.responsive-embed {
    position: relative;
    padding-bottom: 56.25%;/*16:9 is default*/
    height: 0;
    overflow: hidden;
    max-width: 100%;
}
.responsive-embed-16by9 {
    padding-bottom: 56.25%;
}
.responsive-embed iframe, .responsive-embed object, .responsive-embed embed {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}