网络音频API：麦克风流到扬声器音量下降？

Question

I am using the Web audio API to stream my mic input into the speakers, so I can hear myself talk through them:

var aCtx = new AudioContext();
navigator.mediaDevices.getUserMedia({audio: true}).then(function (stream) {
     var microphone = aCtx.createMediaStreamSource(stream);
     microphone.connect(aCtx.destination);
})

It works fine, but whenever I keep a steady long voice input, it seems like the output gain drops after a couple of seconds.

I have followed cwilso's advice and added the echo cancellation constraint. But the results are still the same.

Here's a Fiddle: https://jsfiddle.net/hcrgL9eg/

Help would be appreciated.

Answer 1

Yeah, you're hitting "auto gain control". There are a bunch of features on audio input that are on by default (echo cancellation, AGC, noise reduction). Take a look at Disabling Auto Gain Conctrol with WebRTC App ; it's the same solution.