Fullscreen video without black borders

The problem I have is that the video always gets black bars on the sides or on the top/bottom depending on the screen size.

Any idea how to get it full screen always without showing that annoying black bars? and without using a plugin.

This is my markup:

    <div id="full-bg">
        <div class="box iframe-box" width="1280" height="800">
            <iframe src="http://player.vimeo.com/video/67794477?title=0&amp;byline=0&amp;portrait=0&amp;color=0fb0d4" width="1280" height="720" frameborder="0" webkitAllowFullScreen mozallowfullscreen allowFullScreen></iframe>
        </div>
    </div>

    #full-bg{
        width: 100%;
        height: 100%;
        img{
            display: none;
        }
        .iframe-box{
            width: 100%;
            height: 100%;
            position: absolute;
            background: url(../img/fittobox.png);
            left: 0 !important;
            top: 0 !important;
            iframe{
                width: 100%;
                height: 100%;
            }
        }
    }