Retrieve the MPEG DASH manifest that can be used by a DASH capable player for a given Activity Id. This manifest is dynamically generated, so do not create this XML by hand, always use this API call. The results of this call may be cached. The closed caption track contains the Activity frame timestamps in WEBVTT format.
When processing this DASH manifest, calls to the media elements must utilize the same Authentication tokens as regular API calls.
This API call will include Cache-Control headers in the response that must be honored. The cache duration is 10 sec for an activity in progress and the cache duration for a completed activity is the lifetime of that activity.