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问题:

Is this a BUG in Mac or Canary?

I need to use the screen-capture via Google Canary, which was working before in past old versions.

But since they release Canary M37 or M39 its not working anymore. Is my --enable-usermedia-screen-capturing command invalid the way i am executing it?

$ alias canary="open /Applications/Google\ Chrome\ Canary.app/ --args --enable-usermedia-screen-capturing"
$ canary

Now when i try to start screen capture (which was working in old versions) its giving me error failing:

getUserMedia error:  NavigatorUserMediaError {constraintName: "", message: "", name: "InvalidStateError"}

code:

function start() {
  console.log("Requesting local stream");
  btn1.disabled = true;
  var video_constraints = { 
    audio: false,
    video: {
      mandatory: {
        chromeMediaSource: 'screen',
        maxWidth: 1024,
        maxHeight: 768,
        minWidth:800,
        minHeight:400,
        minFrameRate: 1,
        maxFrameRate: 2,
        //minAspectRatio: 1.333, maxAspectRatio: 1.334,
      }
    }
  };

  navigator.webkitGetUserMedia(video_constraints, function(stream){
    console.log("Received local stream");
    vid1.src = webkitURL.createObjectURL(stream);
    localstream = stream;


  }, function(e){

    console.log("getUserMedia error: ", e);
  });
}

EDIT:

<html>
<head>
<style>
  body {
    background: white;
    display: -webkit-flex;
    -webkit-justify-content: center;
    -webkit-align-items: center;
    -webkit-flex-direction: column;
  }
  video {
    width: 640px;
    height: 480px;
    border: 1px solid #e2e2e2;
    box-shadow: 0 1px 1px rgba(0,0,0,0.2);
  }
</style>
</head>
<body>
  <video id="video" autoplay></video>
  <p><button id="start">Start</button><button id="cancel">Cancel</button></p>
  <script>
// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

function gotStream(stream) {
  console.log("Received local stream");
  var video = document.querySelector("video");
  video.src = URL.createObjectURL(stream);
  localstream = stream;
  stream.onended = function() { console.log("Ended"); };
}

function getUserMediaError() {
  console.log("getUserMedia() failed.");
}

function onAccessApproved(id) {
  if (!id) {
    console.log("Access rejected.");
    return;
  }
  navigator.webkitGetUserMedia({
      audio:false,
      video: { mandatory: { chromeMediaSource: "desktop",
                            chromeMediaSourceId: id } }
  }, gotStream, getUserMediaError);
}

var pending_request_id = null;

document.querySelector('#start').addEventListener('click', function(e) {
  pending_request_id = chrome.desktopCapture.chooseDesktopMedia(
      ["screen", "window"], onAccessApproved);
});

document.querySelector('#cancel').addEventListener('click', function(e) {
  if (pending_request_id != null) {
    chrome.desktopCapture.cancelChooseDesktopMedia(pending_request_id);
  }
});

  </script>
</body>
</html>

回答1:

In the newer versions of Chrome, that type of screen capture is deprecated and I believe removed.

This started with Chrome M36+.

The new DesktopCapture API is much better and gives a greater range of options.

EDIT:

The new API is only available if utilized through an extension. The Chrome team states that this has been changed for security reasons. Possibly, in the future, it will be moved back to not require an extension to be built but as of right now, it is not available directly in the page.

回答2:

Step 1 - download Ready made cake, to get started

https://developer.chrome.com/extensions/examples/api/desktopCapture.zip

Step 2 - RTFM

Load the extension
Extensions that you download from the Chrome Web Store are packaged up as .crx files, which is great for distribution, but not so great for development. Recognizing this, Chrome gives you a quick way of loading up your working directory for testing. Let's do that now.

Visit chrome://extensions in your browser (or open up the Chrome menu by clicking the icon to the far right of the Omnibox:  The menu's icon is three horizontal bars.. and select Extensions under the Tools menu to get to the same place).

Ensure that the Developer mode checkbox in the top right-hand corner is checked.

Click Load unpacked extension… to pop up a file-selection dialog.

Navigate to the directory in which your extension files live, and select it.

Alternatively, you can drag and drop the directory where your extension files live onto chrome://extensions in your browser to load it.

If the extension is valid, it'll be loaded up and active right away! If it's invalid, an error message will be displayed at the top of the page. Correct the error, and try again.

Step 3 - Launch the app

EDIT: References:

https://developer.chrome.com/extensions/manifest#web_accessible_resources

https://stackoverflow.com/a/17098011

https://stackoverflow.com/a/17120647

回答3:

Firefox also now has screen/window/etc capture. For now, for similar reasons to Chrome, we've put access to the feature behind a whitelist (though an extension could extend the whitelist as well; we haven't prototyped that yet).

See http://mozilla.github.io/webrtc-landing/gum_test.html (In Firefox 33 or later - currently that's Beta; no attempt to polyfill was done there as it's an internal testing page).