disable automatic gain control on microphone

AGC really makes the soundqulity way worse than it could be.
Especially since it is so noticeable when entering a Jitsi where AGC is disabled (and suddenly some people sound much better).

In the long run, this should probably be configurable. On the other hand the setting changes the audio _going out_ from a user, so it might be hard for him to judge which settings are a good or a bad idea…

front/src/WebRtc/MediaManager.ts

@@ -18,6 +18,12 @@ let videoConstraint: boolean|MediaTrackConstraints = {
     resizeMode: 'crop-and-scale',
     aspectRatio: 1.777777778
 };
+let audioConstraint: boolean|MediaTrackConstraints = {
+    //TODO: make these values configurable in the game settings menu and store them in localstorage
+    autoGainControl: false,
+    echoCancellation: true,
+    noiseSuppression: false
+};
 
 export type UpdatedLocalStreamCallback = (media: MediaStream|null) => void;
 export type StartScreenSharingCallback = (media: MediaStream) => void;
@@ -40,7 +46,7 @@ export class MediaManager {
     webrtcInAudio: HTMLAudioElement;
     private webrtcOutAudio: HTMLAudioElement;
     constraintsMedia : MediaStreamConstraints = {
-        audio: true,
+        audio: audioConstraint,
         video: videoConstraint
     };
     updatedLocalStreamCallBacks : Set<UpdatedLocalStreamCallback> = new Set<UpdatedLocalStreamCallback>();