationCoordinates/Date/TimePoint
recording (Recording date.)
(Original release
year)
Comment COMM Any comment of CreationInformation/Creation/Abstract/FreeTextAnnotation
any length
Track TRCK CD track number Semantics/SemanticBase[@xsi:type=”SemanticStateType”]/Attrib
of song uteValuePair
(Track number /
Position in set)
Genre TCON ID 3 V1.1 Genre CreationInformation/Classification/Genre[@href=”urn:id3:v1:4”]
(Content type) ID 3 V2 Genre CreationInformation/Classification/Genre[@href=”urn:id3:v1:4”]/T
(4)(Eurodisco) erm[@termID=”urn:id3:v2:Eurodisco”]
CreationInformation/Classification/Genre[@href=”urn:id3:v1:4”]
CreationInformation/Classification/Genre[@type=”secondary][@h
ref=”urn:id3:v2:Eurodisco”]
MPEG-7 Path notation is a shorthand for the full XML notation, and an example of the correspondence
between MPEG-7 Path and XML notation is shown in Annex A.
© ISO/IEC 2008 – All rights reserved 5

4.4 File Conversion
This subclause describes a lossless, reversible conversion of a standard mp3 bitstream file into an MPEG-4
file according to this Music Player Application Format. An MP3 bitstream file (containing mp3 audio frames
and an ID3 tag) is converted using two modules, as shown in Figure 6.
The first module translates an MP3 bitstream into a series of MP3 Access Units. This is accomplished by the
MP3onMP4 formatter, specified in ISO/IEC 14496-3:2005 subpart 9. The Access Units are stored into one
audio track of an MPEG-4 File.
The second module extracts the meta-data information from the input file’s ID3 tag and expresses it as
MPEG-7 descriptor according to 4.3. This MPEG-7 meta-data is stored - together with the optional JPEG
image for cover art - into the corresponding meta-box of the audio track.

MP3 file with ID3 MP3onMP4
MP3onMP4
data
tags formatter
MP4 File
Extract ID3tags
MPEG-7
and express in
metadata
MPEG-7
JPEG
Image
Figure 6 — Encoder System Architecture

4.5 Playback
Playback consists of
⎯ extracting the meta-data from the MPEG-4 file and displaying it on a suitable visual interface.
⎯ extracting the MP3onMP4 data from the MPEG-4 file, filtering it with very light-weight de-formatting
operation, and playing it through a “classic” MP3 decoder.

In practice, it may be that the MP3onMP4 data is played by an “MP3onMP4 decoder,” consisting of the
concatenation of the MP3onMP4 deformatter and the MP3 decoder.

6 © ISO/IEC 2008 – All rights reserved

MP4onMP3
decoder
MP3onMP4
MP3onMP4
MP3 decoder
data
de-formatter
MP4 File
Display
MPEG-7
Artist, Album,
metadata
Song
JPEG
image
JPEG decoder Display album art

Figure 7 — Player System Architecture

4.6 File Structure
This subclause specifies the basic song file format of the Music Player Application Format in detail. The
structure is based on the Playback model described above, however present a detailed view of the internals of
the File Format (based on ISO/IEC 14496-12:2005), and highlight what resources a Playback application
requires in order to decode the file.
For this structure (and the structures of the following Clause 5) the following information is given:
⎯ File Example – a visual example of the file, showing the important boxes for playback (some boxes have
been omitted to minimise complexity).
⎯ File Type – A top level handler which indicates the type of file format that the structure uses. Hence if a
Playback application supports either the major-brand and/or the compatible-brands ftype box field, it can
decode this structure.
⎯ Meta data Handler Type – MAF currently supports file level (ftyp) meta type handlers of mp7t and mp21.
⎯ Resource Lookup/Playback – this is an additional section to the Playback model in order to highlight
which ISO Base File Format boxes are used to decode the file.
⎯ Notes – additional information that may aid understanding of the structure.
Additionally the following common notes apply to all structures:

NOTE The extent_count=1 for all items in the iloc box in each Resource Lookup/Playback section.

