WebRTC - getting 'malformed constraints object' from Chrome but not Firefox

I wonder what I'm doing wrong.

I'm getting 'malformed constraints object' errors from this:

pc.createAnswer( function (answer) {
  ...
}, fail, { offerToReceiveAudio: true, offerToReceiveVideo: true });

Any ideas?

Answers:

Answer

According to the newest Webrtc spec the correct form of the constraint parameter should be:

{ offerToReceiveAudio: true, offerToReceiveVideo: true }

Note the lowercase 'o's at the beginnings of offerToReceiveAudio and offerToReceiveVideo.

This is currently supported only by FF 33 or newer.

Chrome supports only the own way:

{ mandatory: { OfferToReceiveAudio: true, OfferToReceiveVideo: true } }

Chrome will throw and error if you give it a constraint object that has a structure according to the new spec.

The good news is that Firefox still accepts the old form. It just prints a warning message in that case. So, at least for now, use the old version.

Answer

I have fought with this problem for many hours and just a moment ago I found something interesting:

When i add any method to the Object.prototype i get the Uncaught TypeError: Failed to construct 'RTCPeerConnection': Malformed constraints object.

Example:

Object.prototype.nothingSpecial = function() {
    console.log("Here goes nothing ...");
};

This will cause the exception.

Solution: Remove any/all modifications to the Object.prototype.

I believe this is a bug in the browser.

-

Edit: My collegue figured out the exact reason for this error:

  • When adding enumerable fields to Object.prototype the error appears.
  • When adding only non-enumerable fields it works (eg. using defineProperty)

-

I am using the erizo video-streaming library.

Testes with: JX Browser 6.21 (Chromium based)
Version: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.24 Safari/537.36

The full error looks like this:

Uncaught TypeError: Failed to construct 'RTCPeerConnection': Malformed constraints object.
    at Object.Erizo.ChromeStableStack (erizo.js:2405)
    at Object.Erizo.Connection (erizo.js:2910)
    at erizo.js:3670
    at c.<anonymous> (erizo.js:3373)
    at c.onPacket (erizo.js:890)
    at d.onPacket (erizo.js:722)
    at d.c.onPacket (erizo.js:465)
    at d.c.onData (erizo.js:453)
    at WebSocket.websocket.onmessage (erizo.js:929)

The first exception caused a secondary exception:

Uncaught TypeError: Cannot read property 'processSignalingMessage' of undefined
    at c.<anonymous> (erizo.js:3253)
    at c.emit [as $emit] (erizo.js:213)
    at c.onPacket (erizo.js:887)
    at d.onPacket (erizo.js:722)
    at d.c.onPacket (erizo.js:465)
    at d.c.onData (erizo.js:453)
    at WebSocket.websocket.onmessage (erizo.js:929)

(In case you wonder about the erizo.js filename and line numbers: i was using a pretty-printed version of the erizo.min.js for easier debugging.)

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