Transform video into Blob object?

I found this code in a tutorial that to transform the videos into objects and be treated as if it were a url blob , with the first video coming on the page the function works perfectly, however when I call another video through , the only purpose of this code is to help protect the original path of the videos to avoid direct access, which may be wrong?

function mascara()
{
    var ms = new MediaSource();

    var video = document.querySelector('source');
    video.src = window.URL.createObjectURL(ms);

    ms.addEventListener('sourceopen', function(e) {

      var sourceBuffer = ms.addSourceBuffer('video/mp4; codecs="avc1.42E01E, mp4a.40.2"');
      sourceBuffer.appendBuffer(oneVideoWebMChunk);

    }, false);
};