This subclause defines the basic structure of the Music Player Application Format specification: a MPEG-4 file
with a single music track with optional JPEG image and MPEG-7 meta-data. The MPEG-7 Meta Data and
optional JPEG Image are implicitly associated with the MP3 data by using the trak level meta box in the same
track that contains the MP3 data.

© ISO/IEC 2008 – All rights reserved 7

ftyp moov mdat
brand=’mp42’
trak
mdia
MP3onMP4 AUs
meta
hldr=’mp7t’
iloc/iinf
item_count=1
JPEG
item_ID = 1
data bytes
item_name =
content_type = image/jpeg
xml
MPEG-7 XML
Figure 8 — Example of file structure for mp4 song file containing one audio track with MP3onMP4
audio, MPEG-7 meta-data and JPEG image
File Type: major-brand = ‘mp42’, compatible-brands = ‘mp42’, ‘iso2’, ‘MMU2’.
Meta-data Handler Type: MPEG-7 Text (mp7t) at track level
Resource Lookup and Playback:
⎯ A mp4 MAF application uses the mdia box and subsequent child boxes of the sample description to find
and decode the MP3 data (stored as MP3onMP4 Access Units [14496-3:2005]).
⎯ To present the optional JPEG Image, the application uses a combination of iloc and iinf boxes as shown
below:
for(all items in the iloc) {
if(iinf->content_type == image/jpeg) {
//locate image using
iloc->extent_offset
iloc->extent_length
}
}
NOTE 1 This structure contains MPEG-7 XML meta data pertaining to the mandatory track inside the mdat.
NOTE 2 Here the meta box inside the trak box is used to link the MP3 and the JPEG together. The coupling with the
use of this box will suffice for single track MAFs.
5 Album and Playlist Format for the Music Player
5.1 Introduction
This clause describes an extension to the core song file format. It allows to create complete album files as well
as playlist files that references external song files. The MPEG-21 File Format [ISO/IEC 21000-9:2005] and the
MPEG-21 Digital Item Declaration (DID) [ISO/IEC 21000-2] is used to enable this functionality.
8 © ISO/IEC 2008 – All rights reserved

5.2 Single Track Album
The explanation of the structure starts with the special case of an album that contains only one single song.
An MPEG-21 file contains an MPEG-21 DID as entry point and a single, hidden mp4 song file that is built
according to the previous Clause 4. The DID and the mp21 meta box are used to identify and locate the
resources. The relationship between the mp4 song file, its MPEG-7 meta data and the optional JPEG image is
held in the DID to give applications quick access to the meta-data of the album files (artist, title, cover
image,…) without parsing into the hidden mp4 song file(s).
File Type: major-brand = ‘mp21’, compatible-brands = ‘mp21’, ‘MMU2’.
Meta-data Handler Type: MPEG-21 (mp21) at file level
Resource Lookup and Playback:
⎯ The structure uses a parent meta box at the file level to refer to the hidden mp4 file inside the mdat box
and directly to items (MPEG-7 meta data and JPEG image) inside the hidden mp4 file.
⎯ A MAF application shall decode this file using the DID as an entry point to the resource mapping
technique as described in the following stub code:
for (all Resources/Statement elements in a DID) {
//Get ref attribute
if( iinf-> item_name = ref->val && iinf->content_type = ref->mimeType) {
//use extent_offset and extent_length from iloc to find the //chunk of bytes
}
}
⎯ To enable this resource mapping, the DID Resource element must refer directly to the MPEG-7 and
JPEG resource in the hidden mp4 file. This means the offset and length for these items in the iloc box is
worked out directly from the file level meta box, where any complications of having to decode offsets and
lengths inside the hidden mp4 file (moov->trak->meta) are avoided.
ftyp meta mdat
brand=’mp21’  hldr=’mp21’
hidden mp4 file
iloc/iinf
item_count=3
item_ID = 1
item_name =
content_type = audio/mp4
item_ID = 2
item_name =
content_type = image/jpeg
item_ID = 3
item_name =
content_type = text/xml
*)
xml
MPEG-21 DID
Figure 9 — Example of file structure for mp21 file containing one hidden mp4 song file
*) Arrows indicate that there is a resource mapping process from the DID to the hidden mp4 file
© ISO/IEC 2008 – All rights reserved 9

