Если сайт открывается с телефона - показывать картинку, иначе - видео

// was extracted from the spec in January 2013
var media_properties = [ "error", "src", "currentSrc", "crossOrigin", "networkState", "preload", "buffered", "readyState", "seeking", "currentTime", "duration", "startDate", "paused", "defaultPlaybackRate", "playbackRate", "played", "seekable", "ended", "autoplay", "loop", "mediaGroup", "controller", "controls", "volume", "muted", "defaultMuted", "audioTracks", "videoTracks", "textTracks", "width", "height", "videoWidth", "videoHeight", "poster" ];
 
var media_properties_elts = null;
 
var webm = null;
 
function init() {
    document._video = document.getElementById("video_background");
 
    webm = document.getElementById("webm");
 
    init_events();
    init_properties();
    init_mediatypes();
 
    // properties are updated even if no event was triggered
    setInterval(update_properties, 500);
}
document.addEventListener("DOMContentLoaded", init, false);
 
function init_events() {
 
    for (key in media_events) { 
    document._video.addEventListener(key, capture, false);
    }
 
    var tbody = document.getElementById("events");
    var i = 1;
    var tr = null;
    for (key in media_events) { 
    if (tr == null) tr    = document.createElement("tr");
    var th = document.createElement("th");
    th.textContent = key;
    var td = document.createElement("td");
    td.setAttribute("id", "e_" + key);
    td.innerHTML = "0";
    td.className = "false";
    tr.appendChild(th);
    tr.appendChild(td);
 
    if ((i++ % 5) == 0) {
        tbody.appendChild(tr);
        tr = null;
    }
 
 
    }
    if (tr != null) tbody.appendChild(tr);
}