MPEG-4 Part 14 or MP4 is a

digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals **Digital camera, which captures and stores digital i ...

multimedia Multimedia is a form of communication that uses a combination of different content forms such as text, audio, images, animations, or video into a single interactive presentation, in contrast to tradition ...

container format most commonly used to store video and

audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum *Digital audio, representation of sound ...

, but it can also be used to store other data such as subtitles and still images. Like most modern container formats, it allows

streaming Streaming media is multimedia that is delivered and consumed in a continuous manner from a source, with little or no intermediate storage in network elements. ''Streaming'' refers to the delivery method of content, rather than the content it ...

over the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

. The only

filename extension A filename extension, file name extension or file extension is a suffix to the name of a computer file (e.g., .txt, .docx, .md). The extension indicates a characteristic of the file contents or its intended use. A filename extension is typically d ...

for MPEG-4 Part 14 files as defined by the specification is .mp4. MPEG-4 Part 14 (formally

ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Is ...

IEC The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and re ...

14496-14:2003) is a standard specified as a part of

MPEG-4 MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related t ...

Portable media player A portable media player (PMP) (also including the related digital audio player (DAP)) is a portable consumer electronics device capable of storing and playing digital media such as audio, images, and video files. The data is typically stored o ...

s are sometimes advertised as " MP4 players", although some 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.

History

MPEG-4 Part 14 is an instance of the more general

14496-12:2004 (MPEG-4 Part 12:

ISO base media file format The ISO base media file format (ISOBMFF) is a container file format that defines a general structure for files that contain time-based multimedia data such as video and audio. It is standardized in ISO/IEC 14496-12, a.k.a. MPEG-4 Part 12, and wa ...

) which is directly based upon the

QuickTime File Format QuickTime File Format (QTFF) 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, ...

which was published in 2001. 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, 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 the 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 Motion JPEG 2000 (MJ2 or MJP2) is a file format for motion sequences of JPEG 2000 images and associated audio, based on the MP4 and QuickTime format. Filename extensions for Motion JPEG 2000 video files are .mj2 and .mjp2, as defined in RFC 3 ...

). The MP4 file format defined some extensions over the 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. The registration authority for code-points (identifier values) in "MP4 Family" files is Apple 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.

Filename extensions

While the only

defined by the standard is , various filename extensions are commonly used to indicate intended content: * MPEG-4 files with audio and video generally use the standard extension. * Audio-only MPEG-4 files generally have a extension. This is especially true of unprotected content. ** MPEG-4 files with audio streams encrypted by

FairPlay FairPlay is a digital rights management (DRM) technology developed by Apple Inc. It is built into the MP4 multimedia file format as an encrypted AAC audio layer, and was used until April 2009 by the company to protect copyrighted works sold th ...

Digital Rights Management Digital rights management (DRM) is the management of legal access to digital content. Various tools or technological protection measures (TPM) such as access control technologies can restrict the use of proprietary hardware and copyrighted works. ...

as were sold through the iTunes Store use the extension.

iTunes Plus The iTunes Store is a digital media store operated by Apple Inc. It opened on April 28, 2003, as a result of Steve Jobs' push to open a digital marketplace for music. As of April 2020, iTunes offered 60 million songs, 2.2 million apps, 25,000 ...

tracks, that the iTunes Store currently sells, are unencrypted and use accordingly. **

Audiobook An audiobook (or a talking book) is a recording of a book or other work being read out loud. A reading of the complete text is described as "unabridged", while readings of shorter versions are abridgements. Spoken audio has been available in sch ...

and

podcast A podcast is a program made available in digital format for download over the Internet. For example, an episodic series of digital audio or video files that a user can download to a personal device to listen to at a time of their choosing ...

files, which also contain metadata including chapter markers, images, and hyperlinks, can use the extension , but more commonly use the extension. **The Apple iPhone uses MPEG-4 audio for its ringtones but uses the extension rather than the extension. * Raw

MPEG-4 Visual MPEG-4 Part 2, MPEG-4 Visual (formally ISO/ IEC 14496-2) is a video compression format developed by the Moving Picture Experts Group (MPEG). It belongs to the MPEG-4 ISO/IEC standards. It uses block-wise motion compensation and a discrete cosine t ...

bitstreams are named but this extension is also sometimes used for video in MP4 container format. *

Mobile phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link while ...

s use 3GP, an implementation of MPEG-4 Part 12 (a.k.a. MPEG-4/JPEG2000 ISO Base Media file format), similar to MP4. It uses and extensions. These files also store non-MPEG-4 data ( H.263, AMR, TX3G). In practice, most (if not all) low end phones and feature phones record in this format, as most (if not all) other mobile phones and smartphones record MP4 files using the .mp4 file extension, and some high end phones can record in .raw.

