A container or wrapper is a metafile format whose specification describes how different elements of data and metadata coexist in a computer file . 
Among the earliest cross-platform container formats were Distinguished Encoding Rules and the 1985 Interchange File Format . Containers are frequently used in multimedia applications.
Since the container does not describe how data or metadata is encoded, a program ble to Identify and open a container file might not be reliable to decode the contained data. This may be caused by the program lacking the required decoding algorithm .
By definition, a container format could wrap any kind of data. There are some examples of such file formats (eg Microsoft Windows ‘ s DLL files), which are specialized for specific data requirements. For example, a popular family of containers for multimedia files formats. Since audio and video streams can be coded and decoded with Many different algorithms, a container size May be used to Provide a single file format to the user.
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 formats can support multiple audio and video streams, subtitles, chapter-information, and meta-data ( tags ) – along with the synchronization information needed to play 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, streaming video 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 instead blinds offsets. Modular chunks make it easy to recover other chunks in case of file corruption or dropped frames or bit slip , while offsets result in framing errors in boxes of bit slip.
Some containers are exclusive to audio:
- AIFF (IFF file format, widely used on Mac OS platform)
- WAV ( RIFF file format, widely used on Windows platform)
- XMF (Extensible Music Format)
Other containers are exclusive to still pictures:
- Flexible Image Transport System ( FITS ) still images, raw data, and associated metadata.
- Tagged Image File Format ( TIFF ) still images and associated metadata.
Other flexible containers can hold many types of audio and video, as well as other media. The most popular multi-media containers are:
- 3GP (based on many mobile phones; based on ISO base media file format )
- ASF (Container for Microsoft WMA and WMV , which usually does not use a container)
- AVI (the standard Microsoft Windows container, also based on RIFF )
- DVR-MS (“Microsoft Digital Video Recording”, proprietary video container format developed by Microsoft based on ASF )
- Flash Video (FLV, F4V) (container for video and audio from Adobe Systems )
- IFF (first platform-independent container format)
- Matroska (MKV) (not limited to any coding format, it is an open standard container format)
- MJ2 – Motion JPEG 2000 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 standard video container from Apple Inc. )
- MPEG program stream (standard container for MPEG-1 and MPEG-2 elementary streams on DVD-Video discs)
- MPEG-2 transport stream (aka MPEG-TS) (standard container for digital broadcasting and for transport over unreliable media; also used on Blu-ray Disc video; typically contains multiple video and audio streams, and an electronic program guide )
- MP4 (standard audio and video container for the MPEG-4 multimedia portfolio, based on the ISO based media file format in MPEG-4 Part 12 and JPEG 2000 Part 12) which is based on the QuickTime file format.
- Ogg (standard container for Xiph.org audio Vorbis and Opus formats and video format Theora )
- RM (RealMedia, standard container for RealVideo and RealAudio )
There are many other container formats, such as NUT , MXF , GXF , RATDVD , SVI, VOB and DivX Media Format
Single coding formats
In addition to pure container formats, which specify only the wrapper but not the coding, a number of formats formats, both a storage layer and the coding, as part of modular design and forward compatibility .
Examples include JPEG File Interchange Format (JFIF) for containing JPEG 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 (JNG) puts JPEG encoded data into a PNG container; in both cases however the different formats have different numbers – the format specifies the coding, though a MNG can contain both PNG-encoded images and JPEG-encoded images.
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 and 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 .
- Comparison of (audio / video) container formats
- Open source codecs and containers
- FFmpeg , cross-platform , open source , audio and video codec suite / library
- List of multimedia (audio / video) codecs
- Comparison of video codecs
- Comparison of audio coding formats
Similar packaging structures
- Archive format
- Jump up^ Ho, Anthony TS; Li, Shujun (20 May 2016). Handbook of Digital Forensics of Multimedia Data and Devices, Enhanced E-Book . John Wiley & Sons. pp. 146- (?). ISBN 9781118757079 . OCLC 953319457 .