MPEG-4 Part 14
Encyclopedia
MPEG-4 Part 14 or MP4 is a multimedia
container format standard specified as a part of MPEG-4
. It is most commonly used to store digital video
and digital audio
streams, especially those defined by MPEG, but can also be used to store other data such as subtitles and still images. Like most modern container formats, MPEG-4 Part 14 allows streaming
over the Internet
. A separate hint track is used to include streaming information in the file. The only official filename extension
for MPEG-4 Part 14 files is .mp4.
Some devices advertised as "MP4 Players" are simply MP3 Players that also play AMV video
or some other video format, and do not necessarily play the MPEG-4 part 14 format.
/IEC
14496-12:2004 (MPEG-4 Part 12: ISO base media file format
) which is directly based upon QuickTime File Format
.
MPEG-4 Part 14 is essentially identical to the QuickTime file format, but formally specifies support for Initial Object Descriptors (IOD) and other MPEG features. MPEG-4 Part 14 revises and completely replaces Clause 13 of ISO/IEC 14496-1 (MPEG-4 Part 1: Systems), in which the file format for MPEG-4 content was previously specified.
The MPEG-4 file format specification was created on the basis of the QuickTime format specification published in 2001. The MPEG-4 file format, version 1 was published in 2001 as ISO/IEC 14496-1:2001, which is a revision of the MPEG-4 Part 1: Systems specification published in 1999 (ISO/IEC 14496-1:1999). In 2003, the first version of MP4 file format was revised and replaced by MPEG-4 Part 14: MP4 file format (ISO/IEC 14496-14:2003), commonly named as MPEG-4 file format version 2. The MP4 file format was generalized into the ISO Base Media File format ISO/IEC 14496-12:2004, which defines a general structure for time-based media files. It in turn is used as the basis for other file formats in the family (for example MP4, 3GP
, Motion JPEG 2000).
The MP4 file format defined some extensions over ISO Base Media File Format to support MPEG-4 visual/audio codecs and various MPEG-4 Systems features such as object descriptors and scene descriptions. Some of these extensions are also used by other formats based on ISO base media file format (e.g. 3GP). A list of all registered extensions for ISO Base Media File Format is published on the official registration authority website www.mp4ra.org. The registration authority for code-points (identifier values) in "MP4 Family" files is Apple Computer Inc. and it is named in Annex D (informative) in MPEG-4 Part 12. Codec designers should register the codes they invent, but the registration is not mandatory and some invented and used code-points are not registered. When someone is creating a new specification derived from the ISO Base Media File Format, all the existing specifications should be used both as examples and a source of definitions and technology. If an existing specification already covers how a particular media type is stored in the file format (e.g. MPEG-4 audio or video in MP4), that definition should be used and a new one should not be invented.
used to represent audio files.
The existence of two different filename extensions for naming audio-only MP4 files has been a source of confusion among users and multimedia playback software. Some file manager
s, such as Windows Explorer, look up the media type and associated applications of a file based on its filename extension. But since MPEG-4 Part 14 is a container format, MPEG-4 files may contain any number of audio, video, and even subtitle streams, making it impossible to determine the type of streams in an MPEG-4 file based on its filename extension alone. In response, Apple Inc. started using and popularizing the .m4a filename extension, which is used for MP4 containers with audio data in the Advanced Audio Coding
(AAC) or its own Apple Lossless
(ALE, ALAC) formats. Software capable of audio/video playback should recognize files with either .m4a or .mp4 filename extensions, as would be expected, as there are no file format differences between the two. Most software capable of creating MPEG-4 audio will allow the user to choose the filename extension of the created MPEG-4 files.
While the only official filename extension defined by the standard is .mp4, various filename extensions are commonly used to indicate intended content:
as defined by the format standard, and in addition, can contain Extensible Metadata Platform
(XMP) metadata.
Multimedia
Multimedia is media and content that uses a combination of different content forms. The term can be used as a noun or as an adjective describing a medium as having multiple content forms. The term is used in contrast to media which use only rudimentary computer display such as text-only, or...
container format standard specified as a part of MPEG-4
MPEG-4
MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
. It is most commonly used to store digital video
Digital video
Digital video is a type of digital recording system that works by using a digital rather than an analog video signal.The terms camera, video camera, and camcorder are used interchangeably in this article.- History :...
and digital audio
Digital audio
Digital audio is sound reproduction using pulse-code modulation and digital signals. Digital audio systems include analog-to-digital conversion , digital-to-analog conversion , digital storage, processing and transmission components...
streams, especially those defined by MPEG, but can also be used to store other data such as subtitles and still images. Like most modern container formats, MPEG-4 Part 14 allows streaming
Streaming media
Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a streaming provider.The term "presented" is used in this article in a general sense that includes audio or video playback. The name refers to the delivery method of the medium rather...
over the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
. A separate hint track is used to include streaming information in the file. The only official filename extension
Filename extension
A filename extension is a suffix to the name of a computer file applied to indicate the encoding of its contents or usage....
for MPEG-4 Part 14 files is .mp4.
