The Microsoft Video API Face Tracking: Cognitive Services
Many of the Microsoft Cognitive Services APIs can be used together. This gives you a large amount of flexibility whether working with video or images. For example, you can use the Microsoft Video APIs to pull images from a video file, and then you can use the Face or Emotion APIs to extract additional information about the subject within the video images.
At the time of this writing, many of these APIs are in a Preview status, and you can start with most of them at no cost. You can find more information on the Microsoft site at https://www.microsoft.com/cognitive-services/en-us/computer-vision-api.