Data streams

Most kinds of data can be embedded in MPEG-4 Part 14 files through ''private streams''. A separate hint track is used to include streaming information in the file. 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 A codec is a device or computer program that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder on a signal or ...

and additional data streams are: * Video: MPEG-H Part 2 (H.265/HEVC), MPEG-4 Part 10 (H.264/AVC) and

MPEG-4 Part 2 MPEG-4 Part 2, MPEG-4 Visual (formally ISO/IEC 14496-2) is a video compression format developed by the Moving Picture Experts Group (MPEG). It belongs to the MPEG-4 ISO/IEC standards. It uses block-wise motion compensation and a discrete cosine tr ...

: Other compression formats are less used:

MPEG-2 MPEG-2 (a.k.a. H.222/H.262 as was defined by the ITU) 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, w ...

and

MPEG-1 MPEG-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 about 1.5 Mbit/s (26:1 and 6:1 compression ratios respectively) without excessive quality loss, making ...

* Audio: Advanced Audio Coding (AAC) : Also

MPEG-4 Part 3 MPEG-4 Part 3 or MPEG-4 Audio (formally ISO/ IEC 14496-3) is the third part of the ISO/ IEC MPEG-4 international standard developed by Moving Picture Experts Group. It specifies audio coding methods. The first version of ISO/IEC 14496-3 was publis ...

audio objects, such as

Audio Lossless Coding MPEG-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),

MP3 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany, with support from other digital scientists in the United States and elsewhere. Origin ...

MPEG-1 Audio Layer II MPEG-1 Audio Layer II or MPEG-2 Audio Layer II (MP2, sometimes incorrectly called Musicam or MUSICAM) is a lossy audio compression format defined by ISO/IEC 11172-3 alongside MPEG-1 Audio Layer I and MPEG-1 Audio Layer III (MP3). While MP3 is ...

(MP2), MPEG-1 Audio Layer I (MP1),

CELP Code-excited linear prediction (CELP) is a linear predictive speech coding algorithm originally proposed by Manfred R. Schroeder and Bishnu S. Atal in 1985. At the time, it provided significantly better quality than existing low bit-rate algori ...

HVXC Harmonic Vector Excitation Coding, abbreviated as HVXC is a speech coding algorithm specified in MPEG-4 Part 3 (MPEG-4 Audio) standard for very low bit rate speech coding. HVXC supports bit rates of 2 and 4 kbit/s in the fixed and variable bit rat ...

(speech),

TwinVQ TwinVQ (transform-domain weighted interleave vector quantization) is an audio compression technique developed by Nippon Telegraph and Telephone Corporation (NTT) Human Interface Laboratories (now Cyber Space Laboratories) in 1994. The compression ...

, Text To Speech Interface (TTSI) and Structured Audio Orchestra Language (SAOL) : Other compression formats are less used:

Apple Lossless The Apple Lossless Audio Codec (ALAC), also known as Apple Lossless, or Apple Lossless Encoder (ALE), is an audio coding format, and its reference audio codec implementation, developed by Apple Inc. for lossless data compression of digital musi ...

, Free Lossless Audio Codec (added in late 2018), and Opus (added in late 2018) * Subtitles: MPEG-4 Timed Text (also known as 3GPP Timed Text). :

Nero Digital Nero 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. The audio codecs are integrated into the ''Nero Digital Audio+'' audio encoding tool for ...

uses DVD Video subtitles in MP4 files The so-called moov atom contains information about video resolution, frame rates, orientation, display characteristics, and more. It might be placed at the beginning or end of the file. In the latter case, the video file is not playable if the file is incomplete (truncated).

Metadata

MP4 files can contain

metadata Metadata is "data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive metadata – the descriptive ...

as defined by the format standard, and in addition, can contain

Extensible Metadata Platform The Extensible Metadata Platform (XMP) is an ISO standard, originally created by Adobe Systems Inc., for the creation, processing and interchange of standardized and custom metadata for digital documents and data sets. XMP standardizes a data ...

(XMP) metadata.

References

External links

The MP4 registration authority
* - MIME Type Registration for MPEG-4
Elements of the H.264 Video/AAC Audio MP4 Movie
{{ISO standards Computer-related introductions in 2003 Digital container formats MPEG-4 pl:MPEG-4 część 14