The value depends on the stream and platform. Typical values include:
- 'main': The primary track.
- 'alternative': An alternative to the primary track.
- 'commentary': A commentary track.
- 'descriptions': Audio descriptions of the video content.
- 'description': A variant of 'descriptions' used by some streams or platforms.
- 'main-desc': The primary audio track with audio descriptions.
- 'translation': A translated audio track.
- 'captions': A video track with captions.
- 'sign': A sign-language video track.
- 'subtitles': A video track with subtitles.
- '': No kind is specified.
This list is not exhaustive. Other string values are accepted and are not normalized.
Represents the category of a media track (audio or video).