Identifying content in an MP4 source

The content in an MP4 source always consists of one video track, and one or more audio tracks. It might also contain embedded-style captions.

Obtain identifying information from the content provider:

• For audio – Obtain the track numbers or three-character language codes of the languages that you want.

  Note

  We recommend that you obtain the tracks for the audio assets. They are a more reliable way of identifying an audio asset. Use the language only if there is only one instance of each audio language in the audio asset.

• For captions – Obtain the languages in the channel numbers. For example, "channel 1 is French". The captions are always embedded-style, containing up to four languages, each with its own channel number. The captions might be embedded in the video track or might be embedded in an ancillary track.