… for Codecs & Media

Tip #414: What is a Container Format?

Larry Jordan – LarryJordan.com

Containers hold stuff – like media.

QuickTime and MXF are often described as media “containers.” But, what is a container?

A “container,” also called a “wrapper,” is a metafile (analogous to a folder) whose specification describes how the different elements inside it are stored. Similar to a Keynote file or a Library in Final Cut Pro X, a container is a file that holds files, but still acts like a single file. Unlike a folder, when you double-click it, a container opens the files inside it.

By definition, a container could contain anything, but, generally, they focus on a specific type of data – most often involving media. Containers can hold video, audio, timecode, captions, and metadata that describes the contents of the container.

Popular containers include:

• Both AIFF and WAV are containers, but only hold audio.
• TIFF is a container for still images.
• QuickTime, MXF and MPEG-2 Transport stream are containers for audio, video and related files.

The big benefit to containers is that they are not tied to a single codec, but allow us to use a single container for mutiple codecs, thus hiding the underlying technology inside a familiar format.