Full Screen Video Background with minimal code. Coded with SASS and Coffee Script Requires jQuery!

index.html

<div class="bg-video">
	<video loop autoplay>
	    <!-- Insert your video below -->
		<source src="" type="video/mp4"></source>
	</video>
</div>

scripts.coffee

$(document).ready ->

	# The video element
	video = $('.bg-video video')

	# Ratio of the elements dimensions
	ratio = video.width() / video.height()

	# Background Video
	$(window).on 'load scroll resize', ->

		# If the height multiplied by the raio is larger than the window width
		if $(window).height() * ratio > $(window).width()

			# Give the video the width of the window height multiplied by the ratio
			video.width( $(window).height() * ratio )

		else 

			# Else give it the window width
			video.width( $(window).width() )

style.scss

.bg-video {
	video {
		position: fixed; // Fixed position
		z-index: -1; // Overlay items on top of it
		width: 100%; // Fallback, jQuery or JS doesn't load
	}
}