MP3 (MPEG Layer III Audio Encoding)
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`MP3 (MPEG Layer III Audio Encoding)
`
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`Table of Contents
`
`• Identification and description
`• Local use
`• Sustainability factors
`• Quality and functionality factors
`• File type signifiers
`• Notes
`• Format specifications
`• Useful references
`
`Format Description Properties
`
`• ID: fdd000012
`• Short name: MP3_ENC
`• Content categories: sound
`• Format Category: encoding
`• Other facets: unitary, binary, symbolic
`• Last significant FDD update: 2017-05-03
`• Draft status: Full
`
`Identification and description
`
`Full name
`
`Description
`
`MP3 (common name). MPEG Layer III audio encoding is
`defined in two ISO/IEC specification families (MPEG-1:
`11172-3 and MPEG-2: 13818-3).
`MP3 compression employs perceptual coding, an approach
`based on psychoacoustic models that permit the codec to
`discard or reduce the precision of audio components that are
`less audible to human hearing. The three classes of audio
`compression associated with MPEG-1 and -2 specifications are
`known as Layers I, II, and III; MP3 is shorthand for Layer III.
`
`https://www.loc.gov/preservation/digital/formats/fdd/fdd000012.shtml
`
`12/14/2017
`
`Apple Ex. 1022
`Apple v. Uniloc
`IPR2017-00225
`
`

`

`MP3 (MPEG Layer III Audio Encoding)
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`Each higher level designation increases the trade-off between
`increased syntax and coding complexity and improved coding
`efficiency. An MP3 file created with a bitrate of 128 kbit/s by
`about 1/11 the size of an uncompressed LPCM file at compact
`disk levels of quality (44.1 kHz, 16 bits deep). An MP3 file can
`also be recorded at higher or lower bit rates, with higher or
`lower resulting quality.See Notes for more information.
`Generally used for final-state, end-user delivery.
`Relationship to other formats
`MPEG-1 encoding family (ISO/IEC 11172-3), not separately
`described at this site; see the description for the related
`MPEG-1 (H.261) video encoding format
`MPEG-2_family, MPEG-2 Encoding Family
`MP3, Constant Bit Rate, not described at this site at this time.
`MP3, Variable Bit Rate, not described at this site at this time.
`MP3_FF, MP3 File Format
`AudCom_MP3, Audible.Com MP3
`QTA_MP3, QuickTime Audio, MP3 Codec
`Matroska_MP3, Matroska File Format with MP3 Audio
`Encoding
`Other file or wrapper formats, not documented at this time
`
`MP3_ENC in MP3_FF, used extensively as a service format
`for American Memory. Used as the accepted format for
`electronic registration of sound recordings by the U.S.
`Copyright Office in the CORDS online registration support
`system (late 1990s, early 2000s), and likely to be used in
`successor copyright-related systems.
`General preference for preservation-oriented recorded sound is
`WAVE_LCPM. For compressed sound, MP3 is acceptable,
`especially at data rates of 128 Kb/s (mono) or 256 Kb/s
`(stereo) or higher.
`
`Production phase
`
` Subtype of
`
` Subtype of
` Has subtype
` Has subtype
` Used by
` Used by
` Used by
`
` Used by
`
` Used by
`
`Local use
`
`LC experience or
`existing holdings
`
`LC preference
`
`Sustainability factors
`
`Disclosure
`
` Documentation
`
`Open standard. Developed by the Moving Picture Experts
`Group (MPEG), Coding of audio, picture, multimedia and
`hypermedia information.
`(1) MPEG-1: ISO/IEC 11172-3. Information technology --
`Coding of moving pictures and associated audio for digital
`
`https://www.loc.gov/preservation/digital/formats/fdd/fdd000012.shtml
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`12/14/2017
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`

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`MP3 (MPEG Layer III Audio Encoding)
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`storage media at up to about 1,5 Mbit/s -- Part 3: Audio. (2)
`MPEG-2: ISO/IEC 13818-3. Information technology --
`Generic coding of moving pictures and associated audio
`information -- Part 3: Audio.
`
`Adoption
`
`These specifications describe the syntax and semantics for
`three classes of compression methods known as Layers I, II,
`and III. MP3 is Layer III. See list of ISO documents in Format
`specifications below; see also MPEG-1 and MPEG-2.
`Widely adopted for World Wide Web dissemination and
`playback on specialized devices. Many software tools exist for
`encoding and decoding.
` Licensing and patents Patents associated with MP3 usage expired in April 2017
`according to the Fraunhofer IIS website which states that "on
`April 23, 2017, Technicolor's mp3 licensing program for
`certain mp3 related patents and software of Technicolor and
`Fraunhofer IIS has been terminated." Gary McGrath on his
`Mad File Format Science blog has a informative series of posts
`about the demise of MP3 licensing and Wikipedia provides
`more information about the history and impact of MP3 patents.
`Historically, various authorities cited a number of patent
`claims associated with MP3; see for example A Big List of
`MP3 Patents (and supposed expiration dates) although the
`practical impact of these claims is not clear.
`Depends upon algorithms and tools to read; requires
`sophistication to build tools.
`Technical (coding) information is contained in the headers for
`the "frames" that make up the MP3 bitstream.
`
`Transparency
`
`Self-documentation
`
`The lack of descriptive metadata motivated the producer
`community to develop ID3, a separately specified structure for
`metadata to support discovery and other purposes.
`External dependencies None
`Technical protection
`None
`considerations
`
`Quality and functionality factors
`
`Normal rendering
`Fidelity (high audio
`resolution)
`
`Sound
`
`Good support.
`Moderate to good, given that this is a format for compression.
`Outcome will depend on the type and extent of compression,
`and the encoder used. Most commentators report that, at a
`given data rate, the quality of AAC_MP2 and AAC_MP4
`(Advanced Audio Coding associated with MPEG-2 and -4)
`
`https://www.loc.gov/preservation/digital/formats/fdd/fdd000012.shtml
`
`12/14/2017
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`

