Loop html5 video in firefox

I need a problem with a video loop in chrome my code is:

 <video id="videoId" class="videoUs" autoplay loop >
                    <source src="media/quiver.webm" type="video/webm">
                    <source src="media/quiver.ogv" type="video/ogg" codecs="theora,vorbis">
                    <source src="media/quiver.mp4" type="video/mp4">     
                    <!--Your browser does not support the video tag.-->
                </video>

and in firefox the video loop is freeze image what happens?? I don't know why happens this! thanks!!