- `format_id`: Format code specified by `--format`.
- `duration`: Length of the video in seconds.
-Available for the video that belong to some logical chapter or section:
+Available for the video that belongs to some logical chapter or section:
- `chapter`: Name or title of the chapter the video belongs to.
- `chapter_number`: Number of the chapter the video belongs to, as an integer.
- `chapter_id`: Id of the chapter the video belongs to, as a unicode string.