Some devices advertised as "MP4 Players" are simply MP3 Players that also play AMV video
AMV video format
AMV is a proprietary video file format, produced for MP4 players, as well as S1 MP3 players with video playback. There are now two different MTV formats: the older one for the Actions chip, and a newer one for ALi’s M5661 chip. This format for ALi one was ALIAVI.- Format :The container is a...
or some other video format, and do not necessarily play the MPEG-4 part 14 format.
History of MP4
MPEG-4 Part 14 is an instance of more general ISOInternational Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
/IEC
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
14496-12:2004 (MPEG-4 Part 12: ISO base media file format
ISO base media file format
ISO base media file format defines a general structure for time-based multimedia files such as video and audio. It is used as the basis for other media file formats...
) which is directly based upon QuickTime File Format
QuickTime File Format
QuickTime File Format is a computer file format used natively by the QuickTime framework.- Design :The format specifies a multimedia container file that contains one or more tracks, each of which stores a particular type of data: audio, video, effects, or text...
.
MPEG-4 Part 14 is essentially identical to the QuickTime file format, but formally specifies support for Initial Object Descriptors (IOD) and other MPEG features. MPEG-4 Part 14 revises and completely replaces Clause 13 of ISO/IEC 14496-1 (MPEG-4 Part 1: Systems), in which the file format for MPEG-4 content was previously specified.
The MPEG-4 file format specification was created on the basis of the QuickTime format specification published in 2001. The MPEG-4 file format, version 1 was published in 2001 as ISO/IEC 14496-1:2001, which is a revision of the MPEG-4 Part 1: Systems specification published in 1999 (ISO/IEC 14496-1:1999). In 2003, the first version of MP4 file format was revised and replaced by MPEG-4 Part 14: MP4 file format (ISO/IEC 14496-14:2003), commonly named as MPEG-4 file format version 2. The MP4 file format was generalized into the ISO Base Media File format ISO/IEC 14496-12:2004, which defines a general structure for time-based media files. It in turn is used as the basis for other file formats in the family (for example MP4, 3GP
3GP
3GP is a multimedia container format defined by the Third Generation Partnership Project for 3G UMTS multimedia services. It is used on 3G mobile phones but can also be played on some 2G and 4G phones....
, Motion JPEG 2000).
| Version | Release date | Standard | Description |
|---|---|---|---|
| MP4 file format version 1 | 2001 | ISO/IEC 14496-1:2001 | MPEG-4 Part 1 (Systems), First edition |
| MP4 file format version 2 | 2003 | ISO/IEC 14496-14:2003 | MPEG-4 Part 14 (MP4 file format), Second edition |
The MP4 file format defined some extensions over ISO Base Media File Format to support MPEG-4 visual/audio codecs and various MPEG-4 Systems features such as object descriptors and scene descriptions. Some of these extensions are also used by other formats based on ISO base media file format (e.g. 3GP). A list of all registered extensions for ISO Base Media File Format is published on the official registration authority website www.mp4ra.org. The registration authority for code-points (identifier values) in "MP4 Family" files is Apple Computer Inc. and it is named in Annex D (informative) in MPEG-4 Part 12. Codec designers should register the codes they invent, but the registration is not mandatory and some invented and used code-points are not registered. When someone is creating a new specification derived from the ISO Base Media File Format, all the existing specifications should be used both as examples and a source of definitions and technology. If an existing specification already covers how a particular media type is stored in the file format (e.g. MPEG-4 audio or video in MP4), that definition should be used and a new one should not be invented.
.MP4 versus .M4A filename extensions
M4A stands for MPEG 4 Audio and is a filename extensionFilename extension
A filename extension is a suffix to the name of a computer file applied to indicate the encoding of its contents or usage....
used to represent audio files.
The existence of two different filename extensions for naming audio-only MP4 files has been a source of confusion among users and multimedia playback software. Some file manager
File manager
A file manager or file browser is a computer program that provides a user interface to work with file systems. The most common operations performed on files or groups of files are: create, open, edit, view, print, play, rename, move, copy, delete, search/find, and modify file attributes, properties...
s, such as Windows Explorer, look up the media type and associated applications of a file based on its filename extension. But since MPEG-4 Part 14 is a container format, MPEG-4 files may contain any number of audio, video, and even subtitle streams, making it impossible to determine the type of streams in an MPEG-4 file based on its filename extension alone. In response, Apple Inc. started using and popularizing the .m4a filename extension, which is used for MP4 containers with audio data in the Advanced Audio Coding
Advanced Audio Coding
Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....
