A container format (informally, sometimes called a wrapper) or metafile is a

file format A file format is a Computer standard, standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary format, pr ...

that allows multiple data streams to be embedded into a single file, usually along with metadata for identifying and further detailing those streams. Notable examples of container formats include

archive file In computing, an archive file is a computer file that is composed of one or more files along with metadata. Archive files are used to collect multiple data files together into a single file for easier portability and storage, or simply to compre ...

s (such as the ZIP format) and formats used for multimedia playback (such as

Matroska Matroska is a project to create a container format that can hold an unlimited number of video, audio, picture, or subtitle tracks in one file. The Matroska Multimedia Container is similar in concept to other containers like AVI, MP4, or Advan ...

, MP4, and

AVI Avi is a given name, usually masculine, often a diminutive of Avram, Avraham, etc. It is sometimes feminine and a diminutive of the Hebrew spelling of Abigail. People with the given name include: * Avi (born 1937), Newbery award-winning Americ ...

). Among the earliest

cross-platform In computing, cross-platform software (also called multi-platform software, platform-agnostic software, or platform-independent software) is computer software that is designed to work in several computing platforms. Some cross-platform software ...

container formats were

Distinguished Encoding Rules X.690 is an ITU-T standard specifying several ASN.1 encoding formats: * Basic Encoding Rules (BER) * Canonical Encoding Rules (CER) * Distinguished Encoding Rules (DER) The Basic Encoding Rules (BER) were the original rules laid out by the AS ...

and the 1985

Interchange File Format Interchange File Format (IFF), is a generic container file format originally introduced by Electronic Arts in 1985 (in cooperation with Commodore) in order to facilitate transfer of data between software produced by different companies. IFF fi ...

Design

Although containers may identify how data or metadata is encoded, they do not actually provide instructions about how to decode that data. A program that can open a container must also use an appropriate

codec 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 ...

to decode its contents. If the program doesn't have the required algorithm, it can't use the contained data. In these cases, programs usually emit an error message that complains of a missing codec, which users may be able to acquire. Container formats can be made to wrap any kind of data. Though there are some examples of such file formats (e.g. Microsoft Windows's DLL files), most container formats are specialized for specific data requirements. For example, since

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 soun ...

and

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 ...

streams can be coded and decoded with many different algorithms, a container format may be used to provide the appearance of a single file format to users of multimedia playback software.

Considerations

The differences between various container formats arise from five main issues: # Popularity; how widely supported a container is. # Overhead. This is the difference in file-size between two files with the same content in a different container. # Support for advanced codec functionality. Older formats such as AVI do not support new codec features like B-frames, VBR audio or VFR video natively. The format may be "hacked" to add support, but this creates compatibility problems. # Support for advanced content, such as chapters, subtitles, meta-tags, user-data. # Support of

streaming media 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 i ...

Single coding formats

In addition to pure container formats, which specify ''only'' the wrapper but not the coding, a number of file formats specify ''both'' a storage layer and the coding, as part of

modular design Modular design, or modularity in design, is a design principle that subdivides a system into smaller parts called ''modules'' (such as modular process skids), which can be independently created, modified, replaced, or exchanged with other modules ...

and

forward compatibility Forward compatibility or upward compatibility is a design characteristic that allows a system to accept input intended for a later version of itself. The concept can be applied to entire systems, electrical interfaces, telecommunication signal ...

. Examples include

JPEG File Interchange Format The JPEG File Interchange Format (JFIF) is an image file format standard published as ITU-T Recommendation T.871 and ISO/IEC 10918-5. It defines supplementary specifications for the container format that contains the image data encoded with the JP ...

(JFIF) for containing

JPEG JPEG ( ) is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and im ...

data, and Portable Network Graphics (PNG). In principle, coding can be changed while the storage layer is retained; for example, Multiple-image Network Graphics (MNG) uses the PNG container format but provides animation, while

JPEG Network Graphics JPEG Network Graphics (JNG, ) is a JPEG-based graphics file format which is closely related to PNG: it uses the PNG file structure (with a different signature) as a container format to wrap JPEG-encoded image data. JNG was created as an adjunc ...

(JNG) puts JPEG encoded data in a PNG container; in both cases however, the different formats have different magic numbers – the format specifies the coding, though a MNG can contain both PNG-encoded images and JPEG-encoded images.

Multimedia container formats

The container file is used to identify and interleave different data types. Simpler container formats can contain different types of audio formats, while more advanced container formats can support multiple audio and video streams, subtitles, chapter-information, and meta-data ( tags) — along with the synchronization information needed to play back the various streams together. In most cases, the file header, most of the metadata and the synchro chunks are specified by the container format. For example, container formats exist for optimized, low-quality, internet video streaming which differs from high-quality Blu-ray streaming requirements. Container format parts have various names: "chunks" as in RIFF and PNG, "atoms" in QuickTime/MP4, "packets" in MPEG-TS (from the communications term), and "segments" in JPEG. The main content of a chunk is called the "data" or "payload". Most container formats have chunks in sequence, each with a header, while

TIFF Tag Image File Format, abbreviated TIFF or TIF, is an image file format for storing raster graphics images, popular among graphic artists, the publishing industry, and photographers. TIFF is widely supported by scanning, faxing, word processin ...

instead stores offsets. Modular chunks make it easy to recover other chunks in case of file corruption or dropped frames or

bit slip In digital transmission, bit slip is the loss or gain of a bit or bits, caused by clock drift – variations in the respective clock rates of the transmitting and receiving devices. One cause of bit slippage is overflow of a receive buffer that ...

