Remember, you should always take the time to evaluate videos and documentaries just as you would any other resource you plan to use in your research.
Who:
Who is responsible for the creation of the video? Do they have listed credentials? Are they associated with a reputable institution? Do they have ties to any communities or cultures discussed in the video?
What:
What is the purpose of this video (i.e. was it made to entertain, inform, or persuade)? Is there a video description that provides an explicit summary of that purpose?
Where:
If this is a documentary or informational video, where is the information coming from? Is there a bibliography or listed references? Is the video hosted on the website of an established institution?
When:
When was the video created? Does the currency of the information directly impact your subject?
Why:
Why is this video useful for your research? Is it necessary for your research or could you find the information through a better source?