var sampleVideoData;
function retrieveSampleVideo() {
  var oReq = new XMLHttpRequest();
  oReq.open("GET", "bigbuckbunny.webm", true);
  oReq.responseType = "arraybuffer";

  oReq.onload = function (oEvent) {
    var arrayBuffer = oReq.response;
    if (arrayBuffer) {
      sampleVideoData = new Uint8Array(arrayBuffer);
    }
  };

  oReq.send(null);
}