Chapter 3: Container

A container is a file or stream format that specifies how the content is stored within itself, but not how it is coded (that’s the job of the codec, as described in Chapter 4). If there are multiple streams (e.g. multiple audio and video channels, and a closed captioning stream), it describes how they are interleaved in the file. The container also contains any metadata needed to describe the stream.

Although containers can contain many different types of data, there are some common combinations, as noted in the following table.

There are some audio formats that are often not wrapped in a container, though they could be. For example, MP3, AAC, and WMA often stand alone.