NOTE 1 This Figure outlines how the MPEG-7 meta data can be kept encapsulated inside the hidden mp4 file in the
mdat box, as opposed to inside the DID. To do this the DID Statement element has been used ( mimeType="text/xml" ref="someURI">). Since the DID Resource element and the Statement have a common “ref”
attribute, the algorithm in the Resource Lookup/Playback can be applied to this DID Statement element.
NOTE 2 The hidden mp4 file is structured as described in Clause 4 containing the music track with MP3onMP4 audio
data, MPEG-7 meta-data and optional JPEG data. The hidden mp4 file can be separated from the structure presented in
this clause to form a stand alone file as described in Clause 4. The MPEG-7 meta-data associated with the music track
can be decoded applying the technique in Clause 4.
NOTE 3 Essentially this structure reiterates the Playback model. In order for a MAF application to handle MPEG-21 it
has to contain two mandatory items and a possible optional item, consisting of:
⎯ mp4 file with MP3onMP4 audio track (item_ID = 1) [Mandatory]
⎯ JPEG image (item_ID =2) [Optional]
⎯ MPEG-7 meta-data (item_ID = 3) [Mandatory]

5.3 Multiple Track Album
This structure generalizes the structure defined above by including more than one hidden mp4 file. Multiple
hidden mp4 files are included in the mp21’s mdat box to enable complete music album files with several music
tracks.
File Type: major-brand = ‘mp21’, compatible-brands = ‘mp21’, ‘MMU2’.
Meta-data Handler Type: MPEG-21 (mp21) at file level
Resource Lookup and Playback:
⎯ Even though this structure has multiple music tracks, the processing is identical to that of the structure in
5.2.
⎯ Again the file level meta box contains all information to find the information pertaining to each MP3onMP4,
its MPEG-7 meta-data and possibly its JPEG image. The Statement element mapping also applies to the
multi track structure.
NOTE Refer to Clause 4 for internals of the hidden mp4 files.
EXAMPLE An example DID which would be in the xml box inside the file level meta box can be found in Annex B

10 © ISO/IEC 2008 – All rights reserved

ftyp meta mdat
brand=’mp21’  hldr=’mp21’
hidden mp4 file 1
iloc/iinf
item_count=n+2
item_ID = 1
item_name =
content_type = audio/mp4
item_ID = 2
item_name =
content_type = image/jpeg
item_ID = 3
item_name =
content_type = text/xml
item_ID = 4
hidden mp4 file 2
item_name =
content_type = audio/mp4
item_ID = 5
item_name =
content_type = image/jpeg
item_ID = 6
item_name =
content_type = text/xml
item_ID = n
item_name =
content_type = audio/mp4
item_ID = n+1
item_name =
hidden mp4 file n
content_type = image/jpeg
item_ID = n+2
item_name =
content_type = text/xml
xml
MPEG-21 DID
Figure 10 — Example of file structure for mp21 album file containing several hidden mp4 song file

5.4 Playlist
The playlist format is using the same top level structure as the album, but does not include the songs as
hidden mp4 files, but references them as external files. The mp21 playlist file contains only the meta box and
acts as “parent” of one or more separate mp4 “child” song files.
The dinf/dref box is used for linkage of the mp21 playlist file and the separate mp4 song files.
© ISO/IEC 2008 – All rights reserved 11

mp21 playlist file
ftyp meta mp4 song file 1
brand=
iloc
ftyp moov mdat
’mp21’
mp4 song file 2
ftyp moov mdat
DID mp4 song file 3
ftyp moov mdat
dinf
dref
Figure 11 — Linkage of mp21 playlist file referencing external mp4 song files

The ‘iloc’ box contains for every item a data_reference_index starting with ‘1’ (an index of ‘0’ is used for
internal hidden files as described for the album above). This index selects the entry from the ‘dref’ box inside
the ‘meta’ box that corresponds to this item. The ‘dref’ box in turn contains a list of DataEntryUrnBox entries
with URL and URN strings in UTF-8 form.
The following walkthrough explains how to find the mp4 song file for one entry in the “playlist” DID:
⎯ Choose song from DID
⎯ Use itemID of this song to select the corresponding item locator in the ‘iloc’ box
⎯ Get dref-index from iloc entry for this item
⎯ Go to ‘dref’ box and search for data entry with this index
⎯ Read URL and URN from the DataEntryUrnBox ‘ urn’ of the selected data entry
⎯ Use URL to locate the mp4 song file
12 © ISO/IEC 2008 – All rights reserved

