title: How to avoid echo and noise in javascript for webrtc
body: <p>I am trying to implement a webrtc-based chat room. And I encountered the following problems in laptop. Without connecting to any other peer, just use getUserMedia(), I can get local video stream.</p>
  <p>When I unmuted the <code>&lt;video&gt;</code>, echo happened.</p>
  <p>Then I wear headphones, and found there is a continued noise. And I can hear my voice clearly.</p>
  <p>I tried to turn down the volume, but it doesn't work.</p>
  <p>Thanks in advance.</p>