Implement review changes 3

modules/RTC/RTCUtils.js

         }
 
         constraints.audio = {
-            autoGainControl: { exact: !disableAGC && !disableAP },
+            autoGainControl: !disableAGC && !disableAP,
             deviceId: options.micDeviceId,
-            echoCancellation: { exact: !disableAEC && !disableAP },
-            noiseSuppression: { exact: !disableNS && !disableAP }
+            echoCancellation: !disableAEC && !disableAP,
+            noiseSuppression: !disableNS && !disableAP
         };
 
         if (stereo) {

modules/RTC/ScreenObtainer.js

             getDisplayMedia = navigator.mediaDevices.getDisplayMedia.bind(navigator.mediaDevices);
         }
 
-        const { disableAGC, disableAP, enableHdAudio } = this.options;
-        const audioProcessingValue = !disableAGC && !disableAP;
-        const audio = enableHdAudio ? {
-            autoGainControl: audioProcessingValue,
+        const { stereo } = this.options;
+        const audio = stereo ? {
+            autoGainControl: false,
             channelCount: 2,
-            echoCancellation: audioProcessingValue,
-            noiseSuppression: audioProcessingValue
+            echoCancellation: false,
+            noiseSuppression: false
         } : true;
 
         getDisplayMedia({

modules/RTC/TraceablePeerConnection.js

  * @returns {RTCSessionDescription} the munged description.
  */
 TraceablePeerConnection.prototype._mungeOpus = function(description) {
+    const { opusMaxAverageBitrate, stereo } = this.options;
+
+    if (!opusMaxAverageBitrate || !stereo) {
+        return description;
+    }
+
     const parsedSdp = transform.parse(description.sdp);
     const mLines = parsedSdp.media;
 
             const fmtpConfig = transform.parseParams(fmtpOpus.config);
             let sdpChanged = false;
 
-            if (this.options.stereo) {
+            if (stereo) {
                 fmtpConfig.stereo = 1;
                 sdpChanged = true;
             }
 
-            if (this.options.opusMaxAverageBitrate) {
-                fmtpConfig.opusMaxAverageBitrate = this.options.opusMaxAverageBitrate;
+            if (opusMaxAverageBitrate) {
+                fmtpConfig.opusMaxAverageBitrate = opusMaxAverageBitrate;
                 sdpChanged = true;
             }