If we need to create a URL for stream, why can we

问题:

In a Google's WebRTC tutorial, it has the following example code.

I have two questions for it:

1. Why do we need to set window.stream to stream? (What does "stream available to console" mean?)
2. If we need to create a URL for stream, why can we set video.src to stream which should be a blob?

Thanks.

function successCallback(stream) {
  window.stream = stream; // stream available to console
  if (window.URL) {
    video.src = window.URL.createObjectURL(stream);
  } else {
    video.src = stream;
  }
}

回答1:

Old and wrong code. video.src = stream is wrong. It should be video.srcObject = stream. It just never runs because all browsers today support URL.

Instead, use srcObject whenever available (supported in both Chrome and Firefox) for better life time handling by browsers:

if (typeof video.srcObject == "object") {
  video.srcObject = stream;
} else {
  video.src = URL.createObjectURL(stream);
}

Or use adapter.js and don't worry about it:

video.srcObject = stream;

Oh, and window.stream is just some global variable. Likely used for debugging by the sample author.

2013 is old for WebRTC code. I recommend looking at the official WebRTC samples instead.