node js based live video streaming

I am developing a live streaming project in nodejs. Can anyone explain what is happening in the following nodejs code.

Base64Id.prototype.generateId = function () {  
  var rand = new Buffer(15); // multiple of 3 for base64  
  if (!rand.writeInt32BE) {  
    return Math.abs(Math.random() * Math.random() * Date.now() | 0).toString()  
      + Math.abs(Math.random() * Math.random() * Date.now() | 0).toString();  
  }  
  this.sequenceNumber = (this.sequenceNumber + 1) | 0;  
  rand.writeInt32BE(this.sequenceNumber, 11);  
  if (crypto.randomBytes) {  
    this.getRandomBytes(12).copy(rand);  
  } else {  
    // not secure for node 0.4  
    [0, 4, 8].forEach(function(i) {  
      rand.writeInt32BE(Math.random() * Math.pow(2, 32) | 0, i);  
    });  
  }
  return rand.toString('base64').replace(/\//g, '_').replace(/\+/g, '-');  
}; 

via Krishna Mohan