add option to mute background videos (updated)

README.md

@@ -448,8 +448,8 @@ Slides are contained within a limited portion of the screen by default to allow
 <section data-background="http://example.com/image.png" data-background-size="100px" data-background-repeat="repeat">
 	<h2>This background image will be sized to 100px and repeated.</h2>
 </section>
-<section data-background-video="https://s3.amazonaws.com/static.slid.es/site/homepage/v1/homepage-video-editor.mp4,https://s3.amazonaws.com/static.slid.es/site/homepage/v1/homepage-video-editor.webm" data-background-video-loop>
-	<h2>Video. Multiple sources can be defined using a comma separated list. Video will loop when the data-background-video-loop attribute is provided.</h2>
+<section data-background-video="https://s3.amazonaws.com/static.slid.es/site/homepage/v1/homepage-video-editor.mp4,https://s3.amazonaws.com/static.slid.es/site/homepage/v1/homepage-video-editor.webm" data-background-video-loop data-background-video-muted>
+	<h2>Video. Multiple sources can be defined using a comma separated list. Video will loop when the data-background-video-loop attribute is provided and can be muted with the data-background-video-muted attribute.</h2>
 </section>
 <section data-background-iframe="https://slides.com">
 	<h2>Embeds a web page as a background. Note that the page won't be interactive.</h2>

js/reveal.js

@@ -2873,6 +2873,7 @@
 				var backgroundImage = slide.getAttribute( 'data-background-image' ),
 					backgroundVideo = slide.getAttribute( 'data-background-video' ),
 					backgroundVideoLoop = slide.hasAttribute( 'data-background-video-loop' ),
+					backgroundVideoMuted = slide.hasAttribute( 'data-background-video-muted' ),
 					backgroundIframe = slide.getAttribute( 'data-background-iframe' );
 
 				// Images
@@ -2887,6 +2888,10 @@
 						video.setAttribute( 'loop', '' );
 					}
 
+					if( backgroundVideoMuted ) {
+						video.muted = true;
+					}
+
 					// Support comma separated lists of video sources
 					backgroundVideo.split( ',' ).forEach( function( source ) {
 						video.innerHTML += '<source src="'+ source +'">';