anchor.diff:      "USE_SPEEX_AEC=1" "USE_SPEEX_PP=1" "USE_SPEEX_RESAMP=1" "USE_SRTP=1" 
       "USE_STDIO=1" "USE_SYSLOG=1" "USE_UUID=1" "USE_V4L2=1" "USE_X11=1"
   
  -    "USE_BV32=" "USE_COREAUDIO=" "USE_G711=" "USE_G722=" "USE_G722_1=" 
  +    "USE_BV32=" "USE_COREAUDIO=" "USE_G711=1" "USE_G722=1" "USE_G722_1="
       "USE_ILBC=" "USE_OPUS=" "USE_SILK=" 
     ]
     ++ stdenv.lib.optional (stdenv.cc.cc != null) "SYSROOT_ALT=${stdenv.cc.cc}"
  
positive.code: {stdenv, fetchurl, zlib, openssl, libre, librem, pkgconfig
  , cairo, mpg123, gstreamer, gst_ffmpeg, gst_plugins_base, gst_plugins_bad
  , gst_plugins_good, alsaLib, SDL, libv4l, celt, libsndfile, srtp, ffmpeg
  , gsm, speex, portaudio, spandsp, libuuid
  }:
  stdenv.mkDerivation rec {
    version = "0.4.20";
  
negative.code:   buildInputs = [zlib openssl libre librem pkgconfig
      cairo mpg123 gstreamer gst_ffmpeg gst_plugins_base gst_plugins_bad gst_plugins_good
      alsaLib SDL libv4l celt libsndfile srtp ffmpeg gsm speex portaudio spandsp libuuid
      ccache
      ];
    makeFlags = [
      "LIBRE_MK=${libre}/share/re/re.mk"
  