This post is to explain how views field mapping works currently in the module. It is also to educate users so they know that just because they didn't "pick" something to happen, it still occurs for them in the background.

The module automatically seeks out two things: an image field and a file field. The file is required as the video source. The image is the optional thumbnail.

The module looks for a file source in the view first and foremost. If it also finds an image field, it will suck that up too. The reason is that a thumbnail source for youtube media is different then a thumbnail source for a random entity that happens to also have an image field.

Basically I have the module automatically get the correct video file and poster/image so that users can combine different entity types in their view. In other words, it's okay to combine a file field with a media field in the same view. If users had to map sources, they would be hamstrung.

The title source is another matter. It gets the "filename". That might need to get mapped. Stand by or chime in.