(AAC) or its own Apple Lossless
Apple Lossless
Apple Lossless Apple Lossless Apple Lossless (also known as ALAC (Apple Lossless Audio Codec), or ALE (Apple Lossless Encoder) is an audio codec developed by Apple Inc. for lossless data compression of digital music. After initially being proprietary for many years, in late 2011 Apple open sourced...
(ALE, ALAC) formats. Software capable of audio/video playback should recognize files with either .m4a or .mp4 filename extensions, as would be expected, as there are no file format differences between the two. Most software capable of creating MPEG-4 audio will allow the user to choose the filename extension of the created MPEG-4 files.
While the only official filename extension defined by the standard is .mp4, various filename extensions are commonly used to indicate intended content:
- MPEG-4 files with audio and video generally use the standard .mp4 extension.
- Audio-only MPEG-4 files generally have a .m4a extension. This is especially true of non-protected content.
- MPEG-4 files with audio streams encrypted by FairPlayFairPlayFairPlay is a digital rights management technology created by Apple Inc., based on technology created by the company Veridisc. FairPlay is built into the QuickTime multimedia software and used by the iPhone, iPod, iPad, Apple TV, iTunes, and iTunes Store and the App Store. Formerly, all songs in...
Digital Rights ManagementDigital rights managementDigital rights management is a class of access control technologies that are used by hardware manufacturers, publishers, copyright holders and individuals with the intent to limit the use of digital content and devices after sale. DRM is any technology that inhibits uses of digital content that...
as were sold through the iTunes StoreITunes StoreThe iTunes Store is a software-based online digital media store operated by Apple. Opening as the iTunes Music Store on April 28, 2003, with over 200,000 items to purchase, it is, as of April 2008, the number-one music vendor in the United States...
use the .m4p extension. iTunes Plus tracks, that the iTunes Store currently sells, are unencrypted and use .m4a accordingly. - Audio bookAudio bookAn audiobook or audio book is a recording of a text being read. It is not necessarily an exact audio version of a book or magazine.Spoken audio has been available in schools and public libraries and to a lesser extent in music shops since the 1930s. Many spoken word albums were made prior to the...
and podcastPodcastA podcast is a series of digital media files that are released episodically and often downloaded through web syndication...
files, which also contain metadata including chapter markers, images, and hyperlinks, can use the extension .m4a, but more commonly use the .m4b extension. An .m4a audio file cannot "bookmark" (remember the last listening spot), whereas .m4b extension files can. - The Apple iPhoneIPhoneThe iPhone is a line of Internet and multimedia-enabled smartphones marketed by Apple Inc. The first iPhone was unveiled by Steve Jobs, then CEO of Apple, on January 9, 2007, and released on June 29, 2007...
uses MPEG-4 audio for its ringtones but uses the .m4r extension rather than the .m4a extension.
- MPEG-4 files with audio streams encrypted by FairPlay
- Raw MPEG-4 Visual bitstreams are named .m4v but this extension is also sometimes used for video in MP4 container format.
- Mobile phoneMobile phoneA mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s use 3GP3GP3GP is a multimedia container format defined by the Third Generation Partnership Project for 3G UMTS multimedia services. It is used on 3G mobile phones but can also be played on some 2G and 4G phones....
, an implementation of MPEG-4 Part 12 (a.k.a MPEG-4/JPEG2000 ISO Base Media file format), similar to MP4. It uses .3gp and .3g2 extensions. These files also store non-MPEG-4 data (H.263H.263H.263 is a video compression standard originally designed as a low-bitrate compressed format for videoconferencing. It was developed by the ITU-T Video Coding Experts Group in a project ending in 1995/1996 as one member of the H.26x family of video coding standards in the domain of the ITU-T.H.263...
, AMR, TX3G).
Data streams
Almost any kind of data can be embedded in MPEG-4 Part 14 files through private streams. The registered codecs for MPEG-4 Part 12-based files are published on the website of MP4 Registration authority (mp4ra.org), but most of them are not widely supported by MP4 players. The widely-supported codecs and additional data streams are:- Video: MPEG-4 Part 10 (H.264)H.264/MPEG-4 AVCH.264/MPEG-4 Part 10 or AVC is a standard for video compression, and is currently one of the most commonly used formats for the recording, compression, and distribution of high definition video...
and MPEG-4 Part 2MPEG-4 Part 2MPEG-4 Part 2, MPEG-4 Visual is a video compression technology developed by MPEG. It belongs to the MPEG-4 ISO/IEC standards. It is a discrete cosine transform compression standard, similar to previous standards such as MPEG-1 and MPEG-2...
