mediastream-gain.js

var support = require('webrtcsupport');


function GainController(stream) {
    this.support = support.webAudio && support.mediaStream;

    // set our starting value
    this.gain = 1;

    if (this.support) {
        var context = this.context = new support.AudioContext();
        this.microphone = context.createMediaStreamSource(stream);
        this.gainFilter = context.createGain();
        this.destination = context.createMediaStreamDestination();
        this.outputStream = this.destination.stream;
        this.microphone.connect(this.gainFilter);
        this.gainFilter.connect(this.destination);
        stream.addTrack(this.outputStream.getAudioTracks()[0]);
        stream.removeTrack(stream.getAudioTracks()[0]);
    }
    this.stream = stream;
}

// setting
GainController.prototype.setGain = function (val) {
    // check for support
    if (!this.support) return;
    this.gainFilter.gain.value = val;
    this.gain = val;
};

GainController.prototype.getGain = function () {
    return this.gain;
};

GainController.prototype.off = function () {
    return this.setGain(0);
};

GainController.prototype.on = function () {
    this.setGain(1);
};


module.exports = GainController;