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`MP3 (MPEG Layer III Audio Encoding)
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`encodings surpass the quality of MP3.
`
`As is noted in the section of this document devoted to multi-
`channel sound, MP3 offers a mode called joint stereo, and this
`is seen as having an adverse effect on fidelity. Variable bit rate
`may also have an adverse effect. As an example of preferences,
`the Webcaster SomaFM informs content providers to send files
`at a "256kb constant bit rate, 'normal stereo' (NOT joint
`stereo) . . . encoded at the highest quality setting."
`Supports five main channels and an optional LFE (Low
`Frequency Encoding or Effects) channel, i.e., 5.1 surround
`sound. 1 Note that in addition to a stereo sound field (aural
`space representation), MP3 offers joint stereo, a more efficient
`compression in which the separation of sound is limited to
`mid- to high frequencies.
`None
`
`None
`
`Multiple channels
`
`Support for user-defined
`sounds, samples, and
`patches
`Functionality beyond
`normal rendering
`
`File type signifiers and format identifiers
`
`Value
`Not
`applicable.
`Not
`applicable.
`Not
`applicable.
`fmt/134
`
`Note
`
`See MP3_FF.
`
`See MP3_FF.
`
`See MP3_FF.
`
`See http://www.nationalarchives.gov.uk/PRONOM/fmt/134.
`
`See note. Wikidata's Q42591 for MP3 does not specify if it is relevant to
`the MP3_ENC or MP3_FF.
`
`Tag
`Filename
`extension
`Internet
`Media Type
`Magic
`numbers
`Pronom
`PUID
`Wikidata
`Title ID
`
`Notes
`
`General
`History
`
`The following was paraphrased from the Wikipedia article
`(consulted February 28, 2012): MP3 was designed by the
`Moving Picture Experts Group (MPEG) as part of its MPEG-1
`standard and later extended in MPEG-2 standard. The first
`MPEG audio subgroup included engineers from Fraunhofer
`
`https://www.loc.gov/preservation/digital/formats/fdd/fdd000012.shtml
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`12/14/2017
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`MP3 (MPEG Layer III Audio Encoding)
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`IIS, University of Hannover, AT&T-Bell Labs, Thomson-
`Brandt, CCETT, and others. MPEG-1 Audio (MPEG-1 Part 3),
`which included MPEG-1 Audio Layer I, II and III was
`approved as a committee draft of ISO/IEC standard in 1991,
`finalized in 1992, and published in 1993 (ISO/IEC
`11172-3:1993). Backwards compatible MPEG-2 Audio
`(MPEG-2 Part 3) with additional bit rates and sample rates was
`published in 1995 (ISO/IEC 13818-3:1995).
`
`Format specifications
`
`• 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. Describes syntax and
`semantics for three classes of compression methods known as Layers I, II, and III.
`• ISO/IEC 11172-3:1993/Cor 1:1996
`• ISO/IEC 13818-3 (Second edition, 1998). Information technology -- Coding of moving pictures
`and associated audio information -- Part 3: Audio. Describes syntax and semantics for three
`classes of compression methods known as Layers I, II, and III.
`
`Useful references
`
`URLs
`
`• How Is MP3 Built? (http://www.id3.org/mp3Frame). About the structure of MP3's atoms.
`• MPEG Audio Compression Basics (http://www.datavoyage.com/mpgscript/mpeghdr.htm).
`• Discussion of MP3 patents (http://www.mp3-tech.org/patents.html).
`• SomaFM (http://SomaFM.com/contact/). Information for the providers of sound recordings to
`this Webcaster.
`• A Big List of MP3 Patents (http://www.tunequest.org/a-big-list-of-mp3-patents/20070226/). A
`list of MP3 patents and their expiration dates. (From 2007)
`• PRONOM entry for fmt/134
`(http://www.nationalarchives.gov.uk/pronom/fmt/134). Information in PRONOM from UK
`National Archives about MP3. PUID: fmt/134.
`• Wikidata entry for Q42591 (https://www.wikidata.org/wiki/Q42591). Information in Wikidata
`about MP3. Wikidata Title ID: Q42591.
`• MP3 licensing officially ends April 23
`(https://madfileformatscience.garymcgath.com/2017/04/20/mp3-april-23/). Post by Gary
`McGrath on his Mad File Format Science blog about the sunsetting of patents
`• MP3 Overview - End of MP3 patents
`(https://www.iis.fraunhofer.de/en/ff/amm/prod/audiocodec/audiocodecs/mp3.html). Notice on
`Fraunhofer IIS website about cessation of MP3 patents and discontinutation of MP3 products
`• Wikipedia entry for MP3 (https://en.wikipedia.org/wiki/MP3). Especially helpful for licensing
`information
`
`https://www.loc.gov/preservation/digital/formats/fdd/fdd000012.shtml
`
`12/14/2017
`
`

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`MP3 (MPEG Layer III Audio Encoding)
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`1 On April 8, 2004, the New York Times Circuits Section reported that the Fraunhofer Institute in
`Germany had "announced a new version called MP3 Surround that adds the extra audio channels
`needed for 5.1 sound without appreciably increasing file size."
`
`Last Updated: 07/27/2017
`
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