6 Scope of the Protected Music Player Application Format
The “Protected Music Player” described in the following Clauses 7 to 10 builds on the Music Player as
described above. It adds content protection for mp4 song files, explains a default encryption for the song files
and adds protection to the mp21 album and playlist files with flexible protection tool selection and key
management components.
The following cases are possible in addition to the unprotected case described in Clauses 3 to 5:
a) Protected content files in mp4 file format, without Key Management components, with the default
AES-128 encryption tool and MPEG-4 IPMP-X signalling in the IPMPInfoBox
b) Protected files with flexible tool selection and Key Management components (MPEG-21 IPMP and
REL) using the mp21 file format with embedded mp4 content files
c) Protected mp21 file with Key Management components (MPEG-21 IPMP and REL) but without
embedded mp4 content file (variation of (b) ) that functions as a “license file” for an external protected
mp4 content file (a)
Optional separation of protected content and license supports a broad range of "governed content scenarios"
including “super distribution of protected content” and “subscription models”. The following Figure 12
illustrates the different cases and gives some examples.
Protected
Link to
MP4 file
license/KMS
MP21 file
Protected
MP4 file
MP21 file
Link to
License 1
Protected
Content
MP21 file
Protected MP21 file
Protected
MP4 file
License 1
MP4 file
License 1
License 2 Protected
License 2 Protected
MP4 file
MP4 file
Figure 12 — Examples illustrating the different cases for the relationship of mp4 and mp21 files

© ISO/IEC 2008 – All rights reserved 13

7 Overview of Basic Standards for Protection
7.1 Protection and MPEG-4 File Formats
The ISO Base Media File Format ISO/IEC 14496-12:2005 offers basic box structures to signal content
protection within the sample description of the trak box, as well as within the meta box. This boxes are used to
signal the protection method and all other protection related parameters.
ftyp moov mdat
trak
Sample description
Protection information
meta
Protection information
Figure 13 — Protection information inside of mp4 files

7.2 AES-128 encryption
The Advanced Encryption Standard (AES) is an open standard symmetric encryption algorithm. It is a
thoroughly evaluated and tested encryption algorithm that is widely accepted as a good choice for many
applications. It is the result of an open competition started by NIST to find a successor to DES. Detailed
information about AES can be found on the Official AES-Website of the National Institute of Standards and
Technology (NIST) [1].
Examples for the usage of AES128 are:
• AACS (Advanced Access Content System): Protection of audio-visual data on high density optical disc
formats (HD-DVD, Blu-Ray)
• IPsec, SSH, IEEE 802.11i: protection of general IP (Internet Protocol) based communication
AES uses a symmetric block cipher with variable block length and a key-length of 128, 192 or 256 bit (AES-
128, AES-192 and AES-256). It is easy to implement in either hardware or software and requires only low
resource consumption in regards of CPU, memory and code length. It is resistant to all known methods of
cryptoanalysis and worldwide royalty free.

7.3 MPEG-4 IPMP-X
ISO/IEC 14496-13 “MPEG-4 IPMP Extension” provides tool renewability, which protects MPEG-4 contents
against security breakdown. The flexibility allows the use of various protection tools, as well as decoding tools.
MPEG-4 IPMP Extension key elements which are used for protecting the music player format are described
below.
⎯ IPMP Tools: IPMP tools are modules that perform (one or more) IPMP functions such as authentication,
decryption, watermarking, etc. A given IPMP Tool may coordinate other IPMP Tools. Each IPMP Tool has
a unique IPMP Tool ID that identifies a Tool in an unambiguous way, at the presentation level or at a
universal level.
14 © ISO/IEC 2008 – All rights reserved

⎯ IPMP Descriptors: The IPMP Descriptors are used to denote the IPMP Tool that is used to protect the
object. An independent registration authority (RA) is used so any party can register its own IPMP Tool
and identify this without collisions
...