Usar câmera traseira do celular

Olá pessoal, tudo certo?!

Estou com um código que está funcionando bem. Mas gostaria de que a câmera traseira do celular fosse a padrão.

Abaixo segue o código, caso possam me ajudar a efetuar esta alteração.

Desde já, agradeço!

(function () {
 var video = document.querySelector('video');

 var pictureWidth = 640;
 var pictureHeight = 360;

 var fxCanvas = null;
 var texture = null;

 function checkRequirements() {
 var deferred = new $.Deferred();

 //Check if getUserMedia is available
 if (!Modernizr.getusermedia) {
 deferred.reject('Your browser doesn\'t support getUserMedia (according to Modernizr).');
 }

 //Check if WebGL is available
 if (Modernizr.webgl) {
 try {
 //setup glfx.js
 fxCanvas = fx.canvas();
 } catch (e) {
 deferred.reject('Sorry, glfx.js failed to initialize. WebGL issues?');
 }
 } else {
 deferred.reject('Your browser doesn\'t support WebGL (according to Modernizr).');
 }

 deferred.resolve();

 return deferred.promise();
 }

 function searchForRearCamera() {
 var deferred = new $.Deferred();

 //MediaStreamTrack.getSources seams to be supported only by Chrome
 if (MediaStreamTrack && MediaStreamTrack.getSources) {
 MediaStreamTrack.getSources(function (sources) {
 var rearCameraIds = sources.filter(function (source) {
 return (source.kind === 'video' && source.facing === 'environment');
 }).map(function (source) {
 return source.id;
 });

 if (rearCameraIds.length) {
 deferred.resolve(rearCameraIds[0]);
 } else {
 deferred.resolve(null);
 }
 });
 } else {
 deferred.resolve(null);
 }

 return deferred.promise();
 }

 function setupVideo(rearCameraId) {
 var deferred = new $.Deferred();
 var videoSettings = {
 video: {
 optional: [
 {
 width: { min: pictureWidth }
 },
 {
 height: { min: pictureHeight }
 }
 ]
 }
 };

 //if rear camera is available - use it
 if (rearCameraId) {
 videoSettings.video.optional.push({
 sourceId: rearCameraId
 });
 }

 navigator.mediaDevices.getUserMedia(videoSettings)
 .then(function (stream) {
 //Setup the video stream
 video.srcObject = stream;

 video.addEventListener("loadedmetadata", function (e) {
 //get video width and height as it might be different than we requested
 pictureWidth = this.videoWidth;
 pictureHeight = this.videoHeight;

 if (!pictureWidth && !pictureHeight) {
 //firefox fails to deliver info about video size on time (issue #926753), we have to wait
 var waitingForSize = setInterval(function () {
 if (video.videoWidth && video.videoHeight) {
 pictureWidth = video.videoWidth;
 pictureHeight = video.videoHeight;

 clearInterval(waitingForSize);
 deferred.resolve();
 }
 }, 100);
 } else {
 deferred.resolve();
 }
 }, false);
 }).catch(function () {
 deferred.reject('There is no access to your camera, have you denied it?');
 });

 return deferred.promise();
 }

 function step1() {
 checkRequirements()
 .then(searchForRearCamera)
 .then(setupVideo)
 .done(function () {
 //Enable the 'take picture' button
 $('#takePicture').removeAttr('disabled');
 //Hide the 'enable the camera' info
 $('#step1 figure').removeClass('not-ready');
 })
 .fail(function (error) {
 showError(error);
 });
 }

 function step2() {
 var canvas = document.querySelector('#step2 canvas');
 var img = document.querySelector('#step2 img');

 //setup canvas
 canvas.width = pictureWidth;
 canvas.height = pictureHeight;

 var ctx = canvas.getContext('2d');

 //draw picture from video on canvas
 ctx.drawImage(video, 0, 0);

 //modify the picture using glfx.js filters
 texture = fxCanvas.texture(canvas);
 fxCanvas.draw(texture)
 .hueSaturation(-1, -1)//grayscale
 .unsharpMask(20, 2)
 .brightnessContrast(0.2, 0.9)
 .update();

 window.texture = texture;
 window.fxCanvas = fxCanvas;

 $(img)
 //setup the crop utility
 .one('load', function () {
 if (!$(img).data().Jcrop) {
 $(img).Jcrop({
 onSelect: function () {
 //Enable the 'done' button
 $('#adjust').removeAttr('disabled');
 }
 });
 } else {
 //update crop tool (it creates copies of <img> that we have to update manually)
 $('.jcrop-holder img').attr('src', fxCanvas.toDataURL());
 }
 })
 //show output from glfx.js
 .attr('src', fxCanvas.toDataURL());
 }

 function step3() {
 var canvas = document.querySelector('#step3 canvas');
 var step2Image = document.querySelector('#step2 img');
 var cropData = $(step2Image).data().Jcrop.tellSelect();

 var scale = step2Image.width / $(step2Image).width();

 //draw cropped image on the canvas
 canvas.width = cropData.w * scale;
 canvas.height = cropData.h * scale;

 var ctx = canvas.getContext('2d');
 ctx.drawImage(
 step2Image,
 cropData.x * scale,
 cropData.y * scale,
 cropData.w * scale,
 cropData.h * scale,
 0,
 0,
 cropData.w * scale,
 cropData.h * scale);

 var spinner = $('.spinner');
 spinner.show();
 $('blockquote p').text('');
 $('blockquote footer').text('');

 // do the OCR!
 Tesseract.recognize(ctx).then(function (result) {
 var resultText = result.text ? result.text.trim() : '';

 //show the result
 spinner.hide();
 $('blockquote p').html('&bdquo;' + resultText + '&ldquo;');
 $('blockquote footer').text('(' + resultText.length + ' characters)');
 });
 }

 /*********************************
 * UI Stuff
 *********************************/

 //start step1 immediately
 step1();
 $('.help').popover();

 function changeStep(step) {
 if (step === 1) {
 video.play();
 } else {
 video.pause();
 }

 $('body').attr('class', 'step' + step);
 $('.nav li.active').removeClass('active');
 $('.nav li:eq(' + (step - 1) + ')').removeClass('disabled').addClass('active');
 }

 function showError(text) {
 $('.alert').show().find('span').text(text);
 }

 //handle brightness/contrast change
 $('#brightness, #contrast').on('change', function () {
 var brightness = $('#brightness').val() / 100;
 var contrast = $('#contrast').val() / 100;
 var img = document.querySelector('#step2 img');

 fxCanvas.draw(texture)
 .hueSaturation(-1, -1)
 .unsharpMask(20, 2)
 .brightnessContrast(brightness, contrast)
 .update();

 img.src = fxCanvas.toDataURL();

 //update crop tool (it creates copies of <img> that we have to update manually)
 $('.jcrop-holder img').attr('src', fxCanvas.toDataURL());
 });

 $('#takePicture').click(function () {
 step2();
 changeStep(2);
 });

 $('#adjust').click(function () {
 step3();
 changeStep(3);
 });

 $('#go-back').click(function () {
 changeStep(2);
 });

 $('#start-over').click(function () {
 changeStep(1);
 });

 $('.nav').on('click', 'a', function () {
 if (!$(this).parent().is('.disabled')) {
 var step = $(this).data('step');
 changeStep(step);
 }

 return false;
 });
})();