MP4 (formally MPEG-4 Part 14), is a

digital Digital usually refers to something using discrete digits, often binary digits. Businesses *Digital bank, a form of financial institution *Digital Equipment Corporation (DEC) or Digital, a computer company *Digital Research (DR or DRI), a software ...

multimedia Multimedia is a form of communication that uses a combination of different content forms, such as Text (literary theory), writing, Sound, audio, images, animations, or video, into a single presentation. T ...

container format A container format (informally, sometimes called a wrapper) or metafile is a file format that allows multiple data streams to be embedded into a single file, usually along with metadata for identifying and further detailing those streams. Nota ...

most commonly used to store

video Video is an Electronics, electronic medium for the recording, copying, playback, broadcasting, and display of moving picture, moving image, visual Media (communication), media. Video was first developed for mechanical television systems, whi ...

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 Subtitles are texts representing the contents of the audio in a film, television show, opera or other audiovisual media. Subtitles might provide a transcription or translation of spoken dialogue. Although naming conventions can vary, caption ...

and still images. Like most modern container formats, it allows

streaming Streaming media refers to multimedia delivered through a network for playback using a media player. Media is transferred in a ''stream'' of packets from a server to a client and is rendered in real-time; this contrasts with file downl ...

over the

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

. The only

filename extension A filename extension, file name extension or file extension is a suffix to the name of a computer file (for example, .txt, .mp3, .exe) that 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 is a standard specified as a part of the

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 ...

specifications, formally as

ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...

IEC The International Electrotechnical Commission (IEC; ) is an international standards organization that prepares and publishes international standards for all electrical, electronic and related technologies. IEC standards cover a vast range of ...

14496-14:2003. Unlike the audio-only compression formats

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 under the lead of Karlheinz Brandenburg. It was designed to greatly reduce the amount ...

and

MP2 MP2 or MP-2 may refer to: Aviation * The second terminal of Marseille Provence Airport * Chyetverikov ARK-3 flying-boat Firearms * German Army designation for the Uzi * MP-2 machine pistol Science * MP 2, an abbreviation for a zone during t ...

, MP4 is a container format that can hold various types of media from various codecs. During the 2000s,

portable media player A portable media player (PMP) or digital audio player (DAP) is a portable consumer electronics device capable of storing and playing digital media such as audio, images, and video files. Normally they refer to small, Electric battery, batter ...

s were sometimes erroneously advertised as "MP4 players", even if they may play a different format like AMV video and not necessarily the MPEG-4 Part 14 format.

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 computer hardware or software component 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 o ...

and additional data streams are (but many more are also supported, including audio like FLAC or TrueHD): * Video: MPEG-H Part 2 (H.265/HEVC), MPEG-4 Part 10 (H.264/AVC),

MPEG-4 Part 2 MPEG-4 Part 2, MPEG-4 Visual (formally International Organization for Standardization, ISO/International Electrotechnical Commission, IEC 14496-2) is a video encoding specification designed by the Moving Picture Experts Group (MPEG). It belongs to ...

and

AV1 AOMedia Video 1 (AV1) is an open, royalty-free video coding format initially designed for video transmissions over the Internet. It was developed as a successor to VP9 by the Alliance for Open Media (AOMedia), a consortium founded in 2015 tha ...

: 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 ...

and

MPEG-1 MPEG-1 is a Technical standard, standard for lossy compression of video and Audio frequency, 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 ...

* 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 2 ...

(ALS),

Scalable Lossless Coding MPEG-4 SLS, or MPEG-4 Scalable to Lossless as per ISO/ IEC 14496-3:2005/Amd 3:2006 (Scalable Lossless Coding), is an extension to the MPEG-4 Part 3 (MPEG-4 Audio) standard to allow lossless audio compression scalable to lossy MPEG-4 General Au ...

(SLS),

MPEG-1 Audio Layer II MP2 (formally MPEG-1 Audio Layer II or MPEG-2 Audio Layer II, sometimes incorrectly called Musicam) is a lossy audio compression format. It is standardised as one of the three audio codecs of MPEG-1 alongside MPEG-1 Audio Layer I (MP1) and M ...

(MP2),

MPEG-1 Audio Layer I MPEG-1 Audio Layer I, commonly abbreviated to MP1, is a lossy audio codec and one of three audio formats included in the MPEG-1 standard. For files only containing MP1 audio, the file extension .mp1 is used. It is a deliberately simplified ver ...

(MP1), CELP, HVXC (speech), TwinVQ, 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., Apple for lossless data compression of digit ...

Free Lossless Audio Codec FLAC (; Free Lossless Audio Codec) is an audio coding format for lossless compression of digital audio, developed by the Xiph.Org Foundation, and is also the name of the free software project producing the FLAC tools, the reference softwar ...

(added in late 2018), and

Opus Opus (: opera Opera is a form of History of theatre#European theatre, Western theatre in which music is a fundamental component and dramatic roles are taken by Singing, singers. Such a "work" (the literal translation of the Italian word "opera ...

(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 M ...

uses

DVD Video DVD-Video is a consumer video format used to store digital video on DVDs. DVD-Video was the dominant consumer home video format in most of the world in the 2000s. As of 2024, it competes with the high-definition Blu-ray Disc, while both recei ...

subtitles in MP4 files The 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 (or metainformation) is "data that provides information about other data", but not the content of the data itself, such as the text of a message or the image itself. There are many distinct types of metadata, including: * 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.

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 (''MPEG-4 Audio'') extension. This is especially true of unprotected content. ** MPEG-4 files with audio streams encrypted by

FairPlay FairPlay is a family of digital rights management (DRM) technologies developed by Apple Inc. for protecting videos, books and apps and historically for music. Music The initial version of FairPlay was created to protect music on the iTunes S ...

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

as were sold through the iTunes Store use the (''MPEG-4 Protected'') extension. iTunes Plus 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 Radio program, program made available in digital format for download over the Internet. Typically, a podcast is an Episode, episodic series of digital audio Computer file, files that users can download to a personal device or str ...

files, which also contain metadata including chapter markers, images, and hyperlinks, can use the extension , but more commonly use the (''MPEG-4 Audiobook'') extension. **The Apple

iPhone The iPhone is a line of smartphones developed and marketed by Apple that run iOS, the company's own mobile operating system. The first-generation iPhone was announced by then–Apple CEO and co-founder Steve Jobs on January 9, 2007, at ...

uses MPEG-4 audio for its ringtones but uses the extension rather than the extension. * Raw MPEG-4 Visual bitstreams are named but this extension is also sometimes used for video in MP4 container format or in the M4V container format. *

Mobile phone A mobile phone or cell phone is a portable telephone that allows users to make and receive calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones ( landline phones). This rad ...

s used to use

3GP 3GP (3GPP file format) is a digital multimedia container format defined by the Third Generation Partnership Project (3GPP) for 3G UMTS multimedia services, largely based on MPEG-4 Part 12. A 3GP container may consist of H.263 or H.264 video ...

, 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 recorded in this format, as most (if not all) other mobile phones and

smartphones A smartphone is a mobile phone with advanced computing capabilities. It typically has a touchscreen interface, allowing users to access a wide range of applications and services, such as web browsing, email, and social media, as well as mult ...

record MP4 files using the .mp4 file extension, and some high end phones can record in .raw. By the time that 4G technology was widespread, 3GP started to be phased out, and is now rarely seen.

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 w ...

), 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: aud ...

, 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,

, and

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 3745 ...

). 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 the 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 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 as 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.

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