Add maxFps option for requesting video

doc/API.md

@@ -61,6 +61,8 @@ JitsiMeetJS.setLogLevel(JitsiMeetJS.logLevels.ERROR);
         2. resolution - the prefered resolution for the local video.
         3. cameraDeviceId - the deviceID for the video device that is going to be used
         4. micDeviceId - the deviceID for the audio device that is going to be used
+        5. minFps - the minimum frame rate for the video stream (passed to GUM)
+        6. maxFps - the maximum frame rate for the video stream (passed to GUM)
 
 * ```JitsiMeetJS.enumerateDevices(callback)``` - returns list of the available devices as a parameter to the callback function. Every device is a object with the following format:
     - label - the name of the device

modules/RTC/RTCUtils.js

@@ -167,14 +167,21 @@ function getConstraints(um, options) {
         }
         constraints.video.optional.push({bandwidth: options.bandwidth});
     }
-    if (options.fps) {
+
+    if(options.minFps || options.maxFps || options.fps) {
         // for some cameras it might be necessary to request 30fps
         // so they choose 30fps mjpg over 10fps yuy2
         if (!constraints.video) {
             // same behaviour as true;
             constraints.video = {mandatory: {}, optional: []};
         }
-        constraints.video.mandatory.minFrameRate = options.fps;
+        if(options.minFps || options.fps) {
+            options.minFps = options.minFps || options.fps; //Fall back to options.fps for backwards compatibility
+            constraints.video.mandatory.minFrameRate = options.minFps;
+        }
+        if(options.maxFps) {
+            constraints.video.mandatory.maxFrameRate = options.maxFps;
+        }
     }
 
     // we turn audio for both audio and video tracks, the fake audio & video seems to work