- Other compression formats are less used: MPEG-2MPEG-2MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods which permit storage and transmission of movies using currently available storage media and transmission...
and MPEG-1MPEG-1MPEG-1 is a standard for lossy compression of video and audio. It is designed to compress VHS-quality raw digital video and CD audio down to 1.5 Mbit/s without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting possible.Today, MPEG-1 has become...
- Audio: Advanced Audio CodingAdvanced Audio CodingAdvanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....
- Audio: Advanced Audio Coding
- Also MPEG-4 Part 3MPEG-4 Part 3MPEG-4 Part 3 or MPEG-4 Audio is the third part of the ISO/IEC MPEG-4 international standard developed by Moving Picture Experts Group. It specifies audio coding methods...
audio objects, such as Audio Lossless CodingAudio Lossless CodingMPEG-4 Audio Lossless Coding, also known as MPEG-4 ALS, is an extension to the MPEG-4 Part 3 audio standard to allow lossless audio compression. The extension was finalized in December 2005 and published as ISO/IEC 14496-3:2005/Amd 2:2006 in 2006...
(ALS), Scalable Lossless Coding (SLS), MP3MP3MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...
, MPEG-1 Audio Layer IIMPEG-1 Audio Layer IIMPEG-1 Audio Layer II or MPEG-2 Audio Layer II is a lossy audio compression format defined by ISO/IEC 11172-3 alongside MPEG-1 Audio Layer I and MPEG-1 Audio Layer III...
(MP2), MPEG-1 Audio Layer IMPEG-1 Audio Layer IMPEG-1 Audio Layer I, commonly abbreviated to MP1, is one of three audio formats included in the MPEG-1 standard. While supported by most media players, the codec is considered largely outdated, and replaced by MP2 or MP3....
(MP1), CELP, HVXC (speech), TwinVQTwinVQTwinVQ is an audio compression technique developed by Nippon Telegraph and Telephone Corporation Human Interface Laboratories in 1994...
, Text To Speech Interface (TTSI) and Structured Audio Orchestra LanguageStructured Audio Orchestra LanguageStructured Audio Orchestra Language is an imperative, MUSIC-N programming language designed for describing virtual instruments, processing digital audio, and applying sound effects...
(SAOL) - Other compression formats are less used: Apple LosslessApple LosslessApple Lossless Apple Lossless Apple Lossless (also known as ALAC (Apple Lossless Audio Codec), or ALE (Apple Lossless Encoder) is an audio codec developed by Apple Inc. for lossless data compression of digital music. After initially being proprietary for many years, in late 2011 Apple open sourced...
- Subtitles: MPEG-4 Timed TextMPEG-4 Part 17MPEG-4 Part 17, or MPEG-4 Timed Text, or MPEG-4 Streaming text format is the text based subtitle format for MPEG-4, published as ISO/IEC 14496-17 in 2006...
(also known as 3GPP Timed Text).
- Subtitles: MPEG-4 Timed Text
- Nero DigitalNero DigitalNero Digital is a brand name applied to a suite of MPEG-4-compatible video and audio compression codecs developed by Nero AG of Germany and Ateme of France...
uses DVD Video subtitles in MP4 files
Metadata
MP4 files can contain metadataMetadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
as defined by the format standard, and in addition, can contain Extensible Metadata Platform
Extensible Metadata Platform
The Adobe Extensible Metadata Platform is a standard, created by Adobe Systems Inc., for processing and storing standardized and proprietary information relating to the contents of a file....
(XMP) metadata.
See also
- Container format (digital) definition and article
- Comparison of (audio/video) container formatsComparison of container formatsThis table compares features of container formats. To see which multimedia players support which container format, look at comparison of media players.-Information:-Audio formats supported:-Video formats supported:-Caption formats supported:...
- List of multimedia (audio/video) codecs
- List of open source codecs
- Comparison of video codecsComparison of video codecsA video codec is software or a device that provides encoding and decoding which may or may not include the use of video compression and/or decompression for digital video....
- Comparison of audio codecsComparison of audio codecsThe following tables compare general and technical information for a variety of audio formats and audio compression formats. For listening tests comparing the perceived audio quality of audio formats and codecs, see the article Codec listening test....
External links
- The MP4 registration authority
- RFC 4337 - MIME Type Registration for MPEG-4