scan frequency as proposed by serratus

src/quagga.js

@@ -296,16 +296,29 @@ function update() {
     }
 }
 
-function start() {
+function startContinuousUpdate() {
+    var next = null,
+        delay = 1000 / (_config.frequency || 60);
+
     _stopped = false;
-    ( function frame() {
+    (function frame(timestamp) {
+        next = next || timestamp;
         if (!_stopped) {
-            update();
-            if (_onUIThread && _config.inputStream.type === "LiveStream") {
-                window.requestAnimFrame(frame);
+            if (timestamp >= next) {
+                next += delay;
+                update();
             }
+            window.requestAnimFrame(frame);
         }
-    }());
+    }(performance.now()));
+}
+
+function start() {
+    if (_onUIThread && _config.inputStream.type === "LiveStream") {
+        startContinuousUpdate();
+    } else {
+        update();
+    }
 }
 
 function initWorker(cb) {
@@ -360,23 +373,21 @@ function workerInterface(factory) {
     var imageWrapper;
 
     self.onmessage = function(e) {
-        setTimeout(function() {
-            if (e.data.cmd === 'init') {
-                var config = e.data.config;
-                config.numOfWorkers = 0;
-                imageWrapper = new Quagga.ImageWrapper({
-                    x: e.data.size.x,
-                    y: e.data.size.y
-                }, new Uint8Array(e.data.imageData));
-                Quagga.init(config, ready, imageWrapper);
-                Quagga.onProcessed(onProcessed);
-            } else if (e.data.cmd === 'process') {
-                imageWrapper.data = new Uint8Array(e.data.imageData);
-                Quagga.start();
-            } else if (e.data.cmd === 'setReaders') {
-                Quagga.setReaders(e.data.readers);
-            }
-        }, Quagga.getConfig().scanDelay || 0);
+        if (e.data.cmd === 'init') {
+            var config = e.data.config;
+            config.numOfWorkers = 0;
+            imageWrapper = new Quagga.ImageWrapper({
+                x: e.data.size.x,
+                y: e.data.size.y
+            }, new Uint8Array(e.data.imageData));
+            Quagga.init(config, ready, imageWrapper);
+            Quagga.onProcessed(onProcessed);
+        } else if (e.data.cmd === 'process') {
+            imageWrapper.data = new Uint8Array(e.data.imageData);
+            Quagga.start();
+        } else if (e.data.cmd === 'setReaders') {
+            Quagga.setReaders(e.data.readers);
+        }
     };
 
     function onProcessed(result) {
@@ -518,8 +529,5 @@ export default {
     },
     ImageWrapper: ImageWrapper,
     ImageDebug: ImageDebug,
-    ResultCollector: ResultCollector,
-    getConfig: function getConfig() {
-        return _config;
-    }
+    ResultCollector: ResultCollector
 };