Specifying Closed Captions

You can include a timeline containing closed captions for the video in the JSON data:

{
  ...
  "timeline": {
    "tracks": {
      "OverlayDefault": [
        {
          "startTime": 2.5,
          "id": "780d02d5-6ba3-46f1-ab82-ffc8e8f09522",
          "endTime": 4.0,
          "title": "Hello"
        },
        {
          "startTime": 5.0,
          "id": "24f2ba48-7741-4053-bf3a-d4a3e3409bb1",
          "endTime": 7.5,
          "title": "world"
        }
      ]
    }
  }
  ...
}

OverlayDefault is an array containing a sequence of captions. Each caption definition must include the following fields:

startTime

The point at which display of the caption is to start, measured from the start in seconds.

id

An ID for the caption.

title

The caption text.

endTime

The point at which display of the caption is to end, measured from the start in seconds.