How to resolve iOS 11 Safari getUserMedia "Invalid constraint" issue

Question

I'm attempting to run the following code in Safari in iOS 11. It should prompt the user to give access to their devices camera and then display it in my <video autoplay id="video"></video> element. However, when running in iOS 11, it results in an OverconstrainedError to be thrown:

{message: "Invalid constraint", constraint: ""}

• The code runs fine in Android and successfully opens the camera.
• I've attempted multiple valid configurations with no luck.

I know iOS 11 just came out so it may be a bug, but any thoughts? Has anyone else run into this?

Code:

var video = document.getElementById('video');
if(navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
     navigator.mediaDevices.getUserMedia({video: true})
         .then(function(stream) {
             video.src = window.URL.createObjectURL(stream);
             video.play();
         })
         .catch(function(err) {
             console.log(err);
         });
}

---

Edit 1

I've run navigator.mediaDevices.getSupportedConstraints() and it returns the following:

{
    aspectRatio: true,
    deviceid: true,
    echoCancellation: false,
    facingMode: true,
    frameRate: true,
    groupId: true,
    height: true,
    sampleRate: false,
    sampleSize: false,
    volume: true,
    width: true
}

I've tried configurations omitting the video property, but had no luck.

Answer 1

The invalid constraint error in safari is because the browser expects that you pass a correct width, one of:

• 320
• 640
• 1280

the height is auto calculate in an aspect ratio of 4:3 for 320 or 640, and 16:9 for 1280, then if you pass a width of 320, you video stream is set in:

• 320x240

if you set a width of 640, you video stream is set in:

• 640x480

And if you set a width of 1280, then you video stream is set in:

• 1280x720

In any other case you got a error "InvalidConstrain" for width value.

Also you can use a min, max, exact or ideal constrains for width, please check the MDN documentation

Here an example in this codepen

var config = { video: { width: 320/*320-640-1280*/ } };
var start = () => navigator.mediaDevices.getUserMedia(config)
  .then(stream => v.srcObject = stream)
  .then(() => new Promise(resolve => v.onloadedmetadata = resolve))
  .then(() => log("Success: " + v.videoWidth + "x" + v.videoHeight))
  .catch(log);

var log = msg => div.innerHTML += "<p>" + msg + "</p>";

PD: In chrome you can set a width of height and the video stream is set in these sizes, Firefox do a fitness distance, and Safari expect a exact match.

Answer 2

Remember that the iOS Simulator that comes with Xcode does not support webcam or microphone, which is why you may get the OverconstrainedError (as per https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getUserMedia docs, that means no device fits the passed options, even if you're not putting specifics)

Answer 3

It appears to have been a bug that was corrected, because I just tried it again and the error message no longer appears.

Note that while the error message went away, I did have to make one more change for it to work, which was adding video.srcObject = stream; in the then callback.