code: function removeVPX(sdp) {
              if (!sdp || typeof sdp !== 'string') {
                  throw 'Invalid arguments.';
              }
  
              // this method is NOT reliable
  
              sdp = sdp.replace('a=rtpmap:100 VP8/90000\r\n', '');
              sdp = sdp.replace('a=rtpmap:101 VP9/90000\r\n', '');
  
              sdp = sdp.replace(/m=video ([0-9]+) RTP\/SAVPF ([0-9 ]*) 100/g, 'm=video $1 RTP\/SAVPF $2');
              sdp = sdp.replace(/m=video ([0-9]+) RTP\/SAVPF ([0-9 ]*) 101/g, 'm=video $1 RTP\/SAVPF $2');
  
              sdp = sdp.replace(/m=video ([0-9]+) RTP\/SAVPF 100([0-9 ]*)/g, 'm=video $1 RTP\/SAVPF$2');
              sdp = sdp.replace(/m=video ([0-9]+) RTP\/SAVPF 101([0-9 ]*)/g, 'm=video $1 RTP\/SAVPF$2');
  
              sdp = sdp.replace('a=rtcp-fb:120 nack\r\n', '');
              sdp = sdp.replace('a=rtcp-fb:120 nack pli\r\n', '');
              sdp = sdp.replace('a=rtcp-fb:120 ccm fir\r\n', '');
  
              sdp = sdp.replace('a=rtcp-fb:101 nack\r\n', '');
              sdp = sdp.replace('a=rtcp-fb:101 nack pli\r\n', '');
              sdp = sdp.replace('a=rtcp-fb:101 ccm fir\r\n', '');
  
              return sdp;
          }
docs: "removeVPX" and "removeNonG722" methods are taken from github/mozilla/webrtc-landing