How to use the Vimeo!
Adding Slug To Your Videos
The slug is both audio and video (the audio is silent and the video is black) that can act as a placeholder for any track. Prevent audio sync issues and black or blank frames from being dropped from your video by inserting slug.
FAQ: vimeo.com/help/faq/uploading/new_entry#what_happened_to_my_fade_to_black?