, while offsets result in framing errors in cases of bit slip. Some containers are exclusive to audio: *

AIFF Audio Interchange File Format (AIFF) is an audio file format standard used for storing sound data for personal computers and other electronic audio devices. The format was developed by Apple Inc. in 1988 based on Electronic Arts' Interchange Fil ...

(

IFF In logic and related fields such as mathematics and philosophy, "if and only if" (shortened as "iff") is a biconditional logical connective between statements, where either both statements are true or both are false. The connective is bicondi ...

file format, widely used on

Mac OS Two major famlies of Mac operating systems were developed by Apple Inc. In 1984, Apple debuted the operating system that is now known as the "Classic" Mac OS with its release of the original Macintosh System Software. The system, rebranded " ...

platform) * WAV (

RIFF A riff is a repeated chord progression or refrain in music (also known as an ostinato figure in classical music); it is a pattern, or melody, often played by the rhythm section instruments or solo instrument, that forms the basis or accompanim ...

file format, widely used on

Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...

platform) * XMF (Extensible Music Format) Other containers are exclusive to still images: *

FITS Flexible Image Transport System (FITS) is an open standard defining a digital file format useful for storage, transmission and processing of data: formatted as multi-dimensional arrays (for example a 2D image), or tables. FITS is the most comm ...

(Flexible Image Transport System) still images, raw data, and associated metadata. *

(Tagged Image File Format) still images and associated metadata. *

Macintosh The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and software en ...

PICT resource (

PICT The Picts were a group of peoples who lived in what is now northern and eastern Scotland (north of the Firth of Forth) during Late Antiquity and the Early Middle Ages. Where they lived and what their culture was like can be inferred from ea ...

), superseded by

PDF Portable Document Format (PDF), standardized as ISO 32000, is a file format developed by Adobe in 1992 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating systems. ...

Mac OS X macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

Windows Metafile Windows Metafile (WMF) is an image file format originally designed for Microsoft Windows in the 1990s. The original Windows Metafile format was not device-independent (though could be made more so with placement headers) and may contain both vecto ...

(WMF) = (EMF)

Enhanced Metafile Windows Metafile (WMF) is an image file format originally designed for Microsoft Windows in the 1990s. The original Windows Metafile format was not device-independent (though could be made more so with placement headers) and may contain both vector ...

Encapsulated PostScript Encapsulated PostScript (EPS) is a Document Structuring Convention (DSC) conforming PostScript document format usable as a graphics file format. The format was developed as early as 1987 by John Warnock and Chuck Geschke, the founders of Adobe ...

(EPS) *

Computer Graphics Metafile Computer Graphics Metafile (CGM) is a free and open international standard file format for 2D vector graphics, raster graphics, and text, and is defined by ISO/ IEC 8632. Overview All graphical elements can be specified in a textual source f ...

(CGM) *

Portable Document Format Portable Document Format (PDF), standardized as ISO 32000, is a file format developed by Adobe in 1992 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating syste ...

(PDF) *

Corel Draw File CorelDRAW is a vector graphics editor developed and marketed by Corel Corporation. It is also the name of the Corel graphics suite, which includes the bitmap-image editor Corel Photo-Paint as well as other graphics-related programs (see below) ...

(CDR) *

Scalable Vector Graphics Scalable Vector Graphics (SVG) is an XML-based vector image format for defining two-dimensional graphics, having support for interactivity and animation. The SVG specification is an open standard developed by the World Wide Web Consortium sin ...

(SVG) *

Rich Text Format ) As an example, the following RTF code would be rendered as follows: This is some bold text. Character encoding A standard RTF file can only consist of 7-bit ASCII characters, but can use escape sequences to encode other characters. T ...

file (RTF) Other flexible containers can hold many types of audio and video, as well as other media. The most popular multi-media containers are: *

3GP 3GP (3GPP file format) is a multimedia container format defined by the Third Generation Partnership Project (3GPP) for 3G UMTS multimedia services. It is used on 3G mobile phones but can also be played on some 2G and 4G phones. 3G2 (3GPP2 ...

(used by many mobile phones; based on the ISO base media file format) * ASF (container for Microsoft WMA and WMV, which today usually do not use a container) *

(the standard Microsoft Windows container, also based on

) *

DVR-MS DVR-MS (''Microsoft Digital Video Recording'') is a proprietary video and audio file container format, developed by Microsoft used for storing TV content recorded by Windows XP Media Center Edition, Windows Vista and Windows 7. Multiple data s ...

("Microsoft Digital Video Recording", proprietary video container format developed by Microsoft based on ASF) *

Flash Video Flash Video is a container file format used to deliver digital video content (e.g., TV shows, movies, etc.) over the Internet using Adobe Flash Player version 6 and newer. Flash Video content may also be embedded within SWF files. There ...

(FLV, F4V) (container for video and audio from Adobe Systems) *

(first platform-independent container format) *

(MKV) (not limited to any coding format, as it can hold virtually anything; it is an

open standard An open standard is a standard that is openly accessible and usable by anyone. It is also a prerequisite to use open license, non-discrimination and extensibility. Typically, anybody can participate in the development. There is no single definitio ...

container format) * MJ2 - Motion

JPEG 2000 JPEG 2000 (JP2) is an image compression standard and coding system. It was developed from 1997 to 2000 by a Joint Photographic Experts Group committee chaired by Touradj Ebrahimi (later the JPEG president), with the intention of superseding th ...

file format, based on the ISO base media file format which is defined in MPEG-4 Part 12 and JPEG 2000 Part 12 *

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, ...

(standard

QuickTime QuickTime is an extensible multimedia framework developed by Apple Inc., capable of handling various formats of digital video, picture, sound, panoramic images, and interactivity. Created in 1991, the latest Mac version, QuickTime X, is a ...

video container from Apple Inc.) * MPEG program stream (standard container for MPEG-1 and MPEG-2

elementary stream An elementary stream (ES) as defined by the MPEG communication protocol is usually the output of an audio encoder or video encoder. An ES contains only one kind of data (e.g. audio, video, or closed caption). An elementary stream is often referred ...

s on reasonably reliable media such as disks; used also on

DVD-Video DVD-Video is a consumer video format used to store digital video on DVD discs. DVD-Video was the dominant consumer home video format in Asia, North America, Europe, and Australia in the 2000s until it was supplanted by the high-definition Bl ...

discs) * MPEG-2 transport stream (a.k.a. MPEG-TS) (standard container for digital broadcasting and for transportation over unreliable media; used also on Blu-ray Disc video; typically contains multiple video and audio streams, and an

electronic program guide Electronic programming guides (EPGs) and interactive programming guides (IPGs) are menu-based systems that provide users of television, radio and other media applications with continuously updated menus that display scheduling information for ...

) * MP4 (standard audio and video container for 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 ...

multimedia portfolio, based on the ISO base media file format defined in MPEG-4 Part 12 and JPEG 2000 Part 12) which in turn was based on the QuickTime file format. *

Ogg Ogg is a free, open container format maintained by the Xiph.Org Foundation. The authors of the Ogg format state that it is unrestricted by software patents and is designed to provide for efficient streaming and manipulation of high-quality di ...

(standard container for

Xiph.org Xiph.Org Foundation is a nonprofit organization that produces free multimedia formats and software tools. It focuses on the Ogg family of formats, the most successful of which has been Vorbis, an open and freely licensed audio format and codec de ...

audio formats

Vorbis Vorbis is a free and open-source software project headed by the Xiph.Org Foundation. The project produces an audio coding format and software reference encoder/decoder (codec) for lossy audio compression. Vorbis is most commonly used in con ...

and

Opus ''Opus'' (pl. ''opera'') is a Latin word meaning " work". Italian equivalents are ''opera'' (singular) and ''opere'' (pl.). Opus or OPUS may refer to: Arts and entertainment Music * Opus number, (abbr. Op.) specifying order of (usually) publicati ...

and video format

Theora Theora is a free lossy video compression format. It is developed by the Xiph.Org Foundation and distributed without licensing fees alongside their other free and open media projects, including the Vorbis audio format and the Ogg container ...

) * RM (RealMedia; standard container for

RealVideo RealVideo, or also spelled as Real Video, is a suite of proprietary video compression formats developed by RealNetworks – the specific format changes with the version. It was first released in 1997 and was at version 10. RealVideo is supporte ...

and

RealAudio RealAudio, or also spelled as Real Audio is a proprietary audio format developed by RealNetworks and first released in April 1995. It uses a variety of audio codecs, ranging from low-bitrate formats that can be used over dialup modems, to high-fi ...

) *

WebM WebM is an audiovisual media file format. It is primarily intended to offer a royalty-free alternative to use in the HTML5 video and the HTML5 audio elements. It has a sister project, WebP, for images. The development of the format is sponso ...

(subset of

, used for web-based media distribution on online platforms; container for royalty-free audio formats

and video formats VP8/ VP9/ AV1) There are many other container formats, such as NUT, MXF, GXF, ratDVD, SVI,

VOB VOB (for video object) is the container format in DVD-Video media. VOB can contain digital video, digital audio, subtitles, DVD menus and navigation contents multiplexed together into a stream form. Files in VOB format may be encrypted. File fo ...

and DivX Media Format

References

External links