Скруглить углы у видео с ютуба

var tag = document.createElement('script'); 
 
tag.src = "https://www.youtube.com/iframe_api"; 
var firstScriptTag = document.getElementsByTagName('script')[0]; 
firstScriptTag.parentNode.insertBefore(tag, firstScriptTag); 
 
var player; 
function onYouTubeIframeAPIReady() { 
    player = new YT.Player('player', { 
        height: '160', 
        width: '340', 
        videoId: 'M7lc1UVf-VE', 
        playerVars: { 
            rel: 0, 
            controls: 0, 
            showinfo: 0 
        } 
    }); 
}

.player{ 
  -webkit-mask-image: -webkit-radial-gradient(circle, white 100%, black 100%); /*ios 7 border-radius-bug */ 
  -webkit-transform: rotate(0.000001deg); /*mac os 10.6 safari 5 border-radius-bug */ 
  -webkit-border-radius: 15px;  
  -moz-border-radius: 15px; 
  border-radius: 15px;  
  overflow: hidden;  
 }

<div class="player" id="player"></div>