How can I disable automatic gain control (AGC) in WebRTC web-apps such as Google Hangouts or OpenTokRTC

The googAutoGainControl as MediaTrackConstraints is specific to Chrome (WebKit).

The WebRTC Working Group Charter still writing the standard and they will finish the next 30 June 2015.

Firefox not support right now.

Note: Use AGC is not recommended that you specify any browser-specific constraint as mandatory, as your call will fail in a browser that does not support the constraint. Instead, specify your constraints as optional. Your browser will do its best to satisfy as many optional constraints as possible.

BTW you can play with the GainNode interface in Firefox:https://developer.mozilla.org/en-US/docs/Web/API/GainNode

Example to disable the googAutoGainControl:

  var webrtc = new SimpleWebRTC({    localVideoEl: 'localVideo',    remoteVideosEl: '',    autoRequestMedia: true,    //detectSpeakingEvents: true,    adjustPeerVolume: false,    peerVolumeWhenSpeaking: 1,      media: {      audio: {        optional: [          //{sourceId: audio_source},          {googAutoGainControl: false},           {googAutoGainControl2: false},           {googEchoCancellation: false},          {googEchoCancellation2: false},          {googNoiseSuppression: false},          {googNoiseSuppression2: false},          {googHighpassFilter: false},          {googTypingNoiseDetection: false},          {googAudioMirroring: false}        ]     },     video: {        optional: [          //{sourceId: video_source}        ]      }    }    //autoAdjustMic: false          });

The end-user cannot disable in the browser this functionality right now.The advanced user can edit preferences in the about:config in Firefox but in Chrome does not exist.

It looks like FireFox added some support for this in 46: https://wiki.mozilla.org/Media/WebRTC/ReleaseNotes/46

Implemented echoCancellation, mozAutoGainControl and mozNoiseSuppression gUM constraints. (See bug 987186.)