javascript - trying to use the getUserMedia framerate constraint -

i trying adjust framerate display of getusermedia webcam stream. method trying use is

var constraints = { video: { framerate: { ideal: 10, max: 15 } } }; 

as referenced in moz developer network.

i create several functions can called change framerate different settings, in trying implement constraint not seem have effect. i've tried using alone

function setfps1() { var constraints ... } 

and within functions (re)declare stream

    function usevideo(){     // query user device permission     navigator.mediadevices.getusermedia({video: true})     // if granted      .then(function(stream) {          // stream & play video webcam           var video = document.getelementbyid('uservideo');           var constraints = { video: { framerate: { ideal: 10, max: 15 } } };           video.src = window.url.createobjecturl(stream);           video.play();         })     // if not     .catch(function(error) {         alert(error.message);     });     } 

and tried

    function usevideo(){     // query user device permission     navigator.mediadevices.getusermedia({video: true})     // if granted      .then(function(stream) {          // stream & play video webcam           var video = document.getelementbyid('uservideo');           video.src = window.url.createobjecturl(stream);           video.play();           var constraints = { video: { framerate: { ideal: 10, max: 15 } } };         })     // if not     .catch(function(error) {         alert(error.message);     });     } 

for measure, thinking maybe video had first playing before framerate set.

how framerate constraint meant used, or preventing me using it?

the line:

var constraints = { video: { framerate: { ideal: 10, max: 15 } } }; 

just initializates local variable constraints object specified. no effect on else.

you set constraints on camera functions getusermedia or applyconstraints, e.g.:

navigator.mediadevices.getusermedia(constraints)   .then(function(stream) {     var video = document.getelementbyid('uservideo');     video.srcobject = stream;     video.play();   })   .catch(error => console.log(error)); 

or

var track = video.srcobject.getvideotracks()[0];  track.applyconstraints(constraints).catch(e => console.log(e)); 

once working, note browsers implement constraints a bit differently.