video.js

        grabFrame: function() {
            var self = this;

            this.canvasCtx.drawImage(this.video, 0, 0, this.canvas.width, this.canvas.height);
            this.canvas.toBlob(function(imageData) {
                var postImageReq = new XMLHttpRequest();
                postImageReq.open("POST", "/prediction", true);
                postImageReq.responseType = "json";

                postImageReq.onload = function(event) {
                    var faces = postImageReq.response.faces;

                    self.drawFaces(faces);
                    self.scheduleFrameGrab();
                };

                postImageReq.send(imageData);
            }, "image/jpeg", 70);

        },