#1770, set 'data-paused-by-reveal' attribute only for the media elements, which are not already in paused state.

js/reveal.js

@@ -3071,7 +3071,7 @@
 		if( slide && slide.parentNode ) {
 			// HTML5 media elements
 			toArray( slide.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
-				if( !el.hasAttribute( 'data-ignore' ) && typeof el.pause === 'function' ) {
+				if( !el.hasAttribute( 'data-ignore' ) && typeof el.pause === 'function' && el.paused === false ) {
 					el.setAttribute('data-paused-by-reveal', '');
 					el.pause();
 				}