A cross-browser way to start a video stream. Here the video element is created and appended to the DOM, but you could as well use a pre-existing video element.

cross browser video stream

function getVideo(){
  var videoElement = document.createElement('video');
  document.body.appendChild(videoElement);
	var getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia ||
	                   navigator.mozGetUserMedia || navigator.msGetUserMedia;
	var params = [
    {video: true}, 
		function(stream){
			try{
				videoElement.src = window.URL.createObjectURL(stream);
			}
			catch (e){
				videoElement.src = stream;
			}
				
			videoElement.play();
		},
		function(){
  		console.log('failed');
		}];
	getUserMedia.apply(navigator, params);
}