Attempts to prevent blackness when switching simulcast streams.

index.html

@@ -47,7 +47,7 @@
     <script src="analytics.js?v=1"></script><!-- google analytics plugin -->
     <script src="rtp_sts.js?v=3"></script><!-- RTP stats processing -->
     <script src="local_sts.js?v=2"></script><!-- Local stats processing -->
-    <script src="videolayout.js?v=18"></script><!-- video ui -->
+    <script src="videolayout.js?v=19"></script><!-- video ui -->
     <script src="connectionquality.js?v=1"></script>
     <script src="toolbar.js?v=6"></script><!-- toolbar ui -->
     <script src="toolbar_toggler.js?v=2"></script>
@@ -249,6 +249,7 @@
                 <a target="_new"><div class="watermark leftwatermark"></div></a>
                 <a target="_new"><div class="watermark rightwatermark"></div></a>
                 <a class="poweredby" href="http://jitsi.org" target="_new" >powered by jitsi.org</a>
+                <video id="preload" style="display: none"></video>
                 <video id="largeVideo" autoplay oncontextmenu="return false;"></video>
             </div>
             <div id="remoteVideos">

videolayout.js

@@ -227,7 +227,13 @@ var VideoLayout = (function (my) {
                 if (fade) {
                     $('#largeVideo').fadeOut(300, doUpdate);
                 } else {
-                    doUpdate();
+                    $("#preload").attr("src", largeVideoState.newSrc);
+                    // The 'canplay' event occurs when the browser can start
+                    // playing the specified audio/video. See:
+                    // http://www.w3schools.com/tags/av_event_canplay.asp
+                    $("#preload").one("canplay",function(){
+                        doUpdate();
+                    });
